JP5818566B2 - Resin composition and adhesive, multilayer structure and infusion bag using the same - Google Patents

Description

  The present invention relates to a resin composition containing a polyvinyl alcohol resin (hereinafter abbreviated as PVA resin) and a styrene thermoplastic elastomer, and more specifically, both a polyolefin resin and a vinyl alcohol resin. The present invention relates to a resin composition having good adhesiveness.

  Conventionally, infusion bags used for medical and welfare purposes have mainly used soft polyvinyl chloride in terms of excellent toughness. However, soft polyvinyl chloride contains a large amount of a plasticizer such as dioctyl phthalate, and there is a possibility that such a plasticizer may elute into a drug in an infusion bag, which causes a problem in safety. In addition, medical infusion bags are not reused and are incinerated to prevent infection. However, depending on the incineration method, polyvinyl chloride generates toxic chlorine-based substances such as dioxins, which may cause environmental pollution. Problems may arise.

Therefore, an infusion bag using a polyolefin resin such as polyethylene or polypropylene instead of polyvinyl chloride has been proposed.
Such an infusion bag is made by folding a single resin film or overlapping two sheets and bonding the edges with heat seal or adhesive. In order to prevent outside air contamination and infection, strong adhesive strength is required. For example, in an infusion bag using a polyolefin resin film, a styrene thermoplastic elastomer has been proposed as an adhesive. Such an adhesive is not only excellent in adhesive strength but also has flexibility and is suitable as an adhesive for an infusion bag because of a small decrease in adhesive strength due to sterilization operation. (For example, refer to Patent Document 1.)

  On the other hand, the infusion bag is required to have a characteristic of stably maintaining the quality of the contents from the viewpoint of storage. In particular, amino acid preparations, glucose preparations, fat emulsions, electrolyte infusions, and the like used for medical treatment are easily altered by oxygen and the like, and therefore need an excellent oxygen gas barrier property. However, since the polyolefin-based resins mentioned above do not have sufficient gas barrier properties, a technique for forming a multilayer structure with a resin having excellent gas barrier properties is required.

  As such a gas barrier resin, for example, vinyl alcohol resins such as PVA resins and ethylene-vinyl alcohol copolymers are known. Since the vinyl alcohol resin and the polyolefin resin are poor in adhesiveness, it is necessary to interpose an adhesive layer when laminating them. However, few of these resins have good adhesion. For example, styrene-based thermoplastic elastomers with excellent adhesion to the above-mentioned polyolefin resins have adhesion to vinyl alcohol resins. Was insufficient.

JP 2000-239635 A

  An object of this invention is to provide the resin composition which has the adhesiveness outstanding with respect to both polyolefin resin and vinyl alcohol-type resin.

As a result of intensive studies in view of the above circumstances, the present inventors have found that a PVA resin (A) having a structural unit represented by the general formula (1) and a styrene thermoplastic elastomer (B) (hereinafter referred to as elastomer ( B) and a weight ratio (A / B) of the PVA resin (A) to the elastomer (B) is 75/25 to 55/45, and the weight of the resin composition. It has been found that the object of the present invention can be achieved by a resin composition characterized in that the PVA-based resin (A) having a large ratio has an island component and the elastomer (B) having a small weight ratio has a sea-island structure having a sea component. The present invention has been completed.
[Wherein R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. Indicates an atom or an organic group. ]

  Usually, a resin composition comprising two or more incompatible components forms a sea-island structure in which a resin having a large weight ratio is a sea component and a resin having a small weight ratio is an island component. Therefore, surface properties such as adhesion of the resin composition are governed by sea components. However, in the resin composition of the present invention, a resin having a small weight ratio is a sea component, and a resin having a large weight ratio is an island component. Therefore, when a film such as a film is formed, a surface in which both components are mixed is formed. , Presumed to have both surface properties.

  Since the resin composition of the present invention has excellent adhesion to both polyolefin-based resins and vinyl alcohol-based resins, in a multilayer structure including a polyolefin-based resin layer and a vinyl alcohol-based resin layer, both layers It is suitable as a material for the adhesive layer.

It is an electron micrograph (2000 times) what etched the adhesive film by the resin composition produced in Example 1 with water. It is an electron micrograph (2000 times) what etched the adhesive film by the resin composition produced in the comparative example 5 with xylene. It is an electron micrograph (2000 times) what etched the cross section of the adhesive film by the resin composition produced in the comparative example 6 with xylene.

  Hereinafter, although this invention is demonstrated in detail, these are examples of desirable embodiment, and are not specified by these content.

  The resin composition of the present invention contains a PVA resin (A) having a structural unit represented by the general formula (1) described below and a styrene thermoplastic elastomer (B).

[PVA resin (A)]
The PVA-based resin (A) used in the resin composition of the present invention has a structural unit represented by the following general formula (1), and R ¹ , R ² and R ³ in the general formula (1) are Each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group.

In particular, it is desirable that R ^{1 to} R ³ and R ^{4 to} R ⁶ in the structural unit represented by the general formula (1) are all hydrogen and X is a single bond, and the following general formula (1 ′ PVA resin (A) having a structural unit represented by The PVA resin (A) having the structural unit represented by the general formula (1 ′) has no bulky organic group or alkyl group in the structural unit of the 1,2-diol component. In some cases, it is difficult to achieve high viscosity and workability is improved, which is suitable for forming an adhesive layer of a multilayer structure.

However, R ^{1 to} R ³ and R ^{4 to} R ⁶ in the structural unit represented by the general formula (1) may be an organic group in an amount that does not significantly impair the properties of the resin, Examples of the organic group include alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, and tert-butyl group. In addition, the above alkyl group may be substituted with a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, a sulfonic acid group, or the like as necessary for the purpose of improving the adhesion with a vinyl alcohol resin that is a gas barrier resin. It may have a group.

Further, X in the structural unit represented by the general formula (1) is a point of thermal stability at the time of melt-kneading or formation of an adhesive layer of a multilayer structure or a point of stability under high temperature / acid conditions. The bond is most preferably a single bond, but may be a bonded chain as long as the effects of the present invention are not inhibited. Examples of the bonding chain include hydrocarbon groups such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbon groups may have halogen such as fluorine, chlorine, and bromine), and the like. _{O -, - (CH 2 O} ) m -, - (OCH 2) m -, - (CH 2 O) mCH 2 -, - CO -, - COCO -, - CO (CH 2) mCO -, - CO ( _{C 6 H 4) CO -,} - S -, - CS -, - SO -, - SO 2 -, - NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - NRNR -, - _{HPO 4 -, - Si (OR} ) 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi (OR) _{2 O -, - Al (OR} ) -, - OAl (OR) -, - OA (OR) O-like (R is an optional substituent each independently, a hydrogen atom, an alkyl group are preferred, and m is a natural number.) Are exemplified. Among them, when forming an alkylene group having 6 or less carbon atoms from the viewpoint of stability during production or use, and an adhesive layer of a multilayer structure, the bond chain of X should be small in terms of workability due to viscosity. Therefore, a methylene group or —CH ₂ OCH ₂ — is particularly preferable.

The production method of the PVA resin (A) used in the present invention is not particularly limited, but (i) a method of saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (2) (Ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (3), or (iii) a vinyl ester monomer and the following general formula (4) A method of saponifying and deketalizing a copolymer with a compound to be obtained is preferably used.

In the general formulas (2), (3) and (4), R ¹ , R ² , R ³ , X, R ⁴ , R ⁵ and R ⁶ are all the same as in the case of the general formula (1). . R ⁷ and R ⁸ are each independently a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group). R ¹⁰ and R ¹¹ are each independently a hydrogen atom or an organic group.

  As the methods (i), (ii), and (iii), for example, the method described in JP-A-2006-95825 can be used. Of these, it is preferable to use 3,4-diacyloxy-1-butene as the compound represented by the general formula (2) in the method (i) from the viewpoint of excellent copolymerization reactivity and industrial handleability. Further, 3,4-diacetoxy-1-butene is preferably used. In addition, the reactive ratio of each monomer when vinyl acetate is used as the vinyl ester monomer and 3,4-diacetoxy-1-butene is copolymerized is r (vinyl acetate) = 0.710, r ( 3,4-diacetoxy-1-butene) = 0.701, which is r (acetic acid) in the case of vinyl ethylene carbonate which is a compound represented by the general formula (3) used in the method (ii). Compared with vinyl) = 0.85 and r (vinyl ethylene carbonate) = 5.4, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate.

  The chain transfer constant of 3,4-diacetoxy-1-butene is Cx (3,4-diacetoxy-1-butene) = 0.003 (65 ° C.), which is the same as that in the case of vinyl ethylene carbonate. (Vinylethylene carbonate) = 0.005 (65 ° C.) and 2,2-dimethyl-4-vinyl-1,3-dioxolane which is a compound represented by the general formula (4) used in the method (iii) Compared with Cx (2,2-dimethyl-4-vinyl-1,3-dioxolane) = 0.023 (65 ° C.) in this case, it is difficult to increase the degree of polymerization or cause a decrease in polymerization rate. It indicates that there is no.

  In addition, such 3,4-diacetoxy-1-butene is a by-product generated when saponifying the copolymer, and a by-product generated during the saponification from a structural unit derived from vinyl acetate frequently used as a vinyl ester monomer. It is an industrially significant advantage that it is the same as the resulting compound, and it is not necessary to provide any special equipment or process for the subsequent treatment or solvent recovery system, and conventional equipment can be used.

The 3,4-diacetoxy-1-butene is, for example, a product produced by a synthesis route using 1,3-butadiene as a starting material described in WO00 / 24702, or an epoxy produced by a technique described in USP56223086 and USP6072079. Products manufactured using butene derivatives as intermediates can be obtained, and at the reagent level, Acros products can be obtained from the market. Further, 3,4-diacetoxy-1-butene obtained as a by-product in the production process of 1,4-butanediol can be purified and used.
Further, 1,4-diacetoxy-1-butene, which is an intermediate product in the production process of 1,4-butanediol, is subjected to a known isomerization reaction using a metal catalyst such as palladium chloride to produce 3,4-diacetoxy-1 -It can also be converted to butene. Moreover, it is also possible to manufacture according to the manufacturing method of the organic diester described in re-publication WO00-24702.

  The PVA resin obtained by the method (ii) or (iii) may have a small amount of carbonate ring or acetal ring remaining in the side chain when decarboxylation or deacetalization is insufficient. The method according to (i) is most preferably used because a cross-linking reaction due to such functional groups may occur during melt-kneading or melt-molding to generate a gelled product.

The vinyl ester monomers used for copolymerization include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, and vinyl stearate. , Vinyl benzoate, vinyl versatate, and the like, among which vinyl acetate is preferably used from an economical viewpoint.
In addition to the above-mentioned monomers (vinyl ester monomers, compounds represented by the general formulas (2), (3), and (4)), copolymerization components can be used as long as they do not significantly affect the physical properties of the resin. Α-olefins such as ethylene and propylene, hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1,2-diol, and acylated products thereof Derivatives such as itaconic acid, maleic acid, acrylic acid and the like, or salts or mono- or dialkyl esters thereof; nitriles such as acrylonitrile, amides such as methacrylamide, diacetone acrylamide, ethylene sulfonic acid, allyl sulfonic acid , Olefin sulfonic acids such as methallyl sulfonic acid and AMPS or their salts, etc. May be copolymerized.

  The saponification degree of the PVA resin (A) used in the present invention is usually 70 to 100 mol%, more preferably 85 to 99.9 mol%, particularly preferably, as measured in accordance with JIS K6726. Is 95 to 99 mol%. If the degree of saponification is too low, the adhesiveness between the resin composition and the vinyl alcohol resin may be lowered, and the side chain acetyl group of the PVA resin (A) may be eliminated during melt molding to remove acetic acid. Thus, there may be a case where an odor of acetic acid is produced or a main chain of the PVA resin (A) is decomposed to cause defects such as scorching.

  The average degree of polymerization of the PVA resin (A) is usually 300 to 1100, more preferably 350 to 800, and particularly preferably 400 to 600 as measured according to JIS K6726. If the degree of polymerization is too small, the mechanical strength of the adhesive layer of the multilayer structure may decrease, and if the degree of polymerization is too large, the melt viscosity at the time of melt molding will increase, making it difficult to form an adhesive layer. In addition, there is a case where the shear heat generation becomes large and decomposes during molding.

  The melt viscosity of the PVA resin (A) used in the present invention is usually 300 to 3000 Pa · s, preferably 1000 to 2000 Pa · s, as measured under conditions of a temperature of 210 ° C. and a shear rate of 122 sec−1. Particularly preferred is 1300 to 1800 Pa · s. If the melt viscosity of the PVA-based resin (A) is too high, shear heat generation may occur during melt molding and thermal decomposition may occur. Conversely, if the melt viscosity is too low, the mechanical strength of the adhesive layer of the multilayer structure decreases. There is a case.

  The content of the 1,2-diol component contained in the PVA-based resin (A) is usually 0.5 to 12 mol%, more preferably 2 to 10 mol%, particularly 3 to 8 mol%. preferable. If the content of the 1,2-diol component is too small, the adhesiveness between the resin composition and the vinyl alcohol resin may be lowered, and the decomposition temperature and the melting point are close to each other. In some cases, it may be difficult to melt mold the adhesive layer of the multilayer structure. Conversely, if the content of the 1,2-diol component is too large, metal adhesion during melt molding increases, Fluidity may decrease.

  In addition, the content (molar fraction) of the 1,2-diol component is determined by taking the PVA resin (A) as an example when the 1,2-diol component is a structural unit represented by the general formula (i). It can be determined from the 1H-NMR spectrum (300 MHz, solvent: d6-DMSO, internal standard: tetramethylsilane) of the completely saponified substance, specifically, hydroxyl group proton in 1,2-diol unit, methine proton, It may be calculated from the peak area derived from the methylene proton, the methylene proton of the main chain, the proton of the hydroxyl group linked to the main chain, and the like.

  In addition, the PVA resin (A) used in the present application may be one type or a mixture of two or more types, and may be a mixture with unmodified PVA or other modified PVA, but a mixture is used. The average value of the degree of polymerization, the degree of saponification, and the content of 1,2-diol structural units is preferably within the above range.

[Elastomer (B)]
The elastomer (B) used in the present invention is derived from a hard segment (a) mainly composed of a structural unit derived from an aromatic vinyl compound (hereinafter abbreviated as hard segment (a)), a conjugated diene compound or an olefin compound. And a soft segment (b) (hereinafter abbreviated as soft segment (b)) mainly composed of the structural unit.

  The constitution of each block in the elastomer (B) is as follows: when the hard segment (a) is represented by X and the soft segment (b) is represented by Y, a diblock copolymer represented by XY, X Examples include a triblock copolymer represented by —Y—X or Y—X—Y, and a polyblock copolymer in which X and Y are alternately connected, and the structure thereof is also linear or branched. And a star shape. Especially, the linear triblock copolymer represented by XYX is suitable at the point of a mechanical characteristic.

  First, as monomers used for forming the hard segment (a), styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, 2, Alkyl styrene such as 4-dimethylstyrene and 2,4,6-trimethylstyrene, halogenated styrene such as monofluorostyrene, difluorostyrene, monochlorostyrene and dichlorostyrene, methoxystyrene, ethoxystyrene, propoxystyrene, isopropoxystyrene, butoxy Examples thereof include alkoxystyrenes such as styrene, vinyl compounds having an aromatic ring other than a benzene ring, such as vinyl naphthalene, vinyl anthracene, indene and acetonaphthylene, and derivatives thereof. The hard segment (a) mainly composed of the structural unit derived from the aromatic vinyl compound may be a homopolymer block of the above-mentioned monomer or a copolymer block of a plurality of monomers, but a styrene homopolymer block is preferably used. It is done.

  In addition, the hard segment (a) may be one in which a monomer other than the aromatic vinyl compound is copolymerized in a small amount within a range that does not inhibit the effect of the present invention (usually 10 mol% or less of the entire polymer block), Examples of such monomers include olefins such as butene, pentene and hexene, diene compounds such as butadiene and isoprene, vinyl ether compounds such as methyl vinyl ether, and allyl ether compounds.

  The weight average molecular weight of the hard segment (a) in the elastomer (B) is usually 10,000 to 300,000, particularly 20,000 to 200,000, more preferably 50,000 to 100,000. Used. If the weight average molecular weight is too large, the flexibility of the resin composition may be reduced. Conversely, if the weight average molecular weight is too low, the mechanical strength may be reduced.

  Next, as monomers used for forming the soft segment (b), 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1, Examples thereof include conjugated diene compounds such as 3-pentadiene and olefin compounds such as ethylene, propylene, butylene, isobutylene, 1-isopentene, 2-isopentene, and 3-isopentene. You may use it combining.

In the case where the soft segment (b) is a polymer block of a conjugated diene compound, it may take a plurality of bonding forms by polymerization. For example, in butadiene, a butadiene unit (—CH ₂ —CH ( Butadiene units (—CH ₂ —CH═CH—CH ₂ —) are formed by CH═CH ₂ ) —) and 1,4-bonds. Since these production ratios vary depending on the type of conjugated diene compound, it cannot be generally stated, but in the case of butadiene, the ratio of 1,2-bond production is usually in the range of 20 to 80 mol%.

  In addition, for the purpose of improving the heat resistance and weather resistance of the resin composition and its multilayer structure, the structural unit derived from the conjugated diene compound in the soft segment (b) is part or all of the remaining double bonds. May be hydrogenated. In this case, the hydrogenation rate is preferably 50 to 99.9 mol%, particularly preferably 70 to 99 mol%.

By this hydrogenation, the butadiene unit of 1,2-bond of butadiene becomes a butylene unit (—CH ₂ —CH (CH ₂ —CH ₃ ) —), and the butadiene unit generated by the 1,4-bond is two. Two consecutive ethylene units (—CH ₂ —CH ₂ —CH ₂ —CH ₂ —) are formed, but usually the former is preferred.

  The soft segment (b) may be a copolymer obtained by copolymerizing a small amount of monomers other than the above-mentioned monomers within a range not inhibiting the effects of the present invention. Examples of such monomers include aromatic vinyl compounds such as styrene, butene , Olefins such as pentene and hexene, vinyl ether compounds such as methyl vinyl ether, and allyl ether compounds. The copolymerization ratio thereof is usually 10 mol% or less of the entire polymer block.

  The weight average molecular weight of (b) in the elastomer (B) is usually 10,000 to 300,000, particularly preferably 20,000 to 200,000, more preferably 50,000 to 100,000. It is. If the weight average molecular weight is too large, the viscosity of the resin composition becomes high, and it may be difficult to mold the adhesive layer of the multilayer structure. Conversely, if it is too small, the flexibility may be lowered.

  The content (a / b) of the hard segment (a) and the soft segment (b) in the elastomer (B) used in the present invention is usually 5 to 50% by weight, particularly 10 to 30% by weight. A range is preferred. If the content of the hard segment (a) in the elastomer (B) is too large, the flexibility of the adhesive layer of the multilayer structure of the present invention may be lowered, and conversely if too small, the mechanical properties of the adhesive layer The strength may decrease.

  The polymerization average molecular weight of the elastomer (B) used in the present invention is usually from 50,000 to 500,000, particularly preferably from 120,000 to 450,000, more preferably from 150,000 to 400,000. The weight average molecular weight of the elastomer (B) is a value obtained by using GPC and using polystyrene as a standard.

Further, the melt viscosity of the elastomer (B) is usually 100 to 1500 Pa · m, particularly preferably 200 to 1000 Pa · m, more preferably, as measured under conditions of a temperature of 210 ° C. and a shear rate of 122 sec−1. 300 to 700 Pa · m.
When the polymerization average molecular weight or / and viscosity of the elastomer (B) is too high, shear heat generation may occur at the time of melt molding, and thermal decomposition may occur. In some cases, the adhesive layer may be displaced, and the mechanical strength of the adhesive layer may be reduced.

Such an elastomer (B) obtains a block copolymer having a hard segment (a) and a soft segment (b), and if necessary, double bonds in the soft segment (b) having a conjugated diene compound are hydrogenated. It can be obtained by adding.
First, as a method for producing an elastomer (B) having a hard segment (a) and a soft segment (b), a known method can be used. For example, an alkyl lithium compound or the like is used as an initiator, and an inert organic compound is used. Examples thereof include a method of sequentially polymerizing an aromatic vinyl compound and a conjugated diene compound in a solvent.
Next, as a method for hydrogenating the elastomer (B), a known method can be used. For example, a method using a reducing agent such as a borohydride compound or a metal catalyst such as platinum, palladium, Raney nickel, etc. The hydrogen reduction used can be mentioned.

  Specific examples of the elastomer (B) include styrene / butadiene block copolymer (SBS) using styrene and butadiene as raw materials, and styrene / butadiene / butylene in which side chain double bonds in the butadiene structural unit of SBS are hydrogenated. Block copolymer (SBBS), styrene / ethylene / butylene block copolymer (SEBS) in which main chain double bonds are hydrogenated, styrene / isoprene block copolymer (SIS) using styrene and isoprene as raw materials, etc. Among them, SEBS excellent in thermal stability and weather resistance is preferably used.

  The elastomer (B) described above may be a single type or a mixture of two or more types. When a mixture is used, the polymerization average of the hard segment (a) and the soft segment (b) The molecular weight, the content ratio (a / b), the weight average molecular weight of the block copolymer, the water addition rate of the soft segment (b), and the average value of the melt viscosity are preferably within the above-mentioned ranges.

[Resin composition]
The resin composition of the present invention contains the above PVA resin (A) and elastomer (B), and may contain other additives as necessary.

  The weight ratio (A / B) between the PVA resin (A) and the elastomer (B) of the resin composition is 75/25 to 55/45, particularly preferably 73/27 to 58/42. Preferably it is 70 / 30-60 / 40. If the weight ratio of the PVA resin (A) is too large, the PVA resin (A) becomes a sea component and the elastomer (B) becomes an island component, and the adhesiveness is governed by the PVA resin (A). Adhesiveness with the resin may decrease, and conversely, if the weight ratio of the block copolymer (B) is too large, the PVA resin (A) mixed on the surface when the adhesive film is formed, Adhesiveness with vinyl alcohol resin may be lowered.

  The resin composition of the present invention forms a sea-island structure in which the PVA resin (A) is an island component and the elastomer (B) is a sea component. For this reason, when a thin film such as a film is formed, both components are mixed on the surface, and the film has excellent adhesion to both polyolefin resin and vinyl alcohol resin.

  Examples of a method for forming such a resin composition having a sea-island structure include (1) a method of preparing a melt viscosity ratio (A / B) of a PVA resin (A) and an elastomer (B). The ratio (A / B) is usually 7/1 to 5/3, preferably 6/1 to 2/1, and more preferably 6/1 to 4/1. When the melt viscosity ratio is too large, workability may be deteriorated when forming the adhesive layer of the multilayer structure, and when too small, the dispersibility of the PVA resin (A) and the elastomer (B) is deteriorated. Each component is easily separated, the adhesive layer is difficult to form a specific sea-island structure, the adhesiveness between the adhesive and the polyolefin resin and / or vinyl alcohol resin may be deteriorated, Mechanical strength may decrease.

  In addition, as a method for forming the resin composition having the sea-island structure of the present application, (2) a method for increasing the polymerization degree of the PVA resin (A), (3) a saponification degree of the PVA resin (A) And a method of increasing the crystallinity by increasing (4), a method of increasing the content ratio of the soft segment (b) of the elastomer (B), and the like. However, in the method (2), if the degree of polymerization is excessively high, there may be a drawback such as scorching due to shear heat generation of the resin composition at the time of melt molding. In the method (4), the soft segment (b) If the content ratio of is too large, the mechanical strength of the resin composition may decrease.

  The average particle size of the PVA resin (A), which is an island component of such sea-island structure, is obtained by dividing a molded product of the resin composition under liquid nitrogen and immersing the cross-sectional portion in warm water at 80 ° C. for 2 hours, and etching. The cross-section of the obtained material can be photographed with a scanning electron microscope (SEM), and the morphology can be visually observed to determine. The average particle diameter is usually 0.1 to 10 μm, usually 0.1 to 3 μm, particularly 0.2 to 2 μm, especially 0.3 to 1 μm in the surface layer portion, and usually 3 in the inner layer portion. 10 μm, in particular 4-9 μm, in particular 5-7 μm. The surface layer portion indicates a portion located within 15% from the surface of the resin composition toward the inside, and the inner layer portion refers to a portion located at a position exceeding 15% toward the inside from the resin composition surface. Is. If the average particle size is too large or too small, the adhesion tends to decrease.

  The resin composition of the present invention may contain a plasticizer for the purpose of facilitating melt molding. Examples of the plasticizer include ethylene glycol, hexanediol, glycerin, trimethylolpropane, and diglycerin. Aliphatic polyhydric alcohols such as ethylene oxide, propylene oxide, various alkylene oxides such as mixed adducts of ethylene oxide and propylene oxide, saccharides such as sorbitol, mannitol, pentaerythritol, xylol, arabinose, ribulose, bisphenol A and bisphenol S Phenol derivatives such as N-methylpyrrolidone, glucosides such as α-methyl-D-glucoside, and the like. The blending amount is preferably 100 parts by weight or less, more preferably 20 parts by weight or less, and particularly preferably 10 parts by weight or less with respect to 100 parts by weight of the PVA resin (A).

  In addition, the reinforcing agent, filler, pigment, dye, lubricant, antioxidant, antistatic agent, ultraviolet absorber, heat stabilizer, light stabilizer, interface as necessary, as long as the effect of the present invention is not impaired. Activators, antibacterial agents, antistatic agents, drying agents, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, other thermoplastic resins, and the like may be contained.

  In order to use the resin composition of the present invention as a molding material, it is usually in the form of pellets or powder. Among them, it is preferable to use a pellet shape in view of small problems of charring and defects due to fine powder during charging into a molding machine, handling, and molding.

  As a method for preparing the resin composition of the present application, a method of melt-kneading the PVA resin (A) and the elastomer (B) is usually mentioned. Specific examples include a method of melt-kneading each component after dry blending, and a method of mixing the molten PVA resin (A) and the elastomer (B).

  As the mixing order, for example, a method of simultaneously blending the PVA resin (A) and the elastomer (B), one of the PVA resin (A) and the elastomer (B) is first melted, and then the other resin There is a way to blend.

  Examples of the mixing method include a dry blend method using a Banbury mixer or the like, and a blend method such as pelletizing after melt-kneading using a single or twin screw extruder. The melt kneading temperature and the melt kneading time need to be appropriately adjusted according to the melting point of the PVA resin (A), but the melting temperature is usually 190 to 230 ° C, preferably 200 to 220 ° C. Yes, the melt-kneading time is usually 20 to 120 seconds, preferably 30 to 60 seconds.

  When the resin composition obtained by melt-kneading is made into pellets, for example, after melt-kneading, the resin composition is extruded into a strand shape and cooled, and the resulting strand is cut or extruded into water for cutting (under Water cutting method) or a method of cutting (hot cutting method) immediately after extrusion.

[Multilayer structure]
The multilayer structure of the present invention is a layer mainly composed of a vinyl alcohol resin via an adhesive layer obtained by using the resin composition of the present invention on at least one surface of a layer composed mainly of a polyolefin resin. It is a multilayer structure of three or more layers having a layer structure in which is laminated.

  Typical examples of the polyolefin resin used in the polyolefin resin layer include polyethylene and polypropylene. In addition, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4- Examples thereof include homopolymers of α-olefins having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms such as methyl-1-pentene and 1-octene, and copolymers with other α-olefins. Examples of other α-olefins include the same olefins as described above. Such a layer may be a single olefin copolymer or a mixture of two or more olefin copolymers.

  In addition, as a component of the vinyl alcohol-based resin layer, an unmodified fully saponified PVA-based resin, an unmodified partially saponified PVA-based resin, or an olefin-modified vinyl alcohol-based copolymerized with olefins such as ethylene and propylene. Examples thereof include a resin and a modified PVA resin having various functional groups in the side chain. Such modified PVA resins include those having a 1,2-diol component in the side chain, carboxylic acid groups, sulfonic acid groups, amide groups, oxyalkylene groups, quaternary ammonium bases, acetoacetyl groups, diacetone acrylamide groups. And the like in the side chain. Among them, it has an unmodified fully saponified PVA-based resin from the point that the gas barrier property of the resin is good, and an ethylene-vinyl alcohol-based resin and a 1,2-diol component in the side chain from the point that it can be melt-molded. A layer containing a vinyl alcohol resin as a component is preferable. The vinyl alcohol resin layer may be obtained by containing one or more vinyl alcohol resins alone or two or more.

  The multilayer structure of the present invention has a layer structure in which a vinyl alcohol resin layer is laminated on at least one surface of a polyolefin resin layer via an adhesive layer containing the resin composition of the present invention. The structure is a multi-layered structure having at least one layer, where the polyolefin resin layer is a, the vinyl alcohol resin layer is b, and the adhesive layer is c, for example, a / c / b, a / c / b / c / a, b / c / a / c / b, and the like. Especially, what has the structure which vinyl alcohol-type resin is located in the inner layer of a multilayer structure, such as a / c / b / c / a, from the point of the gas barrier property of a multilayer structure is preferable.

  The thickness of each layer is appropriately changed depending on the layer structure, use and container form of the multilayer structure, but the adhesive layer is usually 1 to 500 μm, preferably 3 to 250 μm. If the thickness of the adhesive layer is too thin, the adhesion between the layers may be insufficient. Conversely, if the thickness is too thick, the weight may increase, and the transparency of the infusion bag may decrease. The polyolefin resin layer is usually 10 to 1000 μm, preferably 20 to 500 μm. If such a layer is too thin, the mechanical strength of the multilayer structure may be lowered. Conversely, if the layer is too thick, the weight may be increased, and the flexibility of the multilayer structure may be lowered. A vinyl alcohol-type resin layer is 1-1000 micrometers normally, Preferably it is 3-500 micrometers. If the layer is too thin, the gas barrier property of the multilayer structure may be reduced. Conversely, if the layer is too thick, the weight may be increased, and the transparency of the infusion bag may be reduced.

  In addition, the vinyl alcohol resin layer and the polyolefin resin layer may be made of a plastic such as a thermoplastic elastomer, if necessary, as long as the adhesion with the adhesive layer containing the resin composition that is the object of the present invention is not impaired. An agent, a stabilizer, a pigment and the like can be blended.

  As a manufacturing method of the multilayer structure, a known method is applied. For example, after melt-extrusion laminating the resin composition of the present application on a polyolefin resin film, a vinyl alcohol resin is melt-extrusion laminated or a vinyl alcohol resin film is used. A laminating method, a method of forming each resin by coextrusion, and the like can be mentioned. Also, a polyolefin resin, a resin composition, a vinyl alcohol resin film, a sheet, and the like are each formed in advance by a T-die method, an inflation method, etc., and these are formed into a polyolefin resin film / resin composition film / vinyl alcohol resin film. The method of carrying out hot lamination after stacking in this order is also included.

  In addition, although it is necessary to adjust suitably the temperature at the time of melt-molding each resin with melting | fusing point and decomposition temperature of each resin, it is normally 160-350 degreeC, and in the case of the resin composition of this application, it is usually 160-220. It is 190 degreeC, Preferably it is 190-210 degreeC. In the case of polyolefin resin, it is usually 200 to 350 ° C, preferably 240 to 340 ° C. In the case of a vinyl alcohol-based resin, it is usually 130 to 250 ° C, preferably 180 to 230 ° C. If the melt molding temperature of each resin is too high, there may be defects such as foreign matter in the multilayer structure due to the burning or decomposition of the resin. Conversely, if it is too low, the resin viscosity may be high and molding may be difficult. May not melt and remain as a defect in the multilayer structure.

  When producing an infusion bag using the above multilayer structure, it can be produced by a conventional bag making method, and formed into an arbitrary shape and size according to the purpose of use and the like. can do. Examples of the bag making method include a method in which the multilayer structure is folded or a plurality of sheets are overlapped, and the periphery is heat-sealed into a predetermined shape, and the bag is made using an adhesive. .

  In the above, as a heat sealing method, for example, a known method such as a bar seal, a rotary roll seal, a belt seal, an impulse seal, a high frequency seal, and an ultrasonic seal can be used. Moreover, as an adhesive agent, the ethylene-type thermoplastic elastomer of Unexamined-Japanese-Patent No. 2000-239635 is used.

  The infusion bag may be provided with a plug member injection-molded with a polyolefin resin or the like. In addition, a port for partitioning the inside of the bag may be attached so that a plurality of medicines can be individually placed as described in JP 2009-282557 A, and a plurality of medicines are mixed when used. The port can be destroyed so that it can be done.

  The resin composition of the present invention has excellent adhesiveness to both polyolefin resins and vinyl alcohol resins having gas barrier properties, and also has flexibility from the elastomer (B) as a matrix. And is suitable as an adhesive for infusion bags.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated still in detail, this invention is not limited to a following example, unless the summary is exceeded.
Further, the following “%” means mass basis unless otherwise specified.

Production Example 1
[Production of PVA resin (A-1)]
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 68.0 parts of vinyl acetate, 23.8 parts of methanol, and 8.2 parts of 3,4-diacetoxy-1-butene, and azobisisobutyronitrile. Was added in an amount of 0.3 mol% (compared with vinyl acetate), and the temperature was raised under a nitrogen stream while stirring to initiate polymerization. When the polymerization rate of vinyl acetate reaches 90%, m-dinitrobenzene is added to complete the polymerization, and then unreacted vinyl acetate monomer is removed out of the system by blowing methanol vapor. A combined methanol solution was obtained.

  Next, the methanol solution was further diluted with methanol, adjusted to a concentration of 45%, charged into a kneader, and a 2% methanol solution of sodium hydroxide was added to the vinyl acetate structural unit in the copolymer while maintaining the solution temperature at 35 ° C. And saponification was performed by adding 10.5 mmol with respect to 1 mol of the total amount of 3,4-diacetoxy-1-butene structural units. When saponification progresses and saponification precipitates and forms particles, it is filtered off, washed well with methanol and dried in a hot air dryer to produce the desired PVA resin (A-1) did.

  The saponification degree of the obtained PVA resin (A-1) was 98.5 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate and 3,4-diacetoxy-1-butene. there were. The average degree of polymerization was 450 when analyzed according to JIS K6726. The content of the 1,2-diol structural unit represented by the general formula (1) is measured by 1H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard substance: tetramethylsilane, 50 ° C.). The calculated value was 6 mol%. The melt viscosity was 1550 Pa · s as measured with Capirolactor 1B (manufactured by Toyo Seiki Co., Ltd.) under the conditions of a temperature of 210 ° C. and a shear rate of 122 sec−1.

Production Example 2
[Production of PVA resin (A-2)]
In a reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer, 81.2 parts of vinyl acetate, 9.8 parts of methanol, 9.0 parts of 3,4-diacetoxy-1-butene (initially 7.1 parts, reaction) 1.9 parts was added dropwise so that the ratio of vinyl acetate was constant), 0.032 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) was added, and the temperature was increased under nitrogen flow while stirring. Raised to initiate polymerization. When the polymerization rate of vinyl acetate reaches 72.5%, m-dinitrobenzene is added to complete the polymerization, and then unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution of the copolymer was obtained.

  Next, the methanol solution was further diluted with methanol, adjusted to a concentration of 42%, charged into a kneader, and the 2% methanol solution of sodium hydroxide was added to the vinyl acetate structural unit in the copolymer while maintaining the solution temperature at 35 ° C. The saponification was carried out by adding 12.6 mmol with respect to 1 mol of the total amount of 3,4-diacetoxy-1-butene structural units. When saponification progresses and saponification precipitates and becomes particulate, it is filtered, washed well with methanol and dried in a hot air dryer to produce the desired PVA resin (A-2) did.

The saponification degree of the obtained PVA resin (A-2) was 98.5 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate and 3.4-diacetoxy-1-butene. there were. The average degree of polymerization was 1100 when analyzed according to JIS K 6726. The content of the 1,2-diol structural unit represented by the general formula (1) is measured by 1H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard substance: tetramethylsilane, 50 ° C.). The calculated value was 6 mol%.
The melt viscosity was 2980 Pa · s as measured with Capirolactor 1B (manufactured by Toyo Seiki Co., Ltd.) at a temperature of 210 ° C. and a shear rate of 122 sec−1.

Production Example 3
[Production of unmodified PVA resin]
In the production of the PVA resin (A-1), 3,4-diacetoxy-1-butene is not charged, but only vinyl acetate is polymerized (S / M = 0.5, S: methanol, M: vinyl acetate), An unmodified PVA resin was obtained in the same manner except that saponification was performed.
The degree of saponification of the obtained unmodified PVA resin was 98.5 mol%. The average degree of polymerization was 500 when analyzed according to JIS K6726. The melt viscosity was 1460 Pa · s as measured with Capirolactor 1B (manufactured by Toyo Seiki) under conditions of a temperature of 210 ° C. and a shear rate of 122 sec−1.

Production Example 4
[Preparation of polypropylene resin film]
A polypropylene resin film having a thickness of 80 μm was produced under the following conditions using a short axis extruder using Prime Polypro F-300SP (manufactured by Prime Polymer Co., Ltd.), which is polypropylene.
-Screw inner diameter: 40mm
・ L / D = 25
-Screw compression ratio: 3.2
-Screw rotation speed: 40rpm
-Die: T-die with 5 layer combining adapter-Die width: 450mm
Extrusion temperature: C1 / C2 / C3 / C4 = 190 ° C./200° C./210° C./210° C., A = 200 ° C., D = 200 ° C.

Production Example 5
[Production of polyethylene resin film]
A polyethylene resin film was produced in the same manner as the polypropylene resin film except that Novatec UF340 (manufactured by Nippon Polyethylene Co., Ltd.), which is polyethylene, was used instead of polypropylene.

Production Example 6
[Preparation of vinyl alcohol resin film]
Using a PVA resin (A-1) as a vinyl alcohol resin, a vinyl alcohol resin film having a thickness of 40 μm was produced using a short screw extruder under the following conditions.
-Screw inner diameter: 40mm
・ L / D = 25
-Screw compression ratio: 3.2
-Screw rotation speed: 20rpm
-Die: T-die with 5 layer combining adapter-Die width: 450mm
Extrusion temperature: C1 / C2 / C3 / C4 = 180 ° C./198° C./198° C./198° C., A = 200 ° C., D = 200 ° C.

Production Example 7
[Preparation of ethylene-vinyl alcohol resin film]
Use ethylene-vinyl alcohol copolymer “Soarnol D2908” (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., ethylene content 28 mol%, saponification degree 99.8 mol%, MFR (210 ° C., 2160 g) 8 g / 10 min). Except for the above, an ethylene-vinyl alcohol resin film was produced in the same manner as the vinyl alcohol resin film.

Example 1
[Preparation of resin composition]
70 parts by weight of the PVA resin (A-1) obtained in Production Example 1 and Kraton G1643 (made by Shell, polyethylene content 18%, temperature 210 ° C., which is a styrene-ethylene-butylene resin as the elastomer (B)) After dry blending 30 parts by weight of melt viscosity 560 Pa · s) measured with Capilloractor 1B (manufactured by Toyo Seiki Co., Ltd.) under a shear rate of 122 sec-1, this was melt kneaded under the following conditions in a twin screw extruder. Then, it was extruded into a strand shape and cut with a pelletizer to obtain a cylindrical pellet resin composition. The viscosity ratio of the obtained composition was 2.76. In addition, the manufacturing conditions of the pellet by a twin-screw extruder are as follows.
-Screw diameter (D): 15mmφ
・ Screen mesh: 90/90 mesh
・ L / D = 60
・ Screw rotation speed: 200rpm
Set temperature: C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 150 ° C / 170 ° C / 180 ° C / 190 ° C / 200 ° C / 210 ° C / 210 ° C / 210 ° C / 210 ° C / 210 ° C
・ Discharge rate: 1.5kg / hr

[Preparation of adhesive film]
Using the obtained resin composition, an adhesive film having a thickness of 20 μm was produced using a short-axis extruder under the following conditions.
-Screw inner diameter: 30mm
・ L / D = 25
-Screw compression ratio: 3.2
-Screw rotation speed: 20rpm
-Die: T-die with 5 layer combining adapter-Die width: 450mm
Extrusion temperature: C1 / C2 / C3 / C4 = 190 ° C./200° C./210° C./210° C., A = 200 ° C., D = 200 ° C.

[Morphological evaluation]
The obtained adhesive film was divided under liquid nitrogen, and the cross-sectional portion was immersed in warm water at 80 ° C. for 2 hours. The etched cross-section was photographed with a scanning electron microscope (SEM), and the morphology was visually observed. . The photograph taken is shown in FIG. In the photograph taken, when the average particle size of the island component was determined, the average was 0.5 μm at the surface layer portion and 6 μm at the inner layer portion. Since pores are formed by etching with water, it can be confirmed that the island component was a water-soluble PVA resin.

[Adhesion evaluation]
The adhesive film and the polypropylene resin film were superposed and pressure-bonded at a temperature of 210 ° C. and a pressure of 1.3 kg / cm ² for 6 seconds, and then cut to a width of 25 mm. This was subjected to a peel test with an autograph (manufactured by Shimadzu Corporation) under conditions of a maximum test force of 50 N and 10 mm / min, and the obtained peel strength value was the value of the adhesive strength between the adhesive film and the polypropylene resin film. It was.
In addition, the adhesive film and the vinyl alcohol-based resin film are overlapped, a sample is prepared in the same manner as described above, a peel test is performed, and the obtained peel strength value is determined based on the adhesive strength between the adhesive film and the vinyl alcohol-based resin film. Value.
The obtained evaluation results are shown in Table 1.

Example 2
In Example 1, a resin composition (viscosity ratio 2.76) was prepared in the same manner as in Example 1 except that a polyethylene resin film was used instead of the polypropylene resin film. The adhesiveness was evaluated. The results are shown in Table 1.

Example 3
In Example 1, the resin composition (viscosity ratio of 2.) was obtained in the same manner as in Example 1 except that the PVA resin (A-1) in the resin composition was 60 parts by weight and the elastomer (B) was 40 parts by weight. 76) was prepared, and the adhesiveness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
In Example 1, adhesive evaluation was performed in the same manner as in Example 1 except that an ethylene-vinyl alcohol resin film was used instead of the vinyl alcohol resin film. The results are shown in Table 1.

Example 5
In Example 1, a resin composition (viscosity ratio of 5.32) was obtained in the same manner as in Example 1 except that the PVA resin (A-2) was used instead of the PVA resin (A-1) in the resin composition. The adhesiveness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
In Example 1, a resin composition (viscosity ratio 2.6) was prepared in the same manner as in Example 1 except that an unmodified PVA resin was used instead of the PVA resin (A-1) in the resin composition. The adhesiveness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
In Example 1, a resin composition was prepared in the same manner as in Example 1 except that only Kraton G1643 was used as the resin composition, and adhesion evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3
In Example 1, the resin composition (viscosity ratio 2.76) was used in the same manner as in Example 1 except that 30 parts by weight of PVA resin (A-1) and 70 parts by weight of elastomer (B) were used in the resin composition. ) And adhesiveness evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4
In Example 1, a resin composition (viscosity ratio of 2.) was used in the same manner as in Example 1 except that 50 parts by weight of PVA resin (A-1) and 50 parts by weight of elastomer (B) were used in the resin composition. 76) was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 5
In Example 1, a resin composition (viscosity ratio of 2.) was used in the same manner as in Example 1 except that 80 parts by weight of PVA resin (A-1) and 20 parts by weight of elastomer (B) were used in the resin composition. 76) was prepared, and the adhesiveness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Morphological evaluation]
The adhesive film was divided under liquid nitrogen, and the cross-sectional portion was immersed in xylene at 60 ° C. for 2 hours. The etched cross-section was photographed with a scanning electron microscope (SEM), and the morphology was visually observed. The photograph taken is shown in FIG. Since voids are formed by etching with xylene, it can be confirmed that the island component was the elastomer (B).

Comparative Example 6
In Example 1, instead of Kraton G1643 as an elastomer (B) in the resin composition, Clayton MD6945 (manufactured by Shell Co., Ltd., polystyrene content 13%, temperature 210 ° C., shear rate 122 sec-1), Capilloractor 1B (Toyo A resin composition (viscosity ratio 1.23) was prepared in the same manner as in Example 1 except that the melt viscosity 1260 Pa · s measured by Seiki Co., Ltd. was used. Evaluated. The results are shown in Table 1.

[Morphological evaluation]
The adhesive film was divided under liquid nitrogen, and the cross-sectional portion was immersed in xylene at 60 ° C. for 2 hours. The etched cross-section was photographed with a scanning electron microscope (SEM), and the morphology was visually observed. The photograph taken is shown in FIG. Since voids are formed by etching with xylene, it can be confirmed that the island component was the elastomer (B).

Example 6
[Manufacture of multilayer structures]
Using the resin composition obtained in Example 1 and using a multi-layer extruder equipped with a multi-layer T die of 5 layers in a single-screw extruder, a polyolefin resin layer (polypropylene [Prime Polypro F-300SP, Prime Manufactured by Polymer Co., Ltd.) / Resin composition layer / vinyl alcohol resin layer (PVA resin (A-1)) / resin composition layer / polyolefin resin layer (polypropylene) (thickness 80/20/40/20/80 μm) ) Was obtained. The multilayer film forming conditions are as follows.
Screw inner diameter: 40 mm (polyolefin resin, vinyl alcohol resin), 30 mm (adhesive resin composition)
・ L / D = 25
-Screw compression ratio: 3.2
Screw rotation speed: 40 rpm (polyolefin resin), 20 rpm (vinyl alcohol resin, resin composition)
-Die: T-die with 5 layer combining adapter-Die width: 450mm
Extrusion temperature: C1 / C2 / C3 / C4 = 180 ° C / 198 ° C / 198 ° C / 198 ° C (vinyl alcohol resin), C1 / C2 / C3 / C4 = 190 ° C / 200 ° C / 210 ° C / 210 ° C ( Polyolefin resin, adhesive resin), A = 200 ° C., D = 200 ° C.
The obtained multilayer structure was not delaminated between the respective layers.

  Since the resin composition of the present invention has excellent adhesion to both polyolefin-based resins and vinyl alcohol-based resins, in a multilayer structure including a polyolefin-based resin layer and a vinyl alcohol-based resin layer, both layers It is suitable as a material for the adhesive layer.

Claims (5)

A resin composition comprising a polyvinyl alcohol resin (A) having a structural unit represented by the general formula (1) and a styrene thermoplastic elastomer (B), the polyvinyl alcohol resin (A) and styrene The weight ratio (A / B) of the thermoplastic elastomer (B) is 75/25 to 55/45, the polyvinyl alcohol resin (A) is an island component, and the styrene thermoplastic elastomer (B) is a sea component. A resin composition having a sea-island structure.

[Wherein R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. Indicates an atom or an organic group. ]   The melt viscosity ratio (A / B) of the polyvinyl alcohol (A) having the structural unit represented by the general formula (1) and the styrene-based thermoplastic elastomer (B) is 7/1 to 5/3. The resin composition according to claim 1.   An adhesive comprising the resin composition according to claim 1.   A multilayer structure characterized by having a layer structure in which a polyolefin resin layer is laminated on at least one surface of a polyvinyl alcohol resin layer via an adhesive layer containing the resin composition according to claim 1 or 2. body.   An infusion bag comprising a bag made of the multilayer structure according to claim 4.