Ethylene-vinyl alcohol copolymer composition

Abstract

An EVOH resin composition capable of improving elongation at break at low temperatures is provided. An ethylene-vinyl alcohol copolymer composition comprising 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 aforementioned composition is subjected to a shear rate of 18 sec at 210°C. ‑1 The melt viscosity (η1) of the aforementioned composition at 210°C and a shear rate of 365 sec is similar to that at 210°C. ‑1 The melt viscosity ratio [(η1) / (η2)] of the melt viscosity (η2) is 5.6 or more, and the mass ratio of ethylene-vinyl alcohol copolymer (A) 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.

Description

Technical Field

[0001] This invention relates to ethylene-vinyl alcohol copolymer compositions (hereinafter sometimes referred to as "EVOH resin compositions") containing ethylene-vinyl alcohol copolymers (hereinafter sometimes referred to as "EVOH"). More specifically, it relates to EVOH resin compositions with excellent elongation at break at low temperatures. Background Technology

[0002] Previously, fuel canisters were made of metal, but recently resins have been used for purposes such as weight reduction. These resin fuel canisters are generally manufactured using processes such as blow molding, injection molding, and tubing. Furthermore, for applications requiring flexibility, a resin composition in which a flexible thermoplastic resin is blended with an ethylene-vinyl acetate copolymer saponified compound has been proposed (Patent Document 1).

[0003] Specifically, the purpose of the technology in Patent Document 1 is to provide a multilayer structure with excellent oxygen barrier properties, high flexibility, and bend resistance by further mixing alkali metal salts on the basis of mixing unmodified ethylene-α-olefin copolymer, acid-modified ethylene-α-olefin copolymer and EVOH with a specific range of melt flow rate (MFR) in a specific ratio. However, it has the problem of insufficient elongation when used at low temperatures.

[0004] In addition, for the purpose of providing hydrogen fuel tanks, a resin composition formed from EVOH and an ethylene-butene copolymer modified with anhydrides of unsaturated carboxylic acids has been proposed (Patent Document 2).

[0005] Specifically, the objective of Patent Document 2 is to provide a resin composition containing EVOH and an acid-modified ethylene-butene copolymer exhibiting a specific energy storage modulus, which can balance the barrier properties of fuel (especially hydrogen) and the impact resistance at low temperatures, and to provide a molded body (fuel canister) using the resin composition.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2015 / 141610

[0009] Patent Document 2: Japanese Patent Application Publication No. 2005-68300 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, the elongation at break at low temperatures in the technology of Patent Document 2 is poor, leaving room for improvement. This can be attributed to the fact that the elastomer component consists only of acid-modified elastomer. Due to the excessively strong interfacial interaction between EVOH and the elastomer, deformation based on interfacial peeling is not easily achieved during deformation, resulting in lower elongation.

[0012] The present invention was made in view of the aforementioned actual situation, and provides an EVOH resin composition that can improve elongation at break at low temperatures.

[0013] Solution for solving the problem

[0014] In view of the aforementioned practical situation, the inventors conducted in-depth research and found that by using specific elastomers (unmodified polyolefin and acid-modified polyolefin) in a specific ratio to prepare an EVOH resin composition with a controlled melt viscosity ratio, the elongation at break at low temperatures can be improved. This can be presumed to be because the moderate interaction at the interface between EVOH and the elastomer leads to increased elongation due to the yield strain of the material and deformation based on interfacial peeling.

[0015] That is, the present invention provides the following [1] to

[10] .

[0016] [1] An ethylene-vinyl alcohol copolymer composition comprising 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) of the aforementioned composition at 210°C and a shear rate of 365 sec is similar to that at 210°C. -1 The melt viscosity ratio [(η1) / (η2)] of the melt viscosity (η2) is 5.6 or more, and the mass ratio of the aforementioned ethylene-vinyl alcohol copolymer (A) to the total content of the aforementioned unmodified polyolefin (B) and the aforementioned acid-modified polyolefin (C) [(A) / ((B)+(C))] is 60 / 40 or more and less than 75 / 25.

[0017] [2] According to the ethylene-vinyl alcohol copolymer composition of [1], wherein the aforementioned unmodified polyolefin (B) is an unmodified ethylene-α-olefin copolymer.

[0018] [3] The ethylene-vinyl alcohol copolymer composition according to [1] or [2], wherein the aforementioned unmodified polyolefin (B) is an unmodified ethylene-butene copolymer.

[0019] [4] An ethylene-vinyl alcohol copolymer composition according to any one of [1] to [3], wherein the aforementioned acid-modified polyolefin (C) is an acid-modified ethylene-α-olefin copolymer.

[0020] [5] An ethylene-vinyl alcohol copolymer composition according to any one of [1] to [4], wherein the aforementioned acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer.

[0021] [6] According to the ethylene-vinyl alcohol copolymer composition of [1], wherein the aforementioned unmodified polyolefin (B) is an unmodified ethylene-butene copolymer and the aforementioned acid-modified polyolefin (C) is an acid-modified ethylene-butene copolymer.

[0022] [7] An ethylene-vinyl alcohol copolymer composition according to any one of [1] to [6], wherein the melt flow rate of the aforementioned acid-modified polyolefin (C) is 1.0 g or more per 10 minutes at 190°C and a load of 2160 g.

[0023] [8] An ethylene-vinyl alcohol copolymer composition according to any one of [1] to [7], wherein the aforementioned melt viscosity (η1) is 10000 (mPa·s) or less.

[0024] [9] An ethylene-vinyl alcohol copolymer composition according to any one of [1] to [8], wherein the mass ratio of the content of the aforementioned ethylene-vinyl alcohol copolymer (A) to the total content of the aforementioned unmodified polyolefin (B) and the aforementioned acid-modified polyolefin (C) [(A) / ((B)+(C))] is 60 / 40 or more and 68 / 32 or less.

[0025]

[10] A molded body having at least one layer formed of an ethylene-vinyl alcohol copolymer composition as described in any one of [1] to [9].

[0026] The effects of the invention

[0027] The EVOH resin composition according to the present invention can improve the elongation at break at low temperatures. Detailed Implementation

[0028] The present invention will now be described in detail, but these descriptions represent examples of preferred embodiments and are not intended to limit the scope of the invention.

[0029] The EVOH resin composition described in the embodiments 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) of the EVOH resin composition at 210°C and a shear rate of 365 sec is compared with that at 210°C. -1 The melt viscosity ratio [(η1) / (η2)] of the melt viscosity (η2) is 5.6 or more, and the mass ratio of ethylene-vinyl alcohol copolymer (A) 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.

[0030] The following is an explanation of each component.

[0031] <EVOH(A)>

[0032] EVOH(A) is typically a resin obtained by saponifying a copolymer of ethylene and vinyl ester monomers (ethylene-vinyl ester copolymer), and is a non-water-soluble thermoplastic resin. Polymerization can be carried out using any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization, typically using a lower alcohol such as methanol as a solvent. The saponification of the resulting ethylene-vinyl ester copolymer can also be carried out using known methods. EVOH(A) produced in this manner has ethylene and vinyl alcohol structural units as its main structural units, containing a certain amount of unsaponified vinyl ester structural units as residues.

[0033] Vinyl acetate is a representative vinyl ester monomer used from the viewpoint of its ease of availability in the market and efficient impurity removal during manufacturing. Other vinyl ester monomers include aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl neovalerate, vinyl decanoate, vinyl laurate, vinyl stearate, and vinyl tert-carbonate; and aromatic vinyl esters such as vinyl benzoate. Aliphatic vinyl esters with 3 to 20 carbon atoms, preferably 4 to 10, and particularly preferably 4 to 7 carbon atoms, are commonly used. They are usually used alone, but multiple types can be used simultaneously as needed.

[0034] The ethylene content in EVOH(A) is not particularly limited, but is preferably 20 to 60 mol%, more preferably 25 to 50 mol%, and particularly preferably 25 to 45 mol%, based on values ​​measured according to ISO 14663. If the content is too low, there is a tendency for reduced oxygen barrier properties and melt formability under high humidity; conversely, if the content is too high, there is a tendency for reduced oxygen barrier properties.

[0035] The degree of saponification of the vinyl ester component in EVOH(A) is not particularly limited, but is preferably 90 to 100 mol%, more preferably 95 to 100 mol%, and particularly preferably 99 to 100 mol%, as measured according to JIS K6726 (where EVOH is used in the form of a solution obtained by uniformly dissolving it in a water / methanol solvent). If the degree of saponification is too low, there is a tendency for a decrease in oxygen barrier properties, thermal stability, and moisture resistance.

[0036] Furthermore, the melt flow rate (MFR) of EVOH(A) (210°C, 2160g load) is not particularly limited, but is preferably 0.5 to 100 g / 10 min, more preferably 1 to 60 g / 10 min, and particularly preferably 3 to 50 g / 10 min. If the MFR is too high, there is a tendency for reduced film-forming properties; if the MFR is too low, there is a tendency for the melt viscosity to become too high, making melt extrusion difficult.

[0037] In EVOH(A), in addition to ethylene structural units and vinyl alcohol structural units (including unsaponified vinyl ester structural units), structural units derived from the comonomers shown below may also be included. Examples of the aforementioned comonomers include, for instance, α-olefins such as propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins or their esters or acylates such as 3-buten-1-ol, 4-penten-1-ol, and 3-buten-1,2-diol; unsaturated carboxylic acids or their salts, their alkyl esters, their alkyl peresters, their nitriles, their amides or their anhydrides; unsaturated sulfonic acids or their salts; vinylsilane compounds; vinyl chloride; styrene, etc.

[0038] Alternatively, EVOH that has undergone "post-modification" such as carbamate, acetalization, cyanoethylation, or oxyalkyleneification can also be used.

[0039] Among the modified compounds as described above, EVOH with primary hydroxyl groups introduced into the side chain through copolymerization is preferred in terms of improved secondary forming properties such as stretching, vacuum / compressed forming, etc., and EVOH with a 1,2-diol structure in the side chain is particularly preferred.

[0040] The aforementioned EVOH having a 1,2-diol structure in the side chain is a substance containing 1,2-diol structural units in the side chain, preferably EVOH containing the structural units shown in the following general formula (1).

[0041]

[0042] In general formula (1), R 1 R 2 R 3 R 4 R5 and R 6 Each can be represented independently as a hydrogen atom or an organic group, and X represents a single bond or a bonded chain.

[0043] Examples of the aforementioned organic groups include alkyl groups with 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. These organic groups may have functional groups such as halogen groups, hydroxyl groups, ester groups, carboxylic acid groups, and sulfonic acid groups as needed.

[0044] In addition to hydrocarbons such as alkylene, alkenylene, ynylene, phenylene, and naphthylene (which may be substituted by halogens such as fluorine, chlorine, and bromine), -O- and -(CH2O) can also be listed as the aforementioned bonded chains. m -、-(OCH2) m -、-(CH2O) m CH2-, -CO-, -COCO-, -CO(CH2) m 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. (R is independently any substituent, preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and m is a natural number). Among these, from the viewpoint of stability during manufacturing or use, alkylene groups having 6 or fewer carbon atoms are preferred, and methylene or -CH2OCH2- are particularly preferred.

[0045] The aforementioned EVOH having a 1,2-diol structure in the side chain is particularly preferably a structural unit comprising the following general formula (1′), namely R 1 R 2 R 3 R 4 R 5 and R 6 EVOH consists entirely of hydrogen atoms, with X being a single bond structural unit.

[0046]

[0047] In addition, EVOH(A) can be a mixture containing two or more different EVOHs. Examples of different EVOHs include substances with different ethylene content, substances with different degrees of saponification, substances with different MFR (210°C, 2160g load), substances with different copolymer components, and substances with different amounts of modification (e.g., substances with different contents of 1,2-diol structural units).

[0048] In the EVOH resin composition described in the embodiments of the present invention, the base resin is EVOH(A), and the content of EVOH(A) relative to the total EVOH resin composition is generally 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.

[0049] <Unmodified polyolefin (B)>

[0050] There are no particular limitations on the unmodified polyolefin (B), and any known unmodified polyolefin can be used. Examples include unmodified olefin homopolymers formed from olefin monomers such as ethylene, propylene, and butene; unmodified olefin block copolymers formed from two or more olefin monomers; and unmodified olefin random copolymers. These can be used alone or in combination of two or more.

[0051] Examples of unmodified olefin homopolymers include, for example, unmodified polyethylene, unmodified polypropylene, unmodified polybutene, and unmodified polymethylpentene. Examples of unmodified olefin block copolymers include, for example, unmodified ethylene-α-olefin copolymers, unmodified propylene-α-olefin copolymers, and unmodified butene-α-olefin copolymers. Examples of unmodified olefin random copolymers include substances obtained by random copolymerization of two or more of the aforementioned olefin monomers.

[0052] Among these unmodified polyolefins (B), from the viewpoint of improving elongation at break at low temperatures, copolymers of ethylene and α-olefins with 3 to 20 carbon atoms, i.e., unmodified ethylene-α-olefin copolymers, are more preferably copolymers of ethylene and α-olefins with 3 to 10 carbon atoms, i.e., unmodified ethylene-α-olefin copolymers, are particularly preferably copolymers of ethylene and α-olefins with 2 to 8 carbon atoms, i.e., unmodified ethylene-α-olefin copolymers, and are especially preferably unmodified ethylene-butene copolymers.

[0053] The density of unmodified polyolefin (B) is not particularly limited, but is typically 0.900 g / cm³. 3 The preferred value is 0.890 g / cm³. 3 The following is particularly preferred: 0.885 g / cm³ 3The following describes how, by using this low-density unmodified polyolefin copolymer (B), molded articles 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 above.

[0054] The MFR (190°C, 2160g load) of the unmodified polyolefin (B) is not particularly limited, but is typically 1.0 to 100 g / 10 min, preferably 2.0 to 60 g / 10 min. By using this unmodified polyolefin (B), the stability of the resulting EVOH resin composition during extrusion processing and the low-temperature elongation at break of the resulting molded article can be further improved.

[0055] The content of unmodified polyolefin (B) is typically 5% by mass or more relative to the total EVOH resin composition, preferably 5 to 40% by mass, more preferably 5 to 35% by mass, and particularly preferably 5 to 30% by mass.

[0056] It should be noted that, here, "unmodified polyolefin" refers to unmodified polyolefin that has not undergone acid modification, such as unmodified polyolefin copolymers that do not belong to "acid-modified polyolefin (C)" below. The acid value of the unmodified polyolefin (B) is not particularly limited, but is preferably less than 0.5 mg KOH / g. The aforementioned acid value is determined according to JIS K 0070 by neutralization titration.

[0057] <Acid-modified polyolefin (C)>

[0058] Acid-modified polyolefins (C) are polyolefins modified with acids. There are no particular limitations. Known acid-modified polyolefins can be used, either alone or in combination of two or more.

[0059] Acid-modified polyolefins (C) are obtained, for example, by copolymerizing a portion of the monomers constituting unmodified polyolefins with α,β-unsaturated carboxylic acids or their anhydrides, or by introducing α,β-unsaturated carboxylic acids or their anhydrides into a portion of the side chain using grafting reactions such as free radical addition.

[0060] The aforementioned unmodified polyolefin is not particularly limited and can use any known unmodified polyolefin, such as unmodified olefin homopolymers formed from olefin monomers such as ethylene, propylene, and butene; unmodified olefin block copolymers formed from 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 substances obtained by random copolymerization of two or more of the aforementioned olefin monomers.

[0061] 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 particularly suitable.

[0062] From the viewpoint of improving elongation at break at low temperatures, the preferred acid-modified ethylene-α-olefin copolymer is obtained by acid modification of a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. More preferably, it is obtained by acid modification of a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. Particularly preferred is an acid-modified ethylene-α-olefin copolymer obtained by acid modification of a copolymer of ethylene and an α-olefin having 2 to 8 carbon atoms. Especially preferred is an acid-modified ethylene-butene copolymer. Most preferably, it is a maleic anhydride-modified ethylene-butene copolymer.

[0063] The acid value of the acid-modified polyolefin (C) is not particularly limited, but is generally below 50 mg KOH / g, preferably below 30 mg KOH / g, and particularly preferably below 20 mg KOH / g. If the acid value is too high, there is a tendency for the reaction sites with the hydroxyl groups in EVOH (A) to increase, leading to the formation of highly polymerized compounds during melt mixing, reduced stability during extrusion processing, and difficulty in obtaining good molded products. On the other hand, if the acid value is too low, there is a tendency for reduced compatibility with EVOH (A), increased resin adhesion to the die during extrusion processing (eye discharge), and reduced elongation at break at low temperatures. The lower limit of this acid value is generally above 1 mg KOH / g, preferably above 2 mg KOH / g. The aforementioned acid value is determined according to JIS K 0070 using neutralization titration.

[0064] The density of acid-modified polyolefins (C) is not particularly limited, but is typically 0.900 g / cm³. 3 The preferred value is 0.890 g / cm³. 3 The following is particularly preferred: 0.885 g / cm³3 The following describes how, by using this low-density acid-modified polyolefin (C), molded articles with particularly excellent elongation at break at low temperatures can be obtained. The lower limit of the density of acid-modified polyolefin (C) is typically 0.850 g / cm³. 3 above.

[0065] The MFR (190°C, 2160g load) of the acid-modified polyolefin (C) is not particularly limited, but is preferably 1.0g or more / 10 minutes, more preferably 1.0 to 60g / 10 minutes, even more preferably 1.5 to 60g / 10 minutes, and particularly preferably 2.0 to 60g / 10 minutes. By using this acid-modified polyolefin (C), the elongation at break at low temperatures can be further improved.

[0066] The content of acid-modified polyolefin (C) is generally 5% by mass or more relative to the total EVOH resin composition, preferably 5 to 40% by mass, more preferably 5 to 35% by mass, and particularly preferably 5 to 30% by mass.

[0067] [The mass ratio of (B) to (C)]

[0068] The EVOH resin composition described in the embodiments of the present invention is characterized by using unmodified polyolefin (B) and acid-modified polyolefin (C) in a specific mass ratio [(B) / (C)], which, from the viewpoint of improving elongation at break at low temperatures, is 75 / 25 to 1 / 99, preferably 70 / 30 to 10 / 90, and particularly preferably 65 / 35 to 15 / 85. When the mass ratio [(B) / (C)] exceeds 75 / 25, the resulting molded article exhibits insufficient elongation at break at low temperatures. On the other hand, when the mass ratio [(B) / (C)] is less than 1 / 99, eye discharge increases, and the moldability becomes insufficient.

[0069] [The mass ratio of (A), (B), and (C)]

[0070] From the viewpoint of improving elongation at break at low temperatures, the mass ratio of EVOH(A) content in the EVOH resin composition according to embodiments of the present invention relative to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) [(A) / ((B)+(C))] is preferably 60 / 40 to 99 / 1, more preferably 60 / 40 to 79 / 21, and particularly preferably 60 / 40 to 75 / 25. That is, from the viewpoint of improving elongation at break at low temperatures, the mass ratio of EVOH(A) content in the EVOH resin composition according to embodiments of the present invention relative to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) [(A) / ((B)+(C))] is particularly preferably 60 / 40 or more and less than 75 / 25.

[0071] In this invention, from the viewpoint of improving elongation at break at low temperatures, the aforementioned mass ratio [(A) / ((B)+(C))] is set to 60 / 40 or more and less than 75 / 25. Preferably, the aforementioned mass ratio [(A) / ((B)+(C))] is set to 60 / 40 or more and 68 / 32 or less.

[0072] When the mass ratio [(A) / ((B)+(C))] exceeds the aforementioned upper limit, or when neither unmodified polyolefin (B) nor acid-modified polyolefin (C) is present, there is a tendency for the elongation at break of the resulting molded article to decrease at low temperatures. On the other hand, when the mass ratio [(A) / ((B)+(C))] is less than 60 / 40, there is a tendency for, for example, EVOH (A) to not form a matrix phase, and for the hydrogen barrier properties of the molded article to decrease.

[0073] <Other Ingredients>

[0074] In the EVOH resin composition described in the embodiments of the present invention, in addition to EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C), other resins may be contained as needed within a range that does not impair the effects of the present invention (e.g., less than 5% by mass of the total EVOH resin composition). Examples of other resins include, for example, polyamide resins such as nylon 11, nylon 12, nylon 6, nylon 66, and nylon 6.66; unmodified vinyl alcohol resins that do not have the structural unit of the aforementioned general formula (1); and other thermoplastic resins. Two or more of these may be used alone or in combination.

[0075] The content of the aforementioned other resins relative to 100 parts by weight of EVOH(A) is generally 50 parts by weight or less, preferably 40 parts by weight or less, more preferably 30 parts by weight or less, particularly preferably 20 parts by weight or less, and especially preferably 10 parts by weight or less.

[0076] In addition, the EVOH resin composition according to the embodiment of the present invention may contain various additives as needed within a range not impairing the effects of the present invention. Examples thereof include plasticizers such as aliphatic polyols such as ethylene glycol, glycerin, and hexanediol; lubricants such as saturated aliphatic amides (such as stearamide, etc.), unsaturated fatty acid amides (such as oleic amide, etc.), bis-fatty acid amides (such as ethylenebisstearamide, etc.); anti-blocking agents; antioxidants; colorants; antistatic agents; ultraviolet absorbers; antibacterial agents; insoluble inorganic salts (such as hydrotalcite, etc.); fillers (such as inorganic fillers, etc.); oxygen absorbers (such as ring-opening polymers of cycloolefins such as polyoctene, etc., cyclized products of conjugated diene polymers such as butadiene, etc.); surfactants, waxes; dispersants (such as monoglyceride stearate, etc.); heat stabilizers; light stabilizers; desiccants; flame retardants; crosslinking agents; curing agents; foaming agents; crystal nucleating agents; antifogging agents; additives for biodegradation; silane coupling agents; conjugated polyene compounds and other known additives. They may be used alone or in combination of two or more.

[0077] The aforementioned heat stabilizer is used for the purpose of improving various physical properties such as thermal stability during melt molding. Examples thereof include organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, etc. or their alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc.; or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, etc. or their alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc. They may be used alone or in combination of two or more.

[0078] <EVOH resin composition>

[0079] The EVOH resin composition according to the embodiment of the present invention can be prepared by blending EVOH (A), unmodified polyolefin (B), acid-modified polyolefin (C), and other resins and additives as needed in a specified ratio, and performing melt-kneading.

[0080] Specifically, it can be manufactured by melt-kneading EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) at a blending ratio of the mass ratio [(B) / (C)] of unmodified polyolefin (B) to acid-modified polyolefin (C) of 75 / 25 to 1 / 99. More preferably, it is manufactured by melt-kneading EVOH (A), unmodified polyolefin (B), and acid-modified polyolefin (C) at a blending ratio of the mass ratio [(B) / (C)] of unmodified polyolefin (B) to acid-modified polyolefin (C) of 75 / 25 to 1 / 99, and the mass ratio [(A) / ((B)+(C))] of the content of EVOH (A) to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) of 60 / 40 to 99 / 1.

[0081] That is, the EVOH resin composition described in the embodiments of the present invention is preferably manufactured by melt-blending EVOH (A), unmodified polyolefin (B) and acid-modified polyolefin (C) at a blending ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) of 75 / 25 to 1 / 99, and the content of EVOH (A) relative to the total content of unmodified polyolefin (B) and acid-modified polyolefin (C) at a blending ratio of 60 / 40 or more and less than 75 / 25.

[0082] Melt compounding can be performed using known compounding machines such as extruders, Banbury mixers, Kneader-Ruder, open mill rolls, and Plastomills. Examples of extruders include single-screw or twin-screw extruders. The EVOH resin composition can be extruded into filaments after melt compounding and then cut into granules.

[0083] The melt blending can be carried out by simultaneously feeding EVOH (A), unmodified polyolefin (B) and acid-modified polyolefin (C), or by simultaneously melt blending EVOH (A) using a twin-screw extruder while side-feeding unmodified polyolefin (B) and acid-modified polyolefin (C) in molten or solid state.

[0084] The melt mixing temperature is appropriately selected according to the type of EVOH (A), unmodified polyolefin (B) and acid-modified polyolefin (C), and is usually 215-270°C, preferably 215-265°C, more preferably 220-260°C, and particularly preferably 220-250°C.

[0085] The melt mixing time is appropriately selected according to the type of unmodified polyolefin (B) and acid-modified polyolefin (C), typically 0.1 to 30 minutes, preferably 0.3 to 10 minutes, and more preferably 0.5 to 5 minutes.

[0086] The EVOH resin composition of the present invention obtained through the foregoing operation is subjected to a shear rate of 18 sec at 210°C. -1 The melt viscosity (η1) is preferably 10000 mPa·s or less, more preferably 9500 mPa·s or less, and particularly preferably 9000 mPa·s or less. If the melt viscosity (η1) is too high, there is a tendency for reduced processability. For example, if the melt viscosity (η1) is too high, there is a tendency for melt fracture to easily occur during single-layer film formation, and there is a tendency for interface disorder to easily occur during multi-layer film formation due to increased shear stress. The lower limit of melt viscosity (η1) is usually 2000 mPa·s or more.

[0087] Furthermore, the EVOH resin composition described in the embodiments of the present invention is subjected to a shear rate of 210°C and 365 sec. -1 The melt viscosity (η2) 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, there is a tendency for reduced processability. For example, if the melt viscosity (η2) is too high, there is a tendency for melt fracture to easily occur during single-layer film formation, and there is a tendency for interface disorder to easily occur during multi-layer film formation due to increased shear stress. The lower limit of melt viscosity (η2) is usually 300 mPa·s or more.

[0088] It should be noted that the aforementioned melt viscosity can be measured according to JIS K7199:1999 using a capillary rheometer such as the "Capilograph 1D" manufactured by Toyo Seiki Co., Ltd.

[0089] [Melt viscosity ratio [(η1) / (η2)]]

[0090] The EVOH resin composition of the embodiments of the present invention is characterized by being controlled to a specific melt viscosity ratio [(η1) / (η2)], and the EVOH resin composition of the embodiments of the present invention is subjected to a specific melt viscosity ratio [(η1) / (η2)] at 210°C and a shear rate of 18 sec. -1 The melt viscosity (η1) at 210°C and the melt viscosity (η1) at a shear rate of 365 sec are compared with those at 210°C and a shear rate of 365 sec. -1 The melt viscosity ratio [(η1) / (η2)] of the melt viscosity (η2) is 5.6 or more, preferably 5.8 or more, more preferably 6.0 or more, and particularly preferably 6.2 or more. If the aforementioned melt viscosity ratio is within the aforementioned range, an EVOH resin composition with excellent elongation at break at low temperature is formed. On the other hand, if the aforementioned melt viscosity ratio is outside the aforementioned range, the elongation at break at low temperature becomes a low value. It should be noted that the upper limit of the aforementioned melt viscosity ratio is generally 7.0 or less, and preferably 6.8 or less.

[0091] In this invention, in order to control the melt viscosity ratio within the aforementioned range, although not particularly limited, it is preferred to use, for example, the following methods: [i] adjusting the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) to 75 / 25 to 1 / 99, preferably to 70 / 30 to 10 / 90, particularly preferably to 65 / 35 to 15 / 85; [ii] preferably adjusting the MFR (190°C, 2160g load) of acid-modified polyolefin (C) to 1.0g or more per 10 minutes, more preferably to 1.5g or more per 10 minutes, and even more preferably to 2g or more per 10 minutes; [iii] adjusting 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 to within 2.0, and even more preferably to within 1.5, etc.

[0092] According to this EVOH resin composition, the weakness of EVOH, namely its elongation at break at low temperatures, can be improved by using unmodified polyolefin (B) and acid-modified polyolefin (C). This can be presumed to be because the moderate interaction at the interface between EVOH and the elastomer leads to increased elongation due to the yield strain of the material and deformation based on interfacial peeling.

[0093] The EVOH resin composition described in the embodiments of the present invention has excellent hydrogen barrier properties based on EVOH(A). Furthermore, it not only exhibits excellent gas barrier properties against hydrogen, but also against other gases such as helium, oxygen, nitrogen, and air, especially against gases with a molecular weight less than 10, such as hydrogen.

[0094] The method for obtaining molded articles using the EVOH resin composition described in the embodiments of the present invention is not particularly limited, and various molding methods using thermoplastic resins such as EVOH that are generally known can be listed. Examples include extrusion molding, co-extrusion molding, injection molding, blow molding, tube forming, rotational molding, and melt forming. Specifically, for hollow molded articles such as fuel canisters, extrusion blow molding is generally used; for pipe-shaped containers, tube forming is used; and for molded articles with complex shapes or requiring dimensional accuracy, injection molding is used.

[0095] <Multi-layer structure>

[0096] The molded body described in the embodiments of the present invention has at least one layer formed of an EVOH resin composition (hereinafter sometimes referred to as a "resin composition layer"). Furthermore, regarding the molded body described in the embodiments of the present invention, for the purpose of imparting various physical properties, it can be a multilayer structure to which at least one other layer is stacked, such as a molded body formed of a multilayer structure containing a thermoplastic resin layer or the like (hereinafter sometimes referred to as a "multilayer structure").

[0097] The multilayer structure described in the embodiments of the present invention includes, for example, an inner layer (i.e., a layer in contact with high-pressure gas or fuel), an intermediate layer, and an outer layer (i.e., a layer in contact with external gas). The inner or intermediate layer preferably comprises a resin composition layer. From the viewpoint of preventing the gas barrier properties of the resin composition layer from decreasing due to moisture, the intermediate layer preferably comprises a resin composition layer. Furthermore, the inner and / or outer layers preferably comprise a thermoplastic resin layer containing a thermoplastic resin other than EVOH that is water-resistant and moisture-proof. It should be noted that the intermediate layer refers to the layer located between the outer and inner layers.

[0098] Furthermore, the multilayer structure described in the embodiments of the present invention may further include a reinforcing layer. The reinforcing layer is not particularly limited, but it is preferably located further outward from the outermost layer, and preferably is the layer in contact with the outside air (the outermost layer). Additionally, an adhesive layer formed of an adhesive resin may be provided between these layers.

[0099] As the thermoplastic resin used in the thermoplastic resin layer, a hydrophobic thermoplastic resin is preferred. 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)), ethylene-vinyl acetate copolymers, ionomers, ethylene-propylene copolymers, ethylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymers, ethylene-acrylate copolymers, polypropylene-based resins such as polypropylene and propylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymers, homopolymers or copolymers of olefins such as polybutene and polypentene, cyclic polyolefins, or homopolymers or copolymers of these olefins coated with unsaturated carboxylic acids. Polyolefin resins, such as those obtained by grafting modification of their esters (carboxylic acid-modified polyolefin resins, ester-modified polyolefin resins); polystyrene resins; polyamide resins such as nylon 11, nylon 12, nylon 6, nylon 66, etc., and copolyamides such as nylon 6.12, nylon 6.66; vinyl ester resins such as polyvinyl chloride, polyvinylidene chloride, acrylic resins, and polyvinyl acetate; polyurethane resins; fluoropolymers such as tetrafluoroethylene, tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers, ethylene / tetrafluoroethylene copolymers, and tetrafluoroethylene / hexafluoropropylene copolymers; chlorinated polyethylene; chlorinated polypropylene; fluoropolymers with polar groups, thermoplastic polyurethanes, etc. These can be used alone or in combination of two or more. Among these, from the viewpoint of mechanical strength and melt molding processability, polyolefin resins are preferred, polyethylene resins and polypropylene resins are more preferred, and polyethylene and polypropylene are particularly preferred.

[0100] As the adhesive resin used as the adhesive layer, known adhesive resins and various substances can be used. Generally, examples include modified olefin polymers containing carboxyl groups obtained by chemically bonding unsaturated carboxylic acids or their anhydrides to olefin polymers (the aforementioned polyolefin resins in a broad sense) through addition reactions, grafting reactions, etc. Specifically, as preferred examples, one or a mixture of two or more 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.

[0101] The aforementioned thermoplastic resin layer and adhesive layer may contain conventionally known plasticizers, fillers, clays (montmorillonite, etc.), colorants, antioxidants, antistatic agents, lubricants, nucleating materials, anti-blocking agents, ultraviolet absorbers, waxes, etc., without impairing the effects of the present invention. These may be used alone or in combination of two or more.

[0102] Examples of reinforcing layers include fiber-reinforced layers using fibers and rubber-reinforced layers using rubber. Fiber-reinforced layers can be made of high-strength fibers such as poly(p-phenylenebenzobisoxazole) (PBO) fibers, aramid fibers, and carbon fibers; nonwoven fabrics, woven fabrics, paper, metal foils, metal filaments, and woody surfaces. A fiber-reinforced layer is preferred, a fiber-reinforced layer using high-strength fibers is particularly preferred, and a sheet layer obtained by weaving high-strength fibers or a fiber-reinforced layer formed by winding the sheet into a spiral is even more preferred.

[0103] As an embodiment of the multilayer structure described in this invention, when the resin composition layer is designated as a (a1, a2, ...), the thermoplastic resin layer as b (b1, b2, ...), and the reinforcing layer as c (c1, c2, ...), the layer structure can be any combination of 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., sequentially from the inside. Adhesive layers can be provided between the layers of these multilayer structures.

[0104] Furthermore, when the reuse layer, which comprises a resin composition obtained by remelting and molding the ends and defective products generated during the manufacturing process of the multilayer structure, and a mixture of thermoplastic resin other than EVOH, is designated as R, the layer structure of the multilayer structure described in the embodiment of the present invention can be any combination of 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 can be provided between the layers of these multilayer structures.

[0105] Among these multilayer structures, multilayer structures having a layer structure of b1 / a / b2 and b1 / a / b2 / c are preferred, and multilayer structures having a layer structure in which an adhesive layer is sandwiched 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 structures described in embodiments of the present invention typically have 2 to 20 layers, preferably 3 to 15 layers, and particularly preferably 4 to 10 layers.

[0106] Examples of methods for manufacturing multilayer structures according to embodiments of the present invention include: a method of molding an EVOH resin composition in a molten state (melt molding); and a method of dissolving an EVOH resin composition in a solvent and molding it (e.g., solution coating). From a productivity point of view, melt molding is preferred.

[0107] Specifically, the following methods can be listed as examples: a method for melt-extruding a thermoplastic resin into a molded article (e.g., film, sheet) of the EVOH resin composition described in the embodiments of the present invention; a method for melt-extruding a resin composition layer onto a substrate such as a thermoplastic resin; and a method for co-extruding a resin composition layer and a thermoplastic resin layer. More specifically, T-die extrusion, tubular extrusion, blow molding, irregular die extrusion, etc., can be used.

[0108] Furthermore, the following methods can be used: dry lamination of substrates such as films formed from the EVOH resin composition described in the embodiments of the present invention and films formed from thermoplastic resins using known adhesives such as organotitanium compounds, isocyanate compounds, polyethyleneimine compounds, polyester compounds, and polyurethane compounds; lamination by clamping the adhesive layer, etc. Additionally, co-injection molding may be used, depending on the circumstances.

[0109] The multilayer structure described in the embodiments of the present invention is then subjected to a (heated) stretching process as needed. The stretching process can use known stretching methods, such as uniaxial stretching and biaxial stretching. In the case of biaxial stretching, either simultaneous biaxial stretching or successive biaxial stretching can be used. The stretching temperature, measured in terms of the temperature of the multilayer structure (temperature near the multilayer structure), is typically 40–170°C, preferably around 60–160°C. The stretching ratio, measured in terms of area ratio, is typically 2–50 times, preferably 2–20 times. Furthermore, for the purpose of imparting dimensional stability to the resulting stretched film, heat setting can be performed after stretching. Heat setting can be carried out using known methods, maintaining the aforementioned stretched film under tension while performing a heat treatment at 80–180°C, preferably 100–165°C, for approximately 2–600 seconds.

[0110] The thickness of the multilayer structure (including stretched multilayer structure) described in the embodiments of the present invention is not particularly limited, but is typically 1 to 1500 μm, preferably 1 to 1000 μm, and more preferably 10 to 700 μm. Furthermore, the thickness of the thermoplastic resin layer in the multilayer structure is not particularly limited, but is typically 0.1 to 1000 μm, preferably 1 to 500 μm. The thickness of the resin composition layer is not particularly limited, but is typically 0.1 to 500 μm, preferably 1 to 100 μm. The thickness of the adhesive layer is not particularly limited, but is typically 0.1 to 250 μm, preferably 0.1 to 100 μm.

[0111] Furthermore, the thickness ratio of the thermoplastic resin layer to the resin composition layer (thermoplastic resin layer / resin composition layer) is not particularly limited. When there are multiple layers, the ratio of the thickest layer to the others is usually greater than 1 and less than 30, preferably 2 to 30. 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.

[0112] As described above, the EVOH resin composition of the embodiments of the present invention is useful as a molded article with excellent elongation at break at low temperatures, especially as a molded article with excellent hydrogen barrier properties and elongation at break at low temperatures. Furthermore, the EVOH resin composition of the preferred embodiments of the present invention is useful as a molded article that has both hydrogen barrier properties and improved elongation at break at low temperatures, as well as excellent processability. Molded articles obtained using the EVOH resin composition of the present invention are useful as fuel tanks for, for example, high-pressure hydrogen (pressure 1 to 100 MPa) and fuel tank components thereof.

[0113] It should be noted that "low temperature" in the context of elongation at break at low temperature refers to temperatures typically below 0°C, preferably around -20 to -50°C.

[0114] Furthermore, the molded articles obtained using the EVOH resin composition described in the embodiments of the present invention are suitable as packaging materials. For example, they can also be processed into tubular, bag-shaped, and other forms, and are used as packaging materials for a wide range of liquids, such as sweet rice wine, soy sauce, seasoning sauce, noodle soup, edible oil, wine, fruit juice, milk, mineral water, Japanese sake, shochu, coffee, black tea, pharmaceuticals, cosmetics, sodium hypochlorite, developer, battery fluid, pesticides, detergents, etc.

[0115] Example

[0116] The following examples illustrate the present invention in more detail, but the invention is not limited to these examples as long as it does not depart from its spirit. It should be noted that "%" and "parts" in the examples refer to mass, and "unmodified PO" in Table 1 refers to unmodified polyolefin, and "acid-modified PO" refers to acid-modified polyolefin.

[0117] [Materials Used]

[0118] The following materials are used as materials for EVOH resin compositions.

[0119] (EVOH(A))

[0120] • A-1: ​​EVOH (ethylene content: 25 mol%, saponification degree: 99.7 mol%, MFR: 4.0 g / 10 min (210 °C, 2160 g load))

[0121] • A-2: EVOH (ethylene content: 38 mol%, saponification degree: 99.7 mol%, MFR: 50 g / 10 min (210 °C, 2160 g load))

[0122] (Unmodified polyolefin (B))

[0123] • B-1: "A4085S" manufactured by Mitsui Chemicals, ethylene-butene copolymer (MFR: 3.6 g / 10 min (190°C, 2160 g load), density: 0.885 g / cm³) 3 )

[0124] • B-2: "P0180" manufactured by Mitsui Chemicals, ethylene-propylene copolymer (MFR: 4.4 g / 10 min (190°C, 2160 g load), density: 0.869 g / cm³) 3 )

[0125] (Acid-modified polyolefin (C))

[0126] • C-1: "MA8510" manufactured by Mitsui Chemicals, maleic anhydride-modified ethylene-butene copolymer (MFR: 2.4 g / 10 min (190 °C, 2160 g load), density: 0.885 g / cm³) 3 The acid value is 5.5 mg KOH / g

[0127] • C-2: Mitsui Chemicals' "MP0610", maleic anhydride-modified ethylene-propylene copolymer (MFR: 0.4 g / 10 min (190 °C, 2160 g load), density: 0.870 g / cm³) 3 The acid value is 6.1 mg KOH / g

[0128] <Example 1>

[0129] [Preparation of EVOH resin composition granules]

[0130] After dry mixing the components in the proportions listed in Table 1, the mixture is melt-mixed using a twin-screw extruder under the following conditions, extruded into filaments, and cut using a granulator to obtain cylindrical granules of the EVOH resin composition.

[0131] (Melting and mixing conditions)

[0132] · Diameter (D) 30mm

[0133] L / D = 56

[0134] Screw speed: 400 rpm

[0135] • Barrel (C) set temperature:

[0136] 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℃

[0137] • Die head set temperature: 80℃

[0138] • Spray volume: 25kg / hr

[0139] Next, the prepared EVOH resin composition granules were evaluated as follows.

[0140] (1) Low-temperature elongation at break (%)

[0141] Using an injection molding machine, ISO 1A dumbbell-shaped tensile test specimens were fabricated from the obtained granules and subjected to tensile testing at -40°C using a tensile testing machine. The specimens were dumbbell-shaped, 10 mm wide, 110 mm long, 200 mm in total length, and 4 mm thick. It should be noted that the fabrication and evaluation of these specimens were carried out according to ISO 527-2, with measurements taken at a tensile speed of 50 mm / min. The results are shown in Table 1. It should be noted that the low-temperature elongation at break (%) is the value obtained by calculating the elongation (%) from the start of the tensile test until the specimen breaks using the following formula.

[0142] (Formula) Low-temperature breaking elongation (%) = [(Length of test piece at break - Length of test piece before test) / Length of test piece before test] × 100

[0143] (2) Melt viscosity (mPa·s)

[0144] The obtained granules were used as samples, and the shear rate was measured using a "Capilograph 1D" manufactured by Toyo Seiki Co., Ltd., under the following conditions: 18 [sec] -1 The melt viscosity (η1) and shear rate at 365 sec are [missing information]. -1 Given the melt viscosity (η2) at a given value, calculate the melt viscosity ratio [(η1) / (η2)]. The results are shown in Table 1.

[0145] (Measurement conditions)

[0146] • Capillary diameter: 1mm

[0147] • Capillary length: 10mm

[0148] • Capillary temperature: 210℃

[0149] • Preheating time (time from filling the capillary with sample to the start of measurement): 5 minutes

[0150] • Shear rate: 18 [sec] -1 ] or 365 [sec -1 ]

[0151] • Sample quantity: 15g

[0152] It should be noted that the melt viscosities (η1) and (η2) shown in Table 1 are obtained by rounding the measured values ​​obtained based on the aforementioned measurement conditions to the first decimal place. In addition, the melt viscosity ratio shown in Table 1 is obtained by rounding the melt viscosity ratio [(η1) / (η2)] calculated based on the melt viscosities (η1) and (η2) shown in Table 1 to the second decimal place.

[0153] <Examples 2-4>

[0154] Except for changing the proportions of each component to those shown in Table 1, EVOH resin composition granules were prepared in the same manner as in Example 1, and were evaluated in the same way.

[0155] <Comparative Examples 1-6>

[0156] Except for changing the proportions of each component to those shown in Table 1, EVOH resin composition granules were prepared in the same manner as in Example 1, and were evaluated in the same way.

[0157] [Table 1]

[0158]

[0159] According to the results in Table 1, Examples 1 to 4, which meet the conditions specified in this invention, namely the mass ratio of unmodified polyolefin (B) to acid-modified polyolefin (C) [(B) / (C)], the specific melt viscosity ratio [(η1) / (η2)], and the mass ratio of 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.

[0160] On the other hand, it can be seen that Comparative Examples 1 to 6, which do not meet the aforementioned conditions specified in this invention, have poor elongation at break at low temperatures compared to Examples 1 to 4.

[0161] It should be noted that a 1% difference in elongation at break at -40°C becomes a significant difference in practical use. For example, when using EVOH resin compositions in automotive fuel containers, due to the large volume of the fuel container (typically 0.5–3 m in long diameter and 0.1–1 m in short diameter), a 1% difference in elongation at break at low temperature becomes a significant difference as acceptable deformation of the fuel container, resulting in a significant difference in acceptable hydrogen filling pressure. The hydrogen filling amount of a fuel container carrying high-pressure hydrogen is proportional to the product of the hydrogen filling volume of the fuel container and the hydrogen pressure. Therefore, differences in hydrogen filling pressure are related to differences in hydrogen filling amount, leading to differences in driving range in the vehicle. Thus, the difference in elongation at break at low temperature becomes a significant difference in practical use and has an impact. Not limited to applications in automotive fuel containers, as mentioned above, a 1% difference in elongation at break at low temperature becomes a significant difference in practical use.

[0162] The above embodiments illustrate specific aspects of the present invention, but these embodiments are merely illustrative and not intended to be limiting. Various modifications that are obvious to those skilled in the art fall within the scope of the present invention.

[0163] Industrial availability

[0164] The EVOH resin composition of the present invention can improve elongation at break at low temperatures. Therefore, molded articles containing a layer formed from the aforementioned EVOH resin composition are useful as raw materials for fuel tanks for high-pressure hydrogen and the like, and for components used in fuel tanks.

Claims

1. An ethylene-vinyl alcohol-based copolymer composition comprising an ethylene-vinyl alcohol-based copolymer A, an unmodified polyolefin B, and an acid-modified polyolefin C, a mass ratio B / C of the unmodified polyolefin B to the acid-modified polyolefin C being 75 / 25 to 1 / 99, a melt viscosity ratio ηι / η2 of a melt viscosity ηι of the composition at 210°C and a shear rate of 18 sec"1 to a melt viscosity η2 of the composition at 210°C and a shear rate of 365 sec"1 being 5.6 or more, a mass ratio A / B+C of the ethylene-vinyl alcohol-based copolymer A to a total content of the unmodified polyolefin B and the acid-modified polyolefin C being 60 / 40 or more and less than 75 / 25, a melt flow rate of the acid-modified polyolefin C at 190°C under a load of 2160 g being 1.0 g / 10 min or more, a difference between a melt flow rate of the unmodified polyolefin B at 190°C under a load of 2160 g and a melt flow rate of the acid-modified polyolefin C at 190°C under a load of 2160 g being 2.0 or less, and the unmodified polyolefin B being an unmodified ethylene-α-olefin copolymer. -1 -1 ​​ 2. The ethylene-vinyl alcohol-based copolymer composition according to claim 1, wherein, The unmodified polyolefin B is an unmodified ethylene-butene copolymer.

3. The ethylene-vinyl alcohol-based 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-based copolymer composition according to claim 1 or 2, 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-based copolymer composition according to claim 1 or 2, wherein, The melt viscosity η1 is 10,000 mPa・s or less.

7. The ethylene-vinyl alcohol-based copolymer composition according to claim 1 or 2, wherein, The content of the ethylene-vinyl alcohol-based copolymer A with respect 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 in terms of a mass ratio A / B+C.

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

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