JP6648453B2 - Method for producing recycled polyester resin - Google Patents

Description

  The present invention has a polyester resin layer and a polyamide resin layer in the body of a hollow container, for example, a packaging container used for storing a liquid, and recovering the polyester resin from the packaging container to form a recycled polyester resin. And a method for producing a recycled polyester resin.

  Various plastic containers have been used as containers for packaging beverages, foods, cosmetics, pharmaceuticals, and the like. Plastic containers are superior in that they are lightweight, highly transparent, have a high degree of freedom in design, and are safe.However, compared to metal cans and glass bottles, plastic containers have a higher gas permeability such as oxygen. However, there is a drawback that is easily transmitted. For this reason, it is important to prevent deterioration of the contents and deterioration of taste and aroma due to oxygen remaining inside the container and oxygen from the outside of the container penetrating through the vessel wall. In particular, in a high temperature environment such as a summer or hot beverage, an oxygen-absorbing beverage container is preferably used.

  Conventionally, as a beverage container having an oxygen absorbing property, the container wall of a plastic container has a multilayer structure, and a transition between a metaxylene group-containing polyamide resin and an organic acid cobalt or the like occurs between a surface layer made of a thermoplastic polyester resin such as polyethylene terephthalate. There is known a device provided with a gas barrier layer containing a metal salt (for example, see Patent Document 1). In this multilayer container, the metaxylylene group-containing polyamide resin of the gas barrier layer can be catalytically oxidized to absorb oxygen.

However, when a transition metal salt is blended in the gas barrier layer, kogation is generated in the polyamide resin during molding, and the productivity may be reduced.
In recent years, in a multilayer container, an attempt has been made to separate a surface layer made of a thermoplastic polyester resin and a gas barrier layer therebetween to recycle and use the polyester resin. However, when the polyamide resin containing the transition metal salt is mixed with the recycled polyester resin (recycled polyester resin) at the time of recycling, there is a problem that the recycled polyester resin is likely to turn yellow when processed.

Further, as the multilayer container, an oxygen-absorbing layer composed of a reaction product of a polyamide resin and a polyamide resin-reactive oxidizable polydiene or oxidizable polyether and a transition metal salt is used as a core layer, and ethylene-vinyl on both sides thereof. It has also been proposed to provide a gas barrier layer made of an alcohol copolymer and a surface layer made of a polyolefin resin on both sides thereof (see Patent Document 2). In the multilayer container, the core layer and the gas barrier layer prevent oxygen from entering from the outside and can remove oxygen remaining in the container.
However, the presence of the barrier layer and the surface layer inside the oxygen absorbing layer makes it difficult for the oxygen inside the container to reach the oxygen absorbing layer, so that the oxygen inside the container may not be collected quickly. In addition, the production of a five-layer bottle using three types of resins requires technical skill due to its complexity, and also has the problem of high cost. Furthermore, since the transition metal salt is blended with the polyamide resin, like the multilayer container disclosed in Patent Literature 1, productivity is reduced due to generation of kogation, and coloring during recycling is also a concern.

Conventionally, as a multilayer plastic container capable of removing oxygen remaining inside the container, an oxygen barrier layer made of a gas barrier resin such as an ethylene-vinyl alcohol copolymer, and a polyolefin resin provided on the inner layer side of the oxygen barrier layer A container having an oxygen-absorbing layer capable of generating a polymer radical, such as a polymer radical, has also been proposed (see Patent Document 3).
However, this container has a problem that it is necessary to irradiate the inside of the container with light or ionizing radiation and to fill and seal the contents before the polymer radicals generated by the irradiation are deactivated, which makes handling difficult. In addition, irradiation of light or ionizing radiation involves forcible deterioration of the resin itself, which may cause yellowing or a decrease in rigidity. In addition, extra cost is required to introduce a device for irradiating light or ionizing radiation. Problem.

  Further, in a packaging container, there is also known a container in which an oxygen absorbent is blended into a liner provided in a lid of a hollow container to absorb oxygen in a head space portion and dissolved oxygen in a liquid (see Patent Document 4). ). However, since the lid of the hollow container has a limited space in which the oxygen absorbent itself can be used, the amount and capacity of the oxygen absorbent that can be used are limited, and it is difficult to give the entire packaging container sufficient oxygen absorbency. . In addition, when a large amount of the oxygen absorbent is used to enhance the oxygen absorbability, the oxygen absorbent may be eluted in the beverage.

JP 2002-321774 A JP 2006-281640 A JP-A-5-32277 JP-A-2003-221076

  Under such circumstances, while preventing the intrusion of oxygen from the outside of the container into the inside of the container, it efficiently absorbs oxygen remaining inside the container and oxygen from the outside of the container that has passed through the vessel wall, and There is a need for a liquid packaging container that can effectively prevent alteration and reduction in flavor such as taste and aroma. Further, it is desired to provide a packaging container which is less likely to deteriorate in quality such as yellowing when the polyester resin is recycled, and which is excellent in recyclability.

The present inventors have conducted intensive studies in view of the above problems, and as a result, while providing a container lid that can be easily separated in the recycling process with oxygen absorption performance, the hollow container body has gas aria properties and By having a specific structure, while effectively preventing the deterioration of the contents such as taste and aroma due to the deterioration of the contents due to oxygen, preventing the deterioration of the quality of the polyester at the time of recycling, the polyester has excellent recyclability. They have found that a packaging container can be provided, and have completed the present invention. The present invention provides the following (1) to (7).
(1) a hollow container including at least one layer of each of a polyester resin layer made of a polyester resin and a polyamide resin layer made of a polyamide resin, and a lid that closes an opening of the hollow container and contains an oxygen absorbent,
The polyamide resin layer does not substantially contain a transition metal, and the ratio (A / B) of the thickness (A) of the polyester resin layer to the thickness (B) of the polyamide resin layer in the body of the hollow container is: A packaging container having a size of 2.5 or more and 200 or less.
(2) The packaging container according to (1), wherein the polyester resin contains polyethylene terephthalate.
(3) The packaging container according to the above (1) or (2), wherein the polyamide resin is a polyamide resin containing a structural unit derived from xylylenediamine.
(4) The above-mentioned (1) to (3), wherein the oxygen-absorbing substance of the oxygen-absorbing agent is at least one selected from the group consisting of iron powder, activated iron oxide, sodium sulfite, ascorbic acid, and oxygen-absorbing resin. The packaging container according to any one of (1) to (4).
(5) The packaging container according to any one of (1) to (4), wherein the concentration of dissolved oxygen in the liquid 60 days after filling the liquid is 0.3 ppm or less.
(6) The packaging container according to any one of (1) to (5), wherein the concentration of dissolved oxygen in the liquid 120 days after filling the liquid is 0.3 ppm or less.
(7) The polyamide resin is removed from the packaging container described in any one of the above (1) to (6) by removing the lid and the polyamide resin, or from the packaging container from which the lid has been removed. A method for producing a recycled polyester resin by removing and recovering the polyester resin.
(8) The method for producing a recycled polyester resin according to the above (7), wherein the removal of the polyamide resin is performed by crushing the hollow container and then separating it by air separation.

  According to the present invention, by suppressing the amount of oxygen in a container quickly and for a long period of time, it is possible to effectively prevent deterioration of the contents such as taste and aroma due to deterioration of contents due to oxygen, and to recycle polyester. It is possible to provide a packaging container excellent in recyclability by preventing quality deterioration at the time.

It is sectional drawing which shows an example of the packaging container of this invention.

Hereinafter, the present invention will be described using embodiments.
The packaging container of the present invention includes a hollow container and a lid for closing a mouth of the hollow container. Hereinafter, the configurations of the hollow container and the lid used in the present invention will be described in more detail.

<Hollow container>
The hollow container includes at least one polyester resin layer and at least one polyamide resin layer, and has a multilayer laminated structure.
[Polyester resin layer]
The polyester resin layer is a layer made of a polyester resin. The polyester resin constituting the polyester resin layer is a polycondensation polymer of a dicarboxylic acid and a diol, and 70 mol% or more of the structural units (dicarboxylic acid units) derived from dicarboxylic acid are derived from aromatic dicarboxylic acid, and It is preferable that 70 mol% or more of the structural unit (diol unit) derived from a diol is derived from an aliphatic diol.
Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, biphenyldicarboxylic acid, diphenylether-dicarboxylic acid, diphenylsulfone-dicarboxylic acid, diphenylketone-dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,4-naphthalene Examples thereof include dicarboxylic acid and 2,7-naphthalenedicarboxylic acid, and terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid are preferable, and terephthalic acid is more preferable.
Examples of the aliphatic diol include linear or branched structures such as ethylene glycol, 2-butene-1,4-diol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, methylpentanediol, and diethylene glycol. Aliphatic diols such as cyclohexanedimethanol, isosorbide, spiroglycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, norbornene dimethanol and tricyclodecanedimethanol. . Among these, ethylene glycol, neopentyl glycol and cyclohexanedimethanol are preferred, and ethylene glycol is more preferred.

Preferred polyester resins used in the present invention include polyethylene terephthalate. Polyethylene terephthalate means a dicarboxylic acid unit containing at least 80 mol% of a terephthalic acid-derived structural unit and a diol unit containing at least 80 mol% of a ethylene glycol-derived structural unit, and preferably a dicarboxylic acid unit. The proportion of the constituent unit derived from terephthalic acid in the diol unit is 90 to 100 mol%, and the proportion of the constituent unit derived from ethylene glycol in the diol unit is 90 to 100 mol%.
By setting the proportion of the unit derived from terephthalic acid in the dicarboxylic acid unit to 80 mol% or more as described above, the polyester resin hardly becomes amorphous. Therefore, the inside of the hollow container is filled with a high-temperature one. In such cases, heat shrinkage becomes difficult, and heat resistance becomes good.
When polyethylene terephthalate is used as the polyester resin, the polyester resin may be composed of polyethylene terephthalate alone, but may contain a polyester resin other than polyethylene terephthalate in addition to polyethylene terephthalate. Polyethylene terephthalate is preferably contained in an amount of 80 to 100% by mass, more preferably 90 to 100% by mass, based on the total amount of the polyester resin.

Polyethylene terephthalate may include a structural unit derived from a bifunctional compound other than terephthalic acid and ethylene glycol, and the bifunctional compound may include the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and ethylene glycol. And difunctional compounds other than aliphatic diols and aromatic dicarboxylic acids and aliphatic diols. At this time, the constitutional unit derived from the bifunctional compound other than terephthalic acid and ethylene glycol is preferably at most 20 mol%, more preferably at most 10 mol%, based on the total mol of all the constitutional units constituting the polyester resin. is there.
In addition, even when the polyester resin is other than polyethylene terephthalate, the polyester resin may include a structural unit derived from a bifunctional compound other than the aromatic dicarboxylic acid and the aliphatic diol.

Examples of the difunctional compound other than the aromatic dicarboxylic acid and the aliphatic diol include an aliphatic difunctional compound other than the aliphatic diol and an aromatic difunctional compound other than the aromatic dicarboxylic acid.
Examples of the aliphatic difunctional compound other than the aliphatic diol include a linear or branched aliphatic difunctional compound, and specifically, malonic acid, succinic acid, adipic acid, azelaic acid and sebacic acid. Aliphatic dicarboxylic acids; examples include aliphatic hydroxycarboxylic acids such as 10-hydroxyoctadecanoyl acid, lactic acid, hydroxyacrylic acid, 2-hydroxy-2-methylpropionic acid, and hydroxybutyric acid.
The above aliphatic bifunctional compound may be an alicyclic difunctional compound, for example, an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, norbornenedicarboxylic acid and tricyclodecanedicarboxylic acid; hydroxymethyl Alicyclic hydroxycarboxylic acids such as cyclohexane-carboxylic acid, hydroxymethylnorbornene-carboxylic acid and hydroxymethyltricyclodecanecarboxylic acid;
Among these, preferred alicyclic bifunctional compounds include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. The copolymerized polyester resin containing a structural unit derived from these alicyclic bifunctional compounds can be easily produced, and can improve the drop impact strength and transparency of the hollow container. Among the above, more preferable ones are 1,4-cyclohexanedicarboxylic acid because they are easily available and can have a high drop impact strength.
The aromatic difunctional compound other than the aromatic dicarboxylic acid is not particularly limited, and specific examples thereof include hydroxybenzoic acid, hydroxytoluic acid, hydroxynaphthoic acid, 3- (hydroxyphenyl) propionic acid, Aromatic hydroxycarboxylic acids such as phenylacetic acid and 3-hydroxy-3-phenylpropionic acid; and aromatic diols such as bisphenol compounds and hydroquinone compounds.

In addition, when polyethylene terephthalate includes a structural unit derived from an aromatic dicarboxylic acid other than terephthalic acid, the aromatic dicarboxylic acid may be isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, or 4,4′-biphenyldicarboxylic acid. Preferably, it is selected. These are low in cost, and a copolyester resin containing one of them is easy to produce. When polyethylene terephthalate contains these aromatic dicarboxylic acid-derived structural units, the ratio of the aromatic dicarboxylic acid-derived structural units is preferably 0.5 to 20 mol% of the dicarboxylic acid units, and more preferably 1 to 20 mol%. 10 mol%.
Of these, particularly preferred aromatic dicarboxylic acids include isophthalic acid and naphthalenedicarboxylic acid, with isophthalic acid being even more preferred. Polyethylene terephthalate containing a structural unit derived from isophthalic acid is excellent in moldability, and is excellent in preventing whitening of a molded article due to a slow crystallization rate. In addition, polyethylene terephthalate containing a structural unit derived from naphthalenedicarboxylic acid raises the glass transition point of the resin, improves heat resistance, and absorbs ultraviolet light. It is preferably used. As the naphthalenedicarboxylic acid, a 2,6-naphthalenedicarboxylic acid component is preferable because of easy production and high economic efficiency.

The polyester resin may include a structural unit derived from a monofunctional compound such as a monocarboxylic acid and a monoalcohol. Specific examples of these compounds include benzoic acid, o-methoxybenzoic acid, m-methoxybenzoic acid, p-methoxybenzoic acid, o-methylbenzoic acid, m-methylbenzoic acid, p-methylbenzoic acid, 2,3 -Dimethylbenzoic acid, 2,4-dimethylbenzoic acid, 2,5-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, 2,4,6 -Trimethylbenzoic acid, 2,4,6-trimethoxybenzoic acid, 3,4,5-trimethoxybenzoic acid, 1-naphthoic acid, 2-naphthoic acid, 2-biphenylcarboxylic acid, 1-naphthaleneacetic acid and 2-naphthaleneacetic acid Aromatic monofunctional carboxylic acids such as propionic acid, butyric acid, n-octanoic acid, n-nonanoic acid, myristic acid, pentadecanoic acid, stearic acid, oleic acid and linoleic acid Aliphatic monocarboxylic acids such as benzyl and linolenic acid; aromatic alcohols such as benzyl alcohol, 2,5-dimethylbenzyl alcohol, 2-phenethyl alcohol, phenol, 1-naphthol and 2-naphthol; butyl alcohol, hexyl alcohol, octyl alcohol And aliphatic or alicyclic monoalcohols such as pentadecyl alcohol, stearyl alcohol, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, polytetramethylene glycol monoalkyl ether, oleyl alcohol and cyclododecanol.
Among these, benzoic acid, 2,4,6-trimethoxybenzoic acid, 2-naphthoic acid, stearic acid, and stearyl alcohol are preferred from the viewpoint of ease of polyester production and their production costs. The proportion of the structural unit derived from the monofunctional compound is at most 5 mol%, preferably at most 3%, more preferably at most 1%, based on the total moles of all the structural units of the polyester resin. The monofunctional compound functions as a capping of the terminal group of the polyester resin molecular chain or the terminal group of the branched chain, thereby suppressing excessive crosslinking of the polyester resin and preventing gelation.

Further, the polyester resin may have, as a copolymer component, a polyfunctional compound having at least three groups selected from a carboxyl group, a hydroxy group, and an ester-forming group thereof. Examples of the polyfunctional compound include aromatic polycarboxylic acids such as trimesic acid, trimellitic acid, 1,2,3-benzenetricarboxylic acid, pyromellitic acid and 1,4,5,8-naphthalenetetracarboxylic acid; Alicyclic polycarboxylic acids such as 1,3,5-cyclohexanetricarboxylic acid; aromatic polyhydric alcohols such as 1,3,5-trihydroxybenzene; trimethylolpropane, pentaerythritol, glycerin and 1,3,5- Aliphatic or alicyclic polyhydric alcohols such as cyclohexanetriol; 4-hydroxyisophthalic acid, 3-hydroxyisophthalic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid; 2,6-dihydroxybenzoic acid, protocatechuic acid, gallic acid and 2,4-di Aliphatic hydroxycarboxylic acids such as tartaric acid and malic acid; aromatic hydroxycarboxylic acids, such as hydroxyphenyl acetic acid and their esters are mentioned.
The proportion of the structural unit derived from the polyfunctional compound in the polyester resin is preferably less than 0.5 mol% based on the total number of moles of all the structural units of the polyester.
Among the above compounds, preferred polyfunctional compounds include trimellitic acid, pyromellitic acid, trimesic acid, trimethylolpropane and pentaerythritol from the viewpoint of ease of production of the polyester resin and production cost.

Further, the polyester resin may contain at least one metal sulfonate.
The metal sulfonate can be introduced into the polyester resin by using the metal sulfonate group-containing compound as a copolymer component of the polyester resin. The metal sulfonate group-containing compounds, the above-mentioned dicarboxylic acid or diol functional groups (i.e., hydroxyl group, carboxyl group) compounds other than hydrogen atoms were substituted by -SO 3 _M, and the like. Note that M is represented by a metal in a +1 or +2 state that can be selected from Li, Na, Zn, Sn, K, and Ca. Among these, Na or Li is preferred from the viewpoint of ease of production and the like.

  For the production of the polyester resin, a known method such as direct esterification or transesterification can be applied. Examples of the polycondensation catalyst used in the production of the polyester resin include, but are not limited to, known antimony trioxide, antimony compounds such as antimony pentoxide, germanium compounds such as germanium oxide, and aluminum compounds such as aluminum chloride. . Other production methods include transesterification of different types of polyester resins by methods such as long residence times and / or high temperature extrusion.

  The polyester resin is a dimer of an ethylene glycol component, and may contain a small amount of a diethylene glycol by-product unit formed in a small amount in the production process of the polyester resin. In order for the hollow container to maintain good physical properties, the ratio of diethylene glycol units in the polyester resin is preferably as low as possible. The proportion of the structural units derived from diethylene glycol is preferably 3 mol% or less, more preferably 1 to 2 mol%, based on all the structural units of the polyester resin.

The polyester resin may also include materials derived from recycled polyester resin or used polyester or industrially recycled polyester (eg, polyester monomers, catalysts and oligomers).
In addition, a polyester resin may be used individually by 1 type, and may use 2 or more types of resins together.

The intrinsic viscosity of the polyester resin is not particularly limited, but is usually 0.5 to 2.0 dl / g, preferably 0.6 to 1.5 dl / g. When the intrinsic viscosity is 0.5 dl / g or more, the molecular weight of the polyester resin is sufficiently high, so that the hollow container can exhibit mechanical properties required as a structure.
The intrinsic viscosity is determined by dissolving the polyester resin to be measured in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (= 6/4 mass ratio), 0.2, 0.4, and 0.6 g. / DL solution was prepared, and the intrinsic viscosity was measured at 25 ° C. with an automatic viscosity measurement device (Viscotek, manufactured by Malvern).

[Polyamide resin layer]
The polyamide resin layer is a layer made of a polyamide resin. Examples of the polyamide resin include a xylylene group-containing polyamide, nylon 6, nylon 66, nylon 666, nylon 610, nylon 11, nylon 12, and a mixture thereof. In the present invention, by providing the hollow container with the polyamide resin layer, the hollow container can have a barrier property. Therefore, it is possible to prevent oxygen from entering from outside through the vessel wall, and furthermore, it is possible to suppress elution of carbon dioxide from the carbonated beverage. Further, by using a polyamide resin layer as a layer for imparting barrier properties (barrier layer), it becomes easy to separate and collect the polyester resin while improving the moldability.
Among the above resins, a xylylene group-containing polyamide is preferable because the barrier performance is easily improved and the resin is easily separated from the polyester resin layer during recycling. The xylylene group-containing polyamide is a polyamide resin containing a constituent unit derived from xylylenediamine.

The xylylene group-containing polyamide is obtained by polycondensing a diamine containing xylylenediamine and a dicarboxylic acid. The xylylene group-containing polyamide usually contains 70 mol% or more of the xylylenediamine-derived structural unit among the diamine-derived structural units (diamine units), preferably 80 to 100 mol%, more preferably 90 to 100 mol. %contains.
The xylylenediamine is preferably meta-xylylenediamine, para-xylylenediamine, or both, but more preferably meta-xylylenediamine. The diamine unit constituting the xylylene group-containing polyamide preferably contains 70 mol% or more of meta-xylylenediamine-derived structural unit, more preferably 80 to 100 mol%, and still more preferably 90 to 100 mol%. When the constituent unit derived from meta-xylylenediamine in the diamine unit is 70 mol% or more, the polyamide resin has better gas barrier properties.

  The diamine unit in the xylylene group-containing polyamide may consist of a single structural unit derived from xylylenediamine, or may contain a structural unit derived from diamine other than xylylenediamine. Here, as the diamine other than xylylenediamine, tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, Aliphatic diamine having a linear or branched structure such as 2,2,4-trimethyl-hexamethylenediamine, 2,4,4-trimethyl-hexamethylenediamine; 1,3-bis (aminomethyl) cyclohexane, 1,4 -Bis (aminomethyl) cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis (4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminomethyl) Alicyclic diamines such as karin and bis (aminomethyl) tricyclodecane; diamines having an aromatic ring such as bis (4-aminophenyl) ether, paraphenylenediamine and bis (aminomethyl) naphthalene; It is not limited to these.

Compounds that can constitute a dicarboxylic acid unit in the xylylene group-containing polyamide include, for example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, and carbon atoms of 4 to 4 such as dodecanedioic acid. Α, ω-linear aliphatic dicarboxylic acids of 20; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; other aliphatic dicarboxylic acids such as dimer acid; terephthalic acid, isophthalic acid, orthophthalic acid, xylyl acid Examples thereof include aromatic dicarboxylic acids such as a dicarboxylic acid and a naphthalenedicarboxylic acid, but are not limited thereto. Among these, α, ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms are preferable, adipic acid and sebacic acid are more preferable, and adipic acid is further preferable from the viewpoint of improving barrier performance.
The xylylene group-containing polyamide preferably contains at least 70 mol% of a structural unit derived from adipic acid, more preferably 80 to 100 mol%, and still more preferably 90 mol%, of the structural units derived from dicarboxylic acid (dicarboxylic acid units). １００100 mol%.

  Further, the xylylene group-containing polyamide is particularly preferably a polyamide resin in which 70 mol% or more of the diamine unit is derived from meta-xylylenediamine and 70 mol% or more of the dicarboxylic acid unit is derived from adipic acid. A polyamide resin having such a monomer composition and a constitutional unit has good barrier properties and is similar in molding workability to a polyester resin such as a polyethylene terephthalate resin, so that the workability of a hollow container is easily improved. In this polyamide resin, as a compound constituting a dicarboxylic acid unit other than adipic acid, one or more kinds of α, ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms are preferably used.

  In addition, as a preferable xylylene group-containing polyamide, 70 mol% or more of the diamine unit is derived from meta-xylylenediamine, 70 to 99 mol% of the dicarboxylic acid unit is derived from adipic acid, and 1 to 30 mol% is isophthalic acid. A polyamide derived from an acid can also be exemplified. By adding an isophthalic acid unit as a dicarboxylic acid unit, the melting point is lowered, and the molding temperature can be lowered, so that thermal deterioration during molding can be suppressed. improves.

  Examples of the xylylene group-containing polyamide that can be preferably used in the present invention include polyamides in which 70 mol% or more of diamine units are derived from meta-xylylenediamine and 70 mol% or more of dicarboxylic acid units are derived from sebacic acid. Can also. When the secarboxylic acid unit is contained in the dicarboxylic acid unit in an amount of 70 mol% or more, a decrease in gas barrier properties and an excessive decrease in crystallinity can be avoided, and a melting point is low, and a molding temperature can be lowered, and a gel is formed. Can be suppressed. In this polyamide resin, as the compound capable of constituting a dicarboxylic acid unit other than sebacic acid, one or more kinds of α, ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms are preferably used.

  In addition to the diamines and dicarboxylic acids, lactams such as ε-caprolactam and laurolactam, and aminocaproic acids and fatty acids such as aminoundecanoic acid, as components constituting the xylylene group-containing polyamide, as long as the effects of the present invention are not impaired. Aromatic aminocarboxylic acids; aromatic aminocarboxylic acids such as p-aminomethylbenzoic acid can also be used as a copolymerization component.

  The xylylene group-containing polyamide is preferably produced by a polycondensation reaction in a molten state (hereinafter, sometimes referred to as “melt polycondensation”). For example, it is preferable to produce by a method in which a nylon salt composed of a diamine and a dicarboxylic acid is heated in the presence of water by a pressure method and polymerized in a molten state while removing added water and condensed water. Alternatively, it may be produced by a method in which a diamine is directly added to a dicarboxylic acid in a molten state and polycondensed under normal pressure. In this case, in order to keep the reaction system in a homogeneous liquid state, the diamine is continuously added to the dicarboxylic acid, during which time the reaction system is heated so that the reaction temperature does not fall below the melting points of the resulting oligoamide and polyamide. It is preferred that the polycondensation proceed. Further, the xylylene group-containing polyamide can be increased in molecular weight by further solid-phase polymerization of the one obtained by melt polycondensation, if necessary.

The xylylene group-containing polyamide may be polycondensed in the presence of a phosphorus atom-containing compound. When the xylylene group-containing polyamide is polycondensed in the presence of a phosphorus atom-containing compound, the processing stability during melt molding is enhanced, and coloring is easily prevented.
Preferable specific examples of the phosphorus atom-containing compound include a hypophosphorous compound (also referred to as a phosphinic acid compound or a phosphonous acid compound) and a phosphorous acid compound (also referred to as a phosphonic acid compound). It is not something to be done. The phosphorus atom-containing compound may be an organic metal salt, and among them, an alkali metal salt is preferable.
Specific examples of the hypophosphorous acid compound include: hypophosphorous acid; metal hypophosphites such as sodium hypophosphite, potassium hypophosphite, and lithium hypophosphite; ethyl hypophosphite, dimethylphosphine Hypophosphorous compounds such as acid, phenylmethylphosphinic acid, phenylphosphonous acid and ethyl phenylphosphonite; metal salts of phenylphosphonous acid such as sodium phenylphosphonite, potassium phenylphosphonite and lithium phenylphosphonite And the like.
Specific examples of the phosphite compound include phosphorous acid and pyrophosphorous acid; metal phosphites such as sodium hydrogen phosphite and sodium phosphite; triethyl phosphite, triphenyl phosphite, and ethylphosphonate Phosphoric acid compounds such as acid, phenylphosphonic acid and diethyl phenylphosphonate; metal salts of phenylphosphonic acid such as sodium ethylphosphonate, potassium ethylphosphonate, sodium phenylphosphonate, potassium phenylphosphonate and lithium phenylphosphonate; No.
The phosphorus atom-containing compound may be used alone or in combination of two or more. Among these, sodium hypophosphite, potassium hypophosphite, and metal hypophosphite salts such as lithium hypophosphite are preferred from the viewpoint of the effect of promoting the polymerization reaction of the polyamide resin and the effect of preventing coloration. And sodium hypophosphite is more preferred.

The polycondensation of the xylylene group-containing polyamide is preferably performed in the presence of a phosphorus atom-containing compound and an alkali metal compound. In order to prevent the polyamide resin from being colored during the polycondensation, it is necessary to have a sufficient amount of the phosphorus atom-containing compound to be present. There is a possibility that the resin may be gelled. Therefore, from the viewpoint of adjusting the amidation reaction rate, it is preferable to coexist an alkali metal compound.
The alkali metal compound is not particularly limited, but preferred specific examples include an alkali metal hydroxide and an alkali metal acetate. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, and examples of the alkali metal acetate include lithium acetate, sodium acetate, potassium acetate, and acetic acid. Rubidium and cesium acetate can be mentioned.
When an alkali metal compound is used during polycondensation of a polyamide resin, the amount of the alkali metal compound used is determined by dividing the number of moles of the alkali metal compound by the number of moles of the phosphorus atom-containing compound from the viewpoint of suppressing gel formation. The value is preferably in the range of preferably 0.5 to 1, more preferably 0.55 to 0.95, and even more preferably 0.6 to 0.9.

The number average molecular weight of the polyamide resin is appropriately selected depending on the use of the hollow container and the molding method, but is usually 10,000 to 60000 from the viewpoint of moldability and strength of the hollow container. Further, from the above viewpoint, the number average molecular weight of the polyamide resin is more preferably 11,000 to 50,000.
The number average molecular weight of the polyamide resin is calculated from the following equation (X).
Number average molecular weight = 2 × 1,000,000 / ([COOH] + [NH2]) (X)
(In the formula, [COOH] represents the terminal carboxyl group concentration (μmol / g) in the polyamide resin, and [NH ₂ ] represents the terminal amino group concentration (μmol / g) in the polyamide resin.)
Here, the terminal amino group concentration is determined by neutralization titration of a polyamide dissolved in a phenol / ethanol mixed solution with a dilute hydrochloric acid aqueous solution, and the terminal carboxyl group concentration is determined by dissolving the polyamide in benzyl alcohol. The value calculated by neutralization titration with an aqueous sodium hydroxide solution is used.

(Transition metal)
The polyamide resin layer of the hollow container of the present invention does not substantially contain a transition metal. In the present invention, the transition metal refers to an element belonging to Group 3 to 11 in the periodic table. A transition metal is a compound that promotes oxygen absorption performance by being contained in a polyamide resin layer, generally in the form of an inorganic acid salt, an organic acid salt, or a complex salt. Such transition metals include cobalt, copper, cerium, manganese, iron, chromium and nickel.
In the present specification, the term "substantially free of a transition metal" means that when the recycled polyester resin is manufactured by recycling the packaging container without intentionally adding the transition metal to the polyamide layer, It means that the transition metal may be contained to the extent that it does not adversely affect the hue.Specifically, when the content of the transition metal is measured by a measurement method described later, each element of the transition metal is determined. Is below the detection limit, or even if it is detected, it becomes less than the content shown below.

  In the polyamide resin layer, among transition metals, transition metals other than iron, chromium, and nickel have a total content of less than 10 ppm based on the total mass of the polyamide resin layer. When the total content of these transition metals is 10 ppm or more, the color tone of the recycled polyester resin is deteriorated when the packaging container is recycled. In addition, kogation may be generated during the molding of the hollow container. In order to improve the color tone of the recycled polyester resin and suppress the occurrence of kogation in the hollow container, the total content of these transition metals is preferably less than 5 ppm, more preferably less than 3 ppm, and further preferably It is less than 1 ppm, particularly preferably less than 0.1 ppm.

On the other hand, the transition metal selected from iron, chromium and nickel, even if not intentionally blended, is brought into contact with the constituent material of a molding machine such as a screw or a mold during molding, and the molten resin is brought into contact with the polyamide resin layer. However, the risk of these metals having an adverse effect on the color tone of the regenerated polyester resin and the occurrence of kogation is lower than that of the above-listed transition metals such as cobalt. Although the clear reason is not clear, one reason is that the transition metal selected from iron, chromium and nickel has the activity of catalyzing the decomposition reaction of the polyamide resin which causes kogation, as described above for the cobalt and copper. , Cerium, and manganese. In addition, since a certain amount of these metals can be included inevitably through the manufacturing process, it is considered that it is difficult to recognize these metals separately from a case where the influence is not included at all.
The total content of iron, chromium and nickel based on the total mass of the polyamide resin layer is preferably less than 200 ppm, particularly preferably less than 100 ppm.
The transition metal content is measured by X-ray fluorescence measurement. In addition, when the value of each transition metal content detected by the fluorescent X-ray measurement is lower than the lower detection limit of the apparatus, the metal is regarded as not contained in the polyamide resin composition (that is, 0 ppm).

In the hollow container of the present invention, the body has at least a multilayer laminated structure. Then, the ratio (thickness ratio A / B) of the thickness (A) of the polyester resin layer in the trunk to the thickness (B) of the polyamide resin layer is 2.5 or more and 200 or less. In addition, the thickness of the polyester resin layer means an average thickness, and when there are a plurality of polyester resin layers in the trunk, the thickness of the plurality of layers is averaged to obtain an average thickness per one layer. is there. The same applies to the thickness of the polyamide resin layer.
When the thickness ratio A / B is less than 2.5, it becomes difficult to separate the polyamide resin from the polyester resin in the separation step described below, particularly in the air separation. On the other hand, when the thickness ratio A / B exceeds 200, it is difficult to secure the gas barrier performance of the hollow container, and the storage performance of the contents may be reduced.
The thickness ratio (A / B) is preferably from 3 to 50, and more preferably from 4 to 15, from the viewpoint of improving the gas barrier property of the hollow container while improving the separation property in the separation step.

  The total thickness of the body of the hollow container (that is, the total thickness of all layers of the body) is usually in the range of 100 μm to 5 mm, preferably 150 μm to 3 mm, and more preferably 300 μm to 2 mm. The thickness (A) of each polyester resin layer is usually in the range of 50 μm to 2 mm, preferably 75 μm to 1 mm, and more preferably 100 μm to 500 μmm. The thickness (B) of each polyamide resin layer is usually in the range of 1 to 200 μm, preferably 3 to 100 μm, more preferably 10 to 50 μm. In the present invention, by setting the polyamide resin layer in such a thickness range, it is easy to separate the polyamide resin from the polyester resin in the separation step described later while securing gas barrier properties.

  The hollow container used in the present invention has at least one polyester resin layer and at least one polyamide resin layer, but may have a layer other than the polyester resin layer and the polyamide resin layer. Specific examples of the layer include a resin layer and an adhesive layer interposed between the polyester resin layer and the polyamide resin layer for bonding these resin layers. However, from the viewpoint of improving heat resistance, moldability, and separability during recycling, it is preferable that no resin layer or adhesive layer is interposed between the polyester resin layer and the polyamide resin layer.

The hollow container preferably has a multilayer laminated structure including at least one polyamide resin layer as an intermediate layer, which is disposed between a pair of polyester resin layers. In the multilayer structure, the outermost layer and the innermost layer are more preferably polyester resin layers. When the polyester resin layer is abbreviated as “PES” and the polyamide resin layer is abbreviated as “PA”, the hollow container has a three-layer structure of “PES / PA / PES” and “PES / PA / PES / PA / PES”. It is preferable to have a multi-layered structure composed of the five-layer structure described above, but the present invention is not limited thereto.
The hollow container is preferably a multilayer blow molded container. More preferably, the hollow container is obtained by molding a co-extruded multilayer preform (multilayer parison) by direct blow, or by molding a co-injected multilayer preform by stretch blow.

  In addition, the polyester resin layer and the polyamide resin layer may contain various additive components. Examples of the additive component include a colorant, a heat stabilizer, a light stabilizer, a moisture proof agent, a waterproof agent, a lubricant and the like. Further, each of the polyester resin layer and the polyamide resin layer may contain a resin component other than the polyester resin and the polyamide resin without departing from the object of the present invention. However, in each of the polyester resin layer and the polyamide resin layer, the polyester resin and the polyamide resin are the main components. Specifically, in each layer, the polyester resin and the polyamide resin are usually added to the total amount of each layer. On the other hand, the content is 80 to 100% by mass, and preferably 90 to 100% by mass.

The hollow container of the present invention will be specifically described with reference to FIG. 1. The hollow container 10 includes a cylindrical body 11, a bottom 12 closing one end of the body 11, and And an opening 13 to be provided. In addition, the trunk | drum 11 may be cylindrical, may be a square cylindrical shape, and may have another cylindrical shape. Further, the diameter of the body 11 may be constant, but may vary along the axial direction. For example, since the diameter of the mouth portion 13 is usually smaller than the diameter of the body portion 11, the diameter of the body portion 11 gradually increases toward the mouth portion 13 at the connection portion with the mouth portion 13 as shown in FIG. Is preferably reduced. Further, as shown in FIG. 1, when a screw portion 24 is provided on an inner peripheral surface of a lid 20 described later, a screw portion 14 is also provided on an outer peripheral surface of the mouth portion 13.
As described above, the hollow container 10 has a multilayered structure in which the body 11 has at least one polyester resin layer and at least one polyamide resin layer, while the mouth 13 is formed of a single polyester resin layer. Is preferred. In addition, since the bottom 12 of the hollow container is generally thick, the bottom 12 may be composed of a single polyester resin layer as shown in FIG. Good.
Further, each of the polyamide resin layer and the polyester resin layer in the body 11 has a shape corresponding to the body 11, and is therefore usually formed in a cylindrical shape.
In FIG. 1, the polyester resin layer is denoted by reference numeral 10A, the polyamide resin layer is denoted by reference numeral 10B, and an example in which the hollow container 10 has a three-layer structure of “PES / PA / PES” is shown. It goes without saying that it may have a structure.

<Lid>
The lid of the present invention contains an oxygen absorbent. Since the surface area of the lid is smaller than that of the hollow container, the area where the oxygen absorbent can be disposed is also smaller. Therefore, the oxygen concentration inside the packaging container cannot be sufficiently reduced only by the oxygen absorbent provided on the lid, but in the present invention, the polyamide resin layer of the hollow container prevents oxygen from entering from the outside. I have. Therefore, the amount of oxygen that penetrates through the vessel wall and enters the inside of the container becomes small, so that even if the area where the oxygen absorbent is disposed is small, the oxygen concentration inside the packaging container can be effectively reduced. become. In addition, as a result of preventing oxygen from entering from outside the packaging container, the oxygen adsorbent quickly absorbs oxygen mixed before or during filling, preventing initial oxygen deterioration of the contents, and maintaining the oxygen absorber's activity for a long period of time. It is also possible to extend the storage period.

[Oxygen absorbent]
The oxygen-absorbing substance (that is, the substance having an oxygen-absorbing function) of the oxygen absorbent used in the present invention is not particularly limited as long as it has a function of removing oxygen in the air by an oxidation reaction or adsorption. Without limitation, for example, reducing metal powders such as iron powder, zinc, and tin powder; low metal oxides such as active iron oxide, ferrous oxide, triiron tetroxide, cerium oxide, and titanium oxide; iron carbide, silicon Reducing metal compounds such as iron, iron carbonyl, and ferrous hydroxide; inorganic compounds such as alkali metal or alkaline earth metal hydroxides, sulfites, and carbonates; ascorbic acid, erythorbic acid, erucic acid, and These salts; gallic acid; a combination of tocopherol and an electron donor; a polymer compound having a polyhydric phenol in its skeleton, such as a phenol-aldehyde resin containing a polyhydric phenol; Rucose, fructose, galactose, maltose, cellobiose and any other known oxygen absorbing substances exemplified by organic compounds such as organic compounds such as combinations of electron donors, especially basic substances or sugar oxidases such as glucose oxidase. Can be used. The inorganic compound such as iron powder has a particle diameter of preferably 1 to 150 μm, more preferably 1 to 100 μm.

Among the above, it is preferable to use iron powder, activated iron oxide, sodium sulfite, ascorbic acid and the like. Use of these is advantageous in terms of cost and oxygen absorption performance. Further, the use of ascorbic acid makes it difficult for the flavor such as aroma and taste to change even when the oxygen absorbent is mixed into the contents.
As the oxygen absorbent, the above-mentioned oxygen absorbing substance may be used alone, but it is generally used in combination with other components as an oxygen absorbent composition containing the oxygen absorbing substance and other components. is there. When used in combination with other components, the amount of the oxygen-absorbing substance composed of an inorganic compound such as iron powder is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass based on the total amount of the oxygen-absorbing composition. Is more preferred. The amount of the oxygen-absorbing substance composed of an organic compound such as ascorbic acid is preferably 15 to 70% by mass, more preferably 45 to 60% by mass, based on the total amount of the oxygen absorbent composition.

Oxygen-absorbing substances are more specifically hydroxides, carbonates, sulfites, thiosulfates, tertiary phosphates, organic acid salts, halides of alkali metals and alkaline earth metals, activated carbon, and activated carbon. It can be used in combination with auxiliaries such as alumina, activated clay, zeolite, diatomaceous earth. The amount of the auxiliary agent is preferably 1 to 50% by mass based on the total amount of the oxygen absorbent composition.
In particular, an oxygen absorbent composition containing iron powder and a metal halide that promotes an oxygen absorption reaction has excellent deoxygenation performance. The metal halide used in the oxygen absorbent composition is not particularly limited, and examples thereof include chlorides, bromides, and iodides of alkali metals or alkaline earth metals. Further, the metal halide may be mixed with the iron powder, or the surface of the iron powder may be coated or dispersed and adhered with the metal halide.

Further, the oxygen absorbing substance may be used by dispersing it in a resin. As the resin to be used, polyolefins such as polyethylene, polypropylene, polybutadiene, and polymethylpentene, elastomers, modified products thereof, and mixed resins thereof are preferably used.
When the oxygen-absorbing substance is used by being dispersed in the resin, the mass ratio of the oxygen-absorbing substance to the resin (oxygen-absorbing substance / resin) is preferably 5/95 to 50/50, more preferably 10/90. ４０40/60. Within this range, good deoxygenation performance can be exhibited without affecting the moldability and the appearance of the product.
Further, the oxygen-absorbing substance or the combination of the oxygen-absorbing substance and other components may be included in a breathable packaging material.
Specific examples of the above oxygen absorbent are commercially available under the name of AGELESS (registered trademark) (manufactured by Mitsubishi Gas Chemical Company, Ltd.).

  Further, the oxygen absorbent may be an oxygen-absorbing resin having an oxygen-absorbing property. Examples of the oxygen-absorbing resin include a resin composition containing at least an oxidizing organic component as an oxygen-absorbing substance and a transition metal catalyst (oxidation catalyst). The resin composition having an oxidizing organic component and a transition metal catalyst may be composed of only the oxidizing organic component and the transition metal catalyst, or may contain a resin other than these. Examples of the resin that can be used in combination with the oxidizing organic component and the transition metal catalyst include an olefin-based resin and a gas barrier resin. In particular, polyamides such as ethylene vinyl alcohol copolymer and meta-xylylene adipamide It is preferable to use a resin.

The oxidizing organic component is a thermoplastic resin having an unsaturated bond, an allyl carbon, a benzyl carbon, a tertiary carbon, and an α carbon. For example, there may be mentioned an ethylenically unsaturated group-containing polymer. This polymer has a carbon-carbon double bond, and the α-methylene adjacent to the double bond portion and especially the double bond portion. Is easily oxidized by oxygen, thereby trapping oxygen.
Such an ethylenically unsaturated group-containing polymer is, for example, derived from a polyene as a monomer, and is a homopolymer of polyene, or a random copolymer obtained by combining two or more of the above-mentioned polyenes or combining with another monomer. A polymer, a block copolymer or the like can be used as the oxidizing polymer.
The polyene monomer that can be used is not particularly limited, and examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-butadiene. Examples thereof include pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene. These monomers may be used alone or in combination of two or more.
Among these, 1,3-butadiene and isoprene are preferred, and isoprene is more preferred.
Examples of other monomers copolymerizable with the conjugated diene monomer include styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, and ethylstyrene. , Pt-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2,4-dibromostyrene, vinyl Aromatic vinyl monomers such as naphthalene; chain olefin monomers such as ethylene, propylene and 1-butene; cyclic olefin monomers such as cyclopentene and 2-norbornene; 1,5-hexadiene and 1,6-heptadiene Non-conjugated diene monomers such as 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-norbornene; And (meth) acrylic acid esters such as methyl acrylate and ethyl (meth) acrylate; and other (meth) acrylic acid derivatives such as (meth) acrylonitrile and (meth) acrylamide. These monomers may be used alone or in combination of two or more. Among these, it is preferable to use an aromatic vinyl monomer.
Polymers derived from polyene include, specifically, polybutadiene (BR), polyisoprene (IR), natural rubber, nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber, ethylene -Propylene-diene rubber (EPDM), styrene-isoprene copolymer rubber, polyoctenylene, polypentenylene, cyclized rubber, and the like are suitable, but are not limited thereto.
Further, in addition to the above-mentioned ethylenically unsaturated group-containing polymer, a polymer which is easily oxidized by itself, such as polypropylene, ethylene-propylene copolymer, or polymethaxylylenediadipamide is also used as the oxidizable organic component. can do.
Each of the above-mentioned polyene-based polymers is preferably an acid-modified polyene polymer into which a carboxylic acid group, a carboxylic acid anhydride group, and a hydroxyl group have been introduced. Further, it is preferable that the oxidizing organic component composed of such an oxidizing polymer or a copolymer thereof is contained in the oxygen-absorbing resin at a ratio of 0.01 to 10% by weight.

Suitable transition metal catalysts include Group VIII metals of the periodic table such as iron, cobalt and nickel. In addition, Group IV metals such as copper and silver, and Group IV metals such as tin, titanium and zirconium. And a Group V metal such as vanadium, a Group VI metal such as chromium, and a Group VII metal such as manganese. The transition metal catalyst is generally used in the form of a low-valent inorganic salt, organic salt or complex salt of the above transition metal. Examples of the inorganic salts include halides such as chlorides, sulfur oxy salts such as sulfates, nitrogen oxy acid salts such as nitrates, phosphorus oxy salts such as phosphates, and silicates. Examples of the organic salt include carboxylate, sulfonate, phosphonate and the like. Examples of the complex of the transition metal include a complex with a β-diketone or a β-keto acid ester.
The transition metal catalyst preferably has a transition metal atom concentration (based on weight concentration) of 100 to 3000 ppm in the oxygen-absorbing resin.

  The amount of the oxygen absorbing substance of the oxygen absorbent depends on the type of the oxygen absorbing substance to be used, but is preferably 0.01 to 10 g / L, more preferably 0.1 to 5 g / L, based on the capacity of the hollow container. More preferred.

The lid of the present invention will be specifically described with reference to FIG. 1. The lid 20 has a cap shell 21 and a liner 25 as shown in FIG. The cap shell 21 includes a top plate portion 22 and a skirt portion 23 hanging from the periphery of the top plate portion 22. On the inner surface of the skirt portion 23, a screw portion 24 that can be screwed to the screw portion 14 of the mouth portion 13 is formed. The screw portion 24 of the lid 20 is screwed to the screw portion 14 of the mouth portion 13. The mouth 13 of the hollow container 10 is closed by the lid 20.
The liner 25 is provided on the inner surface of the top plate portion 22 of the cap shell 21 and is in close contact with the tip of the mouth portion 13 to enhance the sealing performance inside the packaging container. The liner 25 is shown in FIG. 1 as a disk-shaped example, but may be provided at a position where the tip of the mouth portion 13 comes into contact, and may have, for example, an annular shape. The liner 25 is preferably formed on the inner surface of the top plate 22 by in-shell molding.

The oxygen absorbent is preferably provided on the inner surface side of the top plate 22 of the cap shell 21. The oxygen absorbent 30 may be specifically attached to the inner surface of the liner 25 provided on the inner surface of the top plate 22 as a separate member from the liner 25, as shown in FIG. It may be arranged between the top plate portions 22. Further, the oxygen absorbent may be blended with the thermoplastic resin forming the liner 25.
Further, by laminating a barrier film having a gas barrier property between the oxygen absorbent 25 and the top plate portion 22, the penetration of external oxygen can be suppressed and the oxygen absorption performance can be enhanced. Any barrier film may be used as long as it is a known one, but it includes an ethylene-vinyl alcohol copolymer, a polyamide resin such as polymethaxylylene adipamide, a vinylidene chloride resin coated film, a metal-deposited film, or an inorganic-deposited film. Is preferred. Further, in order to avoid direct contact between the oxygen absorbent and the contents, a protective film having high oxygen permeability may be provided on the inner side of the oxygen absorbent (that is, on the side of the contents).
In the lid 20, the liner may be omitted. Even when the liner is omitted, the oxygen absorbent is preferably provided on the inner surface side of the top plate 22 of the cap shell, as described above.
In addition, as shown in FIG. 1, the oxygen absorbent 30 is preferably disposed on the inner peripheral side of the position where the mouth portion 13 is disposed. Since the oxygen absorbent is arranged on the inner peripheral side of the mouth portion 13, it becomes possible to efficiently absorb oxygen inside the hollow container.
In addition, the type of the lid is not limited to a cap provided with a screw as described above as long as the mouth can be closed, and a type without a screw such as a maxi cap, a tear-off cap, a rimple cap, or the like. The skirt portion may be omitted.

  As a material constituting the cap shell in the lid, a material conventionally used for a cap can be used. Specifically, olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer and ethylene-vinyl acetate copolymer And synthetic resins such as polystyrene, styrene-butadiene copolymer, ABS resin and polycarbonate. Particularly, polyethylene or polypropylene is more desirable from the viewpoint of cost and strength, and polypropylene is more desirable from the viewpoint of sealing performance.

  As the liner, a conventionally known thermoplastic resin which can be in-shell molded and has a higher elasticity than the material constituting the cap shell can be suitably used. Specifically, polyethylene, isotactic polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ion Olefin resins such as crosslinked olefin copolymers (ionomers); rubber olefin elastomers such as ethylene-propylene-diene copolymer rubber and hydrogenated ethylene-propylene-diene copolymer; SBS elastomer, SIS elastomer, SEBS elastomer , SEPS elastomer, butyl rubber, SBR, etc., and one or more kinds of soft plastics, soft vinyl chloride resin, and the like.

  The packaging container of the present invention is a liquid packaging container used by filling a hollow container with a liquid, and is preferably a beverage packaging container. Liquids to be filled therein include water, carbonated water, oxygenated water, hydrogenated water, milk, dairy products, juice, carbonated soft drinks, coffee, coffee drinks, teas, drinks such as alcoholic drinks; sauces, soy sauce, Various articles such as liquid seasonings such as syrups, mirins, and dressings; chemicals such as pesticides and pesticides; pharmaceuticals; In particular, beverages that are likely to deteriorate in the presence of oxygen, such as beer, wine, coffee, coffee beverages, fruit juices, carbonated soft drinks, and teas, are preferred.

Further, in the packaging container of the present invention, the dissolved oxygen concentration in the liquid 60 days after filling the liquid is preferably 0.30 ppm or less. In the packaging container, by setting the dissolved oxygen concentration to 0.30 ppm or less, the accumulated amount of oxides (deteriorated products) generated when the contents come into contact with oxygen is reduced, and the contents are stored at a level at which there is no practical problem. It is possible to increase the quality. In order to further enhance the storage stability of the contents, the dissolved oxygen concentration is more preferably 0.25 ppm or less. The lower the dissolved oxygen concentration is, the more the content of the dissolved oxygen can be continuously prevented. However, practically, it is preferably 0.03 ppm or more, and more preferably 0.08 ppm or more.
Further, as long-term storage stability, the dissolved oxygen concentration in the liquid 120 days after filling the liquid is preferably 0.30 ppm or less, more preferably 0.25 ppm or less.

<Production method of recycled polyester resin>
The packaging container of the present invention is suitable for recycling as described above, and it is possible to produce a recycled polyester resin using the packaging container of the present invention as a raw material. In the method for producing a recycled polyester resin of the present invention, the lid and the polyamide resin constituting the polyamide resin layer are removed from the packaging container, the polyester resin constituting the polyester resin layer is recovered, and the polyester resin is recycled. It is a polyester resin. Hereinafter, the method for producing the recycled polyester resin of the present invention will be described in detail.

In the present production method, a used packaging container is usually used, but may be an unused product. As used packaging containers, those once collected in the market are collected.
In the present manufacturing method, first, when a lid is attached to the packaging container, the lid is removed from the hollow container, and then, a step of removing the polyamide resin constituting the polyamide resin layer (hereinafter, also referred to as a removing step). Done. If the lid has already been removed from the packaging container, a removing step is performed on the hollow container from which the lid has been removed.

[Removal step]
The removal step is not particularly limited as long as the polyamide resin constituting the polyamide resin layer can be removed and the polyester resin can be selectively removed.For example, after the hollow container is crushed, the polyester resin and the polyamide resin are separated. Is preferred.
The pulverization of the hollow container can be performed using a pulverizer such as a single-screw pulverizer, a twin-screw pulverizer, a tri-screw pulverizer, and a cutter mill. The pulverized product obtained by pulverization is, for example, a flake, powder, or lump. However, most of the hollow container has a thin multilayered structure having a thickness of several mm or less, such as a trunk portion, and thus most of the pulverized material is usually in the form of flakes. The flake-shaped pulverized material refers to a flaky or flat material having a thickness of about 2 mm or less.

Further, in the multilayer laminated structure, the polyester resin layer and the polyamide resin layer are structurally integrated, but usually they are not bonded to each other, and the polyester resin and the polyamide resin are separated from each other in the pulverizing step. It is easily separated as crushed material. Further, by forming the flakes, it is easy to wind up and separate by an air flow of the air selection separation described later.
However, the polyester resin and the polyamide resin are not necessarily completely separable in the pulverizing step, and the pulverized product has a relatively high content of the polyester resin and a relatively low content of the polyester resin. Thus, it is separated into those having a relatively high polyamide resin content. In the following, for convenience of description, those having a relatively high polyester resin content are simply referred to as polyester resins, and those having a relatively high polyamide resin content are simply referred to as polyamide resins.

As described above, the pulverized material is separated into a polyester resin and a polyamide resin (a separation step). As the separation method, it is preferable to use specific gravity selection utilizing a difference in specific gravity between the polyester resin and the polyamide resin.
Specific gravity sorting includes, for example, wind sorting in which crushed materials are sorted by wind power. In the wind separation, for example, in a separation device capable of generating a rotating airflow inside, among the pulverized materials applied to the airflow generated by the separation device, the specific gravity or the bulk specific gravity is large and naturally falls due to its own weight. There is a method of separating and collecting the material and the material having a low specific gravity or bulk specific gravity and being wound up by an air current.
In this method, the pulverized product of the polyester resin falls naturally by its own weight, while the pulverized product of the polyamide resin is rolled up. Therefore, it is possible to separate and collect the polyester resin and the polyamide resin.
In such wind separation, the same operation may be repeatedly performed on the same pulverized material. For example, those that have fallen naturally may be further subjected to air separation to increase the content of the polyester resin in the recycled polyester resin.
The separation method is not limited to wind separation, but a method of immersing a crushed material in a liquid such as water and separating the crushed material based on a difference in specific gravity of the crushed material with respect to the liquid. For separation and separation.

[Granulation process]
The recovered polyester resin (recycled polyester resin) is preferably granulated to form pellets in order to facilitate handling during molding and the like.
The granulation may be performed before or after the crystallization / solid-state polymerization step described below, but it is better to perform the granulation before the crystallization / solid-state polymerization step. By performing the step before the crystallization / solid-state polymerization step, the handleability in the crystallization / solid-state polymerization step is also improved.
In the granulation step, it is desirable that the pulverized material is plasticized by melt blending and granulated. Examples of a granulating device for plasticizing and granulating include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder, and any known one can be used. . The shape of the pellet is desirably cylindrical, spherical, or elliptical spherical.
For the granulation, for example, it is desirable to extrude the plasticized regenerated polyester resin into a strand shape, cut it with a pelletizer while cooling it in a water tank, and pelletize it. The pellets taken out of the water tank are usually dried to remove moisture adhering to the surface.

[Crystallization / solid-state polymerization process]
The recovered regenerated polyester resin is preferably subjected to a crystallization / solid-state polymerization step of performing crystallization, solid-phase polymerization, or both. However, in this step, it is more preferable to carry out both crystallization and solid phase polymerization. The crystallization / solid-state polymerization step is preferably performed on the above-mentioned pelletized polyester resin, but may be performed on a non-pelletized polyester resin (for example, a pulverized product).
When both crystallization and solid-phase polymerization are performed, it is usually preferable to crystallize the regenerated polyester resin and then perform solid-phase polymerization.
Crystallization of the regenerated polyester resin is performed by maintaining the polyester resin under constant heating. The crystallization is desirably performed by heating the polyester resin at, for example, 100 to 230 ° C. By crystallizing the regenerated polyester resin, it is possible to prevent the regenerated polyester resin from fusing with each other or from adhering to the inner surface of the apparatus during solid phase polymerization or molding.

  The solid-phase polymerization is preferably performed by maintaining the temperature at a temperature equal to or higher than the melting point of the polyester resin −50 ° C. and lower than the melting point of the polyester resin for a certain time. By setting the melting point to be lower than the melting point, the recycled polyester resin is prevented from being melted, and, for example, the work efficiency is prevented from being reduced by the recycled polyester resin adhering to the device surface. Further, when the temperature is (melting point−50 ° C.) or more, polymerization proceeds at a sufficient polymerization rate, and desired physical properties are easily obtained.

The solid phase polymerization may be performed under a vacuum or may be performed under a flow of an inert gas such as nitrogen or argon. When the process is performed under a vacuum, the pressure is preferably 1.0 torr or less, more preferably 0.5 torr or less, and particularly preferably 0.1 torr or less. Further, it is desirable to reduce the concentration of oxygen remaining in the system as much as possible under vacuum or in the flow of an inert gas such as nitrogen or argon. The oxygen concentration is preferably 300 ppm or less, more preferably 30 ppm or less. When the oxygen concentration is 30 ppm or less, poor appearance such as yellowing is less likely to occur.
When the solid phase polymerization is carried out under vacuum, it is desirable to keep the heat transfer uniform while constantly repeating the stirring or mixing of the regenerated polyester resin. When the reaction is carried out in the presence of an inert gas, it is desirable that the surface of the polyester resin is always kept in contact with the dry gas under a dry gas stream.

Solid-state polymerization equipment for performing the crystallization / solid-state polymerization process includes a tumbler-type batch-type apparatus equipped with a heating jacket, a dry silo-type apparatus equipped with an inert gas airflow facility, and a stirring blade and a discharge screw inside. And a reactor equipped with The crystallization and the solid-phase polymerization are usually performed continuously or simultaneously in the same apparatus.
The heating time of the solid-phase polymerization is appropriately determined in consideration of the apparatus and other conditions, but may be any time as long as the polyester resin has sufficient physical properties.
Solid-phase polymerization holds the regenerated polyester resin at a high temperature for a long period of time, so if impurities are present in the regenerated polyester resin, the quality such as color tone may be deteriorated. Has been removed. Even if a small amount of the polyamide resin remains, the transition metal is not substantially contained in the polyamide resin. Therefore, in the present invention, deterioration in quality that may occur during solid-state polymerization is minimized.

In the method for producing a recycled polyester resin of the present invention, steps other than the steps described above may be performed, and a washing step may be performed in order to remove contents attached to the inside of the hollow container. The washing is preferably performed by rinsing with a liquid, and washing with water, washing with an alkaline aqueous solution, or both may be performed.
Further, the washing may be performed before the hollow container is pulverized into a pulverized product, or may be performed after the pulverization, but it is better to perform the granulation, crystallization, or any of solid phase polymerization before the pulverization is performed. . Further, the washing step may be performed simultaneously with the pulverizing step by a pulverizer called a wet pulverizer, which simultaneously performs washing and pulverization.
Further, when the cleaning step is performed, a drying step may be performed after the cleaning step. By performing the drying step, the amount of water in the recycled polyester resin obtained by the present method can be reduced, so that a high-quality recycled polyester resin having high thermal stability and the like can be provided. The drying step can be performed using, for example, air blowing from a dryer or hot air.

  In the obtained recycled polyester resin, the content of the polyamide resin is usually less than 1% by mass, preferably less than 0.8% by mass, and more preferably less than 0.6% by mass. As described above, by reducing the content of the polyamide resin, it is possible to prevent the color tone and the like from being deteriorated due to the polyamide resin, and to easily improve the quality of the recycled polyester resin.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Thickness of each layer]
The thickness of the polyester resin layer and the thickness of the polyamide resin layer are obtained by measuring the thickness of at least four points in the circumferential direction of the body of the hollow container and calculating the average value. When a plurality of polyester resin layers and a plurality of polyamide resin layers are provided in the hollow container, the thickness of each layer measured by the above method is further averaged. In addition, the total thickness of the trunk portion is the total thickness of the respective layers.
[Transition metal content in core layer]
After cutting the body of the obtained hollow container (bottle) and separating the polyester resin layer and the polyamide resin layer, a scanning X-ray fluorescence spectrometer ZSX primusII (manufactured by Rigaku Corporation, measurement model: thin film, substrate: none) Was used to measure the X-ray intensity of each element in the polyamide resin layer, and the content of each element was quantified using semi-quantitative analysis software (SQX). Table 1 shows the measurement results.
[Content of polyamide resin in recycled polyester resin]
Using a trace total nitrogen analyzer TN-2100H (manufactured by Mitsubishi Analytech), a calibration curve was prepared using a pyridine / toluene mixture prepared to a predetermined concentration as a standard concentration, and 4 to 8 mg of a sample collected from the regenerated polyester resin Was used to determine the nitrogen content. The measurement was repeated three times, and the average value was calculated. The average value of the obtained nitrogen content was converted into the content polyamide content by the following formula.
α = β × (MW [polyamide] / MW [nitrogen atom])
(Α: content of polyamide, β: average value of nitrogen content, MW [polyamide]; molecular weight per unit of polyamide, MW [nitrogen atom]; molecular weight of nitrogen atom × number of nitrogen contained in unit of polyamide )

[Gas barrier properties]
A glass substrate type oxygen concentration measurement sensor chip having a diameter of 5 mm was placed in the hollow container obtained in each of Examples and Comparative Examples, and then 350 ml of distilled water obtained by bubbling nitrogen for 20 minutes following the boiling treatment was filled thereinto. Was closed while blowing nitrogen and stored at 23 ° C. and 50% RH. The dissolved oxygen concentration in the solution was measured with a non-contact, non-destructive oxygen concentration meter Fibox3 (manufactured by Taitec Corporation) of a fluorescence extinction time type. When the fluorescence disappearance time is long or the fluorescence intensity is high, that is, the lower the oxygen concentration value of the detector, the smaller the dissolved oxygen amount, indicating that the gas barrier property is excellent. The evaluation was performed by measuring the dissolved oxygen concentration 30 days, 60 days, and 120 days after filling with distilled water.
[Content preservability]
The hollow containers obtained in each of Examples and Comparative Examples were filled with 350 ml of orange juice boiled under nitrogen while blowing nitrogen, and the lid was closed. 120 days after the filling, the appearance of the orange juice was observed and evaluated.
[Recyclability]
In each of the examples and comparative examples, the color tone (b *) in the thickness direction of 3 mm of the regenerated plate manufactured using the regenerated polyester resin was measured using COH400 manufactured by Nippon Denshoku Industries Co., Ltd. (using a 12 V, 50 W halogen lamp as a light source). Was measured by a transmission method based on JIS Z 8722.

[Example 1]
(1) Preform molding One injection cylinder is used by using an injection molding machine having two injection cylinders (manufactured by Sumitomo Heavy Industries, Ltd., model DU130CI) and a two-piece mold (manufactured by Kortec, model). And a polyamide resin from the other injection cylinder, and a three-layer preform consisting of a polyester resin layer / polyamide resin layer / polyester resin layer under the following conditions (a single layer equivalent to 26 g). Was injection-molded such that the mass ratio of the polyester resin to the polyamide resin was 95: 5 to produce a preform. The preform had a total length of 95 mm, an outer diameter of 22 mm, and a thickness of 4.0 mm. The three-layer preform molding conditions are as shown below.
Injection cylinder temperature on skin side: 280 ℃
Core side injection cylinder temperature (only 3 layers): 290 ° C
Resin channel temperature in mold: 290 ° C
Mold cooling water temperature: 15 ° C
Cycle time: 40 seconds The polyester resin and polyamide resin used in Example 1 are as follows.
Polyester resin: polyethylene terephthalate copolymerized with isophthalic acid (intrinsic viscosity: 0.83 dl / g, isophthalic acid content based on the total amount of dicarboxylic acid: 1.5 mol%), trade name: BK2180, polyamide resin manufactured by Nihon Unipet Co., Ltd .: metaxylyl Lenadipamide (MXD6, number average molecular weight Mn = 23,000), trade name: MX nylon S6007, manufactured by Mitsubishi Gas Chemical Co., Ltd.

(2) Molding of hollow container The preform obtained in the above (1) was biaxially stretched and blow-molded by a blow molding device (EFB1000ET, manufactured by Frontier) to obtain a square tubular bottle having a body formed of a reduced-pressure absorption panel. . The total length of the bottle was 165 mm, the outer diameter was 65 mm, and the inner volume was about 370 mL. In the biaxial stretch blow molding, a blow molding machine (model: EFB1000ET) manufactured by Frontier KK was used. The biaxial stretch blow molding conditions are as shown below. The body average thickness of the obtained bottle (hollow container) was measured. Table 1 shows the results.
Preform heating temperature: 108 ° C
Stretching rod pressure: 0.5MPa
Primary blow pressure: 0.7MPa
Secondary blow pressure: 2.5MPa
Primary blow delay time: 0.34 seconds Primary blow time: 0.30 seconds Secondary blow time: 2.0 seconds Blow exhaust time: 0.6 seconds Mold temperature: 30 ° C

(3) Lid preparation A liner comprising a mixture of high-density polyethylene and ethylene-propylene copolymer in a weight ratio of 7: 3, and a coloring agent (phthalocyanine blue) mixed with 0.03% by weight based on the total amount of the liner. Is applied on a commercially available polypropylene cap liner provided on the inner surface of the top plate of the lid, with Ageless T-10 (using active iron oxide as an oxygen absorbing substance; manufactured by Mitsubishi Gas Chemical Co., Ltd.) as an oxygen absorbent. The sample was kept in an aluminum bag until just before evaluation by each evaluation method.

(4) Manufacture of Recycled Polyester Resin In this example, the process from the packaging container to the regenerated polyester resin through various regeneration processes was performed, and the recyclability was evaluated by giving a heat history.
[Removal step]
After crushing 10 kg of the bottle obtained in the above (2) with a crusher to form flakes, the flakes were washed with water. Then, using a floss separator CFS-150 (manufactured by Accor Co., Ltd.), at a supply speed of 10 kg / hr, a suction blower of 35 Hz, and a secondary blower of 30 Hz, the material having a high specific gravity and collected in the support was collected, and further collected. Multiple air separation was performed. Finally, the flake-like pulverized material dropped in the support was recovered as a recycled polyester resin.
[Granulation process]
The recovered polyester resin was heated at a heater temperature of 270 to 290 ° C. and a discharge rate of 25 kg / hour by using an extruder in which a strand die was attached to a twin-screw extruder (diameter: 37 mmφ) equipped with a vacuum vent. It was made into a strand, cut in a pelletizer while being cooled in a water tank, and pelletized. The obtained pellet was dried at 150 ° C. for 4 hours using a hot air dryer.

[Crystallization / solid-state polymerization process]
The pelletized regenerated polyester resin is charged into a rotary 20 L flask evaporator flask equipped with a vacuum pump equipped with a leak valve, a cooling trap, an oil bath, a rotor, and a continuous temperature / internal pressure logger. After repeating three times, the flask was rotated at 20 rpm under a nitrogen flow of 10 L / min. While maintaining this state, the flask is brought into contact with an oil bath previously heated to about 160 ° C. to 180 ° C., and the internal temperature rises until the internal temperature read from a thermocouple provided to directly contact the regenerated polyester resin reaches 160 ° C. After heating and reducing the pressure in the flask to a predetermined pressure or less, the oil bath was continuously heated to 210 ° C. to 230 ° C., and the temperature was raised until the material temperature reached 205 ° C. Thereafter, the rotation was continued for 7 hours after the internal temperature reached 205 ° C. At this time, the degree of vacuum was 0.4 torr. The flask was raised from the oil bath, and when the internal temperature became 150 ° C. or lower, the pressure was restored with nitrogen gas, and the internal temperature was naturally cooled until the internal temperature became 60 ° C. or lower.
The amount of the polyamide resin in the regenerated pellets was 0.52% by mass.
[Plating]
The regenerated pellets were injection-molded using an injection molding device (Model SE130DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.) to obtain regenerated plates having 1, 2, and 3 mm thickness steps.

[Example 2]
The procedure was performed in the same manner as in Example 1 except that a preform was manufactured by injection molding so that the mass ratio of the polyester resin and the polyamide resin was 97: 3. The amount of the polyamide resin in the regenerated pellets was 0.29% by mass.

[Comparative Example 1]
The point that the polyamide resin injected from the other injection cylinder is changed to a polyamide resin and cobalt stearate (manufactured by Kanto Chemical Co., Ltd.) blended at a mass ratio of 4.9: 0.1, and a lid liner The operation was performed in the same manner as in Example 1 except that the oxygen absorbent was not attached thereon. The amount of the polyamide resin in the regenerated pellets was 0.44% by mass.

[Comparative Example 2]
Example 1 Example 1 was repeated except that a hollow container (bottle) composed of a single layer of polyester resin was manufactured without injecting the polyamide resin from the other injection cylinder, and that no oxygen absorbent was stuck on the liner of the lid. Was performed in the same manner as described above.

[Comparative Example 3]
Example 1 was carried out in the same manner as in Example 1 except that a hollow container (bottle) composed of a single layer of polyester resin was manufactured without injecting the polyamide resin from the other injection cylinder.

* ND indicates that the value was below the detection limit of the device.
* Other transition metals indicate the content of each transition metal other than the transition metals specifically described in Table 1.

As in Examples 1 and 2, a polyamide resin layer was provided as a gas barrier layer in a hollow container, and an oxygen absorbent was disposed on the inner surface of a lid. Was able to improve the preservability of the contents while appropriately reducing the oxygen concentration. Further, since the transition metal was not blended in the hollow container, the color tone of the plate molded from the recycled polyester resin could be improved, and the recyclability was also improved.
On the other hand, in Comparative Example 1, although the oxygen concentration in the inside of the packaging container could be reduced by including the transition metal in the hollow container, the color of the plate molded from the recycled polyester resin was changed due to the heat history received in the regeneration process. As is clear from the deterioration, the recyclability was not good. Furthermore, when the body of the hollow container had a single-layer structure as in Comparative Examples 2 and 3, it was difficult to improve the recyclability while improving the storage stability of the contents.

Claims (7)

Polyester resin layer having a polyester resin, and a hollow container each polyamide resin layer comprising at least one layer of a polyamide resin, close the mouth of the hollow vessel, and a packaging container with a lid containing an oxygen absorbing agent A method for producing a recycled polyester resin by removing the lid and the polyamide resin, or removing the polyamide resin from the packaging container from which the lid has been removed, and recovering the polyester resin,
The polyamide resin layer of the hollow container does not substantially contain a transition metal, and the ratio (A / B) of the thickness (A) of the polyester resin layer to the thickness (B) of the polyamide resin layer in the body of the hollow container is ) is 3 or more 5 is 0 or less, the production method of the recycled polyester resin. The method for producing a recycled polyester resin according to claim 1, wherein the polyester resin contains polyethylene terephthalate. The method for producing a recycled polyester resin according to claim 1 or 2, wherein the polyamide resin is a polyamide resin containing a structural unit derived from xylylenediamine. The oxygen-absorbing substance of the oxygen-absorbing agent is at least one selected from the group consisting of iron powder, activated iron oxide, sodium sulfite, ascorbic acid, and an oxygen-absorbing resin. 3. The method for producing a recycled polyester resin according to item 1 . The method for producing a recycled polyester resin according to any one of claims 1 to 4, wherein the dissolved oxygen concentration in the liquid 60 days after filling the liquid is 0.3 ppm or less. The method for producing a recycled polyester resin according to any one of claims 1 to 5, wherein the concentration of dissolved oxygen in the liquid 120 days after filling the liquid is 0.3 ppm or less. The method for producing a recycled polyester resin according to any one of claims 1 to 6 , wherein the removal of the polyamide resin is performed by air separation after the hollow container is pulverized.