JP2010247497A - Plastic multi-layer structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic multi-layer structure excellent in inter-layer adhesion between a polyglycolic acid layer and other thermoplastic resin layer without arranging an adhesive layer. <P>SOLUTION: This plastic multi-layer structure has at least one of the polyglycolic acid layer and at least one of other thermoplastic resin layer. At least one of the polyglycolic acid layer is an oxygen absorbent polyglycolic acid layer which is formed of a polyglycolic acid resin composition containing a polyglycolic acid and an oxygen absorbent. At least one of the other thermoplastic resin layer is an oxygen absorbent thermoplastic resin layer which is formed of a thermoplastic resin composition containing the other thermoplastic resin and the oxygen absorbent. Also, the plastic multi-layer structure has at least one layer constitution wherein the oxygen absorbent polyglycolic acid layer and the oxygen absorbent thermoplastic resin layer are directly adjacent without using the adhesive layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plastic multilayer structure having a polyglycolic acid layer and another thermoplastic resin layer and having excellent gas barrier properties and interlayer adhesion. Plastic multilayer structures generally include a multilayer film or multilayer container. The multilayer container includes a multilayer blow molded container (bottle), a bag, a tray and the like. In particular, the multilayer blow molded container of the present invention can suppress carbon dioxide loss in the container to be low for a long period of time, and can keep the oxygen concentration of the contents at a low level.

  Polyglycolic acid is attracting attention not only as a biodegradable plastic material but also as a plastic material exhibiting high gas barrier properties. In order to make use of the high gas barrier properties of polyglycolic acid, a composite of polyglycolic acid and another thermoplastic resin such as polyethylene terephthalate (PET) has been attempted. More specifically, various proposals have been made for plastic multilayer structures such as multilayer containers and multilayer films in which a polyglycolic acid layer and another thermoplastic resin layer are combined. Here, the other thermoplastic resin layer means a layer made of a thermoplastic resin other than polyglycolic acid.

  For example, Japanese Patent Laid-Open No. 10-80990 (Patent Document 1), Japanese Patent No. 3978070 (Patent Document 2), and International Publication No. 2004/087813 (Patent Document 3) disclose a polyglycolic acid layer and other heat. A multilayer film having a plastic resin layer is disclosed.

  Japanese Patent No. 3838757 (Patent Document 4), Japanese Patent No. 3997102 (Patent Document 5), International Publication No. 03/037624 (Patent Document 6), International Publication No. 2005/032800 (Patent Document 7), International Publication. No. 2005/072944 (Patent Document 8), International Publication No. 2006/107099 (Patent Document 9), and Japanese Patent Application Laid-Open No. 2003-335932 (Patent Document 10) include a polyglycolic acid layer and other thermoplastic resins. A multilayer container having a layer is disclosed.

  Japanese Patent No. 3969524 (Patent Document 11) and International Publication No. 03/099562 (Patent Document 12) disclose a plastic multilayer structure having a polyglycolic acid layer and another thermoplastic resin layer. . Patent Documents 11 and 12 show a multilayer container, a multilayer film, a multilayer stretched film, a multilayer stretch blow molded container and the like as specific examples of the plastic multilayer structure.

  A plastic multilayer structure having a polyglycolic acid layer and another thermoplastic resin layer has a high gas barrier property due to the polyglycolic acid layer in addition to the characteristics of the other thermoplastic resin layers. However, the plastic multilayer structure has a problem that the interlayer adhesion between the polyglycolic acid layer and another thermoplastic resin layer is insufficient.

  In the prior art disclosed in Patent Documents 1 to 12, in order to improve various properties of a plastic multilayer structure having a polyglycolic acid layer and another thermoplastic resin layer, a molding method, a polymer blend method, Improvements by various methods including a combination method and a modification method using additives have been proposed. However, these conventional techniques are still insufficient in terms of improving the interlayer adhesion between the polyglycolic acid layer and the other thermoplastic resin layers.

  In order to improve the interlayer adhesion between the polyglycolic acid layer and the other thermoplastic resin layer, for example, Patent Document 1 and Patent Document 2 include a gap between the polyglycolic acid layer and the other thermoplastic resin layer. Discloses a multilayer film having an adhesive layer disposed thereon. Patent Documents 4 and 5 disclose a multilayer container in which an adhesive layer is disposed between a polyglycolic acid layer and another thermoplastic resin layer. Patent Document 11 discloses a multilayer film in which a polyglycolic acid layer and a thermoplastic resin composition layer containing an oxygen absorbent are adjacent to each other via an adhesive layer.

  However, a plastic multilayer structure in which an adhesive layer is disposed between a polyglycolic acid layer and another thermoplastic resin layer increases the number of extruders in the manufacturing process or requires a laminating process. The manufacturing process becomes complicated. Due to the adhesive layer, the heat resistance of the plastic multilayer structure tends to decrease. Despite the relatively high cost of the adhesive, the adhesive layer itself cannot impart additional functions other than interlaminar adhesion to the plastic multilayer structure. On the other hand, a multilayer film having a layer structure in which a polyglycolic acid layer and another thermoplastic resin layer are directly adjacent to each other without an adhesive layer is easily delaminated when subjected to a strong external force such as an impact or a shearing force.

  Since the multilayer containers disclosed in Patent Documents 6 to 9 have a layer structure in which a polyglycolic acid layer is embedded as a core layer between inner and outer layers formed from a thermoplastic aromatic polyester resin, polyglycolic acid Even if an adhesive layer is not disposed between the layer and the thermoplastic aromatic polyester resin layer, delamination does not easily occur. Patent Document 10 discloses a plastic container having a layer structure in which a polyglycolic acid layer containing an oxygen absorbent and another thermoplastic resin layer are directly adjacent to each other without an adhesive layer interposed therebetween.

  However, since multilayer containers such as multilayer blow molded containers are generally used as beverage containers, there are specific problems associated therewith. Multi-layer containers filled with beverages are quite heavy. When a heavy multilayer container filled with a beverage is accidentally dropped or given an impact during transportation or handling, delamination is likely to occur between the polyglycolic acid layer and another thermoplastic resin layer. When delamination occurs, the commercial value of the multilayer container filled with the beverage is impaired, and the storage stability of the beverage is lowered.

  Recently, as seen in the increase in the size of PET bottles, the size of plastic containers has been increased. A multilayer container having a polyglycolic acid layer (particularly, a multilayer blow-molded container) is excellent in storage stability of the contents, and is required to cope with an increase in size. A large-scale multilayer container can be filled with a larger amount of beverage than before. Therefore, if a large multi-layer container filled with a large amount of beverage is accidentally dropped during transportation or handling, even if the fall distance is as short as about 50 cm, it is between the polyglycolic acid layer and the other thermoplastic resin layer. Delamination is likely to occur.

Japanese Patent Laid-Open No. 10-80990 Japanese Patent No. 3978070 International Publication No. 2004/087813 Japanese Patent No. 3838757 Japanese Patent No. 3997102 International Publication No. 03/037624 International Publication No. 2005/032800 International Publication No. 2005/072944 International Publication No. 2006/107099 JP 2003-335932 A Japanese Patent No. 3969524 International Publication No. 03/099562

  An object of the present invention is to provide a plastic multilayer structure having a polyglycolic acid layer and another thermoplastic resin layer, between the polyglycolic acid layer and the other thermoplastic resin layer without arranging an adhesive layer. An object of the present invention is to provide a plastic multilayer structure having excellent interlayer adhesion.

  In particular, an object of the present invention is a multilayer container having a polyglycolic acid layer and another thermoplastic resin layer, which has excellent interlayer adhesion without an adhesive layer, and can cope with an increase in size. In addition, an object of the present invention is to provide a multilayer container that can suppress the loss of carbon dioxide in the container for a long period of time and can maintain the oxygen concentration of the contents at a low level.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polyglycolic acid layer in a plastic multilayer structure having at least one polyglycolic acid layer and at least one other thermoplastic resin layer. And the other thermoplastic resin layer contain an oxygen absorbent, and the polyglycolic acid layer containing the oxygen absorbent and the other thermoplastic resin layer are directly adjacent to each other without an adhesive layer. It has been found that by including a layer structure, a plastic multilayer structure with significantly improved interlayer adhesion can be obtained.

  In the case where the plastic multilayer structure of the present invention is a multilayer container such as a multilayer stretch blow molded container, delamination due to impact at the time of dropping is suppressed, so that it can cope with an increase in size. The multilayer container is excellent in internal pressure retention, and can suppress carbon dioxide loss in the container to be low over a long period of time. Since the multilayer container can keep the oxygen concentration of the contents at a low level, even a food or beverage that is easily altered by oxygen can be stored for a long period of time. When the plastic multilayer structure of the present invention is a multilayer film or sheet, it has excellent interlayer adhesion and can be subjected to various secondary processes including bag making and sheet molding. The present invention has been completed based on these findings.

According to the present invention, in a plastic multilayer structure having at least one polyglycolic acid layer and at least one other thermoplastic resin layer,
1) At least one layer of the polyglycolic acid layer is an oxygen-absorbing polyglycolic acid layer formed from a polyglycolic acid resin composition containing polyglycolic acid and an oxygen absorbent,
2) At least one of the other thermoplastic resin layers is an oxygen-absorbing thermoplastic resin layer formed from a thermoplastic resin composition containing another thermoplastic resin and an oxygen absorbent, and
3) A plastic multilayer structure comprising at least one layer configuration in which the oxygen-absorbing polyglycolic acid layer and the oxygen-absorbing thermoplastic resin layer are directly adjacent to each other without an adhesive layer interposed therebetween. Provided.

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not arrange | position an adhesive bond layer, the plastic multilayer structure excellent in the interlayer adhesiveness between a polyglycolic acid layer and another thermoplastic resin layer can be provided. A multilayer container representative of the plastic multilayer structure of the present invention can cope with an increase in size because delamination due to impact at the time of dropping is suppressed. The multilayer container of the present invention is excellent in internal pressure retention, and can suppress carbon dioxide gas loss in the container for a long period of time. The multilayer container of the present invention can maintain the oxygen concentration of the contents at a low level.

1. Polyglycolic acid Polyglycolic acid is a homopolymer or copolymer containing a repeating unit represented by the formula — [— O—CH ₂ —CO —] —. The content of the repeating unit represented by the above formula in the polyglycolic acid is usually 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and the upper limit is 100% by mass. When the content ratio of the repeating unit represented by the above formula is too low, gas barrier properties and heat resistance are lowered.

  Polyglycolic acid can be synthesized by dehydration polycondensation of glycolic acid, dealcoholization polycondensation of glycolic acid alkyl ester, ring-opening polymerization of glycolide, and the like. Among these, according to the ring-opening polymerization method of glycolide, polyglycolic acid (also referred to as “polyglycolide”) having a high molecular weight (high melt viscosity) can be easily produced. In the ring-opening polymerization method, glycolide is heated to a temperature of about 120 ° C. to about 250 ° C. in the presence of a small amount of a catalyst (for example, a cationic catalyst such as tin organic carboxylate, tin halide, antimony halide, etc.). And ring-opening polymerization. The ring-opening polymerization is preferably performed by bulk polymerization or solution polymerization.

  In order to synthesize a polyglycolic acid copolymer, for example, ethylene oxalate, lactide, lactones (for example, β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β Cyclic monomers such as -methyl-δ-valerolactone, ε-caprolactone, trimethylene carbonate, and 1,3-dioxane; lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6 A hydroxycarboxylic acid such as hydroxycaproic acid or an alkyl ester thereof; an aliphatic diol such as ethylene glycol or 1,4-butanediol; and an aliphatic dicarboxylic acid such as succinic acid or adipic acid or an alkyl ester thereof. Equimolar mixtures; or these Using the above species, it may be copolymerized. Among these comonomers, the cyclic monomer is preferable. These cyclic monomers can be subjected to ring-opening copolymerization under the glycolide ring-opening polymerization conditions.

  The comonomer is usually used in a proportion of 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, based on the total amount of charged monomers. When the proportion of comonomer used increases, the crystallinity of the polymer produced is impaired. When polyglycolic acid loses its crystallinity, its heat resistance, gas barrier properties, mechanical strength and the like are lowered.

The oxygen gas permeability coefficient of the polyglycolic acid used in the present invention is 5.0 × 10 when measured under conditions of a temperature of 23 ° C. and a relative humidity of 80% (80% RH) in accordance with JIS K-7126. It is preferably ⁻¹⁴ cm ³ · cm / cm ² · sec · cm Hg or less. When the oxygen gas permeability coefficient of polyglycolic acid is too large, it becomes difficult to obtain a multilayer container having excellent oxygen gas barrier properties. The oxygen gas permeability coefficient of the polyglycolic acid used in the present invention is preferably in the range of 1.0 × 10 ^{−14 to} 5.0 × 10 ⁻¹⁴ cm ³ · cm ² · sec · cmHg.

The melt viscosity (measured at a temperature of 270 ° C. and a shear rate of 122 sec ⁻¹ ) of the polyglycolic acid used in the present invention is usually 20 to 3,000 Pa · s, preferably 50 to 2,000 Pa · s, more preferably 100. It is in the range of ˜1,500 Pa · s. If the melt viscosity of the polyglycolic acid is too low, melt molding processing such as co-injection molding with a thermoplastic resin composition containing another thermoplastic resin and an oxygen absorbent becomes difficult. When the melt viscosity of polyglycolic acid is too large, the melt molding processing temperature of polyglycolic acid becomes high, so that thermal decomposition of polyglycolic acid is likely to occur. In many cases, good results can be obtained when the melt viscosity of polyglycolic acid is in the range of 300 to 1,000 Pa · s.

  The weight average molecular weight (Mw) of the polyglycolic acid is usually in the range of 50,000 to 800,000, preferably 100,000 to 500,000, more preferably 150,000 to 300,000. This weight average molecular weight is a value obtained as a standard polymethylmethacrylate conversion value in gel permeation chromatography (GPC) measurement using hexafluoroisopropanol. If the weight average molecular weight of the polyglycolic acid is too low, the strength of the polyglycolic acid layer becomes too weak, and cracks and cracks are likely to occur during stretch molding. If the weight average molecular weight of the polyglycolic acid is too high, melt processing becomes difficult and the thickness of the polyglycolic acid layer becomes nonuniform.

  The melting point Tm of the polyglycolic acid used in the present invention is preferably 200 ° C. or higher, more preferably 210 ° C. or higher. The melting point of the polyglycolic acid homopolymer is about 220 ° C.

  In the present invention, the polyglycolic acid neetresin can be used alone, but within the range that does not impair the purpose of the present invention, the polyglycolic acid is blended with an inorganic filler, other thermoplastic resin, plasticizer, etc. The resin composition obtained can be used. The polyglycolic acid can contain various additives such as a heat stabilizer, a light stabilizer, an ultraviolet absorber, a moisture proofing agent, a waterproofing agent, a lubricant, a pigment, and a dye as necessary.

  If a polyglycolic acid contains a heat stabilizer, the melt stability is improved, and fluctuations in melt viscosity and thermal decomposition are less likely to occur. Examples of heat stabilizers include heavy metal deactivators such as hydrazine-based compounds having —CO—NHNH—CO— units; phosphate esters having a pentaerythritol skeleton structure; at least one hydroxyl group and at least one long-chain alkyl ester group And at least one compound selected from the group consisting of a triazole compound, a hindered phenol compound, and a metal carbonate.

  Examples of heavy metal deactivators include 2-hydroxy-N-1H-1,2,4-triazol-3-yl-benzamide and bis [2- (2-hydroxybenzoyl) hydrazine] dodecanedioic acid. . Examples of the phosphate ester having a pentaerythritol skeleton structure include cyclic neopentanetetrayl bis (2,6-di-tert-butyl-4-methylphenyl) phosphite and cyclic neopentanetetrayl bis (2 , 4-di-tert-butylphenyl) phosphite. Examples of the phosphorus compound having at least one hydroxyl group and at least one long-chain alkyl ester group include mono- or di-stearyl acid phosphate. Examples of the metal carbonate include calcium carbonate and strontium carbonate.

  The blending ratio of the heat stabilizer is usually 0.001 to 5 parts by mass, preferably 0.003 to 3 parts by mass, and more preferably 0.005 to 1 part by mass with respect to 100 parts by mass of polyglycolic acid. When the blending ratio of the heat stabilizer becomes too large, inconveniences such as saturation of the effect and inhibition of transparency are likely to occur.

  In order to seal the carboxyl terminal of polyglycolic acid, sealing agents, such as a carbodiimide compound and an oxazoline compound, can be mix | blended in the ratio of 1 mass part or less with respect to 100 mass parts of polyglycolic acid.

2. Other thermoplastic resins Other thermoplastic resins used in the present invention (thermoplastic resins other than polyglycolic acid) include, for example, polyolefin resins, thermoplastic aromatic polyester resins, polystyrene resins, chlorine-containing resins, polyamide resins, Examples thereof include polycarbonate resins, cyclic olefin resins, polyurethane resins, polyvinylidene chloride resins, ethylene-vinyl alcohol copolymers (EVOH), aliphatic polyester resins other than polyglycolic acid, acrylic resins, and the like.

  Examples of the polyolefin resin include low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), and polypropylene resin ( For example, isotactic polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, propylene-butene copolymer), polybutene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer Examples thereof include polymers, ionomer resins, and blends of two or more thereof.

  As linear low density polyethylene (LLDPE) and very low density polyethylene (VLDPE), not only conventional LLDPE obtained using Ziegler catalyst and Philips catalyst, but also ethylene and α-olefin using single site catalyst. LLDPE obtained by copolymerization can be preferably used. Examples of the α-olefin include 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like.

  Examples of the thermoplastic aromatic polyester resin include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), amorphous polyethylene terephthalate copolymer (PETG) having 1,4-cyclohexanedimethanol as a copolymerization component, poly Examples include butylene terephthalate (PBT), poly 1,4-cyclohexylene dimethylene terephthalate / isophthalate copolymer (PCTA), and mixtures of two or more thereof. Among these, PET and PEN are preferable and PET is more preferable from the viewpoints of availability and molding processability.

  PET is not only polyethylene terephthalate homopolymer, but also copolyester in which part of PET acid component is replaced with isophthalic acid or naphthalene dicarboxylic acid; copolyester in which part of PET glycol component is replaced with special diol such as diethylene glycol Etc. are also included. In these copolyesters (CO-PET), the copolymerization ratio of the third component such as isophthalic acid is not particularly limited, but is usually 2 to 8 mol%.

  PETG is an amorphous polyethylene terephthalate copolymer containing 1,4-cyclohexanedimethanol (CHDM) as a copolymerization component. More specifically, PETG is a copolyester obtained by replacing a part of ethylene glycol, which is a glycol component constituting PET, with 1,4-cyclohexanedimethanol. The proportion of 1,4-cyclohexanedimethanol in the glycol component is usually 30 to 35 mol%. As PETG, those manufactured and sold by Eastman Chemical Company, Sky Green Company, etc. are preferably used.

  PCTA is a thermoplastic saturated copolyester obtained by polycondensation of 1,4-cyclohexanedimethanol with terephthalic acid and isophthalic acid. As PCTA, the product name Kodar THERMX 6761 (registered trademark) of Eastman Chemical Co., USA is preferably used.

  The intrinsic viscosity (IV) of the thermoplastic aromatic polyester resin is preferably 0.5 to 1.5 dl / g, more preferably 0.6 to 1.3 dl / g, and particularly preferably 0.7 to 1.2 dl / g. Within the range of g. The IV value can be measured at 25 ° C. in a phenol / tetrachloroethane (1/1) mixed solvent according to a conventional method.

  Examples of the polyamide resin include nylon 6, nylon 66, nylon 6,66, nylon 610, nylon 11, nylon 12, amorphous nylon (for example, nylon 6I / 6T), nylon MXD6, and the like.

  Examples of the polystyrene resin include polystyrene, ABS resin, styrene-butadiene copolymer, styrene-isoprene copolymer, acrylonitrile-styrene copolymer, α-methylstyrene-styrene copolymer, and high impact polystyrene (HIPS). And styrene / butadiene / styrene block copolymers.

  Examples of the cyclic olefin resin include a ring-opening polymer of a norbornene monomer, a hydrogenated product of the ring-opening polymer, an addition polymer; a random copolymer of a norbornene monomer and ethylene; a hydrogenated product of a polystyrene resin; Can be mentioned.

  Examples of the aliphatic polyester resin other than polyglycolic acid include polylactic acid (polylactide), poly (ε-caprolactone), polybutylene succinate, polybutylene succinate-adipate, and the like.

  Other thermoplastic resins include inorganic fillers, plasticizers, heat stabilizers, light stabilizers, UV absorbers, moisture-proofing agents, waterproofing agents, water repellents, lubricants, mold release agents, coupling agents, and pigments as desired. Various additives such as dyes can be contained.

3. Oxygen Absorbing Agent As the oxygen absorbing agent used in the present invention, any oxygen absorbing agent conventionally used in this technical field can be used. Specific examples of the oxygen absorbent include the following.

(1) Reducing metal powder-based oxygen absorbent:
Examples of oxygen absorbers made of reducing metal powder include reducing iron, reducing zinc, reducing tin, low-level metal oxides (such as ferrous oxide and iron tetroxide), and reducing metal compounds ( Typical examples thereof include reducing metal powders such as iron carbide, silicon iron, iron carbonyl, iron hydroxide, and a mixture of two or more thereof. Of these, reduced iron powder (FeO, etc. _Fe 2 _{O 3)} is preferred.

  The metal powder having reducibility, if necessary, metal hydroxide such as alkali metal, alkaline earth metal, carbonate, sulfite, thiosulfate, tertiary phosphate, secondary phosphate, Organic acid salts, halides; activated carbon, activated clay, activated alumina and the like can be used in combination. Examples of the metal halide include sodium chloride, potassium chloride, calcium chloride, zinc chloride, aluminum chloride, iron chloride, tin chloride, and a mixture of two or more thereof.

(2) Nylon MXD6 / transition metal salt oxygen absorbent:
As an oxygen absorbent containing nylon MXD6 and a transition metal salt, a composition containing transition metal salt such as cobalt organic acid (for example, cobalt neodecanoate, cobalt stearate) as a catalyst in nylon MXD6 is used. can do.

  Transition metal salts are used to shorten the oxygen absorption induction period and increase the oxygen absorption rate and oxygen absorption. As the transition metal salt, a salt of a metal selected from the first, second, or third transition series of the periodic table is used. Preferred transition metals include manganese II, manganese III, iron II, iron III, cobalt II, cobalt III, nickel II, nickel III, copper I, copper II, rhodium II, rhodium III, and ruthenium. Of these transition metals, cobalt is most preferred.

  Metal salt forms include, but are not limited to, chloride, acetate, stearate, palmitate, ethyl 2-ethylhexanoate, neodecanoate, and naphthoate. . Among these, cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate are preferable. The addition amount of the transition metal salt in the oxygen absorbent is usually in the range of 0.1 to 10,000 ppm.

  From the viewpoint of moldability of a thermoplastic resin such as PET, it is preferable to use a blend of a thermoplastic resin such as PET, MXD6, and a transition metal salt in advance as an oxygen absorbent.

(3) Oxygen absorbent comprising a polymer compound having a polyhydric phenol as a skeleton:
As an oxygen absorbent comprising a polymer compound having a polyhydric phenol in its skeleton, for example, a polymer compound having a polyhydric phenol in its skeleton such as a polyphenol-containing phenol / aldehyde resin can be used.

(4) Oxygen absorber containing quinone, glycol, phenols, etc .:
An oxygen absorbent containing quinone, glycol, phenols, or the like can be used.

(5) Carbon-carbon double bond polymer / transition metal salt oxygen absorber:
A composition containing a polymer having a carbon-carbon double bond in the molecule and a transition metal salt such as organic acid cobalt (for example, cobalt neodecanoate) as a catalyst can be used as an oxygen absorbent.

  Examples of the polymer having a carbon-carbon double bond in the molecule include polyisoprene, polyisobutylene, polybutadiene, butadiene / isoprene copolymer, and styrene / butadiene copolymer. These polymers are excellent in oxygen absorption at low temperatures. Examples of the oxygen-absorbing polymer having an unsaturated group having an oxygen scavenging property include polymers of octadienes, hexadienes, butadienes, non-conjugated dienes, and heptadienes.

  In order to shorten the oxygen absorption induction period and increase the oxygen absorption rate and oxygen absorption amount, a transition metal salt is used in combination. Along with the transition metal salt, benzophenone or a derivative thereof having good compatibility with the oxygen-absorbing polymer may be used in combination.

  The transition metal salt is a salt of a metal selected from the first, second, or third transition series of the periodic table. Preferred metals include manganese II, manganese III, iron II, iron III, cobalt II, cobalt III, nickel II, nickel III, copper I, copper II, rhodium II, rhodium III, and ruthenium. Of these, cobalt is most preferred. Forms of metal salts include, but are not limited to, chloride, acetate, stearate, palmitate, ethyl 2-ethylhexanoate, neodecanoate, and naphthoate. Among these, cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate are preferable. The content of the transition metal salt in the oxygen absorbent is usually in the range of 0.1 to 10,000 ppm. From the viewpoint of compatibility with polyglycolic acid and other thermoplastic resins, dispersibility, melt kneading properties, etc., it is preferable to use a polymer obtained by copolymerizing a skeleton having an unsaturated double bond with a thermoplastic resin such as PET. .

(6) Organic oxygen absorbers such as porphyrins, macrocyclic polyamines, ascorbic acid, ascorbate, gallic acid (+ sodium carbonate):
A blend of an organic compound such as ascorbic acid with a resin is used as an oxygen absorbent and can also be used in the present invention.

(7) Enzymatic oxygen absorbers such as glucose oxidase and ascorbate oxidase:
Enzymes such as glucose oxidase and ascorbate oxidase can be used as oxygen absorbers.

  These oxygen absorbents can be used alone or in combination of two or more. The oxygen absorbent is preferably in the form of a master batch (referred to as “pellet master batch”) in which an oxygen absorbent is added at a high concentration to a thermoplastic resin such as PET and pelletized. Many commercially available oxygen absorbents are manufactured and sold in the form of such a pellet masterbatch. The pellet master batch contains an active ingredient (a component acting as an oxygen absorbent) in the resin component, preferably 1 to 99% by mass, more preferably 3 to 90% by mass, and still more preferably 5 to 80% by mass. contains. As an oxygen absorber, a monomer having a conjugated double bond and another comonomer are copolymerized to synthesize a polymer having a carbon-carbon double bond in the molecule, and the polymer and the transition metal salt are mixed to form a pellet. Some have become.

  The amount of oxygen absorbent to be contained in polyglycolic acid and other thermoplastic resins is, for example, in the case of an oxygen absorbent containing two or more components such as nylon MXD6 / transition metal salt-based oxygen absorbent, It shall mean the total amount of ingredients. When the oxygen absorbent is a pellet master batch, in the present invention, the pellet master batch itself is used as the oxygen absorbent, and its blending amount is determined. The reasons are as follows: 1) The oxygen absorption performance of the oxygen absorbent differs depending on the type of the oxygen absorbent, and it is difficult to evaluate the oxygen absorbability only by the content of the active ingredient. 2) The oxygen absorbent is pelleted. When used in the form of a masterbatch, increasing the blending amount improves the oxygen absorption of the polyglycolic acid layer and other thermoplastic resin layers, but due to the resin component contained in the pellet masterbatch, polyglycol The oxygen gas barrier property or carbon dioxide gas barrier property of the acid layer tends to be lowered. 3) The type and amount ratio of the resin component contained in the pellet masterbatch is the adhesion of the polyglycolic acid layer or other thermoplastic resin layer. May affect sex and other characteristics.

  The oxygen absorbent can be used in combination with a water absorbent. Water-absorbing agents include deliquescent inorganic salts such as sodium chloride, potassium chloride, sodium sulfate, magnesium sulfate, disodium hydrogen phosphate, potassium carbonate, sodium nitrate; glucose, fructose, sucrose, gelatin, modified casein, modified starch, etc. Examples include deliquescent organic compounds; superabsorbent resins such as acrylic acid (salt) grafted starch, crosslinked polyacrylic acid (salt), and modified polyvinyl alcohol.

4). Polyglycolic acid resin composition The polyglycolic acid resin composition used in the present invention is a resin composition containing polyglycolic acid and an oxygen absorbent as essential components, and optionally containing other additives. The oxygen absorbent added to the polyglycolic acid is a reducing metal powder-based oxygen absorbent and a carbon-carbon double bond polymer / transition metal salt-based oxygen absorber from the viewpoints of moldability, gas barrier properties, adhesion, and appearance. An agent is preferable, and a carbon-carbon double bond polymer / transition metal salt oxygen absorber is more preferable. An oxygen absorbent that reacts with polyglycolic acid during molding, such as nylon MXD6 / transition metal salt-based oxygen absorbent, is not preferred because its amount and molding conditions are restricted.

  When the oxygen absorbent added to the polyglycolic acid is a pellet master batch, the resin component preferably does not contain a trace component (for example, catalyst residue) that degrades or decomposes the polyglycolic acid during molding. It is preferable to use a thermoplastic aromatic polyester resin such as PET as the resin component of the pellet masterbatch in order to further improve interlayer adhesion. However, the thermoplastic aromatic polyester resin contains a residue of a polymerization catalyst used at the time of polymerization, and this trace amount of catalyst residue may decompose polyglycolic acid into glycolide, thereby reducing the gas barrier property. In contrast, a thermoplastic aromatic polyester resin obtained using a germanium compound as a polymerization catalyst is unlikely to decompose polyglycolic acid due to catalyst residues. For this reason, as a thermoplastic aromatic polyester resin used as a resin component of a pellet masterbatch, what was obtained using a germanium compound as a polymerization catalyst is preferable. As a thermoplastic aromatic polyester resin such as PET using a germanium catalyst, a commercially available product can be used.

  The oxygen absorbent is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 12 parts by weight, still more preferably 0.4 to 10 parts by weight, particularly preferably 100 parts by weight of polyglycolic acid. It is in the range of 0.5 to 8 parts by mass. It is desirable to use the oxygen absorbent in an appropriate amount ratio within the above range, comprehensively considering the type and form of the oxygen absorbent, the oxygen absorption performance, and the like. If the amount ratio of the oxygen absorbent becomes too small, the effect of improving oxygen absorption and interlayer adhesion becomes small, and if it becomes too large, the carbon dioxide gas barrier property and the appearance tend to be lowered.

5). Other Thermoplastic Resin Composition The thermoplastic resin composition used in the present invention contains other thermoplastic resins and an oxygen absorbent as essential components, and optionally contains other additives and the like. It is a thing. The oxygen absorbent is not particularly limited, but from the viewpoint of oxygen absorbability, moldability, interlayer adhesion, and the like, nylon MXD6 / transition metal salt-based oxygen absorbent, and carbon-carbon double bond polymer / transition metal salt-based An oxygen absorbent is preferable, and a carbon-carbon double bond polymer / transition metal salt-based oxygen absorbent is more preferable.

  The oxygen absorbent is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 15 parts by weight, still more preferably 0.4 to 12 parts by weight, particularly 100 parts by weight of other thermoplastic resins. Preferably it exists in the range of 0.5-10 mass parts. It is desirable to use the oxygen absorbent in an appropriate amount ratio within the above range, comprehensively considering the type and form of the oxygen absorbent, the oxygen absorption performance, and the like. If the amount ratio of the oxygen absorbent is too small, the effect of improving oxygen absorption and interlayer adhesion is reduced, and if it is too large, the strength, impact resistance, transparency, appearance, etc. of the plastic multilayer structure tend to decrease. is there.

6). Plastic multilayer structure The plastic multilayer structure of the present invention is generally in the form of a multilayer container or multilayer film (including sheets). The plastic multilayer structure of the present invention is a plastic multilayer structure having at least one polyglycolic acid layer and at least one other thermoplastic resin layer. At least one of the polyglycolic acid layers is an oxygen-absorbing polyglycolic acid layer formed from a polyglycolic acid resin composition containing polyglycolic acid and an oxygen absorbent. At least one of the other thermoplastic resin layers is an oxygen-absorbing thermoplastic resin layer formed from a thermoplastic resin composition containing another thermoplastic resin and an oxygen absorbent. The plastic multilayer structure of the present invention has at least one layer structure in which an oxygen-absorbing polyglycolic acid layer and an oxygen-absorbing thermoplastic resin layer are directly adjacent to each other without an adhesive layer interposed therebetween.

  The plastic multilayer structure of the present invention has a layer structure in which other thermoplastic resin layers are arranged on both sides of the polyglycolic acid layer in order to maintain a high gas barrier property without decomposing even in a high humidity atmosphere. It is preferable to have it. It is preferable that all the polyglycolic acid layers contained in the plastic structure and the other thermoplastic resin layers adjacent to the polyglycolic acid are directly adjacent to each other without an adhesive layer interposed therebetween. Therefore, in the plastic multilayer structure of the present invention, all the polyglycolic acid layers are oxygen-absorbing polyglycolic acid layers, and oxygen absorption is performed on at least one surface or both surfaces of each oxygen-absorbing polyglycolic acid layer. It is preferable that the thermoplastic resin layer has a layer structure directly adjacent to each other without an adhesive layer.

  The polyglycolic acid layer may be a single layer or a plurality of layers of two or more layers. In many cases, the polyglycolic acid layer can exhibit sufficient gas barrier properties in one or two layers. Therefore, the plastic multilayer structure of the present invention has a single polyglycolic acid layer, an oxygen-absorbing polyglycolic acid layer, and an oxygen-absorbing thermoplastic resin on each side of the oxygen-absorbing polyglycolic acid layer. It is preferable that the layer has a layer structure directly adjacent to each other without an adhesive layer.

  As another typical plastic multilayer structure of the present invention, the polyglycolic acid layer is two oxygen-absorbing polyglycolic acid layers, and at least one surface or both surfaces of each oxygen-absorbing polyglycolic acid layer, Examples thereof include those in which the oxygen-absorbing thermoplastic resin layer has a layer structure directly adjacent to each other without interposing an adhesive layer.

  When the plastic multilayer structure of the present invention has two or more kinds of other thermoplastic resin layers, the layers other than the other thermoplastic resin layers adjacent to the oxygen-absorbing polyglycolic acid layer are oxygen absorbents. It may be another thermoplastic resin layer or a recycled layer that does not contain. For example, when the plastic multilayer structure of the present invention is a multilayer film, if a heat-sealable resin layer is disposed on one outermost layer, the heat-sealable resin layer is used to perform secondary processing into a container having a bag shape. can do. When the multilayer film (sheet) is formed into a container such as a tray by sheet forming (vacuum forming and / or pressure forming), the lid material can be heat sealed using the innermost heat seal layer.

  When the plastic multilayer structure of the present invention is a multilayer container, the multilayer container includes a multilayer blow molded container (including a multilayer stretch blow molded container), a packaging bag made from a multilayer film or a sheet, and a multilayer sheet formed into a sheet ( Various shapes such as trays and cups formed by vacuum forming and / or pressure forming) can be used. Among these, a multilayer stretch blow molded container is preferable.

  As the layer structure of the multilayer container, other thermoplastic resin is abbreviated as TP, oxygen absorbent is abbreviated as SC, polyglycolic acid is abbreviated as PGA, and the thermoplastic resin composition containing other thermoplastic resin and oxygen absorbent is used. The oxygen-absorbing thermoplastic resin layer (TP + SC) and the oxygen-absorbing polyglycolic acid layer comprising a polyglycolic acid resin composition containing polyglycolic acid and an oxygen absorber are abbreviated as (PGA + SC), respectively. A simple layer structure can be exemplified. However, the multilayer container of the present invention is not limited to those having these layer configurations.

(1) (TP + SC) / (PGA + SC)
(2) (TP + SC) / (PGA + SC) / (TP + SC)
(3) (TP + SC) / (PGA + SC) / (TP + SC) / (PGA + SC)
(4) (TP + SC) / (PGA + SC) / (TP + SC) / (PGA + SC) / (TP + SC)
(5) (TP + SC) / (PGA + SC) / recycled layer / (PGA + SC) / (TP + SC)
(6) (TP + SC) / (PGA + SC) / (TP + SC) / (PGA + SC) / (TP + SC) / (PGA + SC) / (TP + SC)

  The multilayer container may be a multilayer blow-molded container containing at least one oxygen-absorbing polyglycolic acid layer as an intermediate layer in a resin composition layer containing a thermoplastic aromatic polyester resin and an oxygen absorbent. Preferably, it is a multilayer stretch blow molded container. As the thermoplastic aromatic polyester resin, PET is preferable. Multilayer blow molded containers (including multilayer stretch blow molded containers) are “(PET + SC) / (PGA + SC) / (PET + SC)”, “(PET + SC) / (PGA + SC) / (PET + SC) / (PGA + SC) / (PET + SC)”. And a layer structure of “(PET + SC) / (PGA + SC) / recycled layer / (PGA + SC) / (PET + SC)” is preferable.

  The multilayer blow molded container can be produced by, for example, a direct blow molding method of a coextruded multilayer preform (multilayer parison); a stretch blow molding method of a co-injected multilayer preform. The multilayer pipe can be manufactured by a coextrusion method. This multilayer pipe can be used as a preform for blow molding.

  The mass ratio of the other thermoplastic resin and polyglycolic acid in the plastic multilayer structure is usually within the range of 99.5: 0.5 to 55:45. This mass ratio can be appropriately determined depending on the shape of the multilayer structure and the purpose of use. In a multilayer structure for the purpose of improving gas barrier properties by the polyglycolic acid layer, the mass ratio of other thermoplastic resin and polyglycolic acid is preferable from the viewpoint of balancing gas barrier properties, mechanical strength, heat resistance, etc. Is in the range of 99.5: 0.5 to 80:20, more preferably 99.2: 0.8 to 90:10.

  The thickness ratio of each layer is not particularly limited. When the multilayer structure is a multilayer blow molded container (including a multilayer stretch blow molded container), the total thickness of the container body (side wall) is usually 20 μm to 10 mm, preferably 50 μm to 8 mm, more preferably 80 μm to 5 mm. Within range. The thickness of the oxygen-absorbing thermoplastic resin layer in the barrel portion of the multilayer container (total thickness in the case of a plurality of layers) is usually 10 μm to 9.9 mm, preferably 25 μm to 8.9 mm, more preferably 40 μm to 4.9 mm. Is within the range. The thickness of the oxygen-absorbing polyglycolic acid layer in the body of the multilayer container (total thickness in the case of multiple layers) is usually 0.2 to 1,000 μm, preferably 0.5 to 800 μm, more preferably 0.8 to It is in the range of 500 μm.

  A multilayer container such as a multilayer blow-molded container preferably has an open end (neck) of an oxygen-absorbing thermoplastic resin single layer. Since the bottom of the multilayer container is generally thick, it can be a single layer of an oxygen-absorbing thermoplastic resin, but a core layer made of an oxygen-absorbing polyglycolic acid layer may be disposed at the bottom.

  When producing a multilayer container by the co-injection stretch blow molding method, a polyglycolic acid resin composition and a thermoplastic resin composition are co-injected to form a bottomed multilayer preform, and then the multilayer preform Is subjected to stretch blow molding to produce a multilayer blow molded container. Stretch blow molding is usually biaxial stretch blow molding.

  In the manufacturing process of the multilayer preform, each mold melted through one gate in a single mold clamping operation is carried out in a cavity of a single preform mold using a molding machine having a plurality of injection cylinders. Co-inject resin component. By the co-injection molding method, the inner and outer layers are oxygen-absorbing thermoplastic resin layers (thermoplastic resin composition layers), and the core layer consisting of oxygen-absorbing polyglycolic acid layers (polyglycolic acid resin composition layers) absorbs oxygen. A bottomed multilayer preform having a three-layer structure in which the opening end portion is composed only of the oxygen-absorbing thermoplastic resin layer and the trunk portion is embedded in the heat-resistant thermoplastic resin layer is obtained. The oxygen-absorbing polyglycolic acid layer may not be present on part or all of the bottom of the multilayer preform. Generally, since the thickness of the bottom portion is larger than the thickness of the body portion, the gas barrier property can be exhibited even if the bottom portion is substantially only an oxygen-absorbing thermoplastic resin layer. By disposing the oxygen-absorbing polyglycolic acid layer only on the trunk, it is easy to prevent the mechanical strength of the multilayer container from being lowered and to uniformly control the thickness of the oxygen-absorbing polyglycolic acid layer.

  The injection temperature (hot runner temperature) of the polyglycolic acid resin composition in co-injection molding is usually controlled within the range of 200 to 310 ° C, preferably 230 to 300 ° C. If the injection temperature is too high, the polyglycolic acid resin composition staying in the injection molding machine tends to be thermally decomposed.

  When the other thermoplastic resin is a thermoplastic aromatic polyester resin such as PET or Co-PET, the resin temperature during co-injection molding is usually 265 to 300 ° C, preferably 270 to 295 ° C. If the injection temperature of the thermoplastic aromatic polyester resin composition is too low, the melt fluidity becomes too poor, and it is difficult to obtain a multilayer preform having a three-layer structure in which the thermoplastic aromatic polyester resin composition becomes the inner and outer layers. become. If the injection temperature of the thermoplastic aromatic polyester resin composition becomes too high, thermal decomposition tends to occur. The multilayer preform can be produced by a sequential molding method or a simultaneous molding method.

  Stretch blow molding a multilayer preform. In the stretch blow molding process, the multilayer preform is adjusted to a temperature at which stretching can be performed, and then inserted into a cavity of a blow molding die, and a pressurized fluid such as air is blown to perform stretch blow molding. Stretch blow molding can be performed by either a hot parison system or a cold parison system. Usually, it is preferable to adopt a cold parison method from the viewpoint of temperature control. Here, the parison means a preform.

  In order to stretch blow-mold a multilayer preform with the thermoplastic resin composition layer as the outer layer and the inner layer and the polyglycolic acid resin composition layer as the core layer by the cold parison method, first, the multilayer preform is formed with an infrared heater or the like. Heat until fully softened. In this heating step, the thermoplastic resin composition layer is softened while maintaining an amorphous state, but the polyglycolic acid resin composition layer is crystallized and whitened. At this time, if the crystallization of the polyglycolic acid resin composition layer is non-uniform, the thickness variation of the polyglycolic acid resin composition layer after stretch blow molding becomes large or defects tend to occur. It is necessary to crystallize the glycolic acid resin composition layer uniformly.

  In order to uniformly crystallize the polyglycolic acid resin composition layer, it is preferable to heat the multilayer preform so that the multilayer preform temperature is 90 ° C. or higher. More specifically, the heater power and heating time are adjusted so that the surface temperature of the thermoplastic resin composition layer (outer layer) at the center in the longitudinal direction of the multilayer preform is 90 to 110 ° C. However, the temperature in the vicinity of the mouth portion (where the support ring is located) of the multilayer preform may be set to be 10 to 30 ° C. lower than the surface temperature of the central portion in order to avoid deformation during stretch blow molding. preferable. If the temperature in the vicinity of the mouth (support ring) is lowered, the stretchability of the polyglycolic acid resin composition layer at that part is lowered, and voids and cracks are likely to occur, but the lateral direction at a position 2 cm below the support ring If the size of the multilayer preform and bottle is set so that the draw ratio (outer diameter at 2 cm below the support ring after bottle molding / outer diameter at 2 cm below the support ring of the multilayer preform) is 2 times or less, Generation of surrounding voids and cracks can be suppressed. Here, the support ring means a ring that holds the mouth of the multilayer preform and the multilayer blow molded container at the time of co-injection molding and stretch blow molding.

  After the preliminary heating, a pressurized fluid such as compressed air is blown into the bottomed multilayer preform heated to the stretching temperature to be expanded and stretched. In general, the draw ratio is about 1.5 to 3 times in the axial direction and about 3 to 5 times in the circumferential direction. The blow ratio (total stretch ratio) varies slightly depending on the type of stretch blow molding device (blow molded bottle), but it is 6 to 9 times for general blow molded bottles, 8 to 9.5 times for pressure bottles, heat resistance It is about 6 to 7.5 times for bottles and about 7 to 8 times for large bottles.

  When the thermoplastic aromatic polyester resin is PET or Co-PET, compressed air is blown into the multilayer preform at a temperature range from the glass transition temperature to the crystallization temperature, preferably from 80 to 170 ° C. Then, a stretching rod is inserted, and the multilayer preform is biaxially stretched in the axial (longitudinal) direction and the circumferential (transverse) direction. The glass transition temperature of the polyglycolic acid in the core layer is about 38 ° C., and it is easily stretched following the stretching of the thermoplastic polyester resin in the inner and outer layers.

  In the stretch blow molding process, it is preferable that the mold temperature is heated to a temperature of 100 ° C. or higher, and the body portion of the biaxially oriented multilayer container is heat-set simultaneously with the stretch blow molding. The biaxially oriented state is heat-set by heat treatment in a high-temperature mold, and at the same time, crystallization of the thermoplastic aromatic polyester resin composition layer proceeds. By the heat treatment, internal strain generated in the stretch blow molding process is relaxed, and orientation crystallization is promoted. Unlike the large spherulite produced by the heat treatment of the opening end portion, the orientation crystal in the body portion retains transparency even when orientation crystallization is promoted.

  In particular, when PET or Co-PET is used as the thermoplastic aromatic polyester resin, it is desirable to perform heat setting in order to improve heat resistance. When manufacturing heat-resistant multilayer blow-molded containers suitable for hot fill, the temperature of the stretch blow mold is raised to 100 ° C or higher in order to prevent thermal shrinkage and deformation of the container during hot fill. At the same time as the stretch blow molding, heat treatment (heat setting) is performed in the mold. The specific mold temperature is 100 to 165 ° C., preferably 145 to 155 ° C. for a general heat resistant container, and 160 to 165 ° C. for a high heat resistant container. The heat treatment time varies depending on the thickness of the multilayer container and the heat treatment temperature, but is usually 1 to 30 seconds, preferably 2 to 20 seconds.

  As a method of performing the heat treatment in the mold, a single mold method in which stretch blow molding and heat setting are performed with one mold, a multi-layer blow molded container subjected to primary stretch blow molding is taken out, heat fixed, and then secondary A two-stage blow method in which secondary stretch blow molding is performed using a mold, an oven blow method, or the like can be appropriately applied. When heat treatment is performed during stretch blow molding, the multilayer blow molding container is taken out from the mold after sufficiently cooling.

  The multilayer container of the present invention can be produced not only by the co-injection stretch blow molding method as described above but also by a known bottle molding method such as a direct blow molding method. The number of polyglycolic acid layers can be not only one but also two or more.

  Hereinafter, the present invention will be described more specifically with reference to examples. Evaluation methods for physical properties or characteristics are as follows.

(1) Oxygen concentration test method 1.70 liters of water was filled in a multilayer container having an internal volume of 1.75 liters, and nitrogen gas was bubbled into the water to remove dissolved oxygen. It was 0.5 ppm when the dissolved oxygen concentration in water was measured with the nondestructive oxygen concentration meter (made by PreSens). After this container was stored for 6 months (180 days) in an atmosphere of a temperature of 23 ° C. and a relative humidity (RH) of 50%, the dissolved oxygen concentration in water was measured with the nondestructive oxygen concentration meter. This test is suitable for evaluating the oxygen concentration of the contents when a gas barrier multilayer container is used as a beverage container.

(2) Method for evaluating carbon dioxide gas barrier property A multi-layer container having an internal volume of 1.75 liters was filled with 4 atmospheres of carbon dioxide gas and a small amount of water to adjust the relative humidity in the multi-layer container to 100%. In an actual beverage bottle, the relative humidity is almost 100% due to the contents, so such a humidity condition was adopted. The opening of this multilayer container was sealed with a stopper. This multilayer container was stored for 6 months (180 days) in an atmosphere of a temperature of 23 ° C. and a relative humidity (RH) of 50%. The internal pressure of the multilayer container was measured with a pressure sensor. Carbon dioxide loss was evaluated from changes in the internal pressure of the multilayer container.

(3) Interlayer adhesion evaluation method 1.70 liters of carbonated water of 4 atm is filled in a multi-layer container with an internal volume of 1.75 liters, and the temperature is 23 ° C. and the relative humidity (RH) is 50% for 3 months. Stored for 90 days. After the storage, the multilayer container was dropped on a concrete floor from a height of 50 cm in a state where the multilayer container was laid down horizontally. The measurement temperature was 23 ° C. Since the multilayer container is a large container having an internal volume of 1.75 liters, it is filled with carbonated water and dropped onto the concrete floor from a height of 50 cm on the body side, thereby allowing the PGA layer and the PET layer to be separated. Interlayer adhesion can be evaluated. This delamination test is a practical method for evaluating interlayer adhesion. When delamination occurs, the delamination portion appears rainbow-colored, and therefore the presence or absence of delamination can be evaluated visually. The test number is 20 (n = 20), and the number of delaminations is shown.

[Example 1]
1. Preparation of multilayer container Polyglycolic acid (PGA; weight average molecular weight = 200,000; melt viscosity measured at a temperature of 270 ° C. and a shear rate of 122 sec ⁻¹ = 620 Pa · s), polyethylene terephthalate (PET; Far East CB60S; IV value = 0.82 dl / g), and oxygen absorber [SC; Colormatrix Corp. A two-layer / three-layer co-injection preform having a layer configuration of (PET + SC) / (PGA + SC) / (PET + SC) was produced using Amosorb (registered trademark) DFC 4020].

  The oxygen absorbent (Amosorb DFC 4020) is a polyester-based oxygen absorbent containing a polybutadiene skeleton, and is commercially available in the form of a pellet masterbatch. PET and PGA are also in the form of pellets. For PET and oxygen absorber, and PGA and oxygen absorber, dry blended pellets of each component were used for co-injection. For molding the co-injection preform, a two-type three-layer co-injection molding machine comprising two injection machines and a hot runner was used.

  The temperature at the tip of the injection cylinder on the inner and outer layers side is set to 290 ° C, the temperature at the tip of the injection cylinder on the intermediate layer side is set to 270 ° C, and the temperature of the hot runner block portion to be joined is set to 290 ° C. A bottomed co-injection preform was prepared in which the PGA layer was embedded in the inner and outer PET layers at the bottom and bottom. The filling amount of each component is 2.85% by mass of PGA, 0.15% by mass of oxygen absorbent blended with PGA, 95.5% by mass of PET, and 1.5% of oxygen absorbent blended with PET. % Was adjusted. The weight of this co-injection preform was 49 g.

  The co-injection preform was heated to 140 ° C. and then blow molded by a blow molding machine to produce a petaloid multilayer container having an internal volume of 1.75 liters. The layer structure of the multilayer container is (PET + SC) / (PGA + SC) / (PET + SC), but the PGA layer (PGA + SC) is not disposed in the opening. The body of the multilayer container is in a state in which the PGA layer is embedded in the inner and outer PET layers. The wall thickness of the multilayer container was about 270 μm. The layer structure is shown in Table 1.

2. Oxygen gas barrier property The multilayer container was filled with 1.70 liters of deoxygenated water. Deoxygenated water is obtained by bubbling nitrogen gas into water to remove dissolved oxygen. When the dissolved oxygen concentration in the deoxygenated water was measured with a nondestructive oxygen concentration meter (manufactured by PreSens), it was 0.5 ppm. This multilayer container was stored for 6 months (180 days) in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50% (50% RH). After storage, the dissolved oxygen concentration in water was measured using the same nondestructive oxygen concentration meter as described above, and it was 0.0 ppm. Therefore, the dissolved oxygen concentration change in water was -0.5 ppm. The results are shown in Table 2.

3. Carbon dioxide gas barrier property The multi-layer container was filled with 4 atmospheres of carbon dioxide gas and a small amount of water to adjust the humidity in the multi-layer container to 100% RH. The opening of this multilayer container was sealed with a stopper. This multilayer container was stored for 6 months (180 days) in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50% RH. After storage, the internal pressure of the container was measured with a pressure sensor and found to be 3.68 atmospheres. Therefore, the loss of carbon dioxide was [(4−3.68) / 4] × 100 = 8%. The results are shown in Table 2.

4). Evaluation of Adhesiveness of Multilayer Container The multilayer container was filled with carbonated water of 4 atm and stored in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50% RH for 3 months (90 days). After the storage, the multilayer container was placed in a horizontal (side-down) direction, dropped from a height of 50 cm, the appearance was observed, and the number of delaminated layers in 20 samples was counted. The results are shown in Table 2.

[Example 2]
The oxygen absorber blended with PET was changed from “Amosorb (registered trademark) DFC 4020” to “A-100 / Catalyst” (manufactured by Valspar) containing MXD nylon-based skeleton, and the filling amount of each component was changed to Table 1. A multilayer container was produced in the same manner as in Example 1 except that the change was made as shown in FIG. The results are shown in Tables 1 and 2.

[Example 3]
A multilayer container was produced in the same manner as in Example 1 except that the filling amount of the oxygen absorbent was changed as shown in Table 1. The results are shown in Tables 1 and 2.

[Example 4]
1. Preparation of oxygen absorber a Polyethylene terephthalate polymerized using a germanium catalyst (“J125S” manufactured by Mitsui Chemicals, Inc., IV value = 0.77 dl / g, melting point = 255 ° C.) After adding in an amount corresponding to a cobalt concentration of 500 ppm, it was supplied to a twin-screw extruder, and 10 mass% of maleic anhydride-modified polybutadiene was melt-kneaded and pelletized to obtain an oxygen absorbent a.

2. A multilayer container was produced in the same manner as in Example 1 except that the oxygen absorbent blended with PGA was changed from “Amosorb (registered trademark) DFC 4020” to the above “oxygen absorbent a”. The results are shown in Tables 1 and 2.

[Comparative Example 1]
A co-injection preform (49 g) having a layer structure of PET / PGA / PET was prepared in the same manner as in Example 1 except that PGA and PET not containing an oxygen absorber were used. The reform was blow molded to produce a multilayer container. The results are shown in Tables 1 and 2.

[Comparative Examples 2-3]
A co-injection preform (49 g) was produced in the same manner as in Example 1 except that it had the configuration shown in Table 1, and then the co-injection preform was blow-molded to produce a multilayer container. The results are shown in Tables 1 and 2.

<Discussion>
As is clear from the results in Tables 1 and 2, the multilayer container (Comparative Example 1) having a layer configuration of “PET / PGA / PET” has excellent carbon dioxide gas barrier properties, but the oxygen concentration of the contents during storage is high. It tends to increase gradually, and interlayer adhesion is not sufficient.

  The multilayer container (Comparative Example 2) having the layer configuration of “(PET + SC) / PGA / (PET + SC)” is excellent in oxygen gas barrier property and carbon dioxide gas barrier property, but is peeled off when the container is dropped, and has interlayer adhesion. It was insufficient.

  The multilayer container (Comparative Example 3) having the layer configuration of “PET / (PGA + SC) / PET” has excellent carbon dioxide barrier properties, but the oxygen concentration of the contents tends to gradually increase during storage, and the interlayer adhesion Is not enough.

  On the other hand, when the oxygen absorber is contained in all of the PET layer and the PGA layer, the oxygen concentration can be kept at a low level, the carbon dioxide gas loss is suppressed, and the internal pressure holding property is excellent. A multilayer stretch blow molded container without peeling can be obtained (Examples 1 to 4).

  The plastic multilayer structure of the present invention can be used as a multilayer container such as carbonated drinks, fruit juice-containing drinks, sports drinks, teas, coffee drinks, alcoholic drinks such as beer, and natural water. The multilayer container of the present invention can be used not only as a beverage container but also in a wide range of technical fields such as toiletries and chemical containers. The multilayer film or sheet can be used as a packaging material having excellent gas barrier properties as it is or after being secondarily processed into a container such as a packaging bag, tray or cup.

Claims (11)

In a plastic multilayer structure having at least one polyglycolic acid layer and at least one other thermoplastic resin layer,
1) At least one layer of the polyglycolic acid layer is an oxygen-absorbing polyglycolic acid layer formed from a polyglycolic acid resin composition containing polyglycolic acid and an oxygen absorbent,
2) At least one of the other thermoplastic resin layers is an oxygen-absorbing thermoplastic resin layer formed from a thermoplastic resin composition containing another thermoplastic resin and an oxygen absorbent, and
3) A plastic multilayer structure comprising at least one layer configuration in which the oxygen-absorbing polyglycolic acid layer and the oxygen-absorbing thermoplastic resin layer are directly adjacent to each other without an adhesive layer interposed therebetween.   All of the polyglycolic acid layers are oxygen-absorbing polyglycolic acid layers, and at least one surface of each oxygen-absorbing polyglycolic acid layer has no oxygen-absorbing thermoplastic resin layer interposed therebetween. The plastic multilayer structure according to claim 1, wherein the plastic multilayer structure has a directly adjacent layer structure.   The polyglycolic acid layer is a single oxygen-absorbing polyglycolic acid layer, and the oxygen-absorbing thermoplastic resin layers are directly formed on both sides of the oxygen-absorbing polyglycolic acid layer without interposing an adhesive layer. The plastic multilayer structure according to claim 2, comprising adjacent layer structures.   The polyglycolic acid layer is a two-layer oxygen-absorbing polyglycolic acid layer, and the oxygen-absorbing thermoplastic resin layer is directly on at least one surface of each oxygen-absorbing polyglycolic acid layer without an adhesive layer interposed therebetween. The plastic multilayer structure according to claim 2, comprising adjacent layer structures.   The plastic multilayer structure according to any one of claims 1 to 4, which is a multilayer container.   The plastic multilayer structure according to claim 5, wherein the multilayer container is a multilayer blow molded container.   The plastic multilayer structure according to claim 6, wherein the multilayer blow molded container is a multilayer stretch blow molded container.   The oxygen-absorbing polyglycolic acid layer is a layer formed from a polyglycolic acid resin composition containing 0.1 to 20 parts by mass of an oxygen absorbent with respect to 100 parts by mass of polyglycolic acid. 8. The plastic multilayer structure according to any one of 7 above.   2. The oxygen-absorbing thermoplastic resin layer is a layer formed from a thermoplastic resin composition containing 0.1 to 20 parts by mass of an oxygen absorbent with respect to 100 parts by mass of another thermoplastic resin. The plastic multilayer structure according to any one of 1 to 8.   The plastic multilayer structure according to any one of claims 1 to 9, wherein the other thermoplastic resin is a thermoplastic aromatic polyester resin.   The plastic multilayer structure according to claim 10, wherein the thermoplastic aromatic polyester resin is polyethylene terephthalate.