Ethylene-vinyl alcohol copolymer composition

Abstract

Provided is an EVOH resin composition that can provide an improved elongation at break at low temperatures. The ethylene-vinyl alcohol copolymer composition comprises an ethylene-vinyl alcohol copolymer (A), an unmodified polyolefin (B), and an acid-modified polyolefin (C). The mass ratio [(B) / (C)] between the unmodified polyolefin (B) and acid-modified polyolefin (C) is 75 / 25 to 1 / 99; the melt viscosity ratio [(η1) / (η2)] between the melt viscosity (η1) of the composition at 210°C and a shear rate of 18 [sec-1] and the melt viscosity (η2) of the composition at 210°C and a shear rate of 365 [sec-1] is at least 5.6; and the mass ratio [(A) / ((B) + (C))] between the ethylene-vinyl alcohol copolymer (A) and the total content of the unmodified polyolefin (B) and acid-modified polyolefin (C) is at least 60 / 40 but less than 75 / 25.

Description

[Technical Field]

[0001] The present invention relates to an ethylene-vinyl alcohol copolymer composition (hereinafter sometimes referred to as "EVOH resin composition") containing an ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH"). More specifically, the present invention relates to an EVOH resin composition that exhibits excellent elongation at low temperatures. [Background technology]

[0002] Traditionally, metal was used as the material for fuel tanks, but recently, resins have been used for weight reduction and other reasons. Such resin fuel tanks are generally molded by blow molding, injection molding, tube molding, etc. Furthermore, for applications where flexibility is required, for example, a resin composition has been proposed in which a flexible thermoplastic resin is blended with an ethylene-vinyl acetate copolymer saponified product (Patent Document 1).

[0003] Specifically, the technology described in Patent Document 1 aims to provide a multilayer structure with excellent oxygen barrier properties, high flexibility, and flexural resistance by blending an unmodified ethylene-α-olefin copolymer, an acid-modified ethylene-α-olefin copolymer, and EVOH having a specific range of melt flow rates (MFRs) in specific proportions, in addition to further blending an alkali metal salt. However, it had the problem of insufficient elongation when used at low temperatures.

[0004] Furthermore, a resin composition comprising EVOH and an ethylene-butene copolymer acid-modified with an anhydride of an unsaturated carboxylic acid has been proposed for the purpose of providing hydrogen fuel tanks (Patent Document 2).

[0005] Specifically, the technology described in Patent Document 2 aims to provide a resin composition containing EVOH and an acid-modified ethylene-butene copolymer exhibiting a specific storage modulus, which can achieve both a barrier property for fuel (especially hydrogen) and impact resistance at low temperatures, and a molded article (fuel tank) using the same. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2015 / 141610 [Patent Document 2] Japanese Patent Publication No. 2005-68300 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the technology described in Patent Document 2 did not exhibit good elongation at low temperatures, and there was room for improvement. This is thought to be because the elastomer component consists solely of acid-modified elastomer, and the interaction at the interface between EVOH and elastomer is too strong, making it difficult for deformation due to interfacial delamination to occur when deformed, resulting in less elongation.

[0008] The present invention has been made in view of the above circumstances, and provides an EVOH resin composition with improved elongation at break at low temperatures. [Means for solving the problem]

[0009] In view of the above circumstances, the inventors conducted diligent studies and found that by using a specific ratio of elastomers (unmodified polyolefin and acid-modified polyolefin) in an EVOH resin composition with a controlled melt viscosity ratio, the elongation at low temperatures can be improved. This is presumed to be because there is an appropriate interaction at the interface between EVOH and the elastomer, resulting in increased elongation due to yield deformation and deformation due to interfacial delamination.

[0010] In other words, the present invention provides the following [1] to

[10] . [1] An ethylene-vinyl alcohol copolymer composition containing an ethylene-vinyl alcohol copolymer (A), an unmodified polyolefin (B), and an acid-modified polyolefin (C), wherein the mass ratio [(B) / (C)] of the unmodified polyolefin (B) to the acid-modified polyolefin (C) is 75 / 25 to 1 / 99, and the melt viscosity (η1) of the composition at 210°C and a shear rate of 18 [sec -1 and the melt viscosity ratio [(η1) / (η2)] of the melt viscosity (η2) of the composition at 210°C and a shear rate of 365 [sec -1 are 5.6 or more, and the mass ratio [(A) / ((B)+(C))] of the total content of the ethylene-vinyl alcohol copolymer (A) to the unmodified polyolefin (B) and the acid-modified polyolefin (C) is 60 / 40 or more and less than 75 / 25. An ethylene-vinyl alcohol copolymer composition. [2] The ethylene-vinyl alcohol copolymer composition according to [1], wherein the unmodified polyolefin (B) is an unmodified ethylene-α-olefin copolymer. [3] The ethylene-vinyl alcohol copolymer composition according to [1] or [2], wherein the unmodified polyolefin (B) is an unmodified ethylene-butene copolymer. [4] The ethylene-vinyl alcohol copolymer composition according to any one of [1] to [3], wherein the acid-modified polyolefin (C) is an acid-modified ethylene-α-olefin copolymer. [5] The ethylene-vinyl alcohol copolymer composition according to any one of [1] to [4], wherein the acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer. [6] The ethylene-vinyl alcohol copolymer composition according to [1], wherein the unmodified polyolefin (B) is an unmodified ethylene-butene copolymer and the acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer. [7] The ethylene-vinyl alcohol copolymer composition according to any one of [1] to [6], wherein the melt flow rate of the acid-modified polyolefin (C) is 1.0 g or more / 10 min under the conditions of 190°C and a load of 2160 g. [8] The ethylene-vinyl alcohol copolymer composition according to any one of [1] to [7], wherein the melt viscosity (η1) is 10,000 (mPa·s) or less. [9] The ethylene-vinyl alcohol copolymer composition according to any one of [1] to [8], wherein the mass ratio [(A) / ((B)+(C))] of the content of the ethylene-vinyl alcohol copolymer (A) to the total content of the unmodified polyolefin (B) and the acid-modified polyolefin (C) is 60 / 40 or more and 68 / 32 or less.

[10] A molded article having at least one layer made of an ethylene-vinyl alcohol copolymer composition as described in any of [1] to [9]. [Effects of the Invention]

[0011] The EVOH resin composition of the present invention can improve elongation at low temperatures. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below, but these are merely examples of preferred embodiments and are not limited to these.

[0013] The EVOH resin composition according to an embodiment of the present invention is an EVOH resin composition containing EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C), wherein the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)] is 75 / 25 to 1 / 99, and the EVOH resin composition is subjected to a shear rate of 18 [sec] at 210°C. -1 The melt viscosity (η1) at ] and the EVOH resin composition at 210°C and a shear rate of 365 [sec -1The EVOH resin composition has a melt viscosity ratio [(η1) / (η2)] of 5.6 or higher with respect to the melt viscosity (η2) in [ ], and a mass ratio [(A) / ((B)+(C))] of 60 / 40 or higher to the total content of ethylene-vinyl alcohol copolymer (A), unmodified polyolefin (B), and acid-modified polyolefin (C). The following describes each component.

[0014] <EVOH(A)> EVOH(A) is a resin typically obtained by saponifying a copolymer of ethylene and vinyl ester monomers (ethylene-vinyl ester copolymer), and is a water-insoluble thermoplastic resin. Polymerization can be carried out using any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization, but generally, solution polymerization using a lower alcohol such as methanol as a solvent is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be carried out by known methods. The EVOH(A) produced in this way mainly consists of ethylene structural units and vinyl alcohol structural units, and contains a small amount of vinyl ester structural units that remain unsaponified.

[0015] As the vinyl ester monomer, vinyl acetate is typically used due to its availability from the market and its efficient impurity removal during manufacturing. Other vinyl ester monomers include, for example, aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, and aromatic vinyl esters such as vinyl benzoate. Typically, aliphatic vinyl esters with 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms can be used. These are usually used individually, but multiple types may be used simultaneously as needed.

[0016] The ethylene content in EVOH(A) is not particularly limited, but is preferably 20 to 60 mol%, more preferably 25 to 50 mol%, and most preferably 25 to 45 mol%, based on values ​​measured according to ISO 14663. If the content is too low, the oxygen barrier properties and melt moldability under high humidity tend to decrease, and conversely, if the content is too high, the oxygen barrier properties tend to decrease.

[0017] The degree of saponification of the vinyl ester component in EVOH(A) is not particularly limited, but is preferably 90-100 mol%, more preferably 95-100 mol%, and most preferably 99-100 mol%, based on values ​​measured according to JIS K6726 (where EVOH is used as a solution uniformly dissolved in water / methanol solvent). If the degree of saponification is too low, the oxygen barrier properties, thermal stability, moisture resistance, etc. tend to decrease.

[0018] Furthermore, the melt flow rate (MFR) of EVOH(A) (210°C, load 2160g) is not particularly limited, but is preferably 0.5 to 100g / 10min, more preferably 1 to 60g / 10min, and particularly preferably 3 to 50g / 10min. If the MFR is too high, the film-forming ability tends to decrease, and if the MFR is too low, the melt viscosity tends to become too high, making melt extrusion difficult.

[0019] In addition to ethylene structural units and vinyl alcohol structural units (including un-saponified vinyl ester structural units), EVOH (A) may further contain structural units derived from the following comonomers. Examples of the comonomers include α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 3-butene-1,2-diol, and hydroxy group-containing α-olefin derivatives such as their esterified products and acylated products; unsaturated carboxylic acids or their salts, their partial alkyl esters, their complete alkyl esters, their nitriles, their amides or their anhydrides; unsaturated sulfonic acids or their salts; vinyl silane compounds; vinyl chloride; styrene and the like.

[0020] Furthermore, "post-modified" EVOH such as urethanized, acetalized, cyanoethylated, oxyalkylenated EVOH can also be used.

[0021] Among the modified products as described above, EVOH in which a primary hydroxyl group is introduced into the side chain by copolymerization is preferable in that it has good secondary formability such as stretching treatment and vacuum / pressure air forming. Among them, EVOH having a 1,2-diol structure in the side chain is particularly preferable.

[0022] The EVOH having a 1,2-diol structure in the side chain contains a 1,2-diol structural unit in the side chain, and EVOH containing a structural unit represented by the following general formula (1) is preferable.

[0023]

Chemical formula

[0024] In general formula (1), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently represent a hydrogen atom or an organic group, and X represents a single bond or a bonding chain.

[0025] Examples of the organic group include C1-C4 alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, and tert-butyl group. Such organic groups may optionally have functional groups such as halogen groups, hydroxyl groups, ester groups, carboxylic acid groups, and sulfonic acid groups.

[0026] The aforementioned bonding chains may include, for example, hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons may be substituted with halogens such as fluorine, chlorine, or bromine), as well as -O-, -(CH2O) m -,-(OCH2) m -,-(CH2O) m CH2-, -CO-, -COCO-, -CO(CH2) m Examples include CO-, -CO(C6H4)CO-, -S-, -CS-, -SO-, -SO2-, -NR-, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO4-, -Si(OR)2-, -OSi(OR)2-, -OSi(OR)2O-, -Ti(OR)2-, -OTi(OR)2-, -OTi(OR)2O-, -Al(OR)-, -OAl(OR)-, -OAl(OR)O-, etc. (where R is an arbitrary substituent that can be used independently, preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and m is a natural number). Among these, alkylene groups having 6 or fewer carbon atoms, especially methylene groups, or -CH2OCH2- are preferred in terms of stability during production or use.

[0027] The EVOH having the aforementioned 1,2-diol structure in its side chain is a structural unit represented by the following general formula (1'), namely R 1 , R 2 , R 3 , R 4 , R 5 and R 6 EVOH containing a structural unit in which all are hydrogen atoms and X is a single bond is particularly preferred.

[0028] [ka]

[0029] Furthermore, EVOH(A) may be a mixture containing two or more different EVOHs. Examples of such different EVOHs include those with different ethylene content, different degrees of saponification, different MFRs (210°C, 2160g load), different copolymer components, and different modification levels (for example, those with different 1,2-diol structural unit content).

[0030] In the embodiment of the present invention, the EVOH resin composition has EVOH(A) as the base resin, and the EVOH(A) content is usually 50% by mass or more, preferably 50 to 90% by mass, more preferably 55 to 85% by mass, and particularly preferably 60 to 80% by mass, based on the total EVOH resin composition.

[0031] <Unmodified polyolefin (B)> The unmodified polyolefin (B) is not particularly limited, and known unmodified polyolefins can be used. Examples include unmodified olefin homopolymers composed of olefin monomers such as ethylene, propylene, and butene; unmodified olefin block copolymers composed of two or more olefin monomers; and unmodified olefin random copolymers. These can be used individually or in combination of two or more types.

[0032] Examples of unmodified olefin homopolymers include unmodified polyethylene, unmodified polypropylene, unmodified polybutene, and unmodified polymethylpentene. Examples of unmodified olefin block copolymers include unmodified ethylene-α-olefin copolymers, unmodified propylene-α-olefin copolymers, and unmodified butene-α-olefin copolymers. Examples of unmodified olefin random copolymers include those obtained by randomly copolymerizing two or more of the above-mentioned olefin monomers.

[0033] Among these unmodified polyolefins (B), from the viewpoint of improving the elongation at break at low temperatures, unmodified ethylene-α-olefin copolymers, which are copolymers of ethylene and α-olefins having 3 to 20 carbon atoms, are preferred, more preferably unmodified ethylene-α-olefin copolymers, which are copolymers of ethylene and α-olefins having 3 to 10 carbon atoms, particularly preferably unmodified ethylene-α-olefin copolymers, which are copolymers of ethylene and α-olefins having 2 to 8 carbon atoms, and especially preferably unmodified ethylene-butene copolymers.

[0034] The density of unmodified polyolefin (B) is not particularly limited, but is typically 0.900 g / cm³. 3 The following, preferably 0.890 g / cm³ 3 The following, and especially preferably 0.885 g / cm³ 3 The following applies: By using such a low-density, unmodified polyolefin copolymer (B), a molded article with excellent elongation at break at low temperatures can be obtained. The lower limit of the density of the unmodified polyolefin copolymer (B) is typically 0.850 g / cm³. 3 That's all.

[0035] The MFR (190°C, 2160g load) of the unmodified polyolefin (B) is not particularly limited, but is usually 1.0 to 100 g / 10 min, preferably 2.0 to 60 g / 10 min. By using such an unmodified polyolefin (B), the stability of the resulting EVOH resin composition during extrusion and the low-temperature elongation at break of the resulting molded article can be further improved.

[0036] The content of unmodified polyolefin (B) is usually 5% by mass or more, preferably 5 to 40% by mass, more preferably 5 to 35% by mass, and particularly preferably 5 to 30% by mass, relative to the entire EVOH resin composition.

[0037] Here, "unmodified polyolefin" refers to an unmodified polyolefin that has not undergone acid modification, and for example, it refers to an unmodified polyolefin copolymer that is not "acid-modified polyolefin (C)" as described below. The acid value of unmodified polyolefin (B) is not particularly limited, but is preferably less than 0.5 mg KOH / g. The acid value is determined by neutralization titration in accordance with JIS K 0070.

[0038] <Acid-modified polyolefin (C)> Acid-modified polyolefin (C) is a polyolefin modified with acid, and is not particularly limited; known acid-modified polyolefins can be used, and these can be used individually or in combination of two or more types.

[0039] Acid-modified polyolefins (C) can be obtained, for example, by copolymerizing an unmodified polyolefin by replacing some of the monomers with α,β-unsaturated carboxylic acids or their anhydride monomers, or by introducing α,β-unsaturated carboxylic acids or their anhydrides into part of the side chains through graft reactions such as radical addition.

[0040] The aforementioned unmodified polyolefin is not particularly limited, and known unmodified polyolefins can be used. Examples include unmodified olefin homopolymers composed of olefin monomers such as ethylene, propylene, and butene; unmodified olefin block copolymers composed of two or more olefin monomers; and unmodified olefin random copolymers. Examples of unmodified olefin homopolymers include unmodified polyethylene, unmodified polypropylene, unmodified polybutene, and unmodified polymethylpentene. Examples of unmodified olefin block copolymers include unmodified ethylene-α-olefin copolymers, unmodified propylene-α-olefin copolymers, and unmodified butene-α-olefin copolymers. Examples of unmodified olefin random copolymers include those obtained by randomly copolymerizing two or more of the aforementioned olefin monomers.

[0041] Examples of α,β-unsaturated carboxylic acids or their anhydrides used in the aforementioned acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. Among these, maleic anhydride is preferably used.

[0042] As for the acid-modified polyolefin (C), from the viewpoint of improving the elongation at break at low temperatures, an acid-modified ethylene-α-olefin copolymer obtained by acid-modifying a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is preferred, more preferably an acid-modified ethylene-α-olefin copolymer obtained by acid-modifying a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms is preferred, particularly preferably an acid-modified ethylene-α-olefin copolymer obtained by acid-modifying a copolymer of ethylene and an α-olefin having 2 to 8 carbon atoms is preferred, especially preferably an acid-modified ethylene-butene copolymer, and most preferably a maleic anhydride-modified ethylene-butene copolymer.

[0043] The acid value of the acid-modified polyolefin (C) is not particularly limited, but is usually 50 mg KOH / g or less, preferably 30 mg KOH / g or less, and especially preferably 20 mg KOH / g or less. If the acid value is too high, the number of reaction sites with hydroxyl groups in EVOH(A) increases, and high-molecular-weight compounds are formed during the melt-kneading process, which tends to reduce stability during extrusion processing and make it difficult to obtain a good molded product. On the other hand, if the acid value is too low, the compatibility with EVOH(A) decreases, which tends to increase the amount of resin adhering to the die during extrusion processing (deadheading) and tends to reduce the elongation at break at low temperatures. The lower limit of the acid value is usually 1 mg KOH / g or more, and preferably 2 mg KOH / g or more. The acid value is determined by neutralization titration based on JIS K 0070.

[0044] The density of acid-modified polyolefin (C) is not particularly limited, but is typically 0.900 g / cm³. 3 The following, preferably 0.890 g / cm³ 3 The following, and especially preferably 0.885 g / cm³ 3The following applies: By using such low-density acid-modified polyolefin (C), molded articles with particularly excellent elongation at break, especially at low temperatures, can be obtained. The lower limit of the density of acid-modified polyolefin (C) is typically 0.850 g / cm³. 3 That's all.

[0045] The MFR (190°C, 2160g load) of the acid-modified polyolefin (C) is not particularly limited, but is preferably 1.0 g or more / 10 min, more preferably 1.0 to 60 g / 10 min, even more preferably 1.5 to 60 g / 10 min, and particularly preferably 2.0 to 60 g / 10 min. By using such an acid-modified polyolefin (C), the elongation at break at low temperatures can be further improved.

[0046] The content of acid-modified polyolefin (C) is usually 5% by mass or more, preferably 5 to 40% by mass, more preferably 5 to 35% by mass, and particularly preferably 5 to 30% by mass, relative to the entire EVOH resin composition.

[0047] [Mass ratio of (B) and (C)] The EVOH resin composition according to the embodiment of the present invention is characterized by the combined use of an unmodified polyolefin (B) and an acid-modified polyolefin (C) in a specific mass ratio [(B) / (C)], wherein the mass ratio [(B) / (C)] of the unmodified polyolefin (B) to the acid-modified polyolefin (C) is 75 / 25 to 1 / 99, preferably 70 / 30 to 10 / 90, and particularly preferably 65 / 35 to 15 / 85, from the viewpoint of improving the elongation at break at low temperatures. If the mass ratio [(B) / (C)] exceeds 75 / 25, the elongation at break at low temperatures of the resulting molded article will be insufficient. On the other hand, if the mass ratio [(B) / (C)] is less than 1 / 99, the generation of eye discharge will increase and the moldability will be insufficient.

[0048] [Mass ratios of (A), (B), and (C)] In the EVOH resin composition according to the embodiment of the present invention, the mass ratio [(A) / ((B)+(C))] of the EVOH (A) content to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) is preferably 60 / 40 to 99 / 1, more preferably 60 / 40 to 79 / 21, and particularly preferably 60 / 40 to 75 / 25, from the viewpoint of improving elongation at low temperatures. That is, in the EVOH resin composition according to the embodiment of the present invention, the mass ratio [(A) / ((B)+(C))] of the EVOH (A) content to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) is particularly preferably 60 / 40 or more and less than 75 / 25, from the viewpoint of improving elongation at low temperatures. In the present invention, from the viewpoint of improving the elongation at break at low temperatures, the mass ratio [(A) / ((B)+(C))] is set to 60 / 40 or more and less than 75 / 25. In particular, it is preferable that the mass ratio [(A) / ((B)+(C))] is set to 60 / 40 or more and 68 / 32 or less. If the mass ratio [(A) / ((B)+(C))] exceeds the aforementioned upper limit, or if unmodified polyolefin (B) and acid-modified polyolefin (C) are not included, the resulting molded article tends to have reduced elongation at low temperatures. On the other hand, if the mass ratio [(A) / ((B)+(C))] is less than 60 / 40, for example, EVOH (A) does not become the matrix phase, and the hydrogen barrier properties of the molded article tend to decrease.

[0049] <Other ingredients> The EVOH resin composition according to the embodiment of the present invention may contain, in addition to EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C), other resins as needed, provided that they do not impair the effects of the present invention (for example, less than 5% by mass of the total EVOH resin composition). Examples of other resins include polyamide resins such as nylon 11, nylon 12, nylon 6, nylon 66, and nylon 6·66; unmodified vinyl alcohol-based resins that do not have the structural unit of general formula (1); and other thermoplastic resins. These can be used individually or in mixtures of two or more types. The content of the other resin is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, particularly preferably 20% by mass or less, and especially preferably 10% by mass or less with respect to EVOH (A).

[0050] In addition, the EVOH resin composition according to the embodiment of the present invention may contain various additives as long as the effects of the present invention are not impaired. For example, plasticizers such as aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol; lubricants such as saturated fatty acid amides (e.g., stearic acid amide, etc.), unsaturated fatty acid amides (e.g., oleic acid amide, etc.), bis-fatty acid amides (e.g., ethylene bis-stearic acid amide, etc.); antiblocking agents; antioxidants; colorants; antistatic agents; ultraviolet absorbers; antibacterial agents; insoluble inorganic salts (e.g., hydrotalcite, etc.); fillers (e.g., inorganic fillers, etc.); oxygen absorbers (e.g., ring-opening polymers of cycloalkenes such as polyoctenylene, and cyclized products of conjugated diene polymers such as butadiene, etc.); surfactants, waxes; dispersants (e.g., monoglyceride stearate, etc.); heat stabilizers; light stabilizers; desiccants; flame retardants; crosslinking agents; curing agents; foaming agents; crystal nucleating agents; antifogging agents; biodegradable additives; silane coupling agents; known additives such as conjugated polyene compounds. These can be used alone or in combination of two or more.

[0051] The heat stabilizer is used for the purpose of improving various physical properties such as heat stability during melt molding. For example, organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, etc., or alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc. of these; or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, etc., or alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc. of these. These can be used alone or in combination of two or more.

[0052] <EVOH Resin Composition> The EVOH resin composition according to the embodiment of the present invention can be prepared by blending EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C), and optionally other resins and additives, in predetermined proportions, and then melt-kneading them together. Specifically, EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) can be produced by melt-kneading them in a blending ratio where the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)] is 75 / 25 to 1 / 99. More preferably, EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) can be produced by melt-kneading them in a blending ratio where the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)] is 75 / 25 to 1 / 99, and the mass ratio of the EVOH (A) content to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) [(A) / ((B)+(C))] is 60 / 40 to 99 / 1. In other words, the EVOH resin composition according to the embodiment of the present invention is preferably produced by melt-kneading EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) in a blending ratio where the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)] is 75 / 25 to 1 / 99, and the mass ratio of the EVOH (A) content to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) [(A) / ((B)+(C))] is 60 / 40 or more and less than 75 / 25.

[0053] For melt kneading, known kneaders such as extruders, Banbury mixers, kneader-ruders, mixing rolls, and blast mills can be used. Examples of extruders include single-screw or twin-screw extruders. After melt kneading, a method can be employed in which the EVOH resin composition is extruded into strands, cut, and pelletized. Such melt-kneading may be carried out by adding EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) all at once, or EVOH (A) may be melt-kneaded in a twin-screw extruder while the unmodified polyolefin (B) and acid-modified polyolefin (C) are side-fed in a molten or solid state.

[0054] The melt-mixing temperature is appropriately selected depending on the type of EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C), but is usually 215 to 270°C, preferably 215 to 265°C, more preferably 220 to 260°C, and particularly preferably 220 to 250°C. The melt mixing time is appropriately selected depending on the type of unmodified polyolefin (B) and acid-modified polyolefin (C), but is usually 0.1 to 30 minutes, preferably 0.3 to 10 minutes, and more preferably 0.5 to 5 minutes.

[0055] The EVOH resin composition obtained according to the embodiment of the present invention was measured at 210°C and a shear rate of 18 [sec]. -1 The melt viscosity (η1) in [ ] is preferably 10,000 (mPa·s) or less, more preferably 9,500 (mPa·s) or less, and particularly preferably 9,000 (mPa·s) or less. If the melt viscosity (η1) is too high, the moldability tends to decrease. For example, if the melt viscosity (η1) is too high, melt fracture tends to occur more easily in the case of single-layer film formation, and in the case of multi-layer film formation, interfacial disturbance tends to occur more easily due to increased shear stress. The lower limit of the melt viscosity (η1) is usually 2,000 (mPa·s) or more.

[0056] Furthermore, the EVOH resin composition according to the embodiment of the present invention was measured at 210°C and a shear rate of 365 [sec]. -1The melt viscosity (η2) in [ ] is preferably 4000 (mPa·s) or less, more preferably 3000 (mPa·s) or less, and particularly preferably 2000 (mPa·s) or less. If the melt viscosity (η2) is too high, the moldability tends to decrease. For example, if the melt viscosity (η2) is too high, melt fracture tends to occur more easily in the case of single-layer film formation, and in the case of multi-layer film formation, interfacial disturbance tends to occur more easily due to increased shear stress. The lower limit of the melt viscosity (η2) is usually 300 (mPa·s) or more.

[0057] The melt viscosity can be measured in accordance with JIS K7199:1999, for example, using a capillary rheometer such as the "Capillograph 1D" manufactured by Toyo Seiki Seisakusho Co., Ltd.

[0058] [Melting viscosity ratio (η1) / η2)] The EVOH resin composition according to the embodiment of the present invention is characterized by controlling the melt viscosity ratio to a specific value [(η1) / (η2)], and the EVOH resin composition according to the embodiment of the present invention is measured at 210°C and a shear rate of 18 [sec]. -1 The melt viscosity (η1) at ] and the shear rate at 210°C and 365 [sec -1 The melt viscosity ratio [(η1) / (η2)] between the melt viscosity (η2) in [ ] is 5.6 or higher, preferably 5.8 or higher, more preferably 6.0 or higher, and particularly preferably 6.2 or higher. When the melt viscosity ratio is within the above range, the EVOH resin composition exhibits excellent elongation at low temperatures, while when the melt viscosity ratio is outside the above range, the elongation at low temperatures is low. The upper limit of the melt viscosity ratio is usually 7.0 or lower, preferably 6.8 or lower.

[0059] In the present invention, there are no particular limitations on how the melt viscosity ratio can be controlled to the above range, but for example, it is preferable to: (i) adjust the mass ratio of unmodified polyolefin (B) and acid-modified polyolefin (C) to 75 / 25 to 1 / 99, preferably 70 / 30 to 10 / 90, and particularly preferably 65 / 35 to 15 / 85; (ii) adjust the MFR (190°C, 2160g load) of acid-modified polyolefin (C) to preferably 1.0g or more / 10min, more preferably 1.5g or more / 10min, and even more preferably 2g or more / 10min; and (iii) adjust the difference between the MFR (190°C, 2160g load) of unmodified polyolefin (B) and the MFR (190°C, 2160g load) of acid-modified polyolefin (C) to within 2.5, preferably within 2.0, and even more preferably within 1.5.

[0060] In this EVOH resin composition, the unmodified polyolefin (B) and acid-modified polyolefin (C) improve the low-temperature elongation at break, which was a weakness of EVOH. This is presumed to be because the appropriate interaction at the EVOH / elastomer interface leads to increased elongation due to yield deformation and deformation due to interfacial delamination.

[0061] The EVOH resin composition according to the embodiment of the present invention has excellent hydrogen gas barrier properties based on EVOH(A). In addition to having excellent gas barrier properties against hydrogen gas, it also has excellent gas barrier properties against other gases such as helium, oxygen, nitrogen, and air, but is particularly excellent against gases with a molecular weight of less than 10, such as hydrogen.

[0062] The method for obtaining a molded article using the EVOH resin composition according to an embodiment of the present invention is not particularly limited, but various molding methods applicable to thermoplastic resins such as EVOH that are known in general can be used. For example, melt molding methods such as extrusion molding, co-extrusion molding, injection molding, blow molding, tube molding, and rotational molding can be used. Specifically, extrusion blow molding is generally used for hollow molded articles such as fuel tanks, tube molding is used for tube (pipe) shaped containers, and injection molding is used for molded articles with complex shapes or molded articles that require dimensional accuracy.

[0063] <Multilayer structure> A molded article according to an embodiment of the present invention has at least one layer made of an EVOH resin composition (hereinafter sometimes referred to as the "resin composition layer"). Alternatively, a molded article according to an embodiment of the present invention may be a multilayer structure in which at least one other layer is laminated to the resin composition layer for the purpose of adding various physical properties, for example, a thermoplastic resin layer containing another thermoplastic resin is laminated (hereinafter sometimes referred to as the "multilayer structure").

[0064] A multilayer structure according to an embodiment of the present invention includes, for example, an inner layer (i.e., a layer in contact with high-pressure gas and fuel), an intermediate layer, and an outer layer (i.e., a layer in contact with the outside air). Preferably, the inner layer or intermediate layer includes a resin composition layer, and from the viewpoint of preventing a decrease in the gas barrier performance of the resin composition layer due to moisture, it is preferable that the intermediate layer includes a resin composition layer. Furthermore, it is preferable that the inner layer and / or outer layer include a thermoplastic resin layer containing a thermoplastic resin other than EVOH that is water-resistant and moisture-impermeable. Note that the intermediate layer refers to a layer located between the outer layer and the inner layer. Furthermore, the multilayer structure according to the embodiment of the present invention may further include a reinforcing layer. The reinforcing layer is not particularly limited, but it is preferably located outside the outer layer, and it is preferable that the reinforcing layer is the layer that comes into contact with the outside air (the outermost layer). Furthermore, an adhesive layer made of an adhesive resin may be provided between these layers.

[0065] As the thermoplastic resin used in the thermoplastic resin layer, for example, a hydrophobic thermoplastic resin is preferably used. Examples of hydrophobic thermoplastic resins include polyethylene-based resins such as polyethylene (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE)), polypropylene-based resins such as ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymer, olefins alone or copolymers such as polybutene and polypentene, cyclic polyolefins, or graft-modified versions of these olefins alone or copolymers with unsaturated carboxylic acids or their esters (carb Examples include polyolefin resins (such as nitrate-modified polyolefin resins and ester-modified polyolefin resins); polystyrene resins; polyamide resins such as polyamides like nylon 11, nylon 12, nylon 6, and nylon 66, and copolymer polyamides like nylon 6-12 and nylon 6-66; vinyl ester resins such as polyvinyl chloride, polyvinylidene chloride, acrylic resins, and polyvinyl acetate; polyurethane resins; fluorine polymers such as tetrafluoroethylene, tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers, ethylene / tetrafluoroethylene copolymers, and tetrafluoroethylene / hexafluoropropylene copolymers; chlorinated polyethylene; chlorinated polypropylene; fluorine resins having polar groups, thermoplastic polyurethanes, etc. These can be used individually or in combination of two or more types. Among these, polyolefin resins are preferred in terms of mechanical strength and melt-molding processability, more preferably polyethylene resins and polypropylene resins, and particularly preferably polyethylene and polypropylene.

[0066] As the adhesive resin used as the adhesive layer, known adhesive resins can be used, and various types can be used. Generally, examples include modified olefin polymers containing carboxyl groups obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin polymer (the broad-sense polyolefin resin mentioned above) by addition reaction or graft reaction. Specifically, one or more mixtures selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, etc., are preferred.

[0067] The thermoplastic resin layer and adhesive layer may contain conventionally known plasticizers, fillers, clays (such as montmorillonite), colorants, antioxidants, antistatic agents, lubricants, nucleating agents, antiblocking agents, ultraviolet absorbers, waxes, etc., as long as they do not impair the effects of the present invention. These can be used individually or in combination of two or more types.

[0068] Examples of reinforcing layers include reinforcing fiber layers using fibers and reinforcing rubber layers using rubber. Examples of reinforcing fiber layers include high-strength fibers such as poly(p-phenylenebenzbisoxazole) (PBO) fibers, aramid fibers, and carbon fibers, as well as nonwoven fabrics, woven fabrics, paper, metal foils, metal cotton strips, and wood surfaces. Preferably, it is a reinforcing fiber layer, particularly preferably a reinforcing fiber layer using high-strength fibers, and even more preferably a sheet layer made of braided high-strength fibers or a reinforcing fiber layer made by spirally winding such a sheet.

[0069] In the multilayer structure according to the embodiment of the present invention, when the resin composition layers are a(a1, a2, ...), the thermoplastic resin layers are b(b1, b2, ...), and the reinforcing layers are c(c1, c2, ...), any combination is possible from the inside out, such as b / a, a / b, a1 / b / a2, b1 / a / b1, a1 / b / a1, a1 / a2 / b, a / b1 / b2, a / b / c, b / a / c, b2 / b1 / a / b1 / b2, b1 / a / b2 / c, b2 / b1 / a / b1 / a / b1 / b2, etc. Adhesive layers may be provided between each layer of these multilayer structures. Furthermore, when R is defined as a recycled layer containing a mixture of a resin composition obtained by remelting edges and defective products generated during the manufacturing process of a multilayer structure and a thermoplastic resin other than EVOH, any combination of layers is possible for the multilayer structure according to the embodiment of the present invention, such as b / a / R, R / b / a, b / R / a / b, b / R / a / R / b, b / a / R / a / b, b / R / a / R / a / R / b, b / a / R / c, R / b / a, b / R / a / b / c, b / R / a / R / b / c, etc. Adhesive layers may be provided between each layer of these multilayer structures. Among these multilayer structures, multilayer structures having a layer structure of b1 / a / b2 or b1 / a / b2 / c are preferred, and multilayer structures having a layer structure in which adhesive layers are interposed between each of the b1 / a / b2 layers (thermoplastic resin layer / adhesive layer / resin composition layer / adhesive layer / thermoplastic resin layer) are particularly preferred. The multilayer structure according to the embodiment of the present invention usually has 2 to 20 layers, preferably 3 to 15 layers, and particularly preferably 4 to 10 layers.

[0070] Examples of methods for manufacturing the multilayer structure according to the embodiment of the present invention include a method of molding the EVOH resin composition in a molten state (melt molding method) and a method of molding the EVOH resin composition by dissolving it in a solvent (e.g., solution coating method). Among these, the melt molding method is preferred from the viewpoint of productivity. Specifically, examples include a method of melt-extruding a thermoplastic resin onto a molded article (e.g., a film or sheet) of an EVOH resin composition according to an embodiment of the present invention, a method of melt-extruding a resin composition layer onto a substrate such as a thermoplastic resin, and a method of co-extruding a resin composition layer and a thermoplastic resin layer. In particular, T-die extrusion, tubular extrusion, blow molding, and mold extrusion are employed. Furthermore, methods such as dry lamination using known adhesives such as organic titanium compounds, isocyanate compounds, polyethyleneimine compounds, polyester compounds, and polyurethane compounds, or lamination with an adhesive layer interposed, can be employed to laminate a film made of an EVOH resin composition according to an embodiment of the present invention to a substrate such as a film made of a thermoplastic resin. In some cases, co-injection molding can also be employed.

[0071] The multilayer structure according to the embodiment of the present invention is then subjected to (heat) stretching as necessary. The stretching can be carried out using known stretching methods, such as uniaxial stretching and biaxial stretching. In the case of biaxial stretching, either simultaneous biaxial stretching or sequential biaxial stretching can be employed. The stretching temperature is the temperature of the multilayer structure (temperature near the multilayer structure), usually 40 to 170°C, preferably 60 to 160°C. The stretching ratio is usually 2 to 50 times, preferably 2 to 20 times, in terms of area ratio. Furthermore, in order to impart dimensional stability to the obtained stretched film, heat setting may be performed after the stretching is completed. Heat setting can be carried out by known means, and the stretched film is heat-treated at 80 to 180°C, preferably 100 to 165°C, for about 2 to 600 seconds while maintaining the tension of the stretched film.

[0072] The thickness of the multilayer structure (including stretched structures) according to the embodiment of the present invention is not particularly limited, but is usually 1 to 1500 μm, preferably 1 to 1000 μm, and more preferably 10 to 700 μm. The thickness of the thermoplastic resin layer in the multilayer structure is not particularly limited, but is usually 0.1 to 1000 μm, preferably 1 to 500 μm. The thickness of the resin composition layer is not particularly limited, but is usually 0.1 to 500 μm, preferably 1 to 100 μm. The thickness of the adhesive layer is not particularly limited, but is usually 0.1 to 250 μm, preferably 0.1 to 100 μm.

[0073] Furthermore, the thickness ratio of the thermoplastic resin layer to the resin composition layer (thermoplastic resin layer / resin composition layer) is not particularly limited, but if there are multiple layers, it is the ratio of the thickest layers, which is usually greater than 1 to 30, preferably 2 to 30, and the thickness ratio of the adhesive layer to the resin composition layer (adhesive layer / resin composition layer) is usually 0.1 to 2, preferably 0.1 to 1.

[0074] As described above, the EVOH resin compositions according to the embodiments of the present invention are useful as molded articles with excellent elongation at low temperatures, and are particularly useful as molded articles with excellent hydrogen gas barrier properties and elongation at low temperatures. Furthermore, the EVOH resin compositions according to preferred embodiments of the present invention are useful as molded articles that have hydrogen barrier properties, improved elongation at low temperatures, and excellent moldability. Molded articles using the EVOH resin compositions of the present invention are useful, for example, as fuel tanks for high-pressure hydrogen gas (pressure 1 to 100 MPa) and as components for such fuel tanks. In the context of elongation at break at low temperatures, "low temperature" usually refers to temperatures below 0°C, preferably around -20 to -50°C.

[0075] Furthermore, molded articles using the EVOH resin composition according to the embodiment of the present invention are suitable as packaging materials and can be processed into shapes such as tubes or bags and used in a wide range of applications as packaging materials for various liquids, including foods such as mirin, soy sauce, sauces, noodle soup, and edible oils; beverages such as wine, juice, milk, mineral water, sake, shochu, coffee, and tea; pharmaceuticals; cosmetics; industrial chemicals such as sodium hypochlorite, developing solutions, and battery fluids; pesticides such as liquid fertilizers; and detergents. [Examples]

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. In the examples, "%" and "parts" refer to mass, and in Table 1, "unmodified PO" refers to unmodified polyolefin, and "acid-modified PO" refers to acid-modified polyolefin.

[0077] [Materials used] The following materials were used as components of the EVOH resin composition.

[0078] (EVOH(A)) A-1: EVOH (Ethylene content: 25 mol%, Saponification degree: 99.7 mol%, MFR: 4.0 g / 10 min (210°C, 2160 g load)) A-2: EVOH (Ethylene content: 38 mol%, Saponification degree: 99.7 mol%, MFR: 50 g / 10 min (210°C, 2160 g load))

[0079] (Unmodified polyolefin (B)) • B-1: Mitsui Chemicals "A4085S" Ethylene-butene copolymer (MFR: 3.6g / 10min (190℃, 2160g load), Density: 0.885g / cm³) 3 ) • B-2: Mitsui Chemicals "P0180" Ethylene-propylene copolymer (MFR: 4.4g / 10 min (190℃, 2160g load), Density: 0.869g / cm³) 3 )

[0080] (Acid-modified polyolefin (C)) • C-1: "MA8510" manufactured by Mitsui Chemicals, Inc. Maleic anhydride-modified ethylene-butene copolymer (MFR: 2.4g / 10min (190℃, 2160g load), Density: 0.885g / cm³) 3 ), acid value 5.5mgKOH / g • C-2: Mitsui Chemicals, Inc. "MP0610" Maleic anhydride-modified ethylene-propylene copolymer (MFR: 0.4g / 10 min (190℃, 2160g load), Density: 0.870g / cm³) 3 ), acid value 6.1mgKOH / g

[0081] <Example 1> [Preparation of EVOH resin composition pellets] After dry blending each component in the proportions shown in Table 1, the mixture was melt-kneaded in a twin-screw extruder under the following conditions, extruded into strands, and cut with a pelletizer to obtain cylindrical pellets of the EVOH resin composition. (Melting and mixing conditions) ·Diameter (D) 30mm L / D = 56 Screw rotation speed: 400 rpm • Cylinder (C) setting temperature: C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15 / C16=120℃ / 190℃ / 2 10℃ / 210℃ / 210℃ / 210℃ / 220℃ / 220℃ / 220℃ / 230℃ / 230℃ / 230℃ / 230℃ / 230℃ / 230℃ • Dice setting temperature: 80℃ ·Discharge amount: 25kg / hr

[0082] Next, the following evaluations were performed using the prepared EVOH resin composition pellets.

[0083] (1) Low-temperature elongation at break (%) A dumbbell-shaped tensile test specimen of ISO 1A was prepared from the obtained pellets using an injection molding machine, and a tensile test was performed at -40°C using a tensile testing machine. The test specimen was dumbbell-shaped, with a width of 10 mm, a length of 110 mm, a total length of 200 mm, and a thickness of 4 mm. The preparation and evaluation of the test specimen were carried out in accordance with ISO 527-2, and measurements were taken at a tensile speed of 50 mm / min. The results are shown in Table 1. The low-temperature elongation at break (%) is the value calculated by the following formula as the elongation (%) until the test specimen breaks during the tensile test. (Formula) Low-temperature elongation at break (%) = [(Length of specimen at break - Length of specimen before test) / Length of specimen before test] × 100

[0084] (2) Melt viscosity (mPa·s) The obtained pellets were used as a sample, and a Capillograph 1D manufactured by Toyo Seiki Co., Ltd. was used to measure the shear rate at 18 [sec] under the following conditions. -1 The melt viscosity (η1) and shear rate at 365 [sec] in ] -1 The melt viscosity (η2) in [ ] was measured, and the melt viscosity ratio [(η1) / (η2)] was determined. The results are shown in Table 1. (Measurement conditions) • Capillary diameter: 1mm • Capillary length: 10mm • Capillary temperature: 210℃ • Preheating time (time from filling the capillary with the sample to starting the measurement): 5 minutes Shear rate: 18 [sec] -1 ] or 365 [sec -1 ] • Sample quantity: 15g

[0085] The melt viscosities (η1) and (η2) shown in Table 1 are the measured values ​​obtained from measurements based on the above measurement conditions, rounded to the first decimal place. The melt viscosity ratio shown in Table 1 is the melt viscosity ratio [(η1) / (η2)] calculated based on the melt viscosities (η1) and (η2) shown in Table 1, rounded to the second decimal place.

[0086] <Examples 2-4> Except for changing the proportions of each component as shown in Table 1, EVOH resin composition pellets were prepared and evaluated in the same manner as in Example 1.

[0087] <Comparative Examples 1-6> Except for changing the proportions of each component as shown in Table 1, EVOH resin composition pellets were prepared and evaluated in the same manner as in Example 1.

[0088] [Table 1]

[0089] As shown in Table 1, Examples 1 to 4 that satisfy the requirements of the present invention, namely the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)], a specific melt viscosity ratio [(η1) / (η2)], and the mass ratio of the ethylene-vinyl alcohol copolymer (A) to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) [(A) / ((B)+(C))], exhibit excellent elongation at break at low temperatures. On the other hand, Comparative Examples 1 to 6, which did not satisfy the requirements defined in the present invention, were found to have inferior elongation at low temperatures compared to Examples 1 to 4.

[0090] Furthermore, a 1% difference in elongation at break at -40°C represents a significant difference in practical use. For example, when using an EVOH resin composition in a fuel container mounted on an automobile, the fuel container has a large volume (typically 0.5-3m in length and 0.1-1m in width), so a 1% difference in elongation at break at low temperatures represents a significant difference in the allowable deformation of the fuel container, resulting in a large difference in the allowable hydrogen filling pressure. Since the amount of hydrogen that can be filled into a fuel container carrying high-pressure hydrogen gas is proportional to the product of the hydrogen gas volume and the hydrogen gas pressure, a difference in hydrogen filling pressure leads to a difference in the amount of hydrogen that can be filled, which in turn results in a difference in the driving range of an automobile. Therefore, a difference in elongation at break at low temperatures has a clear impact in practical use. Regardless of the application, not limited to fuel containers mounted on automobiles, as mentioned above, a 1% difference in elongation at break at low temperatures represents a significant difference in practical use.

[0091] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention. [Industrial applicability]

[0092] The EVOH resin composition of the present invention can improve elongation at low temperatures. Therefore, molded articles containing a layer made of the EVOH resin composition are useful as raw materials for fuel tanks for high-pressure hydrogen gas and the like, and for components for such fuel tanks.

Claims

1. An ethylene-vinyl alcohol copolymer composition containing an ethylene-vinyl alcohol copolymer (A), an unmodified polyolefin (B), and an acid-modified polyolefin (C), wherein the mass ratio of the unmodified polyolefin (B) to the acid-modified polyolefin (C) [(B) / (C)] is 75 / 25 to 1 / 99, and the composition is subjected to a shear rate of 18 [sec] at 210°C. -1 The melt viscosity (η1) at ] and the composition at 210°C and a shear rate of 365 [sec -1 An ethylene-vinyl alcohol copolymer composition wherein the melt viscosity ratio [(η1) / (η2)] with the melt viscosity (η2) in [ ] is 5.6 or more, the mass ratio [(A) / ((B)+(C))] of the total content of the ethylene-vinyl alcohol copolymer (A) to the unmodified polyolefin (B) and the acid-modified polyolefin (C) is 60 / 40 or more and 68 / 32 or less, the difference (unit g / 10 min) between the MFR (190°C, 2160 g load) of the unmodified polyolefin (B) and the MFR (190°C, 2160 g load) of the acid-modified polyolefin (C) is 2.0 or less, and the unmodified polyolefin (B) is an unmodified ethylene-α-olefin copolymer.

2. The ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the unmodified polyolefin (B) is an unmodified ethylene-butene copolymer.

3. The ethylene-vinyl alcohol copolymer composition according to claim 1 or 2, wherein the acid-modified polyolefin (C) is an acid-modified ethylene-α-olefin copolymer.

4. The ethylene-vinyl alcohol copolymer composition according to any one of claims 1 to 3, wherein the acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer.

5. The ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the unmodified polyolefin (B) is an unmodified ethylene-butene copolymer, and the acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer.

6. The ethylene-vinyl alcohol copolymer composition according to any one of claims 1 to 5, wherein the melt flow rate of the acid-modified polyolefin (C) is 1.0 g or more / 10 min under the conditions of 190°C and a load of 2160 g.

7. The ethylene-vinyl alcohol copolymer composition according to any one of claims 1 to 6, wherein the melt viscosity (η1) is 10,000 (mPa·s) or less.

8. A molded article having at least one layer made of the ethylene-vinyl alcohol copolymer composition according to any one of claims 1 to 7.

Images