JP5452311B2 - Resin composition, molded article using the same, and multilayer structure - Google Patents

Description

  The present invention relates to a resin composition that imparts flexibility to an EVOH resin, and in particular, can withstand specifications such as deformation repeatedly applied over a long period of time, such as a liquid container represented by a bag for a bag-in-box. The present invention relates to a resin composition that can provide a molded product such as a film, a molded product using the resin composition, and a multilayer structure.

  The saponified ethylene-vinyl ester copolymer (hereinafter sometimes referred to as “EVOH resin”) has a very strong intermolecular force due to hydrogen bonding between hydroxyl groups present in the polymer side chain. Therefore, since the crystallinity is high and the intermolecular force is high even in the amorphous part, gas molecules and the like cannot pass through the EVOH resin film. For these reasons, films using EVOH resin exhibit excellent gas barrier properties and are used as packaging films for water and food / beverage products, and packaging container materials. On the other hand, EVOH resin molded products have the disadvantage that they lack flexibility due to their high crystallinity.

  Therefore, in applications requiring flexibility, it is generally performed by blending with a soft resin in order to impart flexibility to the EVOH resin molded product.

For example, in JP-A-10-87923 (Patent Document 1), a polymer block composed of a vinyl aromatic monomer unit and an isobutylene unit, such as styrene-isobutylene-styrene triblock copolymer (SIBS), are represented. A resin composition obtained by blending a block copolymer with a polymer block has been proposed.
Here, specifically, EVOH resin: block copolymer = 15: 85 to 85:15, preferably 80: so that the EVOH resin phase and the block copolymer phase independently constitute a continuous phase. 20 to 20:80, more preferably about 65:35 to 35:65 (paragraph 0043). In Patent Document 1, the phase composed of EVOH resin and the phase composed of block copolymer are distributed in an interpenetrating network structure, so that excellent gas barrier properties and the like are blocked based on the EVOH phase forming the network structure. It is described that flexibility can be exerted based on the block copolymer phase that has intruded into the network (paragraph number 0042).
On the other hand, even if the blend ratio of the EVOH resin and the triblock copolymer is within the above range due to the ethylene content and melt viscosity in the EVOH resin, the molecular weight of the triblock copolymer and the composition of the block components, the gas barrier property is inferior. It is also disclosed that JIS D hardness may increase (Reference Example 1 and Reference Example 2 in Table 2).

In JP-A 63-304043 (Patent Document 2), polyvinyl alcohol resins such as EVOH resin and block copolymers such as styrene-butadiene block copolymer and styrene-isoprene block copolymer are described. Modified block copolymer modified with unsaturated carboxylic acid instead of block copolymer because it is difficult to improve desired properties due to poor compatibility and non-uniformity due to poor mixing It has been proposed to use Since the modified block copolymer is more compatible with polar thermoplastic resins such as polyvinyl alcohol resins than the unmodified block copolymer, transparency is improved in a resin composition blended with these. Is disclosed.
Here, the resin composition of modified block copolymer: polar thermoplastic polymer = 98: 2 to 50:50 is useful as a modified composition of the modified block copolymer, and the modified block copolymer : Polar thermoplastic polymer = 2: 98-50: 50 It is described that the impact resistance of the polar thermoplastic polymer is improved. Specifically, it is shown that the resin composition mixed at a ratio of EVOH resin: modified block copolymer = 90: 10 to 75:25 significantly improves the Izod impact strength as compared with the EVOH resin. (Table 5).

Further, JP 2004-189916 A (Patent Document 3) describes a resin composition containing EVOH resin, block copolymer such as SBS, SIS, SEBS, unsaturated carboxylic acid-modified block copolymer, and rubber softener. Things are disclosed.
As the rubber softener, paraffin oil or the like is used as a component for softening or plasticizing the rubber component. The unsaturated carboxylic acid-modified block copolymer is blended as a component that improves gas barrier properties.
And from the point of balance between gas barrier properties and flexibility of the composition, EVOH resin: (block copolymer + unsaturated carboxylic acid-modified block copolymer + total amount of rubber softener) = 10: 90 to 40:60 Is preferred (paragraph 0043). Further, it is described that block copolymer: modified block copolymer = 20: 80 to 80:20 is preferable from the viewpoint of balance between mechanical performance and gas barrier property of the composition (paragraph number 0045).
Here, as mechanical properties, JIS A hardness and tensile breaking strength are measured and evaluated.

JP-A-10-87923 JP-A 63-304043 JP 2004-189916 A

  By the way, in recent years, when used as a film container filled with liquid, such as a bag for a bag in a box, it can be folded, and moreover can be flexibly adapted to irregular bending according to deformation and weight loss of the liquid inside. Is required. The flexibility required in such a case is a property different from hardness, impact resistance, and tensile strength, and the composition as described above does not necessarily have the required property and is an indeterminate shape. In an environment where the liquid is filled for a long time and transported for a long time, the film is repeatedly bent for a long time due to the deformation of the liquid. There is also a case.

  Moreover, when mix | blending a flexible component with EVOH resin, it is important to disperse | distribute a flexible component uniformly. For example, when the soft component can react with the EVOH resin, it may react with the EVOH resin during melt kneading to generate a highly polymerized product. When a highly polymerized product is generated, the melt viscosity becomes high and the molding processability is lowered, so that many fish eyes tend to be generated in the obtained film.

  The present invention has been made in view of the circumstances as described above, and its purpose is to repeatedly bend over a long period of time, such as a bag-in-box, and to specifications that are exposed to deformation, An object of the present invention is to provide a resin composition capable of obtaining a film having flexibility that does not cause pinholes and the like, and that is less likely to generate fish eyes.

The resin composition of the present invention comprises an ethylene-vinyl ester copolymer saponified product (A) having an ethylene content of 20 to 60 mol%; a polymer block (b1) mainly comprising aromatic vinyl units, and unsaturated aliphatic carbonization. A block copolymer (B) having a hydrogenated block (b2) of a polymer obtained by polymerizing hydrogen; a polymer block (c1) mainly comprising an aromatic vinyl unit, and an unsaturated aliphatic hydrocarbon; A block copolymer having a polymer block and / or a hydrogenated block thereof (c2) and a modified block copolymer (C) containing a polar group, wherein the block copolymer coalescing said for (B) an ethylene - the weight ratio of vinyl ester copolymer saponified (a) (a / B) is 70 / 30-99 / 1, wherein the block copolymer (B) The modified block copolymer weight ratio of (C) (C / B) is 0.01 to 10, the ethylene against - to vinyl ester copolymer saponified (A), the block copolymer (B) And the weight ratio (A / B + C) of the total amount of the modified block copolymer (C) is from 50 to less than 50 to 99/1.

  The ratio (A / B) of the melt flow rate value at 230 ° C. and a load of 2160 g between the saponified ethylene-vinyl ester copolymer (A) and the block copolymer (B) is preferably 0.1-10.

The vinyl aromatic content in the block copolymer (B) is preferably 5 to 50% by weight, and the content of polar groups in the modified block copolymer (C) is 0.1 × 10 ^−. It is preferably ² to 1 mmol / g. Furthermore, the polar group is preferably a carboxyl group, and the content of the carboxyl group is preferably 20 mgCH ₃ ONa / g or less.

  The present invention also relates to a molded article using the resin composition of the present invention, a multilayer structure comprising at least one layer comprising the resin composition of the present invention, a liquid container comprising the multilayer structure, and a back-in-box back. Including.

  The resin composition of the present invention includes an ethylene-vinyl ester copolymer saponified product (A), a block copolymer (B) as a soft component, an ethylene-vinyl ester copolymer saponified product (A), and a block copolymer. Since the modified block copolymer (C) having an affinity for both (B) is blended in a specific ratio, the gas barrier property inherent to the saponified ethylene-vinyl ester copolymer (A), melt molding It is flexible enough to withstand specifications that are less susceptible to deformation and are subject to deformation over a long period of time without compromising performance.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
First, the resin composition of the present invention will be described.

<Resin composition>
The resin composition of the present invention comprises an ethylene-vinyl ester copolymer saponified product (A) having an ethylene content of 20 to 60 mol%; a polymer block (b1) mainly comprising aromatic vinyl units, and unsaturated aliphatic carbonization. A block copolymer (B) having a polymer block obtained by polymerizing hydrogen and / or a hydrogenated block (b2) thereof; a polymer block (c1) mainly comprising an aromatic vinyl unit; and an unsaturated aliphatic hydrocarbon A block copolymer having a polymer block obtained by polymerizing and / or its hydrogenated block (c2), and a modified block copolymer (C) containing a polar group, It is the resin composition which mix | blended said A component, B component, and C component in the specific ratio.
Hereinafter, each component will be described in order.

[EVOH resin (A)]
The EVOH resin (A) as the main component of the composition is a water-insoluble resin, and can be obtained by saponifying a copolymer of ethylene and a vinyl ester monomer. Such vinyl ester monomers are typically vinyl acetate. The ethylene-vinyl ester copolymer is produced by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc., and the saponification of the ethylene-vinyl ester copolymer can also be performed by a known method.

  The EVOH resin (A) used in the resin composition of the present invention has an ethylene structural unit content of usually 20 to 60 mol%, preferably 25 to 50 mol%, more preferably 27, as measured based on ISO14663. -35 mol%. When there is too little content rate of an ethylene structural unit, it exists in the tendency for the melt molding processability of a resin composition to fall. On the other hand, if the ethylene structural unit content is too high, the proportion of OH groups contained in the polymer chain is inevitably too low, and the gas barrier property tends to be insufficient. In particular, in the resin composition of the present invention, it is necessary to set the ethylene content in the above range because it is necessary to ensure high gas barrier properties based on the EVOH resin.

  As the vinyl ester monomer, vinyl acetate is typically used from the viewpoint of market availability and good impurity treatment efficiency during production. Other examples include aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and benzoic acid. Examples thereof include aromatic vinyl esters such as vinyl acid, and are usually aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. These are usually used alone, but may be used as a mixture of two or more if necessary.

  The saponification degree of the vinyl ester component is a value measured based on JIS K6726 (however, EVOH resin is a solution uniformly dissolved in water / methanol solvent), and is usually 95 mol% or more, more preferably. Is 95 to 100 mol%, more preferably 98 to 100 mol%. This is because as the saponification degree decreases, the gas barrier property tends to decrease.

  Further, the melt flow rate (MFR) of the EVOH resin (A) is usually 0.1 to 200 g / 10 minutes, preferably 0.5 to 100 g / 10 minutes, at 230 ° C. and a load of 2160 g. Particularly preferably, it is 1 to 40 g / 10 min. When the MFR value is too small, that is, when the melt viscosity is high, uniform melt-kneading with the block copolymer (B) becomes difficult, which causes a decrease in the dispersibility of the block copolymer (B). On the other hand, when the MFR value is too large, the melt viscosity tends to be low, and stable melt extrusion tends to be difficult.

The EVOH resin (A) used in the resin composition of the present invention may be a mixture of two or more different ethylene contents, saponification degrees, and MFRs, as long as the EVOH resin satisfies the above requirements. .
In addition, the EVOH resin used in the present invention includes a small amount of α-olefin such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, 4 in the copolymer. -Hydroxy group-containing α-olefins such as penten-1-ol, esterified products thereof, hydroxy group-containing α-olefin derivatives such as acylated products, unsaturated carboxylic acids or salts thereof, partial alkyl esters, complete alkyl esters, nitriles, Copolymers of co-monomers such as amides / anhydrides, unsaturated sulfonic acids or salts thereof, vinyl silane compounds, vinyl chloride, and styrene may be used. Furthermore, it may be “post-modified” such as urethanization, acetalization, cyanoethylation, oxyalkyleneation and the like.
In particular, an EVOH resin copolymerized with a hydroxy group-containing α-olefin is preferable in terms of good melt molding processability, and among them, an EVOH resin having a 1,2-diol in the side chain is preferable.

  In the EVOH resin (A) used in the present invention, a compounding agent generally blended into the EVOH resin, for example, a heat stabilizer, an antioxidant, an antistatic agent, a colorant, an ultraviolet ray, within a range not inhibiting the effects of the present invention. Absorber, lubricant, plasticizer, light stabilizer, surfactant, antibacterial agent, desiccant, antiblocking agent, flame retardant, crosslinking agent, curing agent, foaming agent, crystal nucleating agent, antifogging agent, biodegradation additive An agent, a silane coupling agent, an oxygen absorbent and the like may be contained.

 The heat stabilizer is an organic acid such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, or an alkali thereof for the purpose of improving various physical properties such as heat stability during melt molding. Salts such as metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.); or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, or their alkali metal salts Additives such as salts such as (sodium, potassium, etc.) and alkaline earth metal salts (calcium, magnesium, etc.) may be added. Of these, it is particularly preferable to add boron compounds, acetates and phosphates including acetic acid, boric acid and salts thereof.

  When acetic acid is added, the amount added is usually 0.001 to 1 part by weight, preferably 0.005 to 0.2 part by weight, particularly preferably 0.010 to 100 parts by weight of EVOH resin (A). 0.1 parts by weight. If the amount of acetic acid added is too small, the effect of acetic acid content tends not to be obtained sufficiently, and conversely if too large, it tends to be difficult to obtain a uniform film.

  Moreover, when adding a boron compound, the addition amount is 0.001-1 weight part normally by boron conversion (after ashing and analyzing by ICP emission spectrometry) with respect to 100 weight part of EVOH resin (A). Yes, preferably 0.002 to 0.2 parts by weight, particularly preferably 0.005 to 0.1 parts by weight. If the addition amount of the boron compound is too small, the effect of adding the boron compound may not be sufficiently obtained. Conversely, if the addition amount is too large, it tends to be difficult to obtain a uniform film.

  In addition, the amount of acetate and phosphate (including hydrogen phosphate) added is usually in metal conversion (after ashing and analyzed by ICP emission spectrometry) with respect to 100 parts by weight of EVOH resin (A). 0.0005 to 0.1 part by weight, preferably 0.001 to 0.05 part by weight, particularly preferably 0.002 to 0.03 part by weight. If the amount added is too small, the content effect may not be sufficiently obtained, while if too large, it tends to be difficult to obtain a uniform film. In addition, when adding 2 or more types of salts to EVOH resin (A), it is preferable that the total amount exists in the range of said addition amount.

The method of adding the boron compound, acetate, and phosphate to the EVOH resin (A) is not particularly limited, and i) adding a porous precipitate of the EVOH resin (A) having a water content of 20 to 80% by weight. A method of bringing the additive into contact with an aqueous solution of the product and drying it; ii) adding the additive to a uniform solution (water / alcohol solution, etc.) of the EVOH resin (A), and then adding the strand into the coagulation liquid A method in which the obtained strand is cut into pellets, and then dried as pellets; iii) a method in which EVOH resin (A) and additives are mixed together and then melt-kneaded with an extruder or the like; iv) During the production of EVOH resin (A), the alkali (sodium hydroxide, potassium hydroxide, etc.) used in the saponification step is neutralized with organic acids such as acetic acid, and the remaining organic acids such as acetic acid and by-products Generation The amount of that salt may be a method like or to adjust the water washing treatment.
In order to obtain the effects of the present invention more remarkably, the method i) and ii), which are excellent in the dispersibility of the additive, and the method iv) are preferred when an organic acid and a salt thereof are contained.

[Block copolymer (B)]
The block copolymer (B) used in the present invention is a polymer obtained by polymerizing a polymer block (b1) mainly composed of an aromatic vinyl that is usually a hard segment and an unsaturated aliphatic hydrocarbon that is usually a soft segment. What has a block and / or its hydrogenated block (b2), and what is generally known as a styrene-type thermoplastic elastomer can be used.

  The block copolymer (B) used in the present invention is a polymer block obtained by polymerizing an aromatic vinyl-based polymer block (hereinafter referred to as “aromatic polymer block”) (b1) and an unsaturated aliphatic hydrocarbon ( (Hereinafter referred to as “aliphatic hydrocarbon polymer block”) or a hydrogenated block (b2) thereof, and a diblock structure represented by b1-b2, b1-b2-b1 or b2-b1-b2 Or a tetrablock structure represented by b1-b2-b1-b2 or a polyblock structure in which b1 and b2 are bonded in a straight chain. Among these, the diblock structure represented by b1-b2, the triblock structure represented by b1-b2-b1, and the tetrablock structure represented by b1-b2-b1-b2 have flexibility and mechanical properties. It is preferable from the point.

  Specific examples of the monomer constituting the aromatic vinyl polymer block (b1) include styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, Styrene derivatives such as t-butylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene; vinylnaphthalene, vinylanthracene, indene, acetonaphthylene And aromatic vinyl compounds. Further, if necessary, other copolymerizable monomers such as ethylene, propylene, 1-butene, pentene, hexene, butadiene, isoprene, and methyl vinyl ether may be used together with these aromatic vinyl monomers. Of the monomers constituting the aromatic vinyl polymer block (b1), styrene and styrene derivatives are preferable, and styrene is particularly preferable.

The aromatic vinyl polymer block (b1) may be a homopolymer block of the aromatic vinyl monomer or a copolymer block of two or more aromatic vinyl monomers.
When other copolymerizable monomer is included, the content of the other copolymerizable monomer in the aromatic vinyl polymer block (b1) is such that the elastomeric property of the block copolymer (B) is not impaired. It is preferably 10% by weight or less of the block weight, and more preferably 5% by weight or less.

  The unsaturated aliphatic hydrocarbon compound monomer constituting the aliphatic hydrocarbon polymer block (b2) is usually an unsaturated aliphatic hydrocarbon compound having 2 to 10 carbon atoms, specifically, 2 to 2 carbon atoms. 6 alkene, C 4-10 diene, and conjugated diene compound are mentioned. Among them, C 4-6 conjugated diene compound is preferably used.

Examples of the conjugated diene compound include isoprene, butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and the like.
Examples of the diene include isobutylene and hexadiene. These dienes may be obtained as a result of hydrogenation of a polymer block comprising the conjugated diene compound.
Examples of the alkene include ethylene, propylene, butylene and the like. These alkenes may be obtained as a result of hydrogenation of the polymer block composed of the conjugated diene or diene.

  The aliphatic hydrocarbon polymer block (b2) may be a homopolymer block composed of one of the above unsaturated aliphatic hydrocarbon monomers, or a random copolymer block composed of two or more unsaturated aliphatic hydrocarbons. There may be. The soft segment is preferably a polymer block of a conjugated diene or a hydrogenated block thereof.

  The hydrogenated block of the aliphatic hydrocarbon polymer block is formed by hydrogenation of a part or all of unsaturated bonds in the polymer block of diene and / or conjugated diene. For example, a polybutadiene block becomes an ethylene / butylene polymer block or a butadiene / butylene polymer block by hydrogenation. The polyisoprene block becomes an ethylene / propylene polymer block or the like by hydrogenation. Hydrogenation can be performed by a known method, and a specific vinyl bond moiety may be selectively hydrogenated.

  The block copolymer (B) used in the present invention is a combination of the polymer block (b1) of the aromatic vinyl monomer and the polymer block of unsaturated aliphatic hydrocarbon or the hydrogenated block (b2) thereof, The block structure is not particularly limited, and examples thereof include a radial teleblock copolymer, a multiblock copolymer, a bimodal copolymer, and a tapered block copolymer.

  The content of the aromatic vinyl structural unit (polymer block b1) in the block copolymer (B) is usually 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 10 to 35% by weight. More preferably, it is 15 to 35% by weight. When the content rate of an aromatic vinyl structural unit is moderately large, the difference of refractive index with EVOH resin (A) becomes small, and there exists a tendency for transparency to improve. Furthermore, when the content of the aromatic vinyl structural unit is 15% by weight or more, the effect of improving the bending resistance is increased.

  The content of the aliphatic hydrocarbon polymer block and / or the hydrogenated block block (b2) thereof in the block copolymer (B) is usually 50 to 95% by weight, preferably 60 to 90% by weight, More preferably, it is 65 to 90% by weight.

  Specific examples of the block copolymer (B) having the above-described structure include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and hydrogenation of SBS. Block copolymer (SEBS), SIS hydrogenated block copolymer (SEPS), block copolymer (SBBS) in which vinyl bond part of butadiene block of SBS is hydrogenated, styrene-isobutylene-styrene triblock copolymer (SIBS), styrene-ethylene-butylene-crystalline polyolefin block copolymer (SEBC), and the like. Of these, SEBS which is excellent in thermal stability and weather resistance is preferably used. In SEBS, a polybutadiene block is converted to an ethylene / butylene copolymer block by hydrogenation.

The melt flow rate (MFR) of the block copolymer (B) is usually 0.1 to 200 g / 10 minutes, preferably 1 to 50 g / 10 minutes, at 230 ° C. and a load of 2160 g. Especially preferably, it is 3 to 15 g / 10 min.
The closer the melt viscosity of the EVOH resin (A) and the block copolymer (B) are, the easier the melt kneading becomes and the resin composition in which the block copolymer (B) is uniformly dispersed in the EVOH resin Is easily obtained, and as a result, a resin composition excellent in bending resistance and transparency is easily obtained. Specifically, the MFR ratio (EVOH resin (A) / block copolymer (B)) measured under the conditions of 230 ° C. and a load of 2160 g is usually 0.1 to 10, preferably 0.5 to 4, and more. Preferably it is 0.7-3.0.

  As such a block copolymer (B), a commercially available product may be used. Examples of commercially available products include “Dynalon”, “JSR-TR”, and “JSR-SIS” manufactured by JSR; “Septon” and “Hypler” manufactured by Kuraray; “Quintac” manufactured by Nippon Zeon, Asahi Kasei “Tuftec” “Tufprene” manufactured by Clayton Polymer; “Kraton G” “Kraton D” “Cariflex TR” manufactured by Clayton Polymer; “Electrified STR” manufactured by Denki Kagaku; “Asaprene T” manufactured by Nippon Elastomer.

[Modified block copolymer (C)]
The modified block copolymer (C) used in the present invention comprises a polymer block (c1) mainly composed of aromatic vinyl units, a polymer block obtained by polymerizing an unsaturated aliphatic hydrocarbon, and / or a hydrogenated block thereof. It is a block copolymer having (c2), and further a block copolymer having a polar group. Specifically, the above block copolymer (B) is modified with a polar group-containing compound.

Specific examples of the polar group include a carboxyl group, an amino group, an alkoxyl group, a hydroxyl group, an amide group, and an epoxy group. The carboxyl group includes an acid anhydride group that is a derivative of the carboxyl group.
The modified block copolymer (C) preferably has moderate reactivity with the EVOH resin (A). From this point, it has at least one polar group selected from the group consisting of a carboxyl group and an amino group. A modified block copolymer (C) is preferable, and a modified block copolymer (C) having a carboxyl group is more preferable.

As the aromatic vinyl used for the polymer block of the aromatic vinyl constituting the block copolymer of the modified block copolymer (C), the unsaturated aliphatic hydrocarbon used for the polymer block of the unsaturated aliphatic hydrocarbon, What was used with the said block copolymer (B) can be used.
The block copolymer of the modified block copolymer (C) and the block copolymer (B) may have the same monomer structure (ie, b1 and c1, b2 and c2) and block structure. , May be different.

  The modified block copolymer (C) having a polar group has an affinity for the EVOH resin (A) having a hydroxyl group that is a polar group. On the other hand, since the block copolymer portion of the modified block copolymer (C) has an affinity for the block copolymer (B), the modified block copolymer (C) is combined with the EVOH resin (A) and the block copolymer. It can serve as a compatibilizing agent for the polymer (B).

  The modified block copolymer (C) is a compound having a polar group, for example, and can be obtained by modifying the block copolymer. Although the modification method is not particularly limited, for example, it is carried out by copolymerization or radical addition to the block copolymer.

  In the case of carboxyl group modification, examples of the compound used for modification include unsaturated carboxylic acids or derivatives thereof, for example, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid anhydride. For example, specifically, α, β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; α, β-unsaturated dicarboxylic acids such as maleic acid, succinic acid, itaconic acid, and phthalic acid; glycidyl acrylate Α, β-unsaturated monocarboxylic acid esters such as glycidyl methacrylate, hydroxyethyl acrylate and hydroxymethyl methacrylate; α, β-unsaturated dicarboxylic acid anhydrides such as maleic anhydride, succinic anhydride, itaconic anhydride and phthalic anhydride Things can be mentioned.

  In the case of amino group modification, the compounds used for modification include 3-lithio-1- [N, N-bis (trimethylsilyl)] aminopropane, 2-lithio-1- [N, N-bis (trimethylsilyl)] aminoethane. , 3-lithio-2,2-dimethyl-1- [N, N-bis (trimethylsilyl)] aminopropane and the like, and examples of the unsaturated amine or a derivative thereof include vinylamine.

  In the case of alkoxyl group modification, examples of the compound used for modification include alkoxysilanes such as tetraethoxysilane, tetramethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, and dimethyldiphenoxysilane. Specific examples of the derivatives include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, pentyl vinyl ether, and hexyl vinyl ether.

  In the case of hydroxyl group modification, examples of the compound used for modification include unsaturated alcohols or derivatives thereof, and specific examples thereof include 3-buten-1-ol, 4-penten-1-ol, and 5-hexene-1. -All etc. are mentioned.

  In the case of amide group modification, examples of the compound used for modification include unsaturated amides or derivatives thereof, such as N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylformamide, N -Methyl-N-vinylacetamide, diacetone acrylamide, acrylamide, methacrylamide, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, and the like.

  In the case of epoxy group modification, examples of the compound used for modification include unsaturated epoxides or derivatives thereof, such as vinyl epoxides.

The content of the polar group in the modified block copolymer (C) is usually 0.1 × 10 ⁻² to 1 mmol / g, preferably 0.5 × 10 ^{−2 to} 0.5 mmol / g, more preferably. Is 1 × 10 ^{−2 to} 0.2 mmol / g, more preferably 1 × 10 ^{−2 to} 0.1 mmol / g. If the polar group content is too high, the affinity with the EVOH resin becomes too high, and a highly polymerized product is likely to be generated, and the MFR of the resin composition is lowered, resulting in insufficient melt molding processability, Fish eyes tend to occur. In addition, viscosity deviation occurs in the resin composition, and when the resin composition is used as a film, streaks are likely to occur, and the bending resistance tends to be lowered.

In particular, when the modified block copolymer (C) has a carboxyl group, the content of the carboxyl group is such that the acid value measured by a titration method is usually 20 mgCH ₃ ONa / g or less, preferably 1 to 15mgCH ₃ ONa / g, and more preferably from 1~5mgCH ₃ ONa / g.
If the acid value is too high, the number of reaction points with the EVOH resin increases, so that a highly polymerized product is likely to be generated, the MFR of the resin composition is lowered, the melt processability is insufficient, and fish eyes are generated. It tends to be easy to do. In addition, the occurrence of a highly polymerized product causes uneven viscosity in the resin composition, and when the resin composition is used as a film, streaks are likely to occur, and the flex resistance tends to decrease.

The melt flow rate (MFR) of the modified block copolymer (C) is usually 0.1 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, at 230 ° C. and a load of 2160 g. Yes, more preferably 2 to 15 g / 10 min.
The closer the melt viscosity of the EVOH resin (A) is to that of the modified block copolymer (C), the easier the melt kneading and the easier it is to obtain a resin composition with excellent flex resistance and transparency. Specifically, the MFR ratio (EVOH resin (A) / modified block copolymer (C)) measured at 230 ° C. under a load of 2160 g is usually 0.1 to 10, preferably 0.5 to 4. 0, more preferably 0.7 to 3.0.

  A commercial item may be used as this modified block copolymer (C). Examples of commercially available products include “Tough Tech” M series manufactured by Asahi Kasei Corporation, “Kraton” FG series manufactured by Kraton Polymer, and “f-Dynalon” series manufactured by JSR.

[Combination ratio]
The resin composition of the present invention is characterized in that the above components (A) to (C) are blended at a specific ratio, and in particular, the EVOH resin (A) is present as a matrix.
In the resin composition of the present invention, the weight ratio (A / B) between the EVOH resin (A) and the block copolymer (B) is 70/30 to 99/1, preferably 70/30 to 85/15. Preferably it is 70 / 30-80 / 20. The EVOH resin (A) is a main component, and the EVOH resin (A) is present as a matrix by blending at a ratio twice or more that of the block copolymer (B), and the gas barrier inherent in the EVOH resin (A). Sex can be maintained.

  The weight ratio (C / B) of the modified block copolymer (C) to the block copolymer (B) is usually 0.01 to 10, although it depends on the modification rate of the modified block copolymer (C). , Preferably 0.01 to 1, more preferably 0.05 to 0.8, still more preferably 0.1 to 0.5, particularly preferably 0.1 to 0.25, particularly preferably. It is 0.15-0.23.

In the resin composition of the present invention, the modified block copolymer (C) is used as a compatibilizer between the EVOH resin (A) and the block copolymer (B), and the blending ratio is adjusted as described above. As a result, a large number of small islands of the block copolymer (B) can be dispersed throughout the EVOH resin (A) as a matrix.
If the blending ratio (C / B) is too high, it is difficult to obtain an effect of improving the bending resistance, but high polymerization is achieved by increasing the affinity between the EVOH resin (A) and the modified block copolymer (C). A refined product is likely to be generated, the MFR of the resin composition is decreased, the melt molding processability is decreased, and fish eyes tend to be generated. Moreover, generation | occurrence | production of highly polymerized substance causes the bias | inclination of the viscosity in a resin composition, it becomes easy to generate | occur | produce a streak in the film obtained by shaping | molding, and there exists a tendency for the bending resistance improvement effect to be impaired as a result. In addition, the resin composition is likely to be colored yellow.

  The total content of aromatic vinyl moieties of the block copolymer (B) and the modified block copolymer (C) relative to the total weight of the resin composition of the present invention is usually 0.1 to 50% by weight, preferably 1-30% by weight, particularly preferably 2-20% by weight, particularly preferably 2-15% by weight.

  Furthermore, the total amount of the (B) component and the (C) component relative to the EVOH resin (A) is usually 50 or more / less than 50/99 to 99 / as a weight ratio (A) / [(B) + (C)]. 1, preferably 60/40 to 99/1, particularly preferably 70/30 to 99/1.

  In the resin composition of the present invention blended at the blending ratio as described above, the block copolymer (B) is uniformly dispersed using the EVOH resin (A) as a matrix, and is excellent in melt moldability. Specifically, the melt flow rate (MFR) at 210 ° C. and 2160 g is usually 0.5 to 30 g / 10 minutes, preferably 0.5 to 20 g / 10 minutes, preferably 1.0 to 15 g. / 10 minutes. When the MFR as the resin composition falls within the above range, when supplied to an extruder, a discharge amount suitable for melt molding is obtained, and a film with less streaking and excellent appearance can be obtained.

[Other ingredients]
In the resin composition of the present invention, the EVOH resin (A), the block copolymer (B), and the modified block copolymer are within a range not inhibiting the effects of the present invention (for example, 2% by weight or less of the resin composition). In addition to the coalescence (C), an antioxidant, a lubricant, an antistatic agent, a colorant, an ultraviolet absorber, a plasticizer, a heat stabilizer, a light stabilizer, a surfactant, an antibacterial agent, and a desiccant as necessary. , An anti-blocking agent, a flame retardant, a crosslinking agent, a curing agent, a foaming agent, a crystal nucleating agent, an antifogging agent, an additive for biodegradation, a silane coupling agent, an oxygen absorber, etc. .

[Preparation of resin composition and molded product (single layer film)]
The resin composition of the present invention can be prepared by mixing the above components. Examples of such a mixing method include a melt mixing method and a solution mixing method. From the viewpoint of productivity, the melt mixing method is preferable.
As the melt mixing method, each component can be dry blended and then melted and mixed. For example, a known kneading apparatus such as a kneader ruder, an extruder, a mixing roll, a Banbury mixer, or a plast mill can be used. However, in general, it is industrially preferable to use a single-screw or twin-screw extruder, and it is also preferable to provide a vent suction device, a gear pump device, a screen device or the like as necessary.
Examples of the solution mixing method include a method in which each component is dissolved and mixed in a good solvent and precipitated in a poor solvent.

The resin composition of the present invention having the above composition is excellent in bending resistance while maintaining the gas barrier properties inherent to the EVOH resin (A). Specifically, the oxygen gas permeation amount in a film having a thickness of 30 μm is usually 10 cc / m ² · day · atm or less at 23 ° C. and 65% RH, and can be twisted 500 times with a gelbo flex tester. usually ten generation of pinholes in the area 476cm ² or less, the amount of generation of fish eyes in the area of 100 cm ² and typically 20 or less, MFR (210 ℃, 2160g) of 0.5 to 30 g / It can be 10 minutes.

  That is, the bending resistance in the present invention is not resistance to instantaneous external force such as impact, but resistance to fatigue gradually accumulated over a long time. Such resistance is obtained by absorbing energy generated by bending and reducing accumulated fatigue. In the resin composition of the present invention, the flexible component is uniformly dispersed throughout. It is considered that the block copolymer (B) is playing a role of fatigue absorption.

<Multilayer structure>
The multilayer structure of the present invention is a multilayer structure having at least one layer composed of the resin composition of the present invention (hereinafter simply referred to as “resin composition layer”).
Although it does not specifically limit as resin which comprises layers other than the resin composition layer which comprises the multilayer structure of this invention, Thermoplastic resins other than EVOH resin are mentioned. For example, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-α-olefin (carbon number) 4-20 α-olefin) copolymer, ethylene-acrylate copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene, and other olefins. Homologous polyolefin resins, polystyrene resins, polyesters, polyamides, copolymers such as homo- or copolymers, cyclic polyolefins, or those obtained by graft-modifying homo- or copolymers of these olefins with unsaturated carboxylic acids or esters thereof Polyamide, polyvinyl chloride, polyvinyl chloride Alkylidene, acrylic resin, vinyl ester resin, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, layer is composed of thermoplastic resin such as chlorinated polypropylene. In addition to these resins, it may be a multilayer structure combined with paper, metal foil, uniaxial or biaxially stretched plastic film or sheet, woven fabric, non-woven fabric, metal wool, wood surface, aluminum or silica deposition. . Among these, polyolefin resins are preferable from the viewpoint of mechanical strength and melt molding processability, and polyethylene and polypropylene are particularly preferable.

  Among these, a multilayer structure having a structure in which a thermoplastic resin layer having an excellent water barrier property is used as an outer surface layer and a resin composition layer is used as an intermediate layer is preferably used for packaging films and packaging containers having gas barrier properties. It is done. The thermoplastic resin having excellent water barrier properties is preferably a polyolefin resin, and particularly preferably polyethylene or polypropylene.

  The method for producing the multilayer structure is roughly divided into a method in which the resin composition is melted (melt molding method), a method in which the resin composition is dissolved in a solvent (for example, solution coating method), and the like. Is done. Among these, the melt molding method is preferable from the viewpoint of productivity. Specifically, for example, a method of melt-extruding a thermoplastic resin to a molded article (for example, a film or a sheet) of an EVOH resin composition, a method of melt-extruding a resin composition layer to a substrate such as a thermoplastic resin, a resin composition A method of co-extrusion of a physical layer and a thermoplastic resin layer, and further, an EVOH resin composition film and a substrate such as a thermoplastic resin film, an organic titanium compound, an isocyanate compound, a polyethyleneimine compound, a polyester compound, Examples thereof include a dry lamination method using a known adhesive such as a polyurethane compound, and a lamination method in which an adhesive resin layer is interposed.

  The adhesive resin constituting the adhesive resin layer is not particularly limited, and various resins can be used. Generally, an unsaturated carboxylic acid or an anhydride thereof is an olefin polymer (the above-mentioned broad sense). Modified olefin polymers containing a carboxyl group obtained by chemically bonding to a polyolefin group) by an addition reaction or a graft reaction, specifically, maleic anhydride graft-modified polyethylene, maleic anhydride Preferred examples include one or a mixture of two or more selected from acid graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, and the like. .

  As described above, the multilayer structure of the present invention only needs to include at least one resin composition layer according to the present invention, and the configuration thereof is not particularly limited, but the gas barrier ability of the resin composition is reduced by moisture. In order to prevent this, the resin composition layer is preferably an intermediate layer.

The layer structure of the multilayer structure is usually 3 when the resin composition layer is a (a1, a2,...) And the thermoplastic resin layer other than the EVOH resin is b (b1, b2,...). 20 layers, preferably 3 to 15 layers, particularly preferably 3 to 10 layers. For example, specifically, b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 / b1 / a / b1 / b2, b2 / b1 / a / b1 / a / Arbitrary combinations such as b1 / b2 are possible.
In addition, when R is a recycled layer containing a mixture of a resin composition and a thermoplastic resin other than EVOH, which is obtained by remelt molding an edge portion or defective product generated in the process of producing the multilayer structure, 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 or the like can also be used.
Further, a known adhesive resin may be used between the layers of the multilayer structure.

  Among these, in order to prevent the gas barrier performance of the resin composition layer from being lowered, a multilayer structure in which the resin composition layer serves as an intermediate layer is most preferable so that moisture can be prevented from passing through the resin composition layer. For example, specifically, a multilayer structure having a thermoplastic resin layer / adhesive resin layer / resin composition layer / adhesive resin layer / thermoplastic resin layer as a structural unit is most preferable.

  The thickness of the multilayer structure of the present invention is usually 1-1500 μm, preferably 1-1000 μm, more preferably 10-700 μm. Moreover, the thickness of the thermoplastic resin layer in the multilayer structure is not particularly limited, but usually 0.1 to 1000 μm and 1 to 500 μm are preferable. Although the thickness of a resin composition layer is not specifically limited, Usually, 0.1-500 micrometers, Preferably it is 1-100 micrometers. The thickness of the adhesive resin layer is not particularly limited, but is usually 0.1 to 250 μm, preferably 0.1 to 100 μm.

  The thickness ratio of the thermoplastic resin layer / resin composition layer is usually more than 1 to 30, preferably 2 to 30, in the ratio of the thickest layers when there are a plurality of layers. The thickness ratio of the conductive resin layer / resin composition layer is usually 0.1 to 2, preferably 0.1 to 1.

  As described above, the multilayer structure of the present invention is a multilayer structure that is simply laminated with another thermoplastic resin or a base material, but may be stretched.

  In addition, about extending | stretching, a well-known extending | stretching method may be sufficient, for example, uniaxial stretching, biaxial stretching, etc. are mentioned. In the case of biaxial stretching, both a simultaneous biaxial stretching method and a sequential biaxial stretching method can be employed. The stretching temperature is the temperature of the multilayer structure (the temperature in the vicinity of the multilayer structure) and is usually selected from the range of about 40 to 170 ° C, preferably about 60 to 160 ° C. A draw ratio is 2-50 times normally by an area ratio, Preferably it is 2-20 times.

<Molded product>
The multilayer structure of the present invention can be used as various molded article materials. For example, the multilayer structure of the present invention is processed into, for example, a tube shape or a bag shape, food such as mirin, soy sauce, sauce, noodle soup, edible oil, wine, juice, milk, mineral water, sake, Used in a wide range of applications as packaging materials for various liquids such as shochu, coffee and tea beverages, pharmaceuticals, cosmetics, sodium hypochlorite, industrial chemicals such as developer and battery fluid, agricultural chemicals such as liquid fertilizer, and detergents Is possible.

  As mentioned above, EVOH resin (A) has resistance to accumulated fatigue such as deformation for a long period of time or repeatedly, such as bending resistance, without impairing the gas barrier properties inherent to EVOH resin (A). ing. Therefore, it can be applied to molded products that are repeatedly deformed for a long period of time, so liquid that folds or deforms as the amount of contents changes, such as bags used in bag-in-box containers. Suitable for containers.

  The bag-in-box is a container in which a foldable plastic thin inner container is combined with an outer box (bag-in box) having stackability, portability, inner container protection, and printability. The base material of the exterior box may be plastic or metal in addition to paper or cardboard, and the shape includes, for example, a box, a carton (square, rectangular parallelepiped), and a drum (cylinder). Are collectively referred to as a bag-in-box.

  Hereinafter, the manufacturing method will be described using a bag-like liquid container such as a bag for a bag-in-box as an example.

A bag-like liquid container such as a bag for a bag-in-box can be manufactured mainly by a heat seal method and a blow molding method.
In the heat sealing method, the laminated body formed by the co-extrusion method or the like is left as it is, or is overlapped in a double or triple as necessary, and a hole for hermetically attaching the liquid inlet is punched, and the hole is put into the hole. Then, the sealing plug of the liquid inlet formed in advance by injection molding is fused by the heat seal method. At this time, the laminated body and another laminated body that has not been punched out can be combined and heat-sealed to form a bag-like liquid container.
In the blow molding method, the cylindrical multilayer structure (parison) extruded from a plurality of extruders by co-extrusion is clamped with a die and molded. The sealing plug of the liquid inlet is previously molded by injection molding and set in a mold, and is fused to the molding container at the time of blow molding. Then, a bag-like liquid container can be obtained by opening the liquid inlet.

  The molded article using the multilayer structure of the present invention may be a cup or tray-like multilayer container in addition to the liquid container. In the case of such a multilayer container, usually a drawing method is employed, and specifically, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, a plug assist type vacuum pressure forming method, or the like is used.

  Further, a tube or bottle-shaped multilayer container may be manufactured from a multilayer parison (a hollow tubular preform before blow). In this case, a blow molding method is adopted, specifically, an extrusion blow molding method (double head type, mold movement type, parison shift type, rotary type, accumulator type, horizontal parison type, etc.), cold parison type blow molding method. Injection blow molding method, biaxial stretch blow molding method (extruded cold parison biaxial stretch blow molding method, injection cold parison biaxial stretch blow molding method, injection molding inline biaxial stretch blow molding method, etc.) It is done.

  The molded products as described above can be further subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making processing, deep drawing processing, box processing, tube processing, splitting as necessary. Processing etc. may be given.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “parts” means weight basis unless otherwise specified.

[Measurement evaluation method]
(1) Gas barrier property With respect to a single-layer film having a thickness of 30 μm prepared from the prepared resin composition, oxygen permeability per 30 μm thickness (cc) using OXTRAN 2/20 manufactured by MOCON at 20 ° C. and 65% RH. / M ² · day · atm).

(2) Bending resistance A single-layer film having a dry size of A4 and a thickness of 30 μm in a dry state is subjected to a twist test using a gelboflex tester manufactured by Rigaku Corporation under the conditions of 23 ° C. and 50% RH. went.
The twisting conditions of the gelboflex tester are 440 ° twisting: 3.5 inches and linear horizontal: 2.5 inches. After the twist test was applied 500 times (40 cycles / min), the number of pinholes generated per 28 cm × 17 cm in the center of the single-layer film was counted. This test was tried 5 times, and the average value was obtained.

(3) Fish Eye A 30 μm thick single layer film made of the prepared resin composition has a diameter of 0.1 m or more in a range of 10 cm × 10 cm using a digital surface defect inspection system GX70LT-HS manufactured by Mamiya Orby. The number of fish eyes was measured. Further, the number of fish eyes having a diameter of 0.2 mm or more in the fish eyes having a diameter of 0.1 mm or more was counted.

(4) Melt flow rate measurement MFR (g / 10min) was measured for the resin composition using a melt indexer F-BO1 manufactured by Toyo Seiki Co., Ltd. at a load of 2160g and a temperature of 210 ° C.

[Production of resin composition pellets and film]
As the EVOH resin (A), two types of saponified ethylene-vinyl acetate copolymers (EVOH1, EVOH2) shown in Table 1 were used. EVOH 1 and 2 are added with boron compounds having a boric acid amount shown in Table 1.

As the block copolymer (B), four kinds of SEBS (SEBS1 to 4) shown in Table 2 and as the modified block copolymer (C), three kinds of modified SEBS (modified SEBS1 to 3) were used. SEBS is a hydrogenated block copolymer of SBS. Modified SEBS contains a carboxyl group as a polar group in the SEBS block copolymer. The amount of modification is shown in Table 2 as the acid value (mgCH ₃ ONa / g). As the block copolymer (B) and the modified block copolymer (C), “Tough Tech” series manufactured by Asahi Kasei Chemicals Corporation was used.
The melt flow rates (MFR) shown in Tables 1 and 2 are both measured values at 230 ° C. and a load of 2160 g.

EVOH resin, SEBS, and modified SEBS shown in Tables 1 and 2 were dry blended at the ratio shown in Table 3, and the resulting resin composition was melt-kneaded under the following conditions, extruded into a strand, and cut with a pelletizer. A resin composition of a cylindrical pellet was obtained.
Extruder: Diameter (D) 30 mm, twin screw extruder, L / D = 42
Screen pack: 90/90 mesh Screw rotation speed: 160 rpm
Set temperature: C1 / C2 / C3 / C4 / C5 / C6-D = 150/200/220/220/220 / 220- ° C.
Discharge rate: 18kg / hr

The obtained pellet No. Films 1 to 14 were formed (thickness 30 μm) under the following conditions.
Extruder: Diameter (D) 40 mm, L / D = 28
Screw: Full flight type Compression ratio = 3.5
Screen pack: 90/120/90 mesh Die: 450 mm wide, coat hanger type Setting temperature: C1 / C2 / C3 / C4 / A / D = 190/210/230/230/220/220 ° C.
Screw rotation speed: 10rpm
Take-off speed: 3m / min
Roll temperature: 80 ° C
Air gap: 15cm

  Film No. obtained from each resin composition For Nos. 1 to 14, the flex resistance was measured based on the above evaluation method, and Gas barrier properties of Nos. 6, 10, 11 and 14; No. 1,3,6,7,10,11,13 fish eyes, The MFRs of 4, 6, 7, 9-11 and 13 were measured and evaluated. The results are also shown in Table 3. In Table 3, “Fish Eye [Total]” indicates the number of fish eyes having a diameter of 0.1 mm or more within a predetermined range, and “Fish Eye [0.2]” indicates the above diameter. The number of fish eyes having a diameter of 0.2 mm or more among fish eyes of 0.1 mm or more is shown. Moreover, the compounding ratio (A / B) has shown the value converted into the ratio when the total amount 100 is distributed.

  No. 1 and 2, the EVOH resin (A), the block copolymer (B), and the modified block copolymer (C) have the same blending ratio, and the block copolymer (B) has the same styrene content. Degree. However, No. with an MFR ratio (A / B) of 4.4. No. 2 with an MFR ratio (A / B) of 1.6. No. 1 was superior in bending resistance. This is because when the MFR ratio between the block copolymer (B) and the EVOH resin (A) is increased, the dispersibility of the block copolymer (B) is improved even in the presence of the modified block copolymer (C). It shows that the bending resistance tends to decrease.

No. In 3-6, the EVOH resin (A), the block copolymer (B), and the modified block copolymer (C) have the same blending ratio and the same MFR ratio (A / B).
SEBS4 in which the styrene content of the block copolymer (B) is 18 wt% higher than that in the case where SEBS3 having a low styrene content of 12 wt% in the block copolymer (B) is used (No. 4, 5) When No. 3 was used (Nos. 3 and 6), the effect of improving the bending resistance was greater. It can be seen that the higher the styrene content of the block copolymer (B), the more the flex resistance tends to improve.

  On the other hand, no. When attention is focused on the modified block copolymer (C) in Nos. 3, 4, 5, and 6, No. 1 using modified SEBS1 having a styrene content of 20% by weight. No. 3 and 4 and No. 2 using modified SEBS2 having a styrene content of 30% by weight. 5 and 6, the combination using the same block copolymer (B) (the combination of No. 3 and 6 and the combination of No. 4 and 5) showed the same degree of bending resistance. Therefore, the influence of the styrene content of the modified block copolymer (C) on the bending resistance is not so great.

  No. 6 and 7, the EVOH resin (A), the block copolymer (B), and the modified block copolymer (C) have the same blending ratio, and the carboxyl group content (acid value) of the modified block copolymer (C). ) Are different combinations. Bending resistance is higher when SEBS3 having a lower carboxyl group content (acid value) is used (No. 7) than when modified SEBS2 having a higher carboxyl group content (acid value) is used (No. 6). The property was remarkably excellent.

No. 4, 8, and 9 are the same EVOH resin (A), block copolymer (B), and modified block copolymer (C), and the block copolymer (B) and the modified block copolymer (C). The combination ratio (C / B) is different.
The blending ratio (C / B) of the block copolymer (B) and the modified block copolymer (C) is 0.11. In No. 8, since the amount of the modified SEBS serving as a compatibilizer is small, the dispersion of the block copolymer (B) in the EVOH resin (A) becomes insufficient, or the block copolymer (B) and the modification No. in which the blending ratio (C / B) of the block copolymer (C) is 0.2. The bending resistance tended to be inferior to 4.
On the other hand, when the blending ratio of the modified block copolymer (C) to the block copolymer (B) is 0.2 (No. 4) and 0.5 (No. 9), The bending resistance evaluations were all good. More preferably, it is understood that C / B should be 0.15 or more from the viewpoint of flex resistance. However, no. With respect to the film obtained in No. 9, there was room for improvement in transparency, although it was sufficient for practical use because it was possible to visually determine that there were many fine streaks. No. No. 9 has an MFR value of 0.8 g / 10 min. Compared to 4 and 8, there was a tendency to decrease. No. In No. 9, since the value of the blending ratio (C / B) of the modified block copolymer (C) to the block copolymer (B) was increased, the EVOH resin (A) and the modified block copolymer (C) reacted. This is thought to be due to the fact that a highly polymerized product was generated, which caused a viscosity deviation in the resin composition and the resin uniformity was slightly insufficient. Therefore, it can be seen that C / B is preferably less than 0.25 from the viewpoint of film appearance and melt moldability.

No. 10 and 11, EVOH 2 having an ethylene content of 29 mol% was used as the EVOH resin (A), and the blending ratio (A / B) of the EVOH resin (A) and the block copolymer (B) was 78/22 (≈ 3.6). As the EOVH resin (A), EVOH 1 having an ethylene content of 32 mol% was used, and the blending ratio (A / B) of the EVOH resin (A) and the block copolymer (B) was 74/26 (≈2.8). No. Although the bending resistance was slightly lowered as compared with 7, it showed sufficiently good bending resistance. The slight decrease in flex resistance is presumed to be due to the decrease in the ethylene content in the EVOH resin (A), but the blending ratio (A / B) of the block copolymer (B) to the EVOH resin (A) is One reason may be that it is slightly smaller.
On the other hand, no. Nos. 10 and 11 are No. regarding the number of fish eyes and the MFR value. It was better than 7. When the gas barrier properties, flex resistance, fish eye number and MFR value are comprehensively judged, 10 and 11 show that all of the above characteristics are excellent in balance.

  No. No. 12 is a comparative example in which only the block copolymer (B) is blended in the EVOH resin (A) and the modified block copolymer (C) serving as a compatibilizer is not blended. No. The flex resistance evaluation of the film obtained from the resin composition of No. 12 was 21.8. It can be seen that the bending resistance was lower than the bending resistance evaluation (0.2 to 6.0) of the film obtained from the resin composition of 1-11. No. No. 12, since the modified block copolymer (C) serving as a compatibilizer did not coexist, the dispersion state of the block copolymer (B) was poor, and the block copolymer (B) had a sufficient effect of absorbing external force. It is presumed that it was not possible to demonstrate.

  No. No. 13 is a comparative example in which only the modified block copolymer (C) is blended with the EVOH resin (A) and the block copolymer (B) is not blended. Although the bending resistance showed a good value, the MFR value was a very low value of 0.3 g / 10 minutes, and a large amount of fish eyes were generated in the obtained film. This is because the amount of the modified block copolymer (C) was large, so a large amount of highly polymerized product was generated due to the reaction between the hydroxyl group of the EVOH resin (A) and the carboxyl group of the modified block copolymer (C). It is presumed that it was because of it.

  No. No. 14, the blending ratio (A / B) of EVOH resin (A) and block copolymer (B) is 57/43 (≈1.3), and the content of block copolymer (B) is relatively large. In order to form a matrix, the resin composition corresponding to the comparative example has a relatively low EVOH resin (A) content. Since the modified block copolymer (C) serving as a compatibilizing agent coexists, the block copolymer (B) could be uniformly dispersed, or the bending resistance could be satisfied. However, since the EVOH resin (A) content is not sufficient in the blending ratio (A / B), the gas barrier property is insufficient.

  The resin composition of the present invention has improved flex resistance without impairing the gas barrier properties inherent to EVOH resin, suppresses the generation of fish eyes, and has a good MFR value for melt molding processing. It is useful as a liquid container for water and beverages.

Claims (11)

Saponified ethylene-vinyl ester copolymer (A) having an ethylene content of 20 to 60 mol%; a polymer block (b1) mainly composed of aromatic vinyl units and a polymer obtained by polymerizing unsaturated aliphatic hydrocarbons A block copolymer (B) having a hydrogenated block (b2); a polymer block (c1) mainly comprising an aromatic vinyl unit; a polymer block obtained by polymerizing an unsaturated aliphatic hydrocarbon and / or its hydrogen A resin composition comprising a block copolymer having an added block (c2) and a modified block copolymer (C) containing a polar group,
The weight ratio (A / B) of the saponified ethylene-vinyl ester copolymer (A) to the block copolymer (B) is 70/30 to 99/1,
The weight ratio (C / B) of the modified block copolymer (C) to the block copolymer (B) is 0.01 to 10,
The weight ratio (A / B + C) of the total amount of the block copolymer (B) and the modified block copolymer (C) to the saponified ethylene-vinyl ester copolymer (A) is 50 or more and less than 50. Resin composition which is -99/1. The ratio (A / B) of the melt flow rate value at 230 ° C. and a load of 2160 g between the saponified ethylene-vinyl ester copolymer (A) and the block copolymer (B) is 0.1 to 10. The resin composition as described. The resin composition according to claim 1 or 2, wherein an aromatic vinyl content in the block copolymer (B) is 5 to 50% by weight. 4. The resin composition according to claim 1, wherein the content of the polar group in the modified block copolymer (C) is 0.1 × 10 ⁻² to 1 mmol / g. The resin composition according to any one of claims 1 to 4, wherein the polar group of the modified block copolymer (C) is a carboxyl group. The resin composition according to claim 5, wherein a content of the carboxyl group of the block copolymer (C) is 20 mgCH ₃ ONa / g or less. The molded article which consists of a resin composition in any one of Claims 1-6. A multilayer structure comprising at least one layer comprising the resin composition according to claim 1. The multilayer structure according to claim 6, which has a thickness of 1 to 1500 µm. A liquid container comprising the multilayer structure according to claim 8. A back-in-box bag comprising the multilayer structure according to claim 8 or 9.