JP2010260878A - Resin composition and multi-layered structure using the resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a saponified ethylene-vinyl ester copolymer resin capable of giving a molded article which is excellent in a gas-barrier property and is little in the irregularity of the thickness of the saponified ethylene-vinyl ester copolymer rein layer, even when subjected to a molding method including such a drawing treatment as adding large tensions different at sites in a short time, such as a deep drawing molding method, a vacuum molding method or a pressure molding method, and to provide a multi-layered structure using the resin composition. <P>SOLUTION: This saponified ethylene-vinyl ester copolymer resin composition includes a saponified ethylene-vinyl ester copolymer having an ethylene content of 20 to 60 mol% and PVA containing a side chain of 1, 2-diol structural units represented by formula (1) (wherein, R<SP>1</SP>to R<SP>6</SP>are each independently H or an organic group; X is a single bond or a bond chain). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin composition (EVOH resin composition) of a saponified ethylene-vinyl ester copolymer with improved stretchability, and is accompanied by stretching treatment such as film, sheet, bottle, cup, tube, etc., particularly bottles and cups. The present invention relates to an EVOH resin composition used for a multilayer structure suitable for a molded article.

  The saponified ethylene-vinyl ester copolymer (hereinafter sometimes referred to as “EVOH resin”) has a gas barrier property in the same manner as polyvinyl alcohol (hereinafter sometimes referred to as “PVA”), which is a saponified polyvinyl ester. Excellent. Moreover, while PVA is water-soluble and its melting point is close to the decomposition point and cannot be melt-molded, EVOH resin is insoluble in water, and since the difference between the melting point and the decomposition point is large, it can be melt-molded. Widely used in various packaging applications such as pharmaceutical packaging materials. The EVOH resin film itself can be used alone, but the gas barrier property and film strength are reduced by moisture absorption. Therefore, a multilayer structure in which the outer surface layer is usually composed of a thermoplastic resin film or the like that hardly permeates moisture. Used as a body.

  A multilayer structure such as a sheet is preferably stretched to increase the strength, and the EVOH resin layer can also be improved in gas barrier properties when molecular chains are aligned in a high density state by stretching. The structure is used after being stretched.

  However, when the multilayer structure including the EVOH resin layer is stretched, the EVOH resin layer does not stretch well as compared with the thermoplastic resin layer. For this reason, during stretching treatment such as uniaxial stretching and biaxial stretching, the EVOH resin layer is difficult to be stretched uniformly, and cannot follow the elongation of the outer surface layer, causing streaks in the stretched multilayer structure, In some cases, there is a problem of breaking.

In order to improve the stretchability of a multilayer structure having an EVOH resin layer, for example, JP-A 63-114645 proposes an EVOH resin composition containing a specific polyamide resin.
JP-A-8-311276 proposes to use a resin composition in which two types of EVOH resins having different ethylene contents are mixed.

JP 63-114645 A JP-A-8-311276

  As described above, extensibility is improved by mixing EVOH resin with another thermoplastic resin or by devising the configuration of EVOH resin itself, but there is still room for improvement. In particular, it is a molding method that involves a stretching process, as in the case of molding a cup-shaped container by a molding method such as deep drawing molding or vacuum pressure molding using a multilayer structure, and the tension applied during stretching depends on the site. When applied to different moldings, the EVOH resin layer may not be evenly stretched, resulting in uneven thickness, or the uneven thickness may look like streaks and affect the appearance. Further, the thickness unevenness causes a deterioration in the uniformity of the polymer after stretching, and thus affects the gas barrier properties of the entire molded product.

  The present invention has been made in view of the above circumstances, and its purpose is to apply different tensions depending on the part, such as deep drawing and vacuum / pressure forming, and to apply large tensions in a short time. An EVOH resin composition that can provide a molded article with little variation in the thickness of the EVOH resin layer and excellent gas barrier properties even when a molding method including additional stretching treatment is applied, and a multilayer using the resin composition It is to provide a structure.

As a result of studying various resins to improve the stretchability of EVOH resin, the present inventors have found that stretchability and gas barrier properties can be improved by adding polyvinyl alcohol having a specific structure. Was completed. That is, the resin composition (ethylene-vinyl ester copolymer saponified resin composition) of the present invention is converted to an ethylene-vinyl ester copolymer saponified product having an ethylene content of 20 to 60 mol% by the general formula (1 ), Which contains polyvinyl alcohol containing a side chain 1,2-diol structural unit. (1) In the formula, R ^{1 to} R ⁶ each independently represent a hydrogen atom or an organic group, and X represents a single bond or a bond chain.

  The blending amount of the polyvinyl alcohol is preferably 1 part by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the ethylene-vinyl ester copolymer saponified resin, and is represented by the general formula (1) in the polyvinyl alcohol. The content of the side chain 1,2-diol structural unit shown is preferably 1 to 30 mol%.

  The multilayer structure of the present invention has at least one thermoplastic resin layer other than the ethylene-vinyl ester copolymer saponified resin composition layer of the present invention and the ethylene-vinyl ester copolymer, The thermoplastic resin other than the saponified ethylene-vinyl ester copolymer is preferably at least one selected from the group consisting of polyolefin resins, polyamide resins, and polyester resins.

  The multilayer structure of the present invention preferably has a thermoplastic resin layer / ethylene-vinyl ester copolymer saponified resin composition layer thickness ratio of more than 1 to 30, and the multilayer structure has a thickness of 1 to 1 It is preferable that it is 30000 micrometers.

  The multilayer structure of the present invention may be stretched, and a molded product obtained by heat-stretching the multilayer structure of the present invention is also included in the scope of the present invention. As the heat stretch molding, mold molding is preferable, and in the case of mold molding, the drawing ratio is preferably 0.1-3.

  The ethylene-vinyl ester copolymer saponified resin composition (EVOH resin composition) of the present invention and the multilayer structure having the resin composition layer are applied to stretch-processing molding in which different sizes of tension are applied depending on the part. Even so, it is possible to provide a molded product with little variation in the thickness of the EVOH resin layer and excellent gas barrier properties.

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 ethylene-vinyl ester copolymer saponified resin composition (EVOH resin composition) of the present invention will be described.

<EVOH resin composition>
The EVOH resin composition of the present invention is obtained by adding polyvinyl alcohol containing a side chain 1,2-diol structural unit to an ethylene-vinyl ester copolymer saponified product (EVOH resin) having an ethylene content of 20 to 60 mol%. It is a blend.

[EVOH resin]
The EVOH resin as the main component of the composition is a water-insoluble thermoplastic resin obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerizing ethylene and a vinyl ester monomer. The ethylene-vinyl ester copolymer is produced by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc., and saponification of the ethylene-vinyl ester copolymer can also be performed by a known method. .

As the vinyl ester monomer, vinyl acetate is typically used. In some cases, for example, vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and other aliphatic vinyl esters, Aromatic vinyl esters such as vinyl benzoate, vinyl trifluoroacetate and the like can be mentioned. Usually, it is an aliphatic vinyl ester having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. These vinyl ester monomers are usually used alone, but a plurality of them may be used simultaneously as necessary.
In particular, an ethylene-vinyl acetate copolymer using vinyl acetate as a vinyl ester monomer is referred to as EVA resin.

  The EVOH resin used in the resin composition of the present invention has an ethylene content of 20 to 60 mol%, preferably 25 to 55 mol%, more preferably 28 to 48 mol%, measured based on ISO4663. When the ethylene content is too low, the melt moldability of the resin composition tends to be lowered. On the other hand, if the ethylene content is too high, the proportion of OH groups contained in the polymer chain will inevitably decrease, and the gas barrier property tends to be insufficient.

  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 80 to 100 mol%, preferably Is 90 to 100 mol%, more preferably 95 to 100 mol%. This is because when the saponification degree decreases, the gas barrier property tends to decrease.

  Further, in the melt flow rate of EVOH resin (may be expressed as MFR), it is usually 1 to 30 g / min, preferably 2 to 15 g / min, particularly preferably at 210 ° C. and a load of 2160 g. Is 3 to 10 g / min. If this value is too large, the melt viscosity tends to be low and stable melt extrusion tends to be difficult, and if it is too small, the melt viscosity tends to be high and stable melt extrusion tends to be difficult.

As the EVOH resin used in the resin composition of the present invention, two or more kinds different in ethylene content and saponification degree may be mixed and used 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 the EVOH resin used in the present invention, a compounding agent generally blended with the EVOH resin, for example, an antioxidant, an antistatic agent, a colorant, an ultraviolet absorber, a lubricant, and a plasticizer, as long as the effects of the present invention are not impaired. , Heat stabilizer, light stabilizer, surfactant, antibacterial agent, drying agent, antiblocking agent, flame retardant, crosslinking agent, curing agent, foaming agent, crystal nucleating agent, antifogging agent, biodegradation additive, silane A coupling agent, an oxygen absorbent, etc. may be contained.
[Polyvinyl alcohol]
The polyvinyl alcohol used in the resin composition of the present invention is a polyvinyl alcohol having a side chain 1,2-diol structural unit represented by the general formula (1) (hereinafter referred to as “side chain 1,2-diol structural unit-containing PVA”). ). Such resins are water soluble.

In the general formula (1) ^represents a hydrogen atom or an organic group R 1 to R ⁶ each independently. R ^{1 to} R ⁶ are preferably all hydrogen atoms, but may be organic groups as long as the resin properties are not significantly impaired. Although it does not specifically limit as this organic group, For example, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, are preferable, You may have substituents, such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, and a sulfonic acid group, as needed.

In the above general formula (1), X is a single bond or a bond chain, and is preferably a single bond from the viewpoint of thermal stability and stability under high temperature and acidic conditions. The bonding chain is not particularly limited, but other hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine, bromine, etc.) _{, -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) -, - OAl (O ) Although O- and the like (R is an optional substituent each independently, a hydrogen atom, an alkyl group are preferred, and m is a natural number) and the like. Among these, an alkylene group having 6 or less carbon atoms, particularly a methylene group, or —CH ₂ OCH ₂ — is preferable from the viewpoint of stability during production or use.

  The side chain 1,2-diol structural unit-containing PVA having the above structure generally has a melting point of 150 to 205 ° C., although it depends on the degree of saponification and the side chain 1,2-diol structural unit content. Since this melting point is lower than normal PVA obtained by saponifying polyvinyl ester (hereinafter referred to as “unmodified PVA”), it has a feature that a wide range of temperature conditions can be selected during stretching. In addition, the side chain 1,2-diol structural unit-containing PVA has a gas barrier property based on the OH group content contained in the polymer chain and the height of the hydrogen bond due to the primary hydroxyl group, similarly to the unmodified PVA. In spite of having a characteristic that crystallization is slower than that of native PVA. The reason and mechanism are not clear, but the hydrogen bond due to the primary hydroxyl group of the side chain 1,2-diol structure is strong, so the relaxation time of the side chain diol part is much longer than the crystal part due to the hydroxyl group of the main chain. This is presumed to be due to the long period of time.

Such a side chain 1,2-diol structural unit containing PVA should just be contained in the resin composition of this invention only by the quantity smaller than the amount of EVOH resin. Specifically, the content of the side chain 1,2-diol structural unit-containing PVA per 100 parts by weight of EVOH resin is 1 part by weight or more and less than 100 parts by weight, preferably 3 to 70 parts by weight, more preferably 5 to 70 parts by weight, particularly preferably 10 to 50 parts by weight.
Thus, blending the PVA resin that is a water-soluble resin into the EVOH resin that is a water-insoluble thermoplastic resin is not usually performed from the viewpoint of water resistance, and in this respect, It can be said that the composition is characteristic.

  Since the side chain 1,2-diol structural unit-containing PVA as described above has a higher gas barrier property than that of the EVOH resin, the gas barrier property of the layer formed of the EVOH resin composition of the present invention can be changed from the EVOH resin alone. The gas barrier property of the layer can be improved.

  Furthermore, the EVOH resin composition layer containing the side chain 1,2-diol structural unit-containing PVA in the above ratio has better stretchability than the EVOH resin single layer, and thereby uniform tension throughout the layer. Can be applied. In addition, since the crystallization is partially suppressed quickly even during cooling, the uniformity of the crystallinity in the EVOH resin composition layer of the present invention is also increased. Therefore, as the EVOH resin composition layer after stretching, it is possible to reduce variation in thickness and the like by being uniformly stretched, and it is possible to achieve better gas barrier properties by enhancing the uniformity of crystallinity.

  The content of the side chain 1,2-diol structural unit contained in the side chain 1,2-diol structural unit-containing PVA is usually preferably 1 to 30 mol%, more preferably 1 to 20 mol%, still more preferably 3 -10 mol%. When the content of the side chain 1,2-diol structural unit becomes too high, the thermal stability during extrusion molding tends to be lowered. On the other hand, if the content of the side chain 1,2-diol structural unit becomes too low, the melting point becomes high and the melt extrusion moldability is lowered, and it approaches the unmodified PVA. As a result, the EVOH resin composition layer is prevented from being homogenized.

The content of the side chain 1,2-diol structural unit in PVA can be determined from ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane) of PVA completely saponified. Specifically, it may be calculated from the peak area derived from the hydroxyl proton, methine proton, and methylene proton in the 1,2-diol unit, the methylene proton in the main chain, the proton in the hydroxyl group linked to the main chain, and the like. .

  The polymerization degree of the side chain 1,2-diol structural unit-containing PVA used in the present invention is usually 100 to 5000, more preferably 100 to 1000, and still more preferably 300 to 500. When the degree of polymerization is too high, the melt viscosity becomes high and stable melt extrusion tends to be difficult. On the other hand, if the degree of polymerization is too low, stable melt extrusion tends to be difficult.

  The degree of saponification of the side chain 1,2-diol structural unit-containing PVA used in the present invention is a value measured based on JIS K6726, and is usually 80 to 100 mol%, preferably 90 to 100 mol%. More preferably, it is 95-100 mol%. If the saponification degree is too low, the gas barrier property is lowered, and it becomes difficult to obtain the gas barrier improvement effect by the side chain 1,2-diol-containing PVA blending.

The most preferred structure of the side chain 1,2-diol structural unit-containing PVA in the present invention is when all of R ^{1 to} R ⁶ in the structural unit (1) are hydrogen atoms and X is a single bond. That is, those containing a structural unit represented by the following structural formula (1a) are preferable.

  The most preferable composition of the side chain 1,2-diol structural unit-containing PVA is that the structural unit (1a) is 3 to 10 mol% and a structural unit derived from vinyl alcohol, and a trace amount of vinyl ester structure remaining after saponification. It consists of units and has a saponification degree of 95 to 100% and a polymerization degree of 300 to 500.

  The method for producing the side chain 1,2-diol structural unit-containing PVA as described above is not particularly limited, but (i) a saponified 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), (iii) a vinyl ester monomer and the following general formula (4) It is preferably produced by a method of saponifying and deketalizing a copolymer with the compound shown.

(2) In the formulas (3) and (4), R ^{1 to} R ⁶ are the same as those in the formula (1). R ⁷ and R ⁸ are each independently hydrogen 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 employed.

Among them, the method in terms of excellent in copolymerization reactivity and industrial handling (i) are preferred, ^R 1 to R ⁶ are hydrogen atoms, X is a single bond, ^{R 7} and ^{R 8} are ^R 9 -CO 3,4-diasiloxy-1-butene in which R ⁹ is an alkyl group is preferred, and among these, 3,4-diacetoxy-1-butene in which R ⁹ is a methyl group is particularly preferred.

  In addition to the above-mentioned monomers (vinyl ester monomers, compounds represented by the general formulas (2), (3), and (4)), in a range not impairing high gas barrier properties and melt extrudability (for example, 10 mol% or less). If present, as copolymerization components, α-olefins such as ethylene and propylene; hydroxy group-containing α-olefins such as 3-buten-1-ol and 4-penten-1-ol, and esterified and acylated products thereof Group-containing α-olefin derivatives; unsaturated acids such as itaconic acid, maleic acid and acrylic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile, amides such as methacrylamide and diacetone acrylamide, ethylene sulfonic acid, Olefin sulfones such as allyl sulfonic acid, methallyl sulfonic acid, and AMPS Or a compound such as a salt thereof, allyl acetate, butadiene derivative and the like may be copolymerized.

[Other ingredients]
In addition to the EVOH resin and the side chain 1,2-diol structure-containing PVA resin, the resin composition of the present invention includes an antioxidant, a lubricant, hydrotalcites, an antistatic agent, and a colorant as necessary. Further, additives such as ultraviolet absorbers may be appropriately contained.

  The resin composition of the present invention is produced by mixing the above components. Such a mixing method includes melt mixing or a method in which EVOH resin is dissolved in a solvent such as water-alcohol or dimethyl sulfoxide and mixed in a solution state.

  In the case of the solution mixing method, the mixing order of each component is not particularly limited. (I) A method in which each component is dry blended and then dissolved in a common good solvent for both resins, and (ii) one of the components is mixed. Examples include a method in which the other resin is mixed with a solution in which the resin is dissolved in a solvent, and (iii) a method in which each resin is separately dissolved in a good solvent and mixed in a solution state.

  In the case of the melt mixing method, the mixing order of each component is not particularly limited, and (i) a method in which each component is dry blended and then mixed, (ii) one resin is in a molten state. Examples include a method of mixing the other resin, and (iii) a method in which each resin is separately melted and mixed in a molten state.

  Among them, the melt mixing method is preferable from the viewpoint of productivity. In the melt mixing, for example, a kneader, a kneader, a mixing roll, a Banbury mixer, a plast mill or the like can be used. Further, it is also preferable to provide a vent suction device, a gear pump device, a screen device and the like as necessary. In particular, in order to remove moisture and by-products (such as pyrolytic low molecular weight substances), one or more vent holes are provided in the extruder and suction is performed under reduced pressure, or oxygen is prevented from entering the extruder. Therefore, by continuously supplying an inert gas such as nitrogen into the hopper, a resin composition having excellent quality with reduced thermal coloring and thermal deterioration can be obtained.

  The EVOH resin composition of the present invention having the composition as described above has an excellent appearance and a high gas barrier property after stretching treatment in addition to the original properties of the EVOH resin that is water-insoluble and has gas barrier properties. Can hold.

  The EVOH resin composition of the present invention can be used alone as a material for various molded articles such as a film, a sheet, a container, a rod-like body, and a tubular body, but is preferably laminated with a moisture-impermeable thermoplastic resin. Used as various molded products of multilayer structures.

  A molded product using the EVOH resin composition of the present invention may be molded as it is into various molded products from the state of being mixed by the above mixing method. Alternatively, the pellets may be once pelletized from the mixed state by the above mixing method, and the pellets may be formed into various molded products.

<Multilayer structure>
The multilayer structure of the present invention has the same meaning as the multilayer laminate, except for the EVOH resin composition layer of the present invention (hereinafter simply referred to as “EVOH resin composition layer”) and the saponified ethylene-vinyl ester copolymer. The multilayer structure having at least one thermoplastic resin layer (hereinafter simply referred to as “thermoplastic resin layer” in this section means the layer).

  The thermoplastic resin constituting the thermoplastic resin layer is not particularly limited, but specifically, for example, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer , Ionomer, ethylene-propylene copolymer, ethylene-acrylic ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene or other olefin alone or Copolymers, or polyolefins such as those obtained by graft-modifying these olefins alone or copolymers with unsaturated carboxylic acids or esters thereof, cyclic olefin resins, polystyrene resins, polyesters, polyamides, copolymers Polyamide, polyvinyl chloride, polyvinyl chloride Den, acrylic resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, and chlorinated polypropylene. Of these, polyolefin resins, polyamide resins, and polyester resins are preferably used in terms of moisture impermeability, more preferably polyolefin resins, and particularly preferably polyethylene and polypropylene. A multilayer structure combined with such a moisture-impermeable thermoplastic resin layer is preferably used as a packaging film, container, tube, pipe or the like having gas barrier properties.

  The multilayer structure of the present invention includes EVOH resin composition layer, thermoplastic resin layer, paper, metal foil, uniaxial or biaxially stretched plastic film or sheet, woven fabric, non-woven fabric, metal strip, wood surface, etc. May be laminated, and aluminum or silica deposition may be performed between these layers and the layer surface.

In order to obtain these multilayer structures, a melt molding method is generally employed in which the EVOH resin composition is heated and melted.
Examples of such a melt molding method include, specifically, a film of EVOH resin composition, a method of melt-extruding a thermoplastic resin on a sheet, a method of melt-extruding an EVOH resin composition layer on a substrate such as a thermoplastic resin, Examples thereof include a method of co-extrusion of the EVOH resin composition layer and the thermoplastic resin layer, and a method of co-injecting the EVOH resin composition layer and the thermoplastic resin layer.
In addition to this, an EVOH resin composition film and a base material such as a thermoplastic resin film can be used with a known adhesive such as an organic titanium compound, an isocyanate compound, a polyethyleneimine compound, a polyester compound, or a polyurethane compound. Examples thereof include a dry laminating method and an adhesive resin layer.

  It does not specifically limit as adhesive resin which comprises an adhesive resin layer, Although a various thing can be used, Generally, the modified olefin polymer containing a carboxyl group is mentioned. Such a polymer can be obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to an olefin polymer (the above-mentioned broad polyolefin system) by an addition reaction or a graft reaction. Specific examples of the unsaturated carboxylic acid or anhydride thereof include maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-acetic acid One or a mixture of two or more selected from vinyl copolymers and the like is preferred.

As described above, the multilayer structure of the present invention before stretching only needs to include at least one EVOH resin composition layer and a thermoplastic resin layer according to the present invention, and the configuration thereof is not particularly limited. However, when the EVOH resin composition layer is a (a1, a2,...) And the thermoplastic resin layer other than the EVOH resin is b (b1, b2,...), Usually 3 to 15 layers, preferably It has a layer structure of 3 to 7 layers, particularly preferably 5 to 7 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.
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 more preferable so that the permeation of moisture into the resin composition layer can be prevented. Specifically, a multilayer structure having a thermoplastic resin layer / adhesive resin layer / EVOH resin composition layer / adhesive resin layer / thermoplastic resin layer as a structural unit is preferable.

  The thickness of the multilayer structure of the present invention is usually 1 to 30000 μm, preferably 3 to 13000 μm, more preferably 1 to 3000 μm, and particularly preferably 1 to 1300 μm. In the multilayer structure having such a configuration, the thickness of the thermoplastic resin layer is not particularly limited, but is usually 0.1 to 10,000 μm, preferably 0.1 to 5000 μm, more preferably 0.1 to 1000 μm, and particularly preferably 1. ˜500 μm. The thickness of the EVOH resin composition layer is not particularly limited, but is usually 0.1 to 5000 μm, preferably 0.1 to 1000 μm, more preferably 0.1 to 500 μm, and particularly preferably 1 to 100 μm. The thickness of the adhesive resin layer is not particularly limited, but is usually 0.1 to 2500 μm, preferably 0.1 to 1000 μm, more preferably 0.1 to 250 μm, and particularly preferably 0.1 to 100 μm.

  Moreover, the thickness ratio of the thermoplastic resin layer / EVOH resin composition layer is usually more than 1 to 30 and preferably 2 to 20 in the ratio of the thickest layers when there are a plurality of layers. The thickness ratio of the adhesive resin layer / EVOH resin composition layer is usually 0.1 to 1, preferably 0.25 to 1. If the thickness ratio of the thermoplastic resin layer / EVOH resin composition layer is too small, the moisture resistance and strength tend to decrease, and if too large, the transparency tends to decrease and the production cost increases.

  It is preferable that the multilayer structure of the present invention is further stretched by heat stretching. In the multilayer structure with the thermoplastic resin layer, the strength is increased by the stretching treatment, and the gas barrier property of the EVOH resin composition layer can be enhanced. In particular, the EVOH resin composition layer contained in the multilayer structure of the present invention is easily stretched during the stretching treatment as described above. In addition, since the crystallization speed is delayed, even if the film is highly stretched, no breakage, pinholes, cracks, uneven thickness, etc. occur, and a highly uniform layer can be maintained. Therefore, it is excellent in appearance after the stretching treatment, and also has excellent gas barrier properties and transparency due to its uniformity.

In addition, about the said extending | stretching process etc., a well-known extending | stretching method is employable.
For example, specifically, uniaxial stretching and biaxial stretching for grasping and widening both ears of the multilayer structure sheet; deep drawing method, vacuum forming method, and pressure forming method for stretching the multilayer structure sheet using a mold And a molding method using a mold such as a vacuum / pressure forming method; a method of processing a preformed multilayer structure such as a parison by a tubular stretching method, a stretching blow method, or the like.

  The temperature at which the heat-stretching is carried out 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 50 to 300 ° C, preferably about 60 to 160 ° C. A draw ratio is 2-50 times normally by an area ratio, Preferably it is 2-10 times.

For example, in the case of uniaxial stretching or biaxial stretching (both simultaneous biaxial stretching method and sequential biaxial stretching method can be adopted), the temperature at which the stretching is performed is the temperature of the multilayer structure (the temperature near the multilayer structure). Usually, it is selected from the range of about 50 to 300 ° C, preferably about 60 to 160 ° C. A draw ratio is 2-50 times normally by an area ratio, Preferably it is 2-10 times.
When aiming at a film or a sheet-like molded product, it is preferable to employ a uniaxial stretching method or a biaxial stretching method.

In addition, in the case of a mold forming method such as a deep drawing method, vacuum forming method, pressure forming method, vacuum pressure forming method, etc., the sheet of the multilayer structure is made uniform by a hot air oven, a heater type oven or a combination of both. And then uniformly formed into various shapes using a chuck, plug, vacuum force, pneumatic force, and the like.
In such a stretch molding method, the temperature of the multilayer structure (temperature near the multilayer structure) is usually selected from the range of about 50 to 300 ° C., preferably about 60 to 160 ° C.
When a molded product such as a cup or tray whose drawing ratio (depth of molded product (mm) / maximum diameter of molded product (mm)) is usually 0.1 to 3 is used, a deep drawing method, vacuum It is preferable to adopt a mold forming method such as a forming method, a pressure forming method, a vacuum pressure forming method, or the like that is stretched using a mold.

In particular, vacuum / pressure forming including an abrupt stretching process is employed, but when vacuum / pressure forming is performed, the magnitude of the tension applied to the resin differs between the cup side surface portion and the bottom surface portion. For this reason, if the stretchability of the resin is inferior, thickness unevenness tends to occur. However, since the EVOH resin composition layer contained in the multilayer structure of the present invention is easily stretched and slow in crystallization, a molded product with little thickness unevenness can be obtained even when manufactured by vacuum / pressure forming. Therefore, by using the EVOH resin composition of the present invention, a molded product having an excellent appearance and gas barrier property even when adopting stretch molding under severe conditions such that vacuum tensioning is difficult to apply tension uniformly. Can provide.
The drawing ratio (depth of molded product (mm) / maximum diameter of molded product (mm)) of a molded product using the EVOH resin composition of the present invention is usually 0.1 to 3, preferably 0.2 to 2. .5, particularly preferably 0.3-2. When this value is too large, cracks and the like of the EVOH resin composition layer are likely to occur, and when it is too small, the stretching effect tends to be insufficient.

In addition, when processing by a tubular stretching method, a stretch blow method, or the like, a preformed multilayer structure such as a parison is uniformly heated by a hot air oven, a heater-type oven or a combination of both, a chuck, It is uniformly formed into various shapes by plug, vacuum force, pneumatic force, etc.
In such a stretch molding method, the temperature of the multilayer structure (temperature near the multilayer structure) is usually selected from the range of about 50 to 300 ° C., preferably about 60 to 160 ° C.
For example, when aiming at a hollow container such as a fuel tank such as gasoline or a beverage tank or a bottle, it is preferable to employ a tubular stretching method, a stretching blow method, or the like.

The thickness of the multilayer structure after the stretching treatment is usually 1 to 13000 μm, preferably 1 to 7000 μm, more preferably 1 to 1300 μm, and particularly preferably 3 to 700 μm. The thickness of the thermoplastic resin layer is usually 0.1 to 5000 μm, more preferably 0.1 to 3000 μm, more preferably 0.1 to 500 μm, and particularly preferably 1 to 300 μm. The thickness of the EVOH resin composition layer is usually 0.1 to 1000 μm, preferably 0.1 to 500 μm, more preferably 0.1 to 100 μm, and particularly preferably 1 to 50 μm. The thickness of the adhesive resin layer is usually 0.1 to 1000 μm, preferably 0.1 to 300 μm, more preferably 0.1 to 100 μm, and particularly preferably 0.1 to 30 μm.
In addition, the thickness ratio between the EVOH resin composition layer and the adhesive resin layer, the total thickness thickness of the EVOH resin composition layer and the total thickness ratio of the thermoplastic resin layer do not change greatly before and after stretching. It becomes the same value as.

  Although the multilayer structure of the present invention can be used as various molded article materials, as described above, it is possible to maintain the uniformity of the EVOH resin composition layer even after the high-stretching treatment, due to variations in thickness. Because there is no noticeable streaking or undulation due to uneven thickness, and gas barrier properties are excellent, for example, as films, sheets, tubes, pipes, cups, tanks, bottles, for example, pharmaceuticals, cosmetics, industrial chemicals, agricultural chemicals Used for packaging of fuel, electronic parts, mechanical parts, etc. In particular, since it can be suitably used for a molded article material that is stretched under heating as described above, a mold molded article having the most preferable drawing ratio of 0.3 to 2 can be suitably provided.

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, “part” means mass basis unless otherwise specified.

[Measurement evaluation method]
(1) Thickness variation (cup)
About the produced cup, 3 portions near the mouth side wall portion, 3 portions near the bottom surface portion side surface portion, 1 portion on the bottom surface portion were cut out by 1 cm × 1 cm, respectively, and the thickness of the EVOH resin composition layer was measured. The difference between the maximum thickness and the minimum thickness was determined.
Moreover, the case where the difference between the maximum thickness and the minimum thickness was less than 10 μm was evaluated as “◯”, the case where the thickness was 11 to 19 μm was evaluated as “Δ”, and the case where the difference was 20 μm or more was evaluated as “X”.

(2) Appearance (cup)
The appearance of the cup was visually observed, and “○” (vertical streaks and local unevenness were hardly recognized), “△” (vertical streaks or local unevenness was recognizable on the side of the cup. ), “×” (longitudinal streaks and local unevenness were remarkably observed on the side surface of the cup).

(3) Thickness variation (film)
The produced film was randomly cut at 6 locations, each 1 cm × 1 cm, and the thickness of the EVOH resin composition layer was measured to determine the average thickness and the difference between the maximum thickness and the minimum thickness.

(4) Appearance (film)
About the created 3 types 5 layer film, the external appearance was evaluated visually. Evaluation was made in two stages: “◯” (streaks and undulations were hardly recognized) and “×” (streaks and undulations were recognized).

(5) Gas barrier properties (cup)
The upper surface of the cup was sealed with an aluminum metal plate, and the oxygen permeation amount at 23 ° C. and 50% RH was measured using “OXTRAN 2/20” manufactured by MOCON. By dividing by the average thickness calculated in (1), the oxygen permeation amount (cc / pkg · day · air) per 20 μm of the EVOH resin composition layer was calculated.
Note that pkg is an abbreviation for Package and means that the measurement target of the oxygen transmission amount is the entire cup, and air is the gas used for measuring the oxygen transmission amount is air (oxygen partial pressure 0.2 atm). It is shown that.

(6) Gas barrier properties (film)
Using “OXTRAN 2/20” manufactured by MOCON, the oxygen permeation amount (cc / m ² · day · atm) per 20 μm of the EVOH resin composition layer of the multilayer film at 23 ° C. and 50% RH was measured.

[Resin used]
Two types of ethylene-vinyl acetate copolymer saponified products (EVOH1, EVOH2) having the characteristics shown in Table 1 and three types of PVA resins (PVA1 to PVA3) were used.
The content of the side chain 1,2-diol structural unit represented by (1a) in the PVA resin is a value measured by ¹ H-NMR.
The saponification degree is a value measured by a titration method (JIS K6726).
The degree of polymerization is a value measured by an aqueous solution viscosity measurement method (JIS K6726).

[Example 1, Comparative Example 1-3]
As shown in Table 2, after compounding the resin and dry blending, it is charged into a twin screw extruder (φ30 mm, L / D = 43) having two mixing zones and melt kneaded (extruder set temperature: C1 / C2) / C3 / C4 / C5 / C6 / C7 / H / D = 200/210/230/230/230/230/230/230 ° C.), extruded into strands, cut and pelletized EVOH resin composition Got.

The EVOH resin composition pellets prepared as described above, polypropylene (Nippon Polypro Co., Ltd.) were added to a coextrusion multilayer film molding apparatus equipped with three extruders and having a three-kind five-layer type feed block, a multilayer film molding die and a take-out machine. EA6A "), and adhesive resin (Mitsubishi Chemical Corporation" MODIC-AP_P604V "), and by coextrusion, polypropylene layer / adhesive resin layer / EVOH resin composition layer / adhesive resin layer / polypropylene layer A multilayer structure having three types and five layers was manufactured. Note that the die temperature of the molding apparatus was all set to 230 ° C. Moreover, the thickness of the obtained multilayer structure is 320 μm, and the thickness of each layer is 120 μm / 20 μm / 40 μm / 20 μm / 120 μm.
The obtained multilayer structure is supplied to a plug-assist type vacuum / pressure forming machine (Asano Laboratories) and subjected to stretch molding at a heater temperature of 430 ° C., and a cup (top diameter 80 mm, bottom diameter 48 mm, depth 52 mm). The drawing ratio (depth of molded product (mm) / maximum diameter of molded product (mm)) was 0.65). About the produced cup, the dispersion | variation in thickness was investigated based on the said measurement evaluation method. The results are also shown in Table 2.
Table 3 shows the results of measuring the appearance and gas barrier properties of the produced cups based on the above measurement evaluation method.

  As can be seen from Table 2, in the multilayer structure (Comparative Example 1) having a layer made of EVOH resin alone, the difference in thickness between the bottom surface and the mouth is large, and the thickness variation as a whole is large. In the multilayer structure having a layer using the EVOH resin composition (Example 1) containing the PVA containing the side chain 1,2-diol structural unit, the vertical stripes or local uneven thickness was remarkably observed in When used, a cup with a small difference in thickness between the bottom surface and the mouth and a small variation in thickness as a whole could be formed. That is, as a molded product cup, in Example 1, vertical streaks and local uneven thickness were hardly recognized. Further, as can be seen from Table 3, the oxygen permeation amount of the entire cup was smaller even though the gas barrier layer of Example 1 was thinner than the gas barrier layer of Comparative Example 1, and the oxygen permeation amount of Example 1 was smaller. Decreased to 27% of that of Comparative Example 1, and the gas barrier properties were improved. When the oxygen permeation amount per the same thickness is compared, the EVOH resin composition layer of Example 1 is less than the EVOH resin layer of Comparative Example 1, and the oxygen permeation amount of Example 1 is the oxygen permeation amount of Comparative Example 1. It can be seen that the gas barrier property was further improved by the reduction to 22%. From this, it can be seen that the EVOH resin composition to which the side chain 1,2-diol structural unit-containing PVA is added has better gas barrier properties than the EVOH resin alone. And, the effect of improving the gas barrier property of the entire cup is greater than the suppressing effect per unit thickness, because the effect of improving the gas barrier property based on the original composition and the stretching treatment is more effectively exhibited by reducing the variation in thickness. It seems that it was possible.

  On the other hand, in the resin composition containing the PVA2 containing no side chain 1,2-diol structural unit (Comparative Example 2), not only the thickness variation was large, but also the EVOH resin layer was broken at the bottom. . This is probably because PVA2 containing no side chain 1,2-diol structural unit is less likely to extend than PVA containing 1,2-diol structural unit. Further, regarding the gas barrier property, since the EVOH resin layer was broken, the gas barrier property inherent to the PVA resin and EVOH resin could not be exhibited.

  In the resin composition (Comparative Example 3) containing the partially saponified EVOH resin (EVOH2) having a large ethylene content instead of the PVA resin, the stretch moldability is improved as the ethylene content is increased, and the thickness is increased. The variation was better than that of the EVOH resin alone, and the stretch moldability comparable to that of Example 1 could be shown. However, the gas barrier property was inferior to that of the EVOH resin alone (Comparative Example 1) because the OH group content contained in the entire resin composition was reduced.

  Therefore, even in severe stretch-molded products such as cup molding, in order to ensure the gas barrier property inherent in EVOH resin, and further high gas barrier property beyond that, it contains side chain 1,2-diol structural units. It turns out that it is suitable to use the resin composition of this invention which mix | blended PVA resin to do.

Example 2 and Comparative Example 4
Using PVA resin (PVA3) with the same 1,2-diol structural unit content and different degree of polymerization, blending the pellets produced by changing the blending ratio of EVOH resin and PVA resin as shown in Table 4 Thus, an EVOH resin composition (Example 2) was obtained.
In the coextrusion multilayer film molding apparatus having a three-type five-layer type feed block, a multilayer film molding die and a take-up machine, the EVOH resin composition pellets prepared above, polypropylene (Nippon Polypro Co., Ltd. “EA7A”), and adhesiveness Resin (Mitsui Chemicals Co., Ltd. “ADMER QF551”) is supplied and co-extruded to produce a multilayer structure of three layers and five layers of polypropylene layer / adhesive resin layer / EVOH resin composition layer / adhesive resin layer / polypropylene layer The body was manufactured. Note that the die temperature of the molding apparatus was all set to 230 ° C. The thickness of the obtained multilayer structure is 140 μm, and the thickness of each layer is 50 μm / 10 μm / 20 μm / 10 μm / 50 μm.

  The produced multilayer film is supplied to a biaxial stretching machine (KARO IV, manufactured by BRUCKNER), and simultaneously biaxially stretched (stretching ratio: 1.3 times in length and width, stretching speed: 100 mm / sec, stretching temperature: 155 ° C., preheating time: 40 Second, test piece: length × width = 9 cm × 9 cm), and the appearance and gas barrier properties of the film were measured based on the evaluation method. The results are shown in Table 4.

  As Comparative Example 4, Table 4 also shows the results of measurement for a multilayer structure of 3 types and 5 layers produced in the same manner as in Example 2 with EVOH 1 alone without containing PVA3.

  When Example 2 and Comparative Example 4 were compared, the average thickness of the EVOH resin (composition) layer of the obtained film was the same, but the difference between the maximum thickness and the minimum thickness was Comparative Example 4. It turns out that it becomes 2 times or more of Example 2, and the variation in the thickness of Example 2 is small. The difference in the variation in the thickness of the EVOH resin (composition) layer not only appears as a difference in the appearance of the film, but also appears in the oxygen permeation amount. The value is five times, indicating that the gas barrier property of Example 2 is excellent. Therefore, by blending the PVA resin containing the side chain 1,2-diol structural unit with the EVOH resin, the variation in the thickness of the stretched molded product is reduced, the surface appearance of the molded product is improved, and the gas barrier property is further improved. It can be seen that it can also be improved.

  The layer composed of the EVOH resin composition of the present invention is excellent in elongation at the time of heat stretching treatment, has little thickness unevenness after the stretching treatment, and is excellent in gas barrier properties. Therefore, even if a high stretching process is employed, an EVOH resin composition layer having a high crystallinity and excellent gas barrier properties can be provided, and therefore, for example, a rapid stretching process such as vacuum / pressure forming is likely to occur. Even if the molding method is applied, it can be used for various molded products that are excellent in appearance and require high gas barrier properties.

Claims (8)

Ethylene obtained by blending a saponified ethylene-vinyl ester copolymer having an ethylene content of 20 to 60 mol% with a polyvinyl alcohol containing a side chain 1,2-diol structural unit represented by the general formula (1) -Vinyl ester copolymer saponified resin composition.

(In formula (1), R ^{1 to} R ⁶ each independently represents a hydrogen atom or an organic group, and X represents a single bond or a bond chain.) 2. The ethylene-vinyl ester copolymer ken according to claim 1, wherein a blending amount of the polyvinyl alcohol is 1 part by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the ethylene-vinyl ester copolymer saponified resin. Compound resin composition. The ethylene-vinyl ester copolymer saponified resin according to claim 1 or 2, wherein the content of the side chain 1,2-diol structural unit represented by the general formula (1) in the polyvinyl alcohol is 1 to 30 mol%. Composition. A multilayer structure having at least one thermoplastic resin layer other than the ethylene-vinyl ester copolymer saponified resin composition layer and the ethylene-vinyl ester copolymer according to any one of claims 1 to 3. . The multilayer structure according to claim 4, wherein the thermoplastic resin other than the saponified ethylene-vinyl ester copolymer is at least one selected from the group consisting of polyolefin resins, polyamide resins, and polyester resins. The multilayer structure according to claim 4 or 5, wherein a thickness ratio of the thermoplastic resin layer / ethylene-vinyl ester copolymer saponified resin composition layer is more than 1 to 30. The multilayer structure according to any one of claims 4 to 6, having a thickness of 1 to 30000 µm. The molded product formed by heat-stretching the multilayer structure of any one of Claims 4-7.