JP2013227530A - Polyvinyl alcohol-based resin composition, method for producing the same, and film using the resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based resin composition from which molded articles, such as films, having all of gas barrier property, flexibility, and biodegradability can be produced, and to provide a method for producing the resin composition and films using the resin composition.SOLUTION: A polyvinyl alcohol-based resin composition has a sea-island structure where an island phase containing a polyvinyl alcohol-based resin (B) having a degree of saponification of 70-90 mol% and a polyhydric alcohol compound (C) is formed in a sea phase of a polyvinyl alcohol-based resin (A) having a degree of saponification of ≥95 mol%. A method for producing the polyvinyl alcohol-based resin composition includes preparing a mixture of the polyvinyl alcohol-based resin (B) and the polyhydric alcohol compound (C) and then melt-kneading the mixture and the polyvinyl alcohol-based resin (A). A film at least has a layer containing the polyvinyl alcohol-based resin composition.

Description

  The present invention uses a polyvinyl alcohol-based resin composition capable of producing a molded article such as a film having gas barrier properties, flexibility, and biodegradability, a method for producing the resin composition, and the resin composition. Related to film.

  Application of biodegradable resins to various packaging materials is progressing, but aliphatic polyester resins widely used as biodegradable resins have poor oxygen gas barrier properties. Therefore, a packaging material that requires oxygen gas barrier properties requires lamination with a gas barrier layer, and the gas barrier layer is also required to have biodegradability. Therefore, polyvinyl alcohol (hereinafter also referred to as “PVA”) resin that has excellent gas barrier properties and is biodegradable has attracted attention.

  However, PVA resin lacks flexibility because of its high crystallinity. Although softening is possible by mix | blending a plasticizer with PVA-type resin, since crystallinity is inhibited, gas-barrier property falls.

  Patent Document 1 discloses that by using a sea-island structure in which an elastomer component is dispersed in a PVA-based resin, a resin composition with improved flexibility and excellent gas barrier properties can be obtained. However, since ordinary elastomers are not biodegradable, the resin composition of Patent Document 1 has a problem in terms of biodegradability.

JP 2012-46744 A

  The present invention uses a polyvinyl alcohol-based resin composition capable of producing a molded article such as a film having gas barrier properties, flexibility, and biodegradability, a method for producing the resin composition, and the resin composition. The purpose is to provide a film.

  The inventors of the present invention provide a PVA resin composition having a sea-island structure in which a PVA resin having a high saponification degree is used as a sea component and a low saponification degree PVA resin containing a polyhydric alcohol compound is used as an island component. The present inventors have found that the problems can be solved and have completed the present invention.

  That is, the present invention relates to a polyvinyl alcohol resin (B) having a saponification degree of 70 to 90 mol% and a polyhydric alcohol compound in the sea phase of the polyvinyl alcohol resin (A) having a saponification degree of 95 mol% or more. A polyvinyl alcohol-based resin composition having a sea-island structure in which an island phase containing (C) is formed is provided.

  In the present invention, the polyvinyl alcohol resin (B) and the polyhydric alcohol compound (C) are prepared, and then the mixture and the polyvinyl alcohol resin (A) are melt-kneaded. A method for producing an alcohol-based resin composition is also provided.

  Furthermore, this invention also provides the film which has at least the layer containing the polyvinyl alcohol-type resin composition of this invention.

  The polyvinyl alcohol resin composition of the present invention comprises an island phase containing a high saponification degree PVA resin (A) as a sea component and a low saponification degree PVA resin (B) and a polyhydric alcohol compound (C). It has a sea-island structure. This sea-island structure is formed due to the difference in the saponification degree of both PVA resins (A) and (B). When both PVA resins (A) and (B) are melt-kneaded, Due to the difference in degree of conversion, the two resins are not compatible with each other, and a sea-island structure is formed in which a highly saponified PVA resin is used as a sea component and a low saponification PVA resin is used as an island component.

  By including the polyhydric alcohol compound (C), this island component has a low elastic modulus and improves the flexibility of the resin composition. On the other hand, because of the sea-island structure, the gas barrier property is controlled by the highly saponified PVA resin (A), which is a sea component, and an excellent gas barrier property can be obtained. Since both PVA resins (A) and (B) are not compatible during melt-kneading, the polyhydric alcohol compound (C) in the island component is a high saponification degree PVA resin (A) which is a sea component. The gas barrier property due to the high saponification degree PVA resin (A) is hardly inhibited. Moreover, since both components of both PVA-type resin (A) and (B) and a polyhydric alcohol compound (C) are biodegradable, the whole resin composition is also biodegradable.

Patent documents that can be prior art documents for the present invention will be described below.
JP 2002-275339 A contains PVA having a saponification degree of 65 mol% or more and less than 75 mol% and PVA having a saponification degree of 75 mol% or more. A PVA-based film that is 3 mol% or more is disclosed. In addition, this patent document describes that a film may be produced by a casting method by blending a polyhydric alcohol compound as a plasticizer in a solution of the composition as necessary (paragraph [ 0023]).
However, since the film of this patent document is produced by casting from an aqueous solution containing a PVA resin and a plasticizer, the plasticizer is present in the entire film, and the present invention in which the plasticizer is present only in the island component. Different.

Japanese Patent Application Laid-Open No. 2006-233178 discloses a PVA film for optical use in which a PVA resin having a 1,2-glycol bond in the side chain and another PVA resin are used in combination, and a polyvalent as a plasticizer. It is described that it is preferable to contain an alcohol compound in the resin composition (paragraphs [0034] and [0035]).
However, since the film of this patent document is an optical film, it is necessary that the two PVA resins need to be compatible, and that the difference in saponification degree is preferably 6 mol% or less is also described. (Claim 7, paragraph [0033]). Therefore, this patent document does not suggest a sea-island structure.

  By using the PVA resin composition of the present invention, a molded product having gas barrier properties and flexibility can be obtained. Therefore, only a single layer containing the resin composition of the present invention is used, and the film has gas barrier properties. Further, flexibility can be imparted and manufacturing costs can be reduced. In addition, since it also has biodegradability, the load on the environment is small.

  The present invention will be described in detail below, but these show examples of desirable embodiments.

  The polyvinyl alcohol-based resin composition of the present invention includes a polyvinyl alcohol-based resin (B) having a saponification degree of 70 to 90 mol% in the sea phase of the polyvinyl alcohol-based resin (A) having a saponification degree of 95 mol% or more. Is a polyvinyl alcohol-based resin composition having a sea-island structure in which an island phase containing the polyhydric alcohol compound (C) is formed. Hereinafter, each component will be described.

[PVA resin (A)]
The PVA resin (A) used in the present invention has a saponification degree of 95 mol% or more, preferably 96 to 99.9 mol%, particularly preferably 98 to 99.9 mol%. If the degree of saponification is too low, the gas barrier property tends to be reduced or an acetic acid odor tends to be generated during molding. If it is too high, the productivity tends to be reduced. The saponification degree can be measured according to JIS K 6726.

  The average degree of polymerization of the PVA resin (A) is preferably 200 to 1000, particularly preferably 250 to 800, and particularly preferably 300 to 600. If the average degree of polymerization is too high, the melt viscosity tends to be high and extrusion tends to be difficult, and if it is too low, the film tends to become brittle. The average degree of polymerization can be measured according to JIS K 6726.

  In the present invention, various modified PVA resins may be used as the PVA resin (A). When using a modified PVA-based resin, if the amount of modification (content of modified vinyl alcohol structural unit) is too large, the gas barrier property tends to be lowered. Therefore, it is usually 10 mol% or less, preferably 5 mol% or less. is there.

  As the modified PVA-based resin, a PVA-based resin containing a structural unit represented by the following general formula (1) is preferable.

[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 a hydrogen atom. Or an organic group is shown. ]

  By introducing the 1,2-diol structure in the side chain represented by the general formula (1), the melting point of the PVA resin is lowered and the fluidity at the time of melting is improved, so that the melt moldability is improved. To do. Further, the decrease in gas barrier property due to the introduction of the same structure is small, and a PVA resin introduced in a larger amount than other modifying groups can be used. The modification amount of the structural unit represented by the general formula (1) is preferably 1 to 20 mol%, particularly preferably 2 to 10 mol%, and particularly preferably 3 to 8 mol%. When the amount of modification is too large, the gas barrier property tends to decrease greatly under high humidity. When the amount is too small, the effect of introducing a modifying group tends to be small.

The content of the 1,2-diol structural unit in the PVA resin (A) is a ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane) of a completely saponified PVA resin. Specifically, from peak areas derived from hydroxyl protons, methine protons, and methylene protons in the 1,2-diol units, methylene protons in the main chain, hydroxyl protons linked to the main chain, etc. Can be calculated.

Particularly, it is most preferable that R ^{1 to} R ³ and R ^{4 to} R ⁶ in the 1,2-diol structural unit represented by the general formula (1) are all hydrogen atoms, and X is a single bond. A PVA resin having a structural unit represented by the formula (1 ′) is preferably used.

In addition, 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 as long as the resin characteristics are not significantly impaired. Examples of the organic group include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. May have a functional group such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, if necessary.

Further, X in the 1,2-diol structural unit represented by the general formula (1) is most preferably a single bond in terms of thermal stability and stability under high temperature or acidic conditions. A bonded chain may be used as long as it does not inhibit the effects of the present invention. Examples of such a bonded chain include hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbons include fluorine, chlorine, bromine, and the like). _other, -O of may be substituted by a _{halogen) -, - (CH 2 O} ) m -, - (OCH 2) m -, - (CH 2 O) m CH 2 -, - CO-, _{-COCO -, - CO (CH 2} ) m CO -, - 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 (OR) O—, and the like (R is each independently an optional substituent, preferably a hydrogen atom or an alkyl group, M is a natural number). Among them, 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.

  A method for producing such a modified PVA resin is not particularly limited, and (ii) a method of saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (2), or (ii) vinyl A method of saponifying and decarboxylating a copolymer of an ester monomer and a compound represented by the following general formula (3), or (iii) a copolymer of a vinyl ester monomer and a compound represented by the following general formula (4) A method of saponifying and deketalizing the polymer 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 having 1 to 4 carbon atoms). R ¹⁰ and R ¹¹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

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. In particular, 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 in the case of vinyl ethylene carbonate which is an example of the compound represented by the general formula (3) used in the method (ii). Compared with (vinyl acetate) = 0.85 and r (vinyl ethylene carbonate) = 5.4, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate. is there.

  The chain transfer constant of 3,4-diacetoxy-1-butene is Cx (3,4-diacetoxy-1-butene) = 0.003 (65 ° C.), which is Cx (vinyl ethylene) of vinyl ethylene carbonate. Carbonate) = 0.005 (65 ° C.) and 2,2-dimethyl-4-vinyl-1,3-dioxolane which is an example of 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.), the degree of polymerization is less likely to increase and the polymerization rate is not reduced. Is shown.

  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 described in, for example, International Publication No. 00/24702, US Pat. No. 5,623,086, US Pat. No. 6,072,079, and the like. By the synthesis method using the synthesized epoxybutene derivative or the reaction of isomerizing 1,4-diacetoxy-1-butene, which is an intermediate product of the production process of 1,4-butanediol, using a metal catalyst such as palladium chloride Can be manufactured.
At the reagent level, Across products can be obtained from the market.

If the modified PVA resin obtained by the method (ii) or (iii) is insufficiently decarboxylated or deacetalized, a carbonate ring or acetal ring remains in the side chain, and such PVA When the resin is melt-molded, the cyclic group may cause the PVA resin to be cross-linked to generate a gel-like material.
Therefore, also from this point, the modified PVA resin obtained by the method (i) is preferably used in the present invention.

Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, versatic. Although vinyl acid acid etc. are mentioned, vinyl acetate is preferably used economically.
In addition to the above-mentioned monomers (vinyl ester monomers, compounds represented by the general formulas (2), (3), (4)), a range that does not significantly affect the physical properties of the resin, specifically 10 mol% If within, α-olefin such as ethylene or propylene as a copolymerization component; hydroxy group-containing α- such as 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1,2-diol Derivatives such as olefins and acylated products thereof; unsaturated acids such as itaconic acid, maleic acid and acrylic acid or salts or mono- or dialkyl esters thereof; nitriles such as acrylonitrile; amides such as methacrylamide and diacetone acrylamide; Olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, AMPS or the like A compound such as a salt thereof may be copolymerized.

  The PVA resin (A) used in the present invention may be one type or a mixture of two or more types, but when a mixture is used, the degree of saponification, the average degree of polymerization, and the amount of modification The average value is preferably within the above-mentioned range.

[PVA resin (B)]
The PVA-based resin (B) used in the present invention has a saponification degree of 70 to 90 mol%, preferably 75 to 88 mol%, particularly preferably 77 to 85 mol%. If the degree of saponification is too low, the thermal stability tends to decrease, and if it is too high, the flexibility tends to decrease.

  The average degree of polymerization of the PVA-based resin (B) is preferably 200 to 1000, particularly preferably 250 to 800, and particularly preferably 300 to 600. If the average degree of polymerization is too high, the melt viscosity tends to be high and extrusion tends to be difficult, and if it is too low, the flexibility improving effect tends to be small. In addition, you may use various modified PVA-type resin as PVA-type resin (B) similarly to PVA-type resin (A).

  The PVA resin (B) used in the present invention may be a single type or a mixture of two or more types, but when a mixture is used, the average value of the degree of saponification and the average degree of polymerization is It is preferable to be within the above range.

  The difference in the saponification degree between the PVA resin (A) and the PVA resin (B) is preferably 10 to 30 mol%, particularly preferably 12 to 28 mol%, and particularly preferably 15 to 25 mol%.

[Polyhydric alcohol compound (C)]
The polyhydric alcohol compound (C) used in the present invention is a compound having a valence of preferably 2 to 10,000, particularly preferably 2 to 1000, and particularly preferably 2 to 400. When the valence is too large, the molecular weight tends to increase and the compatibility tends to decrease, and when it is too small, the plasticizing effect tends to decrease.

  The carbon number of the polyhydric alcohol compound (C) is preferably 1 to 10,000, particularly preferably 1 to 1000, and particularly preferably 2 to 400. If the number of carbon atoms is too large, the compatibility tends to decrease, and if it is too small, the volatility tends to increase.

  Specific examples of the polyhydric alcohol compound (C) include, for example, dihydric alcohols such as ethylene glycol, diethylene glycol, and butanediol; trihydric alcohols such as glycerin; tetrahydric or higher alcohols such as pentaerythritol; polyethylene glycol (PEG) High molecular polyhydric alcohols such as In particular, PEG is preferable because the PVA resin (A), which is a sea component, is considered to have low migration.

  When PEG is used as the polyhydric alcohol compound (C), the average degree of polymerization of PEG is preferably 100 to 10000, particularly preferably 150 to 5000, and particularly preferably 200 to 1000. If the average degree of polymerization is too high, the compatibility tends to decrease, and if it is too low, it tends to shift to the PVA resin (A) that is a sea component.

[PVA resin composition]
The PVA-based resin composition of the present invention has a sea-island structure in which an island phase containing a PVA-based resin (B) and a polyhydric alcohol compound (C) is formed in the sea phase of the PVA-based resin (A).

  The content ratio (B / C) between the content of the PVA resin (B) and the content of the polyhydric alcohol compound (C) is preferably 99/1 to 60/40, and particularly preferably. 95/5 to 65/35, particularly preferably 90/10 to 80/20. When there is too much content of PVA-type resin (B) and a weight ratio is too large, there exists a tendency for barrier property to fall, and when a weight ratio is too small, there exists a tendency for a softness | flexibility improvement effect to become small.

  The content ratio {A / (B + C)} of the content of the PVA resin (A) and the total content of the PVA resin (B) and the polyhydric alcohol compound (C) is preferably 95 / 5 to 55/45, particularly preferably 90/10 to 60/40, particularly preferably 75/25 to 65/35. When there is too much content of PVA-type resin (A) and a weight ratio is too large, there exists a tendency for a softness | flexibility improvement effect to become small, and when too small, there exists a tendency for barrier property to fall.

  The size (diameter) of the island phase is preferably 0.1 to 10 μm, particularly preferably 0.1 to 5 μm, and particularly preferably 0.1 to 2 μm. If the island phase is too large, the barrier property tends to decrease, and if it is too small, the flexibility tends to decrease. In addition, the magnitude | size (diameter) of an island phase can be measured using a scanning electron microscope, for example. The size of the island phase can be adjusted by adjusting the degree of saponification and melt viscosity of the PVA resins (A) and (B), adjusting the shear force during melt mixing, and the like.

  The PVA resin composition of the present invention may contain other polymers as long as the effects of the present invention are not impaired. Examples of the polymer that can be contained include, for example, PVA other than the above-mentioned PVA resins (A) and (B), various modified PVA resins, vinyl alcohol resins such as ethylene-vinyl alcohol copolymers; polyamides, polyesters, Various thermoplastic resins such as polyethylene, polypropylene, and polystyrene can be exemplified.

  In addition, the PVA resin composition of the present invention includes a reinforcing agent, a filler, a plasticizer, a pigment, a dye, a lubricant, an antioxidant, and an antistatic agent as necessary, as long as the effects of the present invention are not impaired. UV absorbers, heat stabilizers, light stabilizers, surfactants, antibacterial agents, antistatic agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, other heat A plastic resin or the like may be contained.

In order to use the PVA resin composition of the present invention as a molding material, it is usually in the form of pellets or powder. Among them, the pellet shape is preferable from the viewpoint of small problems of charging into a molding machine, handling, and generation of fine powder.
In addition, although the well-known method can be used for shaping | molding into this pellet shape, the method of extruding in a strand form from the above-mentioned extruder, cut | disconnecting to predetermined length after cooling, and making a cylindrical pellet is efficient. is there.

[Production method of PVA resin composition]
The PVA resin composition of the present invention is prepared by, for example, melting and kneading a PVA resin (B) and a polyhydric alcohol compound (C) to prepare a mixture, and melting the obtained mixture and the PVA resin (A). It can be manufactured by kneading.

  The melt kneading of the PVA resin (B) and the polyhydric alcohol compound (C) is performed by, for example, supplying the PVA resin (B) from the popper portion of the twin screw extruder and side feeding the polyhydric alcohol compound (C). In the middle of the extruder, it can be supplied by a press-fitting pump. The temperature at the time of melt-kneading is preferably 150 to 230 ° C, particularly preferably 170 to 210 ° C, particularly preferably 180 to 200 ° C. The residence time is preferably from 0.5 to 10 minutes, particularly preferably from 1 to 5 minutes, particularly preferably from 2 to 3 minutes. If the temperature is too high or the residence time is too long, the resin tends to be thermally deteriorated, and if the temperature is too low or the residence time is too short, it is difficult to obtain an integrated resin composition, There is a tendency that the polyhydric alcohol is easily separated.

  The melt-kneading of the PVA resin (A) and the mixture (B + C) can be performed, for example, by dry blending the PVA resin (A) and the mixture (B + C) and then supplying the mixture to a twin screw extruder. The temperature at the time of melt-kneading is preferably 150 to 230 ° C, particularly preferably 170 to 210 ° C, particularly preferably 180 to 200 ° C. The residence time is preferably from 0.5 to 10 minutes, particularly preferably from 1 to 5 minutes, particularly preferably from 2 to 3 minutes. If the temperature is too high or the residence time is too long, the resin tends to be thermally deteriorated.If the temperature is too low or the residence time is too short, the island component is sufficiently finely dispersed in the sea component. There is a tendency to become difficult.

〔Molding〕
The PVA resin composition of the present invention is useful as a molding material because it is excellent in moldability, particularly melt moldability. As the melt molding method, known molding methods such as extrusion molding, inflation molding, injection molding, blow molding, vacuum molding, pressure molding, compression molding, and calendar molding can be used.
Moreover, as a molded article obtained from the PVA-type resin composition of this invention, the thing of various shapes, such as a film, a sheet | seat, a pipe, a disk, a ring, a bag-like thing, a bottle-like thing, and a fibrous thing, is mentioned. be able to.

The film having at least a layer containing the PVA-based resin composition of the present invention (hereinafter also referred to as PVA-based resin layer) may be a film composed of a single layer of the PVA-based resin layer. It is also possible to form a laminated structure with layers made of materials.
In particular, the PVA-based resin composition of the present invention is mainly composed of a PVA-based resin, and although an excellent gas barrier property can be obtained under low humidity conditions, the characteristics may change greatly due to moisture absorption. It is desirable to use it as a laminated structure in which a material having a high water vapor barrier property is arranged on the surface.

  Examples of such a material having a high water vapor barrier property include polyolefin resins such as low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, polyethylene terephthalate, poly Polyester resins such as butylene terephthalate, vinyl chloride resins such as polyvinyl chloride and polyvinylidene chloride, thermoplastic resins typified by polyamide resins such as nylon, thermosetting resins such as epoxy resins and phenol resins, metals, Various metal deposition films can be mentioned, and can be selected according to the use and desired characteristics.

  In such a laminated structure, an adhesive layer may be interposed between the PVA resin layer of the present invention and a layer made of another material. Examples of the adhesive used in the adhesive layer include modified olefin polymers containing carboxyl groups such as maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, and maleic anhydride-modified ethylene-vinyl acetate copolymer. Can be mentioned.

  As a method for forming such a laminated structure, co-extrusion, co-injection and the like are possible when laminating with a thermoplastic resin, and as other methods, extrusion coating or each layer is formed in advance. Various methods such as a method of laminating them can be employed depending on the desired shape and thickness.

Since the molded article made of the PVA-based resin composition of the present invention has excellent barrier properties against various expectations and has excellent flexibility, it can be used for articles that require these characteristics. it can. Examples of such applications include food and beverage packaging materials, containers, bag-in-box inner bags, container packings, medical infusion bags, organic liquid containers, organic liquid transport pipes, various gas containers, tubes, hoses, etc. Is mentioned.
Further, it can be used for various electric parts, automobile parts, industrial parts, leisure goods, sports goods, daily goods, toys, medical equipment, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.

[Example 1]
A mixture of PVA resin (B) (saponification degree 80 mol%, average polymerization degree 1000) and PEG (C) (average polymerization degree 300) in a weight ratio of 70/30 was resin temperature 200 ° C. with a twin screw extruder. Was melt-kneaded, extruded into strands, air-cooled, and then cut to obtain a pellet-like mixture.

  Next, a PVA resin (A) represented by the above formula (1 ′) having a 1,2-diol structure in the side chain (saponification degree 99 mol%, average polymerization degree 450, modification amount 6 mol%) The PVA resin composition of the present invention is prepared by melt-kneading a mixture of 80/20 by weight with the above pellet-like mixture at a resin temperature of 200 ° C. with a twin-screw extruder, extruding into a strand, air-cooling, cutting. Pellets were obtained.

[Examples 2 and 3 and Comparative Examples 1 to 3]
PVA-based resin composition pellets of Examples 2 and 3 and Comparative Examples 1 to 3 were obtained in the same manner as Example 1 under the blending conditions shown in Table 1.
Using the PVA-based resin composition pellets of Examples 1 to 3 and Comparative Examples 1 to 3, observation of the sea-island structure, production of films, measurement of oxygen permeability, and evaluation of flexibility were performed. The results are summarized in Table 2.

<Observation of sea-island structure>
The obtained pellet was frozen with liquid nitrogen and fractured, and the cross section was magnified 10,000 times with a scanning electron microscope and observed. In Examples 1 to 3 and Comparative Example 3, a sea-island structure in which island components having a diameter of about 0.5 μm were uniformly dispersed in the sea component was observed.

<Production of film>
The obtained pellets were melt-kneaded at a resin temperature of 200 ° C. with a twin-screw extruder, and a single-layer film having a thickness of 30 μm was produced by a T-die casting method.

<Oxygen permeability>
The oxygen permeability of the obtained film under conditions of 23 ° C. and 65% RH was measured using an oxygen permeability tester (“Oxtran 2/20” manufactured by MOCON).

<Flexibility>
The flexibility of the obtained film was evaluated by impact resistance (kgf · cm) measured in an atmosphere of 23 ° C. and 50% RH using a YSS type film impact tester (manufactured by Yasuda Seiki Seisakusho, Model 181). did.
The test diameter was 80 mm, the impact ball was an iron ball having a diameter of 12.7 mm, the load was 15 kgf · cm, and the pendulum lift angle was 90 °.

As is clear from these results, the films obtained in Examples 1 to 3 were excellent in flexibility because they were excellent in impact strength.
On the other hand, Comparative Example 1 with only PVA-based resin (A) and Comparative Example 3 with only PVA-based resin (A) and PVA-based resin (B) lacked flexibility. Since the comparative example 2 which mix | blended PEG with PVA-type resin (A) has a large oxygen permeability, it was a thing with poor gas barrier property, and also lacked the softness | flexibility.

  By using the PVA resin composition of the present invention, a molded article having gas barrier properties and flexibility can be obtained. Therefore, the PVA resin composition of the present invention is an article such as food and pharmaceuticals that is desired to avoid deterioration due to oxidation. Can be suitably used for a film, a sheet, a container, a container for hydrogen gas, a tube, a hose, etc. that require high gas barrier properties and flexibility.

Claims (7)

  In the sea phase of the polyvinyl alcohol resin (A) having a saponification degree of 95 mol% or more, the polyvinyl alcohol resin (B) having a saponification degree of 70 to 90 mol% and a polyhydric alcohol compound (C) are contained. A polyvinyl alcohol-based resin composition having a sea-island structure in which an island phase is formed.   The polyvinyl alcohol according to claim 1, wherein the content ratio (B / C) of the content of the polyvinyl alcohol-based resin (B) and the content of the polyhydric alcohol compound (C) is 99/1 to 60/40 by weight. -Based resin composition.   The content ratio {A / (B + C)} of the content of the polyvinyl alcohol resin (A) and the total content of the polyvinyl alcohol resin (B) and the polyhydric alcohol compound (C) is 95/5 to 5/5. The polyvinyl alcohol-based resin composition according to claim 1 or 2, which is 55/45.   The polyvinyl alcohol resin composition according to claim 1, wherein the island phase has a diameter of 0.1 to 10 μm. The polyvinyl alcohol resin composition according to claim 1, wherein the polyvinyl alcohol resin (A) is a polyvinyl alcohol resin containing a structural unit represented by the following general formula (1).

[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 a hydrogen atom. Or an organic group is shown. ]   The polyvinyl alcohol according to any one of claims 1 to 5, wherein a mixture of the polyvinyl alcohol resin (B) and the polyhydric alcohol compound (C) is prepared, and then the mixture and the polyvinyl alcohol resin (A) are melt-kneaded. A method for producing a resin composition.   The film which has at least the layer containing the polyvinyl alcohol-type resin composition in any one of Claims 1-5.