Multilayer structure, recyclable composition, and recyclable molded body

Abstract

Provided is a multilayer structure described below that does not cause a decrease in tear strength before recycling and does not produce a crosslinked gel after being recycled, and in which a decrease in impact resistance is suppressed.　The multilayer structure comprises a resin layer (A) containing an ethylene-vinyl alcohol copolymer and a polyolefin resin layer (B). The polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2). The content of the amine-modified resin (b2) in the polyolefin resin layer (B) is between 12 and 280 parts by mass (both inclusive) with respect to 100 parts by mass of the ethylene-vinyl alcohol copolymer in the resin layer (A). The polyolefin resin layer (B) in the resin layer (A) does not contain an ethylene-vinyl alcohol copolymer.

Description

Multilayer structure, recycled composition, recycled molded body

[0001] The present invention relates to a multilayer structure, and more particularly to a multilayer structure that is easily recyclable.

[0002] Resins such as ethylene-vinyl alcohol copolymers (hereinafter sometimes referred to as "EVOH resins") and polyamides (hereinafter sometimes referred to as "PA resins") are generally used by being molded by a melt molding method into multilayer structures such as packaging films and containers for food and the like.

[0003]

[0003] For the purpose of reducing the amount of plastic packaging waste, a recycling technology is known in which scraps generated during the process of producing multilayer structures using these resins and polyolefin resins are collected, pulverized by grinding or the like, melt-kneaded to form a resin composition, which is then granulated / molded and recycled as a regrind layer for the multilayer structure. However, since the polar group-containing resins such as EVOH resin and PA resin in the resin composition obtained in this manner are poorly compatible with polyolefin resins and have poor recyclability, a compatibilizer is added during the recycling process to improve compatibility. However, it has been difficult to appropriately select the timing and amount of use of the compatibilizer in the recycling process.

[0004] In order to solve such problems, for example, Patent Document 1 discloses the use of a multilayer structure having a resin layer containing an EVOH resin and / or a PA resin, a polyolefin resin layer containing a polyolefin resin and a compatibilizer, and an adhesive resin layer, wherein the compatibilizer has a melt flow rate of 600 g / 10 min or less and the content of the compatibilizer is 10 to 200 parts by mass per 100 parts by mass of the EVOH resin and / or PA resin.

[0005] International Publication No. 2023 / 176784

[0006] Patent Document 1 describes that the recyclability of a multilayer structure can be improved by incorporating a modified polyolefin polymer containing a carboxy group as a compatibilizer in the multilayer structure. However, the inventors' studies have found that when a modified polyolefin polymer containing a carboxy group is used, a chemical reaction occurs with the EVOH resin during the recycling process, generating a crosslinked gel, which can lead to problems such as impaired appearance and reduced impact resistance. Furthermore, it has been found that incorporating a compatibilizer in the multilayer structure in advance can lead to problems such as reduced tear strength of the multilayer structure.

[0007] Therefore, the present invention provides a multilayer structure in which there is no decrease in tear strength even before recycling, and no crosslinked gel is generated even after recycling, and in which the decrease in impact resistance is suppressed.

[0008] In view of the above circumstances, the present inventors have conducted extensive research and have found that the above-mentioned problems can be solved by including a specific amount of an amine-modified resin (b2) as a compatibilizer in a multilayer structure having a resin layer (A) containing an EVOH resin and a polyolefin resin layer (B).

[0009] That is, the present invention has the following aspects. [1] A multilayer structure having a resin layer (A) containing an EVOH resin and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is 12 parts by mass or more and 280 parts by mass or less per 100 parts by mass of the EVOH resin in the resin layer (A), and the polyolefin resin layer (B) does not contain an EVOH resin. [2] The multilayer structure according to [1], wherein the polyolefin resin (b1) is polyethylene. [3] The multilayer structure according to [1], wherein the polyolefin resin (b1) is at least one selected from the group consisting of linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene. [4] The multilayer structure according to any one of [1] to [3], wherein the content of the amine-modified resin (b2) is more than 20 parts by mass per 100 parts by mass of the EVOH resin. [5] The multilayer structure according to any one of [1] to [4], wherein the amine-modified resin (b2) is an amine-modified elastomer. [6] The multilayer structure according to any one of [1] to [5], wherein the amine-modified resin (b2) is an amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene. [7] The multilayer structure according to any one of [1] to [6], wherein the polyolefin resin layer (B) further contains a compatible resin (b3). [8] The multilayer structure according to any one of [1] to [7], further containing an adhesive resin layer (C). [9] The multilayer structure according to any one of [1] to [8], which is for recycling.

[10] A recycled composition obtained by melt-kneading the multilayer structure according to any one of [1] to [9].

[11] A recycled molded article obtained by molding the recycled composition according to

[10] .

[12] A multilayer structure comprising a resin layer (A) containing an EVOH resin and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), and the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is more than 20 parts by mass and not more than 280 parts by mass per 100 parts by mass of the EVOH resin.

[13] The multilayer structure according to

[12] , wherein the polyolefin resin (b1) is polyethylene.

[14] The multilayer structure according to

[12] , wherein the polyolefin resin (b1) is at least one selected from the group consisting of linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

[15] The multilayer structure according to any one of

[12] to

[14] , wherein the amine-modified resin (b2) is an amine-modified elastomer.

[16] The multilayer structure according to any one of

[12] to

[15] , wherein the amine-modified resin (b2) is an amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene.

[17] The multilayer structure according to any one of

[12] to

[16] , wherein the polyolefin resin layer (B) further contains a compatible resin (b3).

[18] The multilayer structure according to any one of

[12] to

[17] , further containing an adhesive resin layer (C).

[19] The multilayer structure according to any one of

[12] to

[18] , wherein the multilayer structure is for recycling.

[20] A recycled composition obtained by melt-kneading the multilayer structure according to any one of

[12] to

[19] .

[21] A recycled molded article obtained by molding the recycled composition according to

[20] .

[0010] The multilayer structure of the present invention does not suffer from a decrease in tear strength even before recycling, and does not generate crosslinked gel even after recycling, so that the appearance is not impaired and further, a decrease in impact resistance can be suppressed.

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0012] As used herein, "x and / or y (x and y are any configuration)" refers to at least one of x and y, and can mean three things: x only, y only, or x and y. In this specification, when "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it also means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." In this specification, when "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also means "preferably greater than X" or "preferably less than Y." For numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described herein, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0013] In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and may be 100% by mass.

[0014] A multilayer structure according to one embodiment of the present invention (hereinafter referred to as "the present multilayer structure (1)") has a resin layer (A) containing an EVOH resin and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is 12 parts by mass or more and 280 parts by mass or less per 100 parts by mass of the EVOH resin in the resin layer (A), and the polyolefin resin layer (B) does not contain EVOH resin. A multilayer structure according to another embodiment of the present invention (hereinafter referred to as "the present multilayer structure (2)") has a resin layer (A) containing an ethylene-vinyl alcohol copolymer and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), and the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is more than 20 parts by mass and not more than 280 parts by mass per 100 parts by mass of the ethylene-vinyl alcohol copolymer. The present multilayer structure (1) and the present multilayer structure (2) are collectively referred to as "the present multilayer structure." Each component will be described below.

[0015] [Resin Layer (A)] The resin layer (A) constituting the present multilayer structure contains an EVOH resin.

[0016] [EVOH Resin] The EVOH resin is a resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, and is a water-insoluble thermoplastic resin.

[0017] Vinyl acetate is typically used as the vinyl ester monomer because of its commercial availability and the efficiency of impurity removal during production. 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. Aliphatic vinyl esters having typically 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms, can be used. These can be used alone or in combination of two or more types.

[0018] For the ethylene and vinyl ester monomers, petroleum-derived raw materials such as naphtha are usually used. However, biomass-derived raw materials may also be used, such as raw materials derived from natural gases such as shale gas, or plant-derived or recycled monomers purified from components such as sugar and starch contained in sugarcane, sugar beet, corn, potato, etc., or components such as cellulose contained in plants such as rice, wheat, and millet.

[0019] The copolymerization of ethylene with a vinyl ester monomer can be carried out by any known polymerization method, such as solution polymerization, suspension polymerization, emulsion polymerization, etc., and solution polymerization using methanol as a solvent is generally used. The saponification of the obtained ethylene-vinyl ester copolymer can also be carried out by a known method.

[0020] The EVOH resin produced in this manner is composed mainly of ethylene structural units and vinyl alcohol structural units, and when the degree of saponification is less than 100 mol %, it contains a small amount of vinyl ester structural units remaining as unsaponified portions.

[0021] The content of the ethylene structural unit in the EVOH resin can be controlled by the ethylene pressure when copolymerizing the vinyl ester monomer with ethylene, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, and particularly preferably 25 to 35 mol%. When the content is equal to or higher than the lower limit, the gas barrier properties and melt moldability under high humidity conditions tend to be good, and when the content is equal to or lower than the upper limit, the gas barrier properties tend to be good. The content of the ethylene structural unit is usually １ It is measured by H-NMR measurement. For example, １ H-NMR measurement was performed using DMSO-d ６ The measurement method is performed using a thermocouple at a measurement temperature of 50°C.

[0022] The saponification degree of the EVOH resin can be controlled by the amount, temperature, time, etc. of the saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used) used when saponifying the ethylene-vinyl ester copolymer, and is usually 90 to 100 mol%, preferably 95 to 100 mol%, particularly preferably 99 to 100 mol%. When the saponification degree is equal to or greater than the lower limit, the gas barrier property, thermal stability, moisture resistance, etc. tend to be good. The saponification degree is usually １ It is measured by H-NMR measurement. For example, １ H-NMR measurement was performed using DMSO-d ６ The measurement method is performed using a thermocouple at a measurement temperature of 50°C.

[0023] The melt flow rate (MFR, 210°C, 2160 g load) of the EVOH resin is typically 0.5 to 100 g / 10 min, preferably 1 to 50 g / 10 min, and particularly preferably 3 to 35 g / 10 min. When the MFR is equal to or less than the upper limit, the resin tends to have excellent film-forming properties, while when the MFR is equal to or greater than the lower limit, the resin tends to have good melt extrudability without becoming too viscous. The MFR is an indicator of the degree of polymerization of the EVOH resin and can be adjusted by the amount of polymerization initiator and the amount of solvent used when copolymerizing ethylene with a vinyl ester monomer. In this specification, the MFR can be measured in accordance with JIS K 7210.

[0024] The EVOH resin may further contain structural units derived from the comonomers shown below within a range that does not impair the effects of the present invention (for example, 10 mol % or less of the EVOH resin).Examples of comonomers include olefins such as propylene, 1-butene, and isobutene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 3-butene-1,2-diol, 4-penten-1-ol, and 5-hexene-1,2-diol, and derivatives thereof such as esters and acylation products; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloyloxy-2-methylenepropane. hydroxyalkylvinylidene diacetates such as hydroxy-2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, or their salts or mono- or di-alkyl esters in which the alkyl group has 1 to 18 carbon atoms; acrylamide, N-alkylacrylamide in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salt, acrylamidopropyldimethylamine or its acid salt or quaternary salt, etc. acrylamides such as methacrylamide, N-alkylmethacrylamides in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or an acid salt or a quaternary salt thereof, and the like; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers in which the alkyl group has 1 to 18 carbon atoms, hydrochlorides, and the like. vinyl ethers such as alkoxyalkyl vinyl ether and alkoxyalkyl vinyl ether; halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamido-2-methylpropanesulfonic acid.These may be used alone or in combination of two or more.

[0025] In particular, EVOH resins copolymerized with hydroxy group-containing α-olefins, i.e., EVOH resins having hydroxy groups in the side chains, are preferred because they exhibit good secondary moldability while maintaining gas barrier properties, more preferred are EVOH resins having primary hydroxy groups in the side chains, and particularly preferred are EVOH resins having a 1,2-diol structure in the side chains.

[0026] As the EVOH resin having a primary hydroxyl group in a side chain, the content of structural units derived from a monomer having the primary hydroxyl group is preferably usually 0.1 to 20 mol %, more preferably 0.5 to 15 mol %, and particularly preferably 1 to 10 mol %, of the structural units of the entire EVOH resin.

[0027] The EVOH resin may also be "post-modified" such as urethanized, acetalized, cyanoethylated, or oxyalkylened.

[0028] Furthermore, the EVOH resin may be a mixture of two or more kinds of EVOH resins, for example, EVOH resins having different degrees of saponification, different degrees of polymerization, or different copolymerization components.

[0029] The content of the EVOH resin in the resin layer (A) is not particularly limited and may be 1% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, etc., but it is preferable that the EVOH resin is the main component. The content of the EVOH resin in the resin layer (A) is more preferably 50% by mass or more, even more preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass.

[0030] The resin layer (A) may contain a PA resin in addition to the EVOH resin.

[0031] [PA Resin] The PA resin is not particularly limited, and examples thereof include homo-PA resins and copolymer PA resins. Examples of the homo-PA resins include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), and polylauryl lactam (nylon 12). Examples of the copolymer PA resins include polyethylenediamineadipamide (nylon 26), polytetramethyleneadipamide (nylon 46), polyhexamethyleneadipamide (nylon 66), polyhexamethylenesebacamide (nylon 610), polyhexamethylenedodecamide (nylon 612), polyoctamethyleneadipamide (nylon 86), polydecamethyleneadipamide (nylon 108), caprolactam / lauryl Lactam copolymer (nylon 6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon 6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon 6 / 66), lauryllactam / hexamethylenediammonium adipate copolymer (nylon 12 / 66), ethylenediamine adipamide / hexamethylenediammonium adipate copolymer (nylon 26 / 66), caprolactam / hexamethylene Examples of the PA resin include aliphatic polyamides such as diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 66 / 610) and ethylene ammonium adipate / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 6 / 66 / 610), aromatic polyamides such as polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polymetaxylylene adipamide, hexamethylene isophthalamide / terephthalamide copolymer, poly-p-phenylene terephthalamide, and poly-p-phenylene-3,4'-diphenyl ether terephthalamide, amorphous polyamides, PA resins modified with aromatic amines such as methylenebenzylamine and metaxylylene diamine (e.g., polyamide MXD6 (polymetaxylylene adipamide)), and metaxylylene diammonium adipate. The PA resin may also be a terminal-modified PA resin.These PA resins can be used alone or in combination of two or more. Among them, terminal-modified PA resins are preferred.

[0032] The melting point of the PA resin is usually preferably 160 to 270°C, more preferably 180 to 250°C, and particularly preferably 200 to 240°C. When the melting point of the PA resin is equal to or higher than the lower limit, the heat resistance tends to be excellent. On the other hand, when the melting point of the PA resin is equal to or lower than the upper limit, the difference in melting point with the resins used in other layers tends to be small, resulting in good moldability. From the above viewpoints, preferred PA resins include, for example, nylon 6 (melting point: about 220°C), nylon 6 / 66 (melting point: about 200°C), and polyamide MXD6 (melting point: about 237°C).

[0033] When the resin layer (A) contains a PA resin, the content thereof is usually 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[0034] The resin layer (A) may contain, as optional components, known additives such as plasticizers, lubricants, heat stabilizers, light stabilizers, UV absorbers, antioxidants, crystal nucleating agents, colorants, antistatic agents, surfactants, antibacterial agents, desiccants, oxygen absorbers, antiblocking agents, and inorganic fillers, within a range that does not impair the effects of the present invention (for example, less than 30% by mass, preferably less than 5% by mass). These may be used alone or in combination of two or more.

[0035] [Polyolefin Resin Layer (B)] The polyolefin resin layer (B) constituting the present multilayer structure (1) contains a polyolefin resin (b1) and an amine-modified resin (b2), but does not contain an EVOH resin. The present multilayer structure (1) has a polyolefin resin layer (B) containing a polyolefin resin (b1) and an amine-modified resin (b2). The amine-modified resin (b2) functions as a compatibilizer, thereby improving the overall compatibility of the present multilayer structure (1) after recycling and facilitating recycling of the multilayer structure. International Publication No. 2023 / 182479 discloses that a resin composition obtained during recycling of scraps generated in the manufacturing process of a multilayer structure using a polyolefin resin and an EVOH resin is used as a regrind resin composition. However, as mentioned above, the present multilayer structure (1) is distinguished from the multilayer structure containing a regrind layer disclosed in International Publication No. 2023 / 182479 because the polyolefin resin layer (B) does not contain an EVOH resin.

[0036] The polyolefin resin layer (B) constituting the present multilayer structure (2) contains a polyolefin resin (b1) and an amine-modified resin (b2). The present multilayer structure (2) has the polyolefin resin layer (B) containing the polyolefin resin (b1) and the amine-modified resin (b2), and the amine-modified resin (b2) functions as a compatibilizer, so that the compatibility of the present multilayer structure (2) as a whole after recycling can be improved, and recycling of the multilayer structure can be facilitated.

[0037] The total content of the polyolefin resin (b1) and the amine-modified resin (b2) in the polyolefin resin layer (B) is not particularly limited, and may be 1% by mass or more, 2% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, etc., but the total content of the polyolefin resin (b1) and the amine-modified resin (b2) in the polyolefin resin layer (B) is more preferably 50% by mass or more, further preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass.

[0038] [Polyolefin Resin (b1)] The polyolefin resin (b1) used in the polyolefin resin layer (B) is not particularly limited, and examples thereof include polyethylenes such as linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ionomers, ethylene-propylene (block or random) copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid copolymers, ethylene-methacrylic acid ester copolymers, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers, ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers, polybutene, polypentene, polymethylpentene, and other olefin homopolymers or copolymers, or blends thereof. These may be used alone or in combination of two or more. Among these, the polyolefin resin (b1) is preferably polyethylene, and is particularly preferably at least one selected from the group consisting of linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene, in that the effects of the present invention are particularly excellent. Note that linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene are terms commonly used to represent types of polyethylene.

[0039] The melt flow rate (MFR) (190° C., load 2160 g) of the polyolefin resin (b1) is usually 0.1 to 50 g / 10 min, preferably 0.5 to 30 g / 10 min.

[0040] The content of the polyolefin resin (b1) in the polyolefin resin layer (B) is not particularly limited, but is preferably 1 to 99% by mass, more preferably 20 to 98% by mass, and particularly preferably 35 to 95% by mass. From the viewpoint of recyclability, it is preferable that the content is within the above range.

[0041] [Amine-modified resin (b2)] The polyolefin resin layer (B) contains an amine-modified resin (b2). The present multilayer structure contains the amine-modified resin (b2), and this amine-modified resin (b2) acts as a compatibilizer, so that a chemical reaction with the EVOH resin does not occur during the recycling process, and the generation of crosslinked gel can be suppressed.

[0042] The amine-modified resin (b2) is preferably an amine-modified elastomer from the viewpoint of recyclability.

[0043] The amine-modified elastomer has an amino group at least partially contained in an elastomer (thermoplastic elastomer) and is obtained by introducing an amino group into the elastomer. The amino group may be a primary amino group, a secondary amino group, or a tertiary amino group, with a primary amino group or a secondary amino group being particularly preferred. An organic amine is usually used to introduce the amino group into the elastomer.

[0044] Specific examples of the organic amine include alkylamines, alkenylamines, arylamines, aralkylamines, and cyclic nitrogen-containing compounds.

[0045] Examples of the alkylamines include methylamine, ethylamine, propylamine, isopropylamine, n-butylamine, s-butylamine, isobutylamine, t-butylamine, and pentylamine. Examples of the alkenylamines include dodecenylamine, octadecenylamine, and docosenylamine. Examples of the arylamines include aniline, methylaniline, ethylaniline, p-isopropylaniline, and N-methylaniline. Examples of the aralkylamines include benzylamine, 1-phenylethylamine, and 2-phenylethylamine. Examples of the cyclic nitrogen-containing compounds include cyclic alkylamines such as cyclohexylamine and dicyclohexylamine; cyclic imides such as imidazolidinone; and heterocyclic amines such as thienylamine and quinolylamine. These organic amines can be used alone or in combination of two or more.

[0046] From the viewpoint of compatibility, the modification amount with the organic amine is preferably 0.1 to 20 mol %. Here, the modification amount with the organic amine represents the ratio (mol %) of the partial structure derived from the organic amine to the total number of moles of the structural units constituting the amine-modified elastomer. It is preferably 0.001 to 10, more preferably 0.01 to 5.0.

[0047] The amine-modified elastomer is preferably an amine-modified block copolymer of an aromatic vinyl compound and an olefin and / or a hydrogenated product thereof, and from the viewpoint of improving compatibility between different resins, an amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene and / or a hydrogenated product thereof is particularly preferred.

[0048] Examples of the aromatic vinyl compound include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, and p-tert-butylstyrene. These compounds can be used alone or in combination of two or more. Among these, styrene is preferred.

[0049] Examples of the olefin include ethylene, butylene, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and farnesene. These can be used alone or in combination of two or more. Of these, conjugated dienes such as 1,3-butadiene and isoprene are preferred.

[0050] The amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene preferably has a block containing structural units derived from styrene and a block containing structural units derived from the conjugated diene, and is preferably a block copolymer containing a block mainly containing structural units derived from styrene and a block mainly containing structural units derived from the conjugated diene. Here, "mainly containing" means that the target block contains 60 mass% or more of the target structural units derived from styrene or the target structural units derived from the conjugated diene.

[0051] As the conjugated diene, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred, from the viewpoints of availability and productivity. That is, as the amine-modified polystyrene elastomer, an amine-modified styrene-butadiene block copolymer elastomer or a hydrogenated product thereof is preferred because it can be easily produced industrially and is already commercially available.

[0052] Furthermore, the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene may contain, in addition to the structural units derived from styrene and the structural units derived from the conjugated diene, structural units derived from other monomers copolymerizable with styrene and the conjugated diene.

[0053] The content of structural units derived from aromatic vinyl compounds in the block copolymer of an aromatic vinyl compound and a conjugated diene is preferably 2 to 40% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass. When the content of structural units derived from aromatic vinyl compounds in the block copolymer of an aromatic vinyl compound and a conjugated diene is equal to or greater than the above-mentioned lower limit, aggregation of the block copolymer of aromatic vinyl compounds and a conjugated diene tends to be prevented, and the generation of gel tends to be effectively suppressed. Furthermore, when the content of structural units derived from aromatic vinyl compounds in the block copolymer of an aromatic vinyl compound and a conjugated diene is equal to or less than the above-mentioned upper limit, good compatibility between different resins tends to be ensured.

[0054] The content of structural units derived from conjugated dienes in the block copolymer of an aromatic vinyl compound and a conjugated diene is preferably 60 to 98% by mass, more preferably 65 to 97% by mass, and even more preferably 70 to 95% by mass. Having the content of structural units derived from conjugated dienes in the block copolymer of an aromatic vinyl compound and a conjugated diene equal to or greater than the above-mentioned lower limit tends to ensure good compatibility between different resins. Furthermore, having the content of structural units derived from conjugated dienes in the block copolymer of an aromatic vinyl compound and a conjugated diene equal to or less than the above-mentioned upper limit tends to prevent aggregation of the block copolymer of an aromatic vinyl compound and a conjugated diene, thereby effectively suppressing gel formation.

[0055] The content of structural units derived from the aromatic vinyl compound in a block copolymer of an aromatic vinyl compound and a conjugated diene can be measured using a nuclear magnetic resonance (NMR) spectrometer after isolating the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene. The content of structural units derived from the aromatic vinyl compound can be controlled by adjusting the amount of aromatic vinyl compound added in the polymerization step of the block copolymer of an aromatic vinyl compound and a conjugated diene.

[0056] The vinyl bond content of the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene (when the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene is a hydrogenated product, the vinyl bond content before hydrogenation) is preferably 20 to 100 mol % from the viewpoints of the flowability of the amine-modified block copolymer component of an aromatic vinyl compound and a conjugated diene and its compatibility with polyolefin resins. The "vinyl bond content before hydrogenation" refers to the 1,2-bond content (mol %) relative to the total amount of 1,4-bonds (cis and trans) and 1,2-bonds (however, when a 3,4-bond is incorporated into the block copolymer of an aromatic vinyl compound and a conjugated diene that has been amine-modified with a 3,4-bond, this refers to the total amount of 1,2-bonds and 3,4-bonds) resulting from the conjugated diene incorporated into the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene before hydrogenation. The vinyl bond content before hydrogenation of the block containing a structural unit derived from a conjugated diene is more preferably 30 to 90 mol %, and even more preferably 35 to 80 mol %.

[0057] The vinyl bond content in the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene can be measured by isolating the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene and then using a nuclear magnetic resonance (NMR) spectrometer, etc. The vinyl bond content can be controlled within the above-mentioned range by using a Lewis base, such as an ether or an amine, as a vinyl bond amount adjuster (hereinafter referred to as a vinylating agent).

[0058] When the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene is a hydrogenated product, the hydrogenation rate of the block containing structural units derived from the conjugated diene is preferably 0 to 100 mol%, and from the viewpoint of compatibility with polyolefin resins, the hydrogenation rate is preferably greater than 0 mol%. The hydrogenation rate of the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene is preferably 40 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%. The hydrogenation rate of the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene can be measured using a nuclear magnetic resonance (NMR) spectrometer or the like. The hydrogenation rate can be controlled within the above numerical range, for example, by adjusting the amount of hydrogen during the hydrogenation step.

[0059] The melt flow rate (MFR: 230°C, load 2.16 kg, in accordance with ISO 1133) of the amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene is preferably in the range of 0.1 to 50 g / 10 min, more preferably in the range of 0.5 to 30 g / 10 min, and even more preferably in the range of 1.0 to 25 g / 10 min, from the viewpoint of processability of the thermoplastic resin composition.

[0060] Amine-modified block copolymers of aromatic vinyl compounds and conjugated dienes are available as commercially available products, including, but not limited to, "TUFTECH (trademark) MP10" manufactured by Asahi Kasei Corporation.

[0061] Specific examples of the amine-modified resin (b2) include amine-modified styrene-ethylene-butylene-styrene block copolymer (amine-modified SEBS), amine-modified styrene-butadiene-butylene-styrene block copolymer (amine-modified SBBS), amine-modified hydrogenated styrene-ethylene-butylene-styrene block copolymer (amine-modified HSEBS), amine-modified hydrogenated styrene-butadiene-butylene-styrene block copolymer (amine-modified HSBBS), amine-modified hydrogenated styrene-butadiene copolymer rubber (amine-modified HSBR), amine-modified styrene-butadiene-styrene block copolymer (amine-modified SBS), amine-modified styrene-isoprene-styrene copolymer (amine-modified SIS), and amine-modified styrene-ethylene-propylene-styrene block copolymer (amine-modified SEPS). These can be used alone or in combination of two or more. Among these, amine-modified hydrogenated styrene-butadiene-butylene-styrene block copolymer (amine-modified HSBBS) is preferred because of its excellent compatibility with polyolefin resins when recycled.

[0062] The content of the amine-modified resin (b2) in the polyolefin resin layer (B) is not particularly limited, but is preferably 1 to 99% by mass, more preferably 5 to 60% by mass, and particularly preferably 5 to 40% by mass. From the viewpoint of moldability, it is preferable that the content be within the above range.

[0063] The content of the amine-modified resin (b2) in the multilayer structure (1) is 12 to 280 parts by mass, preferably 15 to 270 parts by mass, more preferably more than 20 to 250 parts by mass, even more preferably 50 to 200 parts by mass, particularly preferably 80 to 180 parts by mass, and especially preferably 100 to 160 parts by mass, per 100 parts by mass of the EVOH resin. When the content of the amine-modified resin (b2) is within the above range, a decrease in the tear strength of the multilayer structure can be suppressed. Furthermore, when the content of the amine-modified resin (b2) is equal to or greater than the lower limit, the compatibility between the EVOH resin and the polyolefin resin (b1) is improved during the recycling process, which tends to suppress an increase in haze and a decrease in impact resistance after recycling. Furthermore, when the content of the amine-modified resin (b2) is equal to or less than the upper limit, a decrease in the tear strength of the multilayer structure can be suppressed. This is presumably because the amount of amine-modified resin (b2) is not too large, which makes it possible to suppress an increase in the interface between the polyolefin resin (b1) and the amine-modified resin (b2) in the polyolefin matrix in the polyolefin resin layer.

[0064] The content of the amine-modified resin (b2) in the multilayer structure (2) is more than 20 parts by mass and not more than 280 parts by mass, preferably 50 parts by mass or more and not more than 200 parts by mass, more preferably 80 parts by mass or more and not more than 180 parts by mass, and even more preferably 100 parts by mass or more and not more than 160 parts by mass, per 100 parts by mass of the EVOH resin. When the content of the amine-modified resin (b2) is within the above range, a decrease in the tear strength of the multilayer structure can be suppressed. Furthermore, when the content of the amine-modified resin (b2) is equal to or greater than the lower limit, the compatibility between the EVOH resin and the polyolefin resin (b1) is improved during the recycling process, which tends to suppress an increase in haze and a decrease in impact resistance after recycling. Furthermore, when the content of the amine-modified resin (b2) is equal to or less than the upper limit, a decrease in the tear strength of the multilayer structure can be suppressed. This is presumably because the amount of amine-modified resin (b2) is not too large, which makes it possible to suppress an increase in the interface between the polyolefin resin (b1) and the amine-modified resin (b2) in the polyolefin matrix in the polyolefin resin layer.

[0065] The polyolefin resin layer (B) may contain, in addition to the amine-modified resin (b2), a compatible resin (b3) having compatibility with the EVOH resin and the polyolefin resin (b1).

[0066] The compatible resin (b3) is not particularly limited, but examples thereof include olefin resins modified with epoxy groups, carboxy groups, or their anhydride groups, or copolymerized with monomers having epoxy groups, carboxy groups, or their anhydride groups.Among these, the polar group-containing olefin resin is preferably an olefin resin copolymerized with monomers having epoxy groups, carboxy groups, or their anhydride groups, and particularly preferably a multi-component polar group-containing olefin copolymer.As the anhydride, maleic anhydride is preferred.

[0067] The multi-component polar group-containing olefin copolymer contains three components: a non-polar monomer selected from ethylene and an α-olefin having 3 to 10 carbon atoms; a polar group-containing monomer selected from monomers having at least one selected from the group consisting of an epoxy group, a carboxy group, and a dicarboxylic acid anhydride group; and another monomer.

[0068] Specific examples of the multi-component polar group-containing olefin copolymer include ethylene-acrylic acid-methyl acrylate copolymer, ethylene-acrylic acid-ethyl acrylate copolymer, ethylene-acrylic acid-vinyl acetate copolymer, ethylene-methacrylic acid-methyl methacrylate copolymer, ethylene-methacrylic acid-ethyl methacrylate copolymer, ethylene-methacrylic acid-vinyl acetate copolymer, ethylene-maleic anhydride-methyl acrylate copolymer, ethylene-maleic anhydride-ethyl acrylate copolymer, ethylene-maleic anhydride-methyl methacrylate copolymer, ethylene-maleic anhydride-ethyl methacrylate copolymer, and ethylene-maleic anhydride-vinyl acetate copolymer.

[0069] When the polyolefin resin layer (B) contains a compatible resin (b3), the content of the compatible resin in the polyolefin resin layer (B) is usually less than 50% by mass, and may be 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. When the content of the compatible resin is within the above range, the generation of crosslinked gel can be further suppressed during the recycling process.

[0070] The mass ratio of the amine-modified resin (b2) to the compatible resin (b3) (amine-modified resin (b2) / compatible resin (b3)) is usually 95 / 5 to 51 / 49, preferably 90 / 10 to 55 / 45, and more preferably 80 / 20 to 60 / 40. When the mass ratio of the amine-modified resin (b2) to the compatible resin (b3) is within the above range, the generation of crosslinked gel during the recycling step tends to be more effectively suppressed.

[0071] The polyolefin resin layer (B) may contain, as optional components, known additives such as plasticizers, lubricants, heat stabilizers, light stabilizers, UV absorbers, antioxidants, crystal nucleating agents, colorants, antistatic agents, surfactants, antibacterial agents, desiccants, oxygen absorbers, antiblocking agents, and inorganic fillers, within a range that does not impair the effects of the present invention (for example, less than 30% by mass, preferably less than 5% by mass), and may also be blended with other polyolefin resins or compatibilizers. These may be used alone or in combination of two or more.

[0072] Furthermore, the present multilayer structure (2) may contain the EVOH resin within a range that does not impair the effects of the present invention (for example, less than 30% by mass, preferably less than 5% by mass of the polyolefin resin layer (B)).

[0073] [Adhesive Resin Layer (C)] The present multilayer structure preferably further includes an adhesive resin layer (C). The adhesive resin layer (C) can be provided as a layer for adhering the resin layer (A) and the polyolefin resin layer (B) together.

[0074] Examples of the adhesive resin (c) contained in the adhesive resin layer (C) include modified polyolefin polymers containing carboxy groups obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to a polyolefin resin by addition reaction, graft reaction, or the like. Examples of the modified polyolefin polymers containing carboxy groups include maleic anhydride-modified polymers such as maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene (block and random) copolymers, maleic anhydride-modified ethylene-ethyl acrylate copolymers, maleic anhydride-modified ethylene-vinyl acetate copolymers, maleic anhydride-modified polycyclic olefin resins, and maleic anhydride-modified polyolefin resins. These may be used alone or in combination of two or more.

[0075] As the adhesive resin (c), maleic anhydride-modified polymers such as maleic anhydride-modified polyethylene and maleic anhydride-modified ethylene-α-olefin copolymer are particularly suitable, in that they contribute not only to the adhesiveness of the resin but also to the effect of suppressing gel generation during melt heating and the effect of suppressing a decrease in transparency.

[0076] The acid value of the maleic anhydride-modified polymer is usually 50 mgKOH / g or less, preferably 30 mgKOH / g or less, and particularly preferably 20 mgKOH / g or less. When the acid value is below the upper limit, the reaction sites with the hydroxyl groups in the EVOH resin are in an appropriate range, the formation of highly polymerized products during the melt-kneading process is suppressed, stability during extrusion processing is improved, and a good molded product tends to be obtained. The lower limit of the acid value is usually 1 mgKOH / g, preferably 2 mgKOH / g. The acid value is measured in accordance with JIS K 0070.

[0077] When maleic anhydride-modified polyethylene is used as the maleic anhydride-modified polymer, the MFR (190°C, load 2160 g) is usually 0.01 to 150 g / 10 min, preferably 0.1 to 50 g / 10 min, more preferably 1 to 25 g / 10 min, and even more preferably 3 to 10 g / 10 min.

[0078] Furthermore, when a maleic anhydride-modified ethylene-α-olefin copolymer is used as the maleic anhydride-modified polymer, the MFR (230°C, load 2160 g) is usually 0.1 to 150 g / 10 min, preferably 0.5 to 100 g / 10 min, more preferably 1 to 50 g / 10 min, and even more preferably 5 to 35 g / 10 min. When the MFR is within the above range, moldability tends to be improved when molding a multilayer structure.

[0079] The adhesive resin layer (C) may contain any additives, such as heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, neutralizers, rust inhibitors, and pigments, within the range that does not impair the effects of the present invention (e.g., less than 30% by mass).

[0080] <Multilayer structure> Next, the present multilayer structure will be described. The present multilayer structure has the resin layer (A), the polyolefin resin layer (B), and preferably the adhesive resin layer (C), but the layer configuration other than these is not particularly limited.

[0081] Examples of the layer configuration of the multilayer structure include a configuration (A / C / B) in which a polyolefin resin layer (B) is laminated on a resin layer (A) via an adhesive resin layer (C), and a configuration (B / C / A / C / B) in which a polyolefin resin layer (B) is laminated on both sides of a resin layer (A) via an adhesive resin layer (C). Another layer (D), described below, may be laminated between or on the surface of these layers.

[0082] The lamination method of this multilayer structure can be carried out by a known method. For example, a method of melt-extrusion laminating the adhesive resin layer (C) and the polyolefin resin layer (B) onto a film or sheet that will become the resin layer (A), a method of melt-extrusion laminating the resin composition that will become the resin layer (A) onto the adhesive resin layer (C) or the polyolefin resin layer (B), or a method of co-extrusion of three layers (A), (B), and (C). Another example is a method of applying a solution of the resin composition that will become the resin layer (A) onto the polyolefin resin layer (B) provided with the adhesive resin layer (C), and then removing the solvent. Among these, the co-extrusion method is preferred from the viewpoints of cost and environment.

[0083] [Other Layers (D)] The multilayer structure may have at least one other layer (D) laminated between or on the surface of the layers (A) to (C). Examples of the other layer (D) include a substrate layer (D1) for adding strength to the multilayer structure, and an adhesive layer (D2) for bonding the substrate layer (D1) to the layers (A) to (C).

[0084] [Substrate Layer (D1)] Various thermoplastic resins (d1) [hereinafter referred to as "substrate resin (d1)"] are used as materials for the substrate layer (D1). Furthermore, recycled compositions obtained by remelting and molding edges or defective products generated during the manufacturing process of the present multilayer structure may also be used as the material. Such recycled compositions may contain a molten mixture of the resin layer (A), the polyolefin resin layer (B), the adhesive resin layer (C), and another layer (D).

[0085] Examples of the base resin (d1) used in the base layer (D1) include polyethylene resins such as linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; polypropylene resins such as polypropylene and propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; (unmodified) polyolefin resins such as polybutene and polypentene; and polyolefins modified with unsaturated carboxylic acids and / or esters thereof. Examples include polyolefin resins in the broad sense, including modified polyolefin resins such as graft-modified unsaturated carboxylic acid-modified polyolefin resins, cyclic olefin resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polyester resins, PA resins (including copolymerized polyamides), polyvinyl chloride, polyvinylidene chloride, acrylic resins, polystyrene, vinyl ester resins, polyester elastomers, polyurethane elastomers, halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, aromatic or aliphatic polyketones, etc. These can be used alone or in combination of two or more.

[0086] [Adhesive Layer (D2)] As the adhesive (d2) used in the adhesive layer (D2) for bonding the base layer (D1) to the layers (A) to (C), for example, known adhesives such as organic titanium compounds, isocyanate compounds, polyester compounds, polyurethane compounds, etc. can be used, and may be appropriately selected depending on the type of thermoplastic resin constituting the base layer (D1). Furthermore, as a layer for bonding the base layer (D1) to the layers (A) to (B) or the layers (A) to (C), in addition to the adhesive layer (D2), an adhesive resin layer (C) may also be used.

[0087] The base layer (D1) and the adhesive layer (D2) may contain conventionally known plasticizers, fillers, clays (montmorillonite, etc.), colorants, antioxidants, antistatic agents, lubricants, core materials, antiblocking agents, ultraviolet absorbers, waxes, etc., within a range that does not impair the spirit of the present invention (for example, 30% by mass or less, preferably 10% by mass or less).

[0088] When the present multilayer structure includes at least one other layer (D) such as a substrate layer (D1) or an adhesive layer (D2), for example, the following production method can be mentioned.

[0089] (i) a method of laminating all layers by co-extruding a resin that will become the (A)-(B) layers or the (A)-(C) layers with a resin that will become the other layer (D); (ii) a method of forming the other layer (D) by dry laminating a separately formed film, sheet, etc., with the (A)-(B) layers or the (A)-(C) layers; (iii) a method of laminating a separately formed film, sheet, etc., that will become the other layer (D) or a laminate surface of an appropriate combination of these by melt co-extruding a resin that will become the (A)-(B) layers or the (A)-(C) layers; (iv) a method of applying a solution of a resin that will become the other layer (D) to the (A)-(B) layers or the (A)-(C) layers and then removing the solvent.

[0090] Among these, from the viewpoint of productivity, the method (i) of co-extruding the resin for layers (A) and (B) or layers (A) to (C) with the resin for other layer (D) is preferred.

[0091] Furthermore, even when obtaining a multilayer structure having a three-kind five-layer structure in which, for example, polyolefin resin layers (B) are laminated on both sides of a resin layer (A) via adhesive resin layers (C) without using other layers (D), the method of co-extruding these layers all at once is preferred, as already mentioned above.

[0092] In the case of co-extrusion molding, the extrusion molding temperature (barrel temperature of the extruder) of the resin composition is appropriately set in the range of usually 150 to 300°C, preferably 160 to 250°C.

[0093] In the present invention, the barrel temperature of the extruder means the surface temperature of the barrel of the extruder. If the barrel of the extruder has multiple sections and each section is set to a different temperature, the highest temperature among the sections is taken as the barrel temperature.

[0094] The obtained multilayer structure may be subjected to a (heat) stretching treatment, if necessary. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, it may be simultaneous stretching or sequential stretching. Furthermore, the stretching method may be a roll stretching method, tenter stretching method, tubular stretching method, stretch-blow method, vacuum pressure forming, or the like, whichever provides a higher stretch ratio. The stretching temperature is selected from the range of usually 40 to 170°C, preferably about 60 to 160°C, in the vicinity of the multilayer structure. If the stretching temperature is too low, the stretchability will be poor, and if it is too high, it will tend to be difficult to maintain a stable stretched state.

[0095] For the purpose of imparting dimensional stability after stretching, heat setting may be further carried out by known means, for example, by subjecting the multilayer structure (in the form of a stretched film) to heat treatment while maintaining tension, usually at 80 to 180°C, preferably 100 to 165°C, for usually about 2 to 600 seconds.

[0096] The thickness of the present multilayer structure (including the stretched structure), as well as the thickness of the resin layer (A), polyolefin resin layer (B), and adhesive resin layer (C) constituting the present multilayer structure, cannot be generally determined depending on the layer configuration, the type of resin in each layer, the intended use, packaging form, required physical properties, etc., but the overall thickness of the multilayer structure is typically 10 to 5,000 μm, preferably 30 to 3,000 μm, and particularly preferably 50 to 2,000 μm. The thickness of the resin layer (A) (single layer) is typically 1 to 500 μm, preferably 3 to 300 μm, and particularly preferably 5 to 200 μm. The thickness of the polyolefin resin layer (B) (single layer) is typically 1 to 300 μm, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm. The thickness of the adhesive resin layer (C) (single layer) is typically 0.5 to 250 μm, preferably 1 to 150 μm, and particularly preferably 2 to 100 μm. The thickness (single layer) of the substrate layer (D1) is usually 1 to 500 μm, preferably 3 to 300 μm, and particularly preferably 5 to 200 μm. The thickness (single layer) of the adhesive layer (D2) is usually 0.5 to 250 μm, preferably 1 to 150 μm, and particularly preferably 2 to 100 μm.

[0097] The ratio A / B of the thickness of the resin layer (A) to the thickness of the polyolefin resin layer (B) (both are single layer thicknesses) is usually 1 / 50 to 10 / 1, preferably 1 / 30 to 5 / 1, and particularly preferably 1 / 10 to 3 / 1. When A / B is within the above range, the effects of the present invention can be more effectively obtained.

[0098] The tear strength of the present multilayer structure is usually 3.5 N or more, preferably 4.0 N or more, and more preferably 4.5 N or more. There is no particular upper limit, but it is usually 10 N or less. The tear strength of the present multilayer structure can be measured, for example, by the method described in the Examples below.

[0099] [Recyclable multilayer structure, recycled composition, recycled molded article] The present multilayer structure contains a specific amine-modified resin (b2) in a specific proportion, which can suppress a decrease in tear strength before recycling and can be easily recycled, making it suitable as a recyclable multilayer structure. To recycle the present multilayer structure, the present multilayer structure can be melt-kneaded according to a conventional method to form a recycled composition. The obtained recycled composition can be molded and used suitably as a recycled molded article.

[0100] [Uses of Multilayer Structure and Recycled Molded Article] The multilayer structure and recycled molded article can be suitably used as a gas barrier layer for various packaging materials, such as packaging containers and packaging films, for general foods, as well as seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc. In addition, the multilayer structure is suitable for recycling.

[0101] The present multilayer structure has excellent recyclability even when recycling scraps or molded articles of the multilayer structure without the need for a separate compatibilizer. Recycling involves using a recycled composition or the like, which is prepared by crushing and repelletizing scraps or molded articles of the multilayer structure. When films or the like are produced from this recycled composition or the like according to conventional methods, crosslinked gel between the EVOH resin and the amine-modified resin (b2) does not occur, resulting in good appearance and excellent impact resistance.

[0102] 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 as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0103] Prior to the examples, the following ingredients were prepared:

[0104] [EVOH resin] EVOH resin 1: EVOH resin (ethylene structural unit content 29 mol%, MFR 3.8 g / 10 min (210°C, load 2160 g), saponification degree 99.6 mol%) [Polyolefin resin (b1)] Polyolefin resin (b1-1): linear low-density polyethylene (LLDPE) ("UF641" manufactured by Japan Polyethylene Corporation, MFR: 2.1 g / 10 min (190°C, load 2160 g)) [Amine-modified resin (b2)] Amine-modified hydrogenated styrene-based thermoplastic elastomer (b2-1): amine-modified hydrogenated styrene-butadiene-butylene-styrene block copolymer ("TUFTECH (registered trademark) MP10" manufactured by Asahi Kasei Corporation, MFR (230°C, load 2160 g): 4.0 g / 10 min, density: 0.91 g / cm 3 ) [Compatible resin (b3)] Maleic anhydride copolymer resin (b3-1): ethylene-methyl acrylate-maleic anhydride copolymer resin ("Rexpearl (registered trademark) ET530H" manufactured by Japan Polyethylene Corporation, methyl acrylate content: 16%, MFR (190 ° C, load 2.16 kg): 30 g / 10 min, density: 0.945 g / cm 3 Maleic anhydride-modified polyolefin resin (b3-2): Maleic anhydride-modified polyethylene resin (MFR (190 ° C, load 2.16 kg): 2.5 g / 10 min, density: 0.910 g / cm 3 Adhesive resin (c) Adhesive resin (c1): Maleic anhydride-modified polyethylene (MFR: 1.0 g / 10 min (190°C, load 2160 g), density: 0.900 g / cm 3 Adhesive resin (c2): Maleic anhydride-modified polyethylene (MFR: 2.5 g / 10 min (190 ° C, load 2160 g), density: 0.920 g / cm 3 Base resin (d1): Linear low-density polyethylene (LLDPE) (UF230 manufactured by Japan Polyethylene Corporation, MFR: 1.0 g / 10 min (190°C, load 2160 g))

[0105] Example 1 95 parts of polyolefin resin 1 and 5 parts of amine-modified hydrogenated styrene-based thermoplastic elastomer (b2-1) were mixed to prepare a resin composition for the polyolefin resin layer (B). The resin composition for the polyolefin resin layer (B) prepared above, EVOH resin 1, adhesive resin (c1), and substrate resin (d1) were supplied to a five-type, seven-layer multilayer co-extrusion cast film-forming apparatus, and multilayer co-extrusion molding was carried out under the following conditions to obtain a four-type, seven-layer multilayer structure (film) of substrate layer (D1) / polyolefin resin layer (B) / adhesive resin layer (C) / resin layer (A) / adhesive resin layer (C) / polyolefin resin layer (B) / substrate layer (D1). The thicknesses (μm) of each layer of the multilayer structure were 44.6 / 44.6 / 3.1 / 15.6 / 3.1 / 44.6 / 44.6 (total 200 μm). The content of the amine-modified hydrogenated styrene-based thermoplastic elastomer (b2-1) was 20 parts per 100 parts of the EVOH resin in the resin composition containing the EVOH resin.

[0106] (Multilayer co-extrusion molding conditions) Resin layer (A) extruder: 40 mmφ single screw extruder (barrel temperature: 220°C) Polyolefin resin layer (B) extruder: 40 mmφ single screw extruder (barrel temperature: 210°C) Adhesive resin layer (C) extruder: 32 mmφ single screw extruder (barrel temperature: 210°C) Base material layer (D1) extruder: 50 mmφ single screw extruder (barrel temperature: 210°C) Die: 5-type 7-layer feedblock type T-die (die temperature: 210°C) Take-up speed: 11 m / min Roll temperature: 80°C

[0107] Examples 2 to 5, Comparative Examples 1 to 3, Reference Example 1 Multilayer structures were produced in the same manner as in Example 1, except for the changes shown in Table 1, and various evaluations were carried out according to the methods shown below.

[0108] [Tear Strength Evaluation] Using the obtained multilayer structures of Examples 1 to 5, Comparative Examples 1 to 3, and Reference Example 1, the Elmendorf tear strength was measured under the following measurement conditions. Evaluation was also carried out according to the following evaluation criteria. [Measurement Conditions] Apparatus: Elmendorf tear strength tester manufactured by Yasuda Seiki Seisakusho Sample: Width 63 mm, length 76 mm Conditions: Compliant with ISO 6383-2, TD direction Environment: 23°C, 50% RH [Evaluation Criteria] ◎ (excellent): Tear strength value is higher than that of Reference Example 1 ○ (very good): Tear strength value is within -2.0 N of the value of Reference Example 1 and is equal to or lower than that of Reference Example 1 × (poor): Tear strength value is more than -2.0 N from the value of Reference Example 1

[0109] <Evaluation of Recyclability> The multilayer structures of Examples 1 to 5, Comparative Examples 1 to 3, and Reference Example 1 were pulverized and melt-kneaded using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., TEX30α, D=25 mmφ, L / D=56) at a set temperature of 210°C, a screw rotation speed of 300 rpm, and an extrusion rate of 20 kg / h to produce recycled compositions. The resulting recycled compositions were then used in a single-layer T-die film molding machine (manufactured by GM Engineering, 40 mmφ, lip opening: 0.3 mm) at a set temperature of 220°C, a screw rotation speed of 60 rpm, and a recycled film having a film thickness of 0.1 mm. The resulting recycled films were used to perform various evaluations according to the methods described below.

[0110] [Film Impact Evaluation] The impact strength (kgf cm) of the produced recycled film was evaluated using a YSS film impact tester (manufactured by Yasuda Seiki Seisakusho, Model 181) in an atmosphere of 23°C and 50% RH. A total of 10 measurements were performed, and the average value was evaluated as the impact strength of the multilayer structure. The clamp inner diameter was 60 mm, the impact ball radius was 12.7 mm, and the pendulum lift angle was 90°. The impact strength of the multilayer structure indicated that the higher the numerical value, the better the impact strength, and conversely, the lower the numerical value, the worse the impact strength. [Evaluation Criteria] ◎ (excellent): Film impact value is 9.0 kgf cm or more; ○ (very good): Film impact value is 7.0 kgf cm or more but less than 9.0 kgf cm; △ (normal): Film impact value is 6.0 kgf cm or more but less than 7.0 kgf cm; × (poor): Film impact value is less than 6.0 kgf cm

[0111] [Dart Impact Evaluation] The impact strength (g) of the produced recycled film was evaluated by Method A in accordance with JIS K 7124-1 "Plastic Films and Sheets - Impact Test Method by Free Fall Dart Method" using an aluminum dart with a diameter of 38 mm and a mass of 32 g in an atmosphere of 23°C and 50% RH using a No. 613 Dart Impact Tester manufactured by Toyo Seiki Seisaku-sho, Ltd. [Evaluation Criteria] ◎ (excellent): Dart impact value is 500 g or more ○ (very good): Dart impact value is 350 g or more and less than 500 g × (poor): Dart impact value is less than 350 g

[0112] [Internal Haze] The internal haze of the produced recycled film was measured using a haze meter (n = 3) and the average value was calculated. The internal haze is an index for evaluating the dispersibility of the EVOH resin in the resin composition, and a smaller internal haze value means that the EVOH resin is finely dispersed and the appearance is better.

[0113] [Evaluation of Film Appearance] The produced recycled films were visually evaluated for the presence or absence of crosslinked gel.

[0114]

[0115] The results in Table 1 show that in Examples 1 to 5, which used a specific amount of amine-modified resin (b2) as a compatibilizer, no crosslinked gel occurred in the recycled film, and the physical properties of the recycled film were comparable to those of Reference Example 1 and Comparative Examples 1 to 3. On the other hand, in Comparative Example 3, which used a conventional compatibilizer, a modified polyolefin polymer containing a carboxy group, crosslinked gel occurred in the recycled film. Furthermore, in Comparative Example 1, in which the content of amine-modified resin (b2) was too low, the recycled film had slightly high internal haze and also a low dirt impact value. Furthermore, in Comparative Example 2, in which the content of amine-modified resin (b2) was too high, the tear strength when formed into a multilayer structure was low. This is presumably due to interfacial peeling between the polyolefin resin in the polyolefin matrix in the polyolefin resin layer and the amine-modified resin (b2) caused by excessive amine-modified resin (b2). In Comparative Example 3, which used a compatibilizer other than amine-modified resin (b2), gel occurred and the film impact value was also insufficient.

[0116] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0117] The multilayer structure can be suitably used as a gas barrier layer for various packaging materials, such as packaging containers and packaging films, for general foods as well as seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc. In addition, the multilayer structure is suitable for recycling.

Claims

1. A multilayer structure having a resin layer (A) containing an ethylene-vinyl alcohol copolymer and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is 12 parts by mass or more and 280 parts by mass or less per 100 parts by mass of the ethylene-vinyl alcohol copolymer in the resin layer (A), and the polyolefin resin layer (B) does not contain an ethylene-vinyl alcohol copolymer.

2. The multilayer structure according to claim 1, wherein the polyolefin resin (b1) is polyethylene.

3. The multilayer structure according to claim 1, wherein the polyolefin resin (b1) is at least one selected from the group consisting of linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

4. The multilayer structure according to claim 1 or 2, wherein the content of said amine-modified resin (b2) is more than 20 parts by mass per 100 parts by mass of said ethylene-vinyl alcohol copolymer.

5. The multilayer structure according to claim 1 or 2, wherein the amine-modified resin (b2) is an amine-modified elastomer.

6. The multilayer structure according to claim 1 or 2, wherein the amine-modified resin (b2) is an amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene.

7. The multilayer structure according to claim 1 or 2, wherein the polyolefin resin layer (B) further contains a compatible resin (b3).

8. The multilayer structure according to claim 1 or 2, further comprising an adhesive resin layer (C).

9. The multilayer structure according to claim 1 or 2, which is suitable for recycling.

10. A recycled composition obtained by melt-kneading the multilayer structure according to claim 1 or 2.

11. A recycled molded article obtained by molding the recycled composition according to claim 10.

12. A multilayer structure having a resin layer (A) containing an ethylene-vinyl alcohol copolymer and a polyolefin resin layer (B), wherein the polyolefin resin layer (B) contains a polyolefin resin (b1) and an amine-modified resin (b2), and the content of the amine-modified resin (b2) in the polyolefin resin layer (B) is more than 20 parts by mass and not more than 280 parts by mass per 100 parts by mass of the ethylene-vinyl alcohol copolymer.

13. The multilayer structure according to claim 12, wherein the polyolefin resin (b1) is polyethylene.

14. The multilayer structure according to claim 12, wherein the polyolefin resin (b1) is at least one selected from the group consisting of linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

15. The multilayer structure according to claim 13 or 14, wherein the amine-modified resin (b2) is an amine-modified elastomer.

16. The multilayer structure according to claim 13 or 14, wherein the amine-modified resin (b2) is an amine-modified block copolymer of an aromatic vinyl compound and a conjugated diene.

17. The multilayer structure according to claim 13 or 14, wherein the polyolefin resin layer (B) further contains a compatible resin (b3).

18. The multilayer structure according to claim 13 or 14, further comprising an adhesive resin layer (C).

19. The multilayer structure of claim 13 or 14, which is suitable for recycling.

20. A recycled composition obtained by melt-kneading the multilayer structure according to claim 13 or 14.

21. A recycled molded article obtained by molding the recycled composition according to claim 20.

Images