Resin composition, molded article, multilayer structure, and method for manufacturing resin composition

Abstract

The present invention provides a resin composition for which thickening over time is suppressed upon heating, as described below. A resin composition comprising an ethylene-vinyl alcohol copolymer (A), a nitrogen-containing compound (B), an alkali metal compound (C), and an alkaline earth metal compound (D), wherein the metal conversion content of the alkali metal compound (C) relative to the metal conversion content of the alkaline earth metal compound (D) (C / D) is greater than 0.5, and the nitrogen-containing compound (B) comprises a nitrogen atom bonded to each carbon atom in its structure, each having 2 or less nitrogen atoms, and satisfies the following (1) and / or (2): (1) The molecular weight of the nitrogen-containing compound (B) is 280 or less; (2) The amine equivalent of the nitrogen-containing compound (B) as defined by the following formula is less than 225 g / eq. (Formula) Amine equivalent (g / eq) = Molecular weight of nitrogen-containing compound (B) / Number of primary amine groups (-NH2) and secondary amine groups (-NH-) present in the nitrogen-containing compound (B).

Description

Technical Field

[0001] The present invention relates to a resin composition, and more particularly to a resin composition whose thickening over time when heated is suppressed. Prior Art

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH") possesses very strong intermolecular forces due to the hydrogen bonds between the hydroxyl groups in the polymer's side chains. This results in high crystallinity, and even in the amorphous portion, the intermolecular forces remain strong. Therefore, films made with EVOH exhibit excellent gas barrier properties, preventing gas molecules from passing through them.

[0003] However, because EVOH has highly active hydroxyl groups within its molecules, it is susceptible to oxidation and cross-linking reactions in the high-temperature melt state inside the extruder, even in the absence of oxygen. This can cause the material to thicken over time, making stable processing difficult.

[0004] To address this issue, for example, Patent Document 1 discloses a resin composition comprising: a saponified ethylene-vinyl acetate copolymer (A) having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or greater; acetic acid (B); and magnesium acetate and / or calcium acetate (C). The content of (B) is 0.05 parts by mass or less per 100 parts by mass of (A); and the content of (C) is 0.001 to 0.02 parts by mass per 100 parts by mass of (A) on a metal basis. Patent Document 1 also discloses that the use of this resin composition can produce a molded product that exhibits excellent long-run moldability during melt molding, exhibits minimal fisheyes, wrinkles, and coloration, and exhibits excellent appearance. Furthermore, when the molded product is formed into a laminate, odor is reduced, and the laminate maintains excellent interlayer adhesion even after secondary processing such as stretching and deep drawing. [Prior Art Literature] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 11-106592 Summary of the Invention

[0006] [Problems to be solved by the invention]

[0007] In recent years, with the diversification of feed blocks and mold shapes within molding equipment, and demands for higher functionality in multilayer structures, such as thinner films and increased number of layers in final products, molding equipment has been trending towards higher functionality. However, the increased complexity of molding equipment due to higher functionality can lead to the incorporation of degraded resin into the final product, resulting in products that fail to meet quality standards and a decrease in productivity (long-run molding performance). Although the technology disclosed in Patent Document 1 has excellent long-run moldability during melt molding, in molding equipment that has become more complex due to high functionality, the long-run moldability is insufficient due to the mixing of the above-mentioned degraded resin into the final product, and further improvement of the long-run moldability is required.

[0008] The inventors of this invention focused on the inevitable resin retention caused by the structure of molding equipment and speculated that this retention is the cause of the formation of resin degradation products. Therefore, the present invention aims to prevent the formation of these resin degradation products and provides a resin composition in which the time-dependent thickening during heating, which can cause retention, is suppressed; a molded article formed from the resin composition; a multilayer structure having a layer containing the resin composition; and a method for producing the resin composition. [Methods for solving the problem]

[0009] However, in light of this situation, the inventors of the present invention have conducted intensive research and have discovered that by adding specific nitrogen-containing compounds, alkali metal compounds, and alkaline earth metal compounds to EVOH, and setting the ratio of the metal content of the alkali metal compound to the metal content of the alkaline earth metal compound within a specific range, a resin composition can be obtained in which the time-dependent thickening during heating is suppressed.

[0010] That is, the present invention provides the following [1] to

[10] . [1] A resin composition comprising EVOH (A), a nitrogen-containing compound (B), an alkali metal compound (C), and an alkaline earth metal compound (D), The content ratio (C / D) of the metal conversion content of the alkali metal compound (C) to the metal conversion content of the alkaline earth metal compound (D) is greater than 0.5, The nitrogen-containing compound (B) has a nitrogen atom number of 2 or less bonded to each carbon atom in its structure and satisfies the following (1) and / or (2); (1) The molecular weight of the nitrogen-containing compound (B) is 280 or less (2) The amine equivalent of the nitrogen-containing compound (B) as defined by the following formula is less than 225 g / eq Formula) Amine equivalent (g / eq) = molecular weight of nitrogen-containing compound (B) / number of primary amine groups (-NH2) and secondary amine groups (-NH-) present in nitrogen-containing compound (B). [2] The resin composition of [1], wherein the nitrogen-containing compound (B) comprises a primary amino group and / or a secondary amino group. [3] The resin composition of [1] or [2], wherein the melting point of the nitrogen-containing compound (B) is 70-290°C. [4] The resin composition according to any one of [1] to [3], wherein the nitrogen-containing compound (B) is 2-imidazolidinone. [5] The resin composition according to any one of [1] to [3], wherein the nitrogen-containing compound (B) is an amino acid. [6] The resin composition of any one of [1] to [3] and [5], wherein the nitrogen-containing compound (B) is a basic amino acid. [7] The resin composition of any one of [1] to [3], [5], and [6], wherein the nitrogen-containing compound (B) is histidine. [8] A molded article formed by molding the resin composition as described in any one of [1] to [7]. [9] A multilayer structure having at least one layer comprising the resin composition according to any one of [1] to [7].

[10] A method for producing a resin composition, which is the method for producing a resin composition as described in any one of [1] to [7], comprising the step of mixing the EVOH (A), the nitrogen-containing compound (B), the alkali metal compound (C), and the alkaline earth metal compound (D). [Effects of the Invention]

[0011] The resin composition of the present invention suppresses thickening over time during heating, resulting in excellent long-run moldability. Implementation Method

[0012] The present invention will be described in detail below, but these are merely examples of desirable embodiments. In the present invention, the term "x and / or y (x and y are arbitrary components or elements)" refers to three combinations: only x, only y, and x and y. In the present invention, when “X to Y” (X and Y are arbitrary numbers) is expressed, unless otherwise specified, it includes the meaning of “greater than X and less than Y” as well as “preferably greater than X” or “preferably less than Y”. Furthermore, when the term "X or greater" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number) is used in the present invention, it also includes the meaning of "preferably greater than X" or "preferably less than Y."

[0013] A resin composition according to one embodiment of the present invention (hereinafter referred to as the "present resin composition") comprises EVOH (A), a nitrogen-containing compound (B), an alkali metal compound (C), and an alkaline earth metal compound (D), wherein the ratio (C / D) of the metal conversion content of the alkali metal compound (C) to the metal conversion content of the alkaline earth metal compound (D) is greater than 0.5, and the number of nitrogen atoms bonded to each carbon atom contained in the structure of the nitrogen-containing compound (B) is 2 or less, and the following (1) and / or (2) are satisfied. (1) The molecular weight of the nitrogen-containing compound (B) is 280 or less (2) The amine equivalent of the nitrogen-containing compound (B) as defined by the following formula is less than 225 g / eq Formula) Amine equivalent (g / eq) = molecular weight of nitrogen-containing compound (B) / number of primary amine groups (-NH2) and secondary amine groups (-NH-) present in nitrogen-containing compound (B). Below, each component is described.

[0014] 〔EVOH(A)〕 EVOH (A) used in this resin composition is typically obtained by saponifying an ethylene-vinyl ester copolymer, a copolymer of ethylene and a vinyl ester monomer. It is a water-insoluble thermoplastic resin. For economic reasons, vinyl acetate is generally used as the vinyl ester monomer.

[0015] The copolymerization of ethylene and vinyl ester monomers can be carried out by any known polymerization method, such as solution polymerization, suspension polymerization, and emulsion polymerization. Solution polymerization using methanol as the solvent is generally used. The resulting ethylene-vinyl ester copolymer can also be saponified by known methods.

[0016] The EVOH (A) produced in this manner mainly comprises ethylene structural units and vinyl alcohol structural units. When the saponification degree is less than 100 mol%, the unsaponified portion comprises a certain amount of residual vinyl ester structural units.

[0017] Regarding the aforementioned vinyl ester monomers, vinyl acetate is generally used, as described above, from economic perspectives and from the perspective of efficient impurity handling during production. Examples of vinyl ester monomers other than vinyl acetate include aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl trimethylacetate, vinyl decanoate, vinyl laurate, vinyl stearate, and vinyl neodecanoate, and aromatic vinyl esters such as vinyl benzoate. These may be used alone or in combination of two or more. Of these, aliphatic vinyl esters having 3 to 20 carbon atoms are preferred, more preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms.

[0018] The ethylene structural unit content of the EVOH (A) described above, as measured in accordance with ISO 14663, is typically 20-60 mol%, preferably 25-50 mol%, and particularly preferably 27-35 mol%. If this content is too low, gas barrier properties and melt formability at high humidity tend to decrease. On the other hand, if it is too high, gas barrier properties tend to decrease. The ethylene structural unit content can be controlled by adjusting the ethylene pressure during copolymerization of the vinyl ester monomer with ethylene.

[0019] The saponification degree of the aforementioned EVOH (A), as measured in accordance with JIS K6726 (assuming EVOH (A) is uniformly dissolved in a water / methanol solvent), is typically 90-100 mol%, preferably 95-100 mol%, and particularly preferably 99-100 mol%. A lower saponification degree tends to reduce gas barrier properties. The saponification degree can be controlled by adjusting the amount of saponification catalyst (typically an alkaline catalyst such as sodium hydroxide), temperature, and time used during the saponification of the ethylene-vinyl ester copolymer.

[0020] The melt flow rate (MFR) of the EVOH (A) (210°C, 2160g load) is typically 0.5-100 g / 10min, preferably 1-50 g / 10min, and particularly preferably 3-35 g / 10min. Excessively high MFR tends to cause unstable film forming properties, while excessively low MFR tends to cause excessively high viscosity, making melt extrusion difficult.

[0021] This MFR is an indicator of the degree of polymerization of EVOH (A) and can be adjusted by adjusting the amount of polymerization initiator and solvent used in copolymerizing ethylene and vinyl ester monomers.

[0022] Furthermore, the EVOH (A) may further contain structural units derived from the following comonomers within a range that does not inhibit the effects of the present invention (e.g., 10 mol% or less of the EVOH (A)).

[0023] As for the aforementioned comonomers, there may be mentioned olefins such as propylene, 1-butene, isobutylene, etc.; α-olefins containing hydroxyl groups such as 3-butene-1-ol, 3-butene-1,2-diol, 4-pentene-1-ol, 5-hexene-1,2-diol, and their esters, acylates and other derivatives; hydroxyalkyl vinylides such as 2-methylenepropane-1,3-diol, 3-methylenepentane-1,5-diol; 1, 3-Diacetyloxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyryloxy-2-methylenepropane and other hydroxyalkyl vinylene diacetates; acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid and other unsaturated acids or their salts or mono- or dialkyl esters with 1 to 18 carbon atoms in the alkyl group; acrylamide, alkane Acrylamides such as N-alkyl acrylamide with a carbon number of 1 to 18, N,N-dimethylacrylamide, 2-acrylamide propane sulfonic acid or its salts, acrylamidopropyl dimethylamine or its acid salts or quaternary salts; methacrylamide, N-alkyl methacrylamide with a carbon number of 1 to 18, N,N-dimethylmethacrylamide, 2-methacrylamide propane sulfonic acid or its salts, methacrylamidopropyl dimethylamine or its acid salts or quaternary salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide; vinyl cyanides such as acrylic acid nitrile and methacrylic acid nitrile; vinyl ethers such as alkyl vinyl ether, hydroxyalkyl vinyl ether, alkoxyalkyl vinyl ether, etc., with an alkyl group having a carbon number of 1 to 18; vinyl chloride, vinylidene chloride, vinyl fluoride (polyvinyl) These include vinyl halides such as vinyl fluoride, vinylidene fluoride, and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; allyl halides such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamide-2-methylpropanesulfonic acid. These may be used alone or in combination of two or more.

[0024] In particular, EVOH obtained by copolymerizing α-olefins containing hydroxyl groups, that is, EVOH having hydroxyl groups in the side chains, is more ideal from the perspective of maintaining gas barrier properties while also having good secondary moldability. EVOH having primary hydroxyl groups in the side chains is more ideal, and EVOH having a 1,2-diol structure in the side chains is particularly ideal.

[0025] In the case of EVOH having a primary hydroxyl group in the side chain, the content of the structural unit derived from the monomer having the primary hydroxyl group is generally 0.1 to 20 mol %, preferably 0.5 to 15 mol %, and particularly preferably 1 to 10 mol % of the EVOH.

[0026] Furthermore, the EVOH (A) may be "post-modified" by urethanization, acetalization, cyanoethylation, oxyalkylation, or the like.

[0027] The EVOH (A) may be a mixture of two or more EVOHs, for example, EVOHs having different degrees of saponification, different degrees of polymerization, or different copolymerization components.

[0028] The EVOH (A) is preferably the main component of the present resin composition. Here, the term "main component" means that its content is 50% by mass or more of the present resin composition, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0029] [Nitrogen-containing compounds (B)] The nitrogen-containing compound (B) used in the present resin composition is a compound containing nitrogen atoms in its structure, wherein the number of nitrogen atoms bonded to each carbon atom contained in its structure is 2 or less, and the compound satisfies the following (1) and / or (2). (1) Molecular weight is less than 280 (2) The amine equivalent defined by the following formula is less than 225 g / eq Formula) Amine equivalent (g / eq) = molecular weight of nitrogen-containing compound (B) / number of primary amine groups (-NH2) and secondary amine groups (-NH-) in nitrogen-containing compound (B) Furthermore, it is particularly preferable that the nitrogen-containing compound (B) satisfies the above-mentioned (1) and (2).

[0030] The nitrogen-containing compound (B) is an amino compound comprising at least one of a primary amino group (-NH2), a secondary amino group (-NH-), a tertiary amino group (refer to the following general formula (I)), and a quaternary amino group (refer to the following general formula (II)). This is more ideal from the perspective of suppressing thickening over time.

[0031] [Chemistry 1]

[0032] Among them, the nitrogen-containing compound (B) is preferably an amino compound containing a primary amino group (-NH2) and / or a secondary amino group (-NH-). The inclusion of a primary amino group (-NH2) and / or a secondary amino group (-NH-) tends to further enhance the effect of suppressing thickening over time.

[0033] The nitrogen-containing compound (B) has a nitrogen atom number of 2 or less bound to each carbon atom in its structure. That is, each carbon atom in the nitrogen-containing compound (B) is bonded to 0, 1, or 2 nitrogen atoms. By limiting the number of nitrogen atoms bonded to 2 or less per carbon atom, the effect of suppressing thickening over time is enhanced. For example, compounds containing a structure with 3 nitrogen atoms bonded to 1 carbon atom, such as a guanidine skeleton, exhibit significantly less effective suppression of thickening over time than compounds with 2 or less nitrogen atoms bonded to 1 carbon atom.

[0034] The molecular weight of the nitrogen-containing compound (B) having the characteristics of (1) above is 280 or less, preferably 230 or less, more preferably 150 or less, and even more preferably 100 or less. A molecular weight of 280 or less can suppress thickening over time during heating even with a small amount of addition. The lower limit of the molecular weight is not particularly limited, but is preferably 17 or greater, more preferably 30 or greater, even more preferably 40 or greater, and particularly preferably 50 or greater.

[0035] The amine equivalent of the nitrogen-containing compound (B) having the characteristics of (2) above is less than 225 g / eq, preferably less than 200 g / eq, more preferably less than 150 g / eq, and even more preferably less than 100 g / eq. By having an amine equivalent of less than 225 g / eq, thickening over time during heating can be suppressed with a small amount of addition. The lower limit of the amine equivalent is not particularly limited, but an amine equivalent of 10 g / eq or more is preferably, more preferably, more preferably, 20 g / eq or more, even more preferably, more preferably, 30 g / eq or more, and particularly preferably, more preferably, 40 g / eq or more. When the amine equivalent is less than 10 g / eq, the compound is often non-solid at room temperature (23°C) and tends to have poor handling properties. The amine equivalent is the mass of the nitrogen-containing compound (B) including one equivalent of amino groups, and can be obtained by the following formula. Formula) Amine equivalent (g / eq) = molecular weight of nitrogen-containing compound (B) / number of primary amine groups (-NH2) and secondary amine groups (-NH-) in nitrogen-containing compound (B)

[0036] The melting point of the nitrogen-containing compound (B) is not particularly limited, but is preferably 70 to 290°C. The lower limit of the melting point is more preferably 80°C or higher, more preferably 90°C or higher, and particularly preferably 100°C or higher. The upper limit of the melting point is more preferably 260°C or lower, more preferably 230°C or lower, particularly preferably 210°C or lower, extremely preferably 190°C or lower, and most preferably 170°C or lower. By setting the melting point within this range, the nitrogen-containing compound (B) is easier to handle and, because it melts at the melt-forming temperature of EVOH (A), tends to exhibit excellent effects.

[0037] Specific examples of the nitrogen-containing compound (B) include amino acids such as inorganic amino compounds and organic amino compounds. These may be used alone or in combination of two or more.

[0038] Examples of the inorganic amino compounds include hydroxylamine, chloramine, and ammonia.

[0039] Examples of the organic amino compounds include methanolamine, ethanolamine, dimethylamine, diethylamine, isopropylamine, butylamine, ethylenediamine, propylenediamine, diethylenetriamine, 1,2-diaminopropane, 1,3-diaminopropane, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, hexamethylenediamine, 3-azahexane-1,6-diamine, 2-acrylamido-2-methylpropanesulfonic acid, 4,7-diazadecane-1,10-diamine, and other aliphatic amines; proline, hydroxyproline, ethyleneimine, iodine, α-amino-ε-caprolactam, acetaldehyde, and other heterocyclic amines; 2-undecylimidazole, pyrrolidine, piperidine, piperidine, and other heterocyclic aromatic amines; urea, thiourea, methylurea, ethylurea, dimethylurea, diethylurea, and ethyleneurea. (2-imidazolidinone), azodicarbonamide, hydantoin, acetylurea and other compounds having urea bonds, formamide, acetamide, benzoamide, ethylenediamine, oxamic acid, succinamide, malonamide and other compounds having amide bonds, succinimide, o-phthalimide, maleimide, 1-hydroxymethyl-5,5-dimethylhydantoin, isocyanuric acid Compounds with imide bonds, amino acids such as alanine, valine, leucine, isoleucine, phenylalanine, tyrosine, thyroxine, methionine, cysteine, homocysteine, taurine, serine, threonine, asparagine, aspartic acid, glutamine, glutamine, and proline in their L- and / or D- forms, and basic amino acids such as tryptophan and histidine. However, benzotriazole is not included.

[0040] Among these nitrogen-containing compounds (B), organic amino compounds are preferred from the viewpoint of suppressing thickening over time, more preferred are heterocyclic aromatic amines, compounds having a urea bond, and amino acids, even more preferred are 2-undecyl imidazole, 1-dodecyl hydantoin, ethylene urea (2-imidazolidinone), and basic amino acids, and particularly preferred are ethylene urea (2-imidazolidinone) and histidine.

[0041] The upper limit of the content of the nitrogen-containing compound (B) in the present resin composition is not particularly limited, but is preferably less than 9% by mass, more preferably 8% by mass or less, even more preferably 7% by mass or less, particularly preferably 5% by mass or less, extremely preferably 3% by mass or less, and most preferably 1% by mass or less, relative to the combined amount of the EVOH (A) and the nitrogen-containing compound (B). A nitrogen-containing compound (B) content within the aforementioned range tends to further enhance the effect of suppressing thickening during heating.

[0042] The lower limit of the content of the nitrogen-containing compound (B) is not particularly limited, but is preferably 0.000001 mass % or more, more preferably 0.00001 mass % or more, even more preferably 0.0001 mass % or more, particularly preferably 0.001 mass % or more, extremely preferably 0.01 mass % or more, and most preferably 0.1 mass % or more, relative to the total amount of the EVOH (A) and the nitrogen-containing compound (B). The nitrogen-containing compound (B) content within the aforementioned range tends to further enhance the effect of suppressing thickening during heating.

[0043] [Alkali metal compound (C)] The present resin composition contains an alkali metal compound (C). Examples of the alkali metal in the alkali metal compound (C) include lithium, sodium, potassium, rubidium, and cesium. These can be used alone or in combination of two or more. Among these, sodium and potassium are more preferred, with sodium being particularly preferred.

[0044] Examples of the alkali metal compound (C) include alkali metal salts and alkali metal hydroxides. These are preferably water-soluble. Among these, alkali metal salts are particularly preferred from the perspective of dispersibility. Furthermore, the alkali metal compound (C) preferably excludes inorganic layered compounds and double salts from the viewpoints of economic efficiency and dispersibility.

[0045] Examples of the alkali metal salts include inorganic salts such as carbonates, bicarbonates, phosphates, borates, sulfates, and chlorides; monocarboxylates with 2 to 11 carbon atoms such as acetates, butyrates, propionates, heptanoates, and decanoates; dicarboxylates with 2 to 11 carbon atoms such as oxalates, malonates, succinates, adipates, suberates, and sebacates; monocarboxylates with 12 or more carbon atoms such as laurates, palmitates, stearates, 12-hydroxystearates, behenates, and octacosanates; and carboxylates of the terminal carboxyl groups of EVOH. These salts may be used alone or in combination of two or more. Monocarboxylates with 2 to 11 carbon atoms are preferred, with acetates being even more preferred.

[0046] The alkali metal salt may exist in the resin composition in the form of an alkali metal salt, or in the form of an ionized state or a complex with the resin or another substance as a ligand.

[0047] The molecular weight of the alkali metal compound (C) is usually 20 to 10,000, preferably 20 to 1,000, and particularly preferably 20 to 500.

[0048] The content of the alkali metal compound (C) is not particularly limited, but is generally 1 to 1000 ppm, preferably 5 to 800 ppm, more preferably 10 to 700 ppm, and particularly preferably 100 to 600 ppm, based on the mass of the metal relative to the resin composition. Excessive alkali metal compound (C) content tends to impair productivity, while insufficient content tends to reduce thermal stability. When two or more alkali metal compounds (C) are used in combination, the content of the alkali metal compound (C) is the total amount of all alkali metals in terms of metal conversion.

[0049] The content of the alkali metal compound (C) can be determined, for example, by using an atomic absorption spectrophotometer to measure a solution obtained by treating the resin composition with hydrochloric acid or the like and adding pure water to the solution to be fixed to volume.

[0050] [Alkaline earth metal compounds (D)] This resin composition contains an alkaline earth metal compound (D). Examples of the alkaline earth metal in the alkaline earth metal compound (D) include beryllium, magnesium, calcium, strontium, barium, and radium. These can be used alone or in combination of two or more. Among these, magnesium and calcium are particularly preferred from the perspectives of market availability and economic efficiency.

[0051] Examples of the alkaline earth metal compound (D) include alkaline earth metal salts, oxides, and hydroxides. Among these, alkaline earth metal oxides or alkaline earth metal salts are preferred from the perspectives of economic efficiency and dispersibility, and alkaline earth metal salts are particularly preferred. The alkaline earth metal compound (D) preferably excludes layered inorganic compounds such as montmorillonite and complex salts such as hydrotalcite from the viewpoints of economic efficiency and dispersibility.

[0052] Examples of the alkaline earth metal oxides include magnesium oxide and calcium oxide. Examples of the alkaline earth metal salts include inorganic salts such as carbonates, hydrogen carbonates, phosphates, borates, sulfates, and chlorides, and carboxylates.

[0053] Among them, alkaline earth metal phosphates and carboxylates are more preferred from the viewpoint of their excellent effect in suppressing thickening during heating.

[0054] Examples of the carboxylate include saturated and unsaturated carboxylates. The carbon number of the anion of the carboxylate is usually 2 to 25, preferably 2 to 22, and particularly preferably 6 to 20 from the viewpoint of productivity. Specific examples of carboxylates include monovalent carboxylates such as acetate, butyrate, propionate, heptanoate, decanoate, laurate, palmitate, stearate, 12-hydroxystearate, behenate, and octacosinate, and divalent carboxylates such as oxalate, malonate, succinate, adipate, suberate, and sebacate. These may be used alone or in combination of two or more. From the perspective of market availability, linear saturated carboxylates are preferred, monovalent carboxylates are more preferred, and acetates are particularly preferred.

[0055] The alkaline earth metal compound (D) may be in any form, such as solid (powder, fine powder, flakes, etc.), semi-solid, liquid, paste, solution, or emulsion (aqueous dispersion). Powder is particularly preferred.

[0056] The content of the alkaline earth metal compound (D) is not particularly limited, but is generally 0.1 to 500 ppm, preferably 0.5 to 300 ppm, more preferably 1 to 200 ppm, and even more preferably 2 to 150 ppm, based on the mass of the metal relative to the resin composition. Excessive amounts of the alkaline earth metal compound (D) tend to reduce thermal stability, while insufficient amounts tend to reduce the moldability of the resin composition. When two or more alkaline earth metal compounds (D) are used in combination, the content of the alkaline earth metal compound (D) is the total amount of all alkaline earth metals in terms of metal conversion.

[0057] The content of the alkaline earth metal compound (D) can be determined, for example, by using an atomic absorption spectrophotometer to measure a solution obtained by treating the resin composition with hydrochloric acid or the like and adding pure water to the solution to be fixed to volume.

[0058] [Content ratio of the metal-converted content of the alkali metal compound (C) to the metal-converted content of the alkaline earth metal compound (D) (C / D)] In the present resin composition, the metal-equivalent content ratio (C / D) of the alkali metal compound (C) to the metal-equivalent content of the alkaline earth metal compound (D) is greater than 0.5. The above content ratio (C / D) is preferably 1 or greater, more preferably 2 or greater, even more preferably 8 or greater, and particularly preferably 15 or greater. The upper limit of the content ratio (C / D) is not particularly limited, but is generally 10,000 or less, preferably 5,000 or less, more preferably 1,000 or less, even more preferably 300 or less, and particularly preferably 50 or less. When the content ratio (C / D) falls within the above range, the thermal stability of the resin composition can be improved.

[0059] Boron compounds In the present resin composition, it is preferable to further contain a boron compound from the viewpoint of further enhancing the effect of suppressing the thickening over time during heating.

[0060] Examples of the boron compound include boric acid or its metal salts, such as boric acid, calcium borate, cobalt borate, zinc borate (zinc tetraborate, zinc metaborate, etc.), aluminum potassium borate, ammonium borate (ammonium metaborate, ammonium tetraborate, ammonium pentaborate, ammonium octaborate, etc.), cadmium borate (cadmium orthoborate, cadmium tetraborate, etc.), potassium borate (potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium octaborate, etc.), silver borate (silver metaborate, silver tetraborate, etc.), copper borate (copper (II) borate, copper metaborate, copper tetraborate, etc.), sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, etc.), Borate minerals such as borax, borax, colemanite, boraxite, boraxite, boraxite, and boraxite can be used alone or in combination. Among them, borax, boric acid, and sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate, etc.) are more ideal.

[0061] The content of the boron compound is not particularly limited. The lower limit of the content is preferably 1 ppm or more, more preferably 10 ppm or more, particularly preferably 20 ppm or more, and particularly preferably 50 ppm or more, calculated as boron relative to the EVOH (A). The upper limit of the content is preferably 1000 ppm or less, more preferably 500 ppm or less, particularly preferably 300 ppm or less, and particularly preferably 100 ppm or less, calculated as boron relative to the EVOH (A). By keeping the content within this range, the long-run moldability improvement effect can be further enhanced by synergistically acting with the nitrogen-containing compound (B). The reason why the use of a specific amount of the boron compound achieves such superior effects is unknown, but it is presumed to be due to improved discharge properties of the resin composition through adjustment of the melt viscosity.

[0062] The boron content of the boron compound can be determined using known analytical methods. For example, the boron content can be quantified using inductively coupled plasma atomic emission spectrometry (ICP-AES) using a sample solution prepared by wet decomposing the resin composition and then adjusting the volume.

[0063] [Other ingredients] Furthermore, the present resin composition may contain a thermoplastic resin other than the aforementioned EVOH (A) (e.g., various thermoplastic resins such as polyamide, polyester, polyethylene, polypropylene, and polystyrene) within a range that does not impair the effects of the present invention (e.g., generally 30% by mass or less, preferably 20% by mass or less, and particularly preferably 10% by mass or less of the present resin composition). These thermoplastic resins may be used alone or in combination of two or more.

[0064] The present resin composition may also contain, as necessary, plasticizers, reinforcing agents, fillers, pigments, dyes, lubricants, antioxidants, antistatic agents, UV absorbers, heat stabilizers, light stabilizers, surfactants, antimicrobial agents, antistatic agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, hardeners, foaming agents, crystallization nucleating agents, etc., within a range that does not impair the effects of the invention (e.g., 5% by mass or less of the present resin composition). These may be used alone or in combination of two or more.

[0065] [Preparation of resin composition] The present resin composition can be prepared by mixing the aforementioned EVOH (A), the aforementioned nitrogen-containing compound (B), the aforementioned alkali metal compound (C), the aforementioned alkaline earth metal compound (D), and any optional components blended therein as needed.

[0066] The mixing method is not particularly limited, and the components may be mixed by dry blending and used directly as the present resin composition. However, generally, the present resin composition is prepared by mixing by melt mixing, solution mixing, or the like, followed by forming into a pellet or other easily handled form. From the perspective of productivity, the melt mixing method is preferred.

[0067] The aforementioned melt mixing method generally includes dry blending the components and then melting and mixing them. The mixing apparatus can be a kneader, extruder, mixing roll, internal mixer, plastomill, or other known mixing apparatus, but a single-shaft or twin-shaft extruder is generally preferred industrially. Furthermore, the extruder may be equipped with a vent suction device, a gear pump, a screen, or the like, as needed.

[0068] The melt kneading temperature is generally in the range of 160-300°C, preferably 170-260°C, and particularly preferably 180-240°C, based on the set temperature of the extruder and the die. If the temperature is too low, the resin may become unmelted, making the processing unstable. If the temperature is too high, the resin composition may thermally degrade, resulting in a decrease in the quality of the resulting molded article.

[0069] The method for adjusting the amounts of the aforementioned nitrogen-containing compound (B), the aforementioned alkali metal compound (C), the aforementioned alkaline earth metal compound (D), and any other optional components in the present resin composition is not particularly limited. Adjustment can be made by adding the desired amounts, or by preparing a masterbatch and then diluting the mixture. When diluting the masterbatch, any dilution method may be employed, but dry blending is preferred from the perspective of productivity.

[0070] In addition, in addition to the above-mentioned method, the optional components such as the boron compound may be added during the production of the EVOH (A).

[0071] The resin composition obtained in this manner suppresses thickening over time during heating, resulting in excellent long-run moldability. The thickening ratio of the resin composition calculated under the following measurement conditions is usually 1.45 or less, more preferably 1.40 or less, and particularly preferably 1.35 or less. The lower limit of the thickening ratio is preferably as low as possible, and is usually 1.0, more preferably 0.5 or more, and particularly preferably 0.1 or more. [Measurement conditions] The thickening ratio can be calculated by melt-kneading the resin composition and then using the following formula based on the torque value after 60 minutes and the torque value after 180 minutes. Thickening ratio = torque value after 180 minutes / torque value after 60 minutes

[0072] This resin composition is typically formed into articles such as films, sheets, cups, and fibers by melt molding. Examples of such melt molding methods include extrusion (T-die extrusion, blown bag extrusion, blow molding, melt spinning, profile extrusion, etc.) and injection molding. The melt molding temperature can generally be appropriately selected within the range of 150-300°C. The resulting molded article (film, sheet, cup, fiber, etc.) can also be subjected to secondary processing such as uniaxial or biaxial stretching or vacuum forming.

[0073] Furthermore, the molded article obtained by melt molding using the present resin composition may be a molded article composed solely of the present resin composition, or may be a molded article composed of a multilayer structure formed by laminating the resin composition with a substrate such as another resin sheet, film, paper, nonwoven fabric, or metal foil.

[0074] Regarding the production of the aforementioned multilayer structure, there may be adopted a method of melt-extrusion lamination of other substrates on a film, sheet, etc. formed using the present resin composition; a method of melt-extrusion lamination of the present resin composition on other substrates; a method of co-extruding the present resin composition with other substrates; a method of dry lamination of a film, sheet, etc. formed using the present resin composition and a layer composed of other substrates using a known adhesive such as an organic titanium compound, isocyanate compound, polyester compound, polyurethane compound, etc. [Example]

[0075] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless the gist of the invention is exceeded.

[0076] Before the examples, prepare the following ingredients.

[0077] [EVOH(A)] EVOH (A1): Ethylene structural unit content 29 mol%, MFR 3.8 g / 10 min (210°C, 2160 g load), saponification degree 99.6 mol%, alkali metal compound content (metal equivalent) 170 ppm (sodium acetate), alkaline earth metal compound content (metal equivalent) 8.1 ppm (magnesium acetate 0.1 ppm, calcium dihydrogen phosphate 8 ppm), boron compound content (boron equivalent) 70 ppm EVOH (A2): Ethylene structural unit content 30.1 mol%, MFR 8.0 g / 10 min (210°C, 2160 g load), saponification degree 99.8 mol%, alkali metal compound content (metal equivalent) 110 ppm (sodium acetate), alkaline earth metal compound content (metal equivalent) 40.3 ppm (magnesium acetate 0.3 ppm, calcium dihydrogen phosphate 40 ppm), boron compound content (boron equivalent) 0 ppm EVOH (A3): Ethylene structural unit content 29.3 mol%, MFR 8.8 g / 10 min (210°C, 2160 g load), saponification degree 99.6 mol%, alkali metal compound content (metal equivalent) 6 ppm (sodium acetate), alkaline earth metal compound content (metal equivalent) 15 ppm (magnesium acetate 15 ppm, calcium dihydrogen phosphate 0 ppm), boron compound content (boron equivalent) 0 ppm

[0078] <Boron Compound Content in Pellets (Boron Conversion)> The boron compound content in EVOH (A) was determined by microwave decomposition of 0.1 g of EVOH (A) pellets with concentrated nitric acid. The resulting solution was fixed to 0.75 mg / mL with pure water. The resulting solution was then measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES) (Agilent Technologies, Model 720-ES). The boron content measured corresponds to the amount of boron derived from the boron compounds.

[0079] [Nitrogen-containing compound (B)] Nitrogen-containing compound (B1): 2-imidazolidinone (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 86, amine equivalent 43 g / eq, melting point 132°C, number of nitrogen atoms bonded to one carbon atom is 2 or less) Nitrogen-containing compound (B2): L-histidine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 155, amine equivalent 77.5 g / eq, melting point 281°C, number of nitrogen atoms bonded to one carbon atom is 2 or less) Nitrogen-containing compound (B'): Cyanoguanidine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 84, amine equivalent 28 g / eq, melting point 281°C, structure containing three nitrogen atoms bonded to one carbon atom) Nitrogen-containing compound (B"): Bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate ("Tinuvin 770 DF," manufactured by BASF Japan, molecular weight 480, amine equivalent 240 g / eq, number of nitrogen atoms bonded to one carbon atom is 2 or less)

[0080] <Example 1> EVOH (A1) and a nitrogen-containing compound (B1) were dry-blended so that the amount of (B1) relative to the total amount of (A1) and (B1) was 0.1% by mass to prepare a resin composition.

[0081] <Examples 2-5, Comparative Examples 1-3> A resin composition was prepared in the same manner as in Example 1, except that the types and amounts of EVOH (A) and the nitrogen-containing compound (B), and the content ratio (C / D) of the alkali metal compound (C) to the alkaline earth metal compound (D) were changed as described in Table 1 below.

[0082] The prepared resin composition was used to evaluate the following thickening inhibition rate.

[0083] <Evaluation of Thickening Inhibition Rate> 55 g of each resin composition was melt-kneaded under the following melt-kneading conditions, and the change in torque over time was recorded. Furthermore, as a background value, EVOH (A1), EVOH (A2), and EVOH (A3) were similarly melt-kneaded, and the change in torque over time was recorded. [Melt mixing conditions] Device: Brabender plastic spectrometer Conditions: 240°C, 50 rpm, preheating for 5 minutes, mixing for 180 minutes

[0084] The thickening ratio was calculated using the following formula based on the torque values ​​obtained after 60 minutes and after 180 minutes. Thickening ratio = torque value at the time of measurement after 180 minutes / torque value at the time of measurement after 60 minutes Next, the thickening inhibition rate was calculated using the following formula based on the calculated thickening ratio of each Example or Comparative Example and the thickening ratio of the background value (the resin composition not containing the nitrogen-containing compound (B) in each Example or Comparative Example). Thickening inhibition rate (%) = [thickening ratio (background value) - thickening ratio (example or comparative example)] / thickening ratio (background value) × 100

[0085] [Table 1] Resin composition evaluate EVOH(A) Nitrogen Compound (B) alkali metals Compound (C) Alkaline earth metals Compound (D) Content ratio (C / D) Thickening ratio Thickening Inhibition rate (%) type Content ※1 (quality%) Metal Conversion Content ※2 (ppm) Metal Conversion Content ※2 (ppm) Example 1 A1 B1 0.1 170 8.1 twenty one 1.36 twenty three Example 2 A1 B1 0.5 170 8.1 twenty one 1.29 27 Example 3 A1 B1 1.0 170 8.1 twenty one 1.32 26 Example 4 A2 B2 0.5 110 40.3 2.7 1.37 18 Example 5 A2 B2 5 110 40.3 2.7 1.38 17 Comparative Example 1 A3 B2 0.5 6 15 0.4 1.55 - ※3 Comparative Example 2 A2 B' 0.1 110 40.3 2.7 1.62 2 Comparative Example 3 A2 B'' 0.1 110 40.3 2.7 1.67 -2 B1: 2-Imidazolidinone (molecular weight 86, amine equivalent weight 43 g / eq, number of nitrogen atoms bonded to one carbon atom is 2 or less) B2: L-histidine (molecular weight 155, amine equivalent 77.5 g / eq, number of nitrogen atoms bonded to one carbon atom is 2 or less) B': Cyanoguanidine (molecular weight 84, amine equivalent weight 28 g / eq, structure containing three nitrogen atoms bonded to one carbon atom) B'': Bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate (molecular weight 480, amine equivalent weight 240 g / eq, number of nitrogen atoms bonded to one carbon atom is 2 or less) ※1: Content relative to the total amount of EVOH (A) and nitrogen-containing compound (B) ※2: Relative to the content of the resin composition ※3: Since the thickening ratio of EVOH (A3) has not been calculated, it cannot be calculated.

[0086] From the results in Table 1 above, it can be understood that the resin compositions of Examples 1 to 5, which contain EVOH (A), a specific nitrogen-containing compound (B), an alkali metal compound (C), and an alkaline earth metal compound (D), wherein the ratio (C / D) of the metal content of the alkali metal compound (C) to the metal content of the alkaline earth metal compound (D) falls within a specific range, have suppressed thickening over time compared to the background value of EVOH (A1) and (A2) which do not contain the nitrogen-containing compound (B). Consequently, they exhibit excellent long-run moldability. Furthermore, it can be understood that the resin composition of Comparative Example 1, in which the metal-equivalent content ratio (C / D) of the alkali metal compound (C) to the metal-equivalent content of the alkaline earth metal compound (D) is 0.5 or less, has a higher thickening ratio than Examples 1 to 5. Furthermore, it can be understood that the resin composition of Comparative Example 2, in which the nitrogen-containing compound (B) comprises a compound having a structure in which three nitrogen atoms are bonded to one carbon atom, has a higher thickening ratio and a poorer thickening suppression effect than Examples 1 to 5. Furthermore, it can be understood that the resin composition of Comparative Example 3, in which the nitrogen-containing compound (B) is a compound that does not have a specific molecular weight and amine equivalent, has a higher thickening ratio than Examples 1 to 5 and a poorer thickening suppression effect. In addition, the molded articles composed of the resin compositions of Examples 1 to 5, and the multilayer structures having a layer containing the resin compositions of Examples 1 to 5, can also suppress the thickening over time when heated.

[0087] The above embodiments are specific embodiments of the present invention, but are merely illustrative and are not to be construed as limiting. Various modifications known to those skilled in the art are intended to fall within the scope of the present invention. [Industrial Applicability]

[0088] The resin composition of the present invention suppresses thickening over time during heating, resulting in excellent long-run moldability. Therefore, it is particularly useful as packaging materials for various foods, including seasonings such as mayonnaise and salad dressing, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, and pharmaceuticals.

Claims

1. A resin composition comprising an ethylene-vinyl alcohol copolymer (A), a nitrogen-containing compound (B), an alkali metal compound (C), and an alkaline earth metal compound (D), wherein the metal conversion content of the alkali metal compound (C) relative to the metal conversion content of the alkaline earth metal compound (D) (C / D) is greater than 0.5 by mass; wherein the nitrogen-containing compound (B) has two or fewer nitrogen atoms bonded to each carbon atom in its structure, and satisfies the following (1) and / or (2): (1) The molecular weight of the nitrogen-containing compound (B) is 280 or less; (2) The amine equivalent of the nitrogen-containing compound (B) as defined by the following formula is less than 225 g / eq (Formula) Amine equivalent (g / eq) = Molecular weight of nitrogen-containing compound (B) / Number of primary amine groups (-NH2) and secondary amine groups (-NH-) present in the nitrogen-containing compound (B); wherein the nitrogen-containing compound (B) is a 2-imidazolidineone and / or an amino acid.

2. The resin composition as claimed in claim 1, wherein, The nitrogen-containing compound (B) contains primary and / or secondary amino groups.

3. The resin composition as claimed in claim 1 or 2, wherein, The melting point of this nitrogen-containing compound (B) is 70~290℃.

4. The resin composition as claimed in claim 1 or 2, wherein, The nitrogen-containing compound (B) is a basic amino acid.

5. The resin composition as claimed in claim 1 or 2, wherein, The nitrogen-containing compound (B) is histidine.

6. A molded article formed from a resin composition as claimed in any one of claims 1 to 5.

7. A multilayer structure having a layer comprising a resin composition as claimed in any one of claims 1 to 5.

8. A method for manufacturing a resin composition, which is a method for manufacturing a resin composition according to any one of claims 1 to 5, comprising the step of mixing the ethylene-vinyl alcohol copolymer (A), the nitrogen-containing compound (B), the alkali metal compound (C), and the alkaline earth metal compound (D).