JP7528748B2 - Multi-layer container - Google Patents

Description

The present invention relates to a multi-layer container.

Polyester resins, typified by polyethylene terephthalate (PET), are characterized by excellent transparency, mechanical properties, melt stability, recyclability, etc., and are therefore currently widely used in various packaging materials such as films, sheets, hollow containers, etc.
On the other hand, particularly in bottle applications, hollow containers made only of polyester resin do not have sufficient gas barrier properties against carbon dioxide, oxygen, etc., so attempts have been made to improve the gas barrier properties by multi-layering with resins that have excellent gas barrier properties.
For example, Patent Document 1 discloses a multilayer structure having a barrier layer made of a polyamide containing an aromatic ring in the skeleton, which is obtained from a diamine component mainly composed of an aromatic diamine and a dicarboxylic acid, and a polyglycolic acid or a polyethylene oxalate, in order to improve the barrier property under high humidity conditions, heat resistance, and moldability.
As an example of a resin with excellent gas barrier properties, Patent Document 2 discloses a polyglycolic acid resin composition which is a blend of a polyglycolic acid resin, a glycolic acid oligomer, and a heat stabilizer, and has a weight average molecular weight of 50,000 to 700,000 and a glass transition temperature (Tg) of 13 to 37° C. after blending. It is disclosed that by combining this with other thermoplastic resins, a laminated sheet or film with excellent transparency and gas barrier properties can be formed.

JP 2007-211159 A JP 2009-40917 A

In recent years, polyester resin containers have been used not only for soft drinks but also for various drinks and foods. However, it has been found that by forming multiple layers of resins with different properties and molecular structures, there are cases where the resin layers peel off (delamination). For example, the multi-layer container disclosed in Patent Document 1 and the multi-layer container using a polyglycolic acid resin as a barrier layer disclosed in Patent Document 2 are not fully satisfactory in terms of formability and delamination resistance.
Therefore, an object of the present invention is to provide a multilayer container having excellent formability and excellent delamination resistance, and a method for producing the same.

As a result of intensive research in consideration of the above problems, the present inventors have discovered that the above problems can be solved by a multilayer container having a polyester resin layer containing an aromatic polyester resin (X) and a polyglycolic acid resin layer containing polyglycolic acid (Y), in which the polyglycolic acid resin has a specific degree of dispersion, and have completed the present invention. The present invention provides the following [1] to [11].

[1] A multilayer container having a polyester resin layer containing an aromatic polyester resin (X) and a polyglycolic acid resin layer containing polyglycolic acid (Y), wherein the polyglycolic acid (Y) contained in the polyglycolic acid resin layer has a dispersity B ( _Mw /Mn ₎ of 1.5 to 8.0, and the ratio of the dispersity B to the dispersity A ( _Mw /Mn) of the raw material polyglycolic acid (Y0) before the polyglycolic acid resin layer is formed (dispersity B/dispersity _A ) is 1.1 to 2.5.
[2] The multilayer container according to the above [1], wherein the polyglycolic acid-based resin layer further contains a polyamide resin (Z), the polyamide resin (Z) has structural units derived from a diamine and structural units derived from a dicarboxylic acid, and the polyamide resin (Z-1) contains 70 mol % or more of the structural units derived from the diamine that are structural units derived from xylylenediamine and 70 mol % or more of the structural units derived from the dicarboxylic acid that are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and the mass ratio [(Y)/(Z)] of the polyglycolic acid (Y) to the polyamide resin (Z) in the polyglycolic acid-based resin layer is 50/50 to 95/5.
[3] The multilayer container according to the above [1] or [2], wherein the aromatic polyester resin (X) has a constitutional unit derived from a dicarboxylic acid and a constitutional unit derived from a diol, and 90 mol % or more of the constitutional units derived from the dicarboxylic acid are constitutional units derived from terephthalic acid, and 90 mol % or more of the constitutional units derived from the diol are constitutional units derived from ethylene glycol.
[4] The multilayer container according to any one of [1] to [3] above, which has a 2 to 5 layer structure.
[5] The multilayer container according to any one of [1] to [4] above, which has a structure of a two-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer are laminated in this order from the outside of the container, a three-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order, or a five-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order.
[6] The multilayer container according to any one of the above [1] to [5], wherein the thickness of all layers of the multilayer container is 50 to 500 μm.
[7] The multilayer container according to any one of [1] to [6] above, having a capacity of 200 to 600 mL.
[8] A method for producing a multilayer container comprising the following steps 1 and 2, in which the polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer in the multilayer container obtained in step 2 has a dispersity B (Mw _B /Mn _B ) of 1.5 to 8.0, and the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) used in step 1 (dispersity B/dispersity A) is 1.1 to 2.5.
Step 1: A step of supplying a polyester-based resin containing an aromatic polyester resin (X), and a raw material polyglycolic acid (Y0) or a polyglycolic acid-based resin mixture obtained by mixing the raw material polyglycolic acid (Y0) with another resin to a molding machine to form a multilayer preform having a polyester-based resin layer and a polyglycolic acid-based resin layer. Step 2: A step of blow molding the multilayer preform obtained in step 1 to obtain a multilayer container having a polyester-based resin layer containing an aromatic polyester resin (X) and a polyglycolic acid-based resin layer containing polyglycolic acid (Y). [9] The method for producing a multilayer container according to the above item [8], wherein the multilayer preform obtained in step 1 is stored until the moisture content of the multilayer preform reaches 5,000 to 25,000 ppm, and then the multilayer preform is subjected to step 2.
[10] The method for producing a multilayer container according to the above [8] or [9], wherein the polydispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) supplied to the injection molding machine in step 1 is 1.1 to 7.0.
[11] The method for producing a multilayer container according to any one of [8] to [10] above, wherein the other resin used in the polyglycolic acid-based resin mixture in step 1 is a polyamide resin (Z), and the polyamide resin (Z) contains a polyamide resin (Z-1) having structural units derived from a diamine and structural units derived from a dicarboxylic acid, in which 70 mol % or more of the structural units derived from the diamine are structural units derived from xylylenediamine, and 70 mol % or more of the structural units derived from the dicarboxylic acid are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms.

The present invention provides a multilayer container that is excellent in formability and resistance to delamination, and a method for manufacturing the same.

FIG. 1 is a conceptual schematic diagram showing each step of cold parison molding.

The multilayer container of the present invention is a multilayer container having a polyester resin layer containing an aromatic polyester resin (X) and a polyglycolic acid resin layer containing polyglycolic acid (Y), in which the polyglycolic acid resin contained in the polyglycolic acid resin layer has a dispersity B (Mw _B /Mn _B ) of 1.5 to 8.0, and the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) before the polyglycolic acid resin layer is formed (dispersity B/dispersity A) is 1.1 to 2.5.
The present invention will be described in detail below.

[Polyester layer]
The polyester resin layer constituting the multilayer container of the present invention contains an aromatic polyester resin (X).

<Aromatic polyester resin (X)>
The aromatic polyester resin (X) used in the present invention may be a copolymer of a dicarboxylic acid and a diol, a polymer of a lactone or a hydroxycarboxylic acid, or a copolymer of a mixture of these monomers, with a copolymer of a dicarboxylic acid and a diol being preferred.
A preferred aromatic polyester resin (X) has a constitutional unit derived from a dicarboxylic acid (hereinafter also referred to as a "dicarboxylic acid unit") and a constitutional unit derived from a diol (hereinafter also referred to as a "diol unit").

The dicarboxylic acid unit preferably contains 90 mol % or more of constitutional units derived from terephthalic acid, more preferably 95 mol % or more, and even more preferably 99 mol % or more. If the constitutional units derived from terephthalic acid in the dicarboxylic acid unit are 90 mol % or more, the polyester resin is unlikely to become amorphous, and therefore, when a container is produced using the polyester resin, the heat shrinkage is unlikely to occur and the heat resistance is good.
The diol units preferably contain 90 mol % or more of constitutional units derived from ethylene glycol, more preferably 95 mol % or more, and even more preferably 99 mol % or more.
In other words, as a combination of dicarboxylic acid units and diol units of the aromatic polyester resin (X), the aromatic polyester resin (X) preferably has constitutional units derived from dicarboxylic acid containing 90 mol % or more of constitutional units derived from terephthalic acid and constitutional units derived from diol containing 90 mol % or more of constitutional units derived from ethylene glycol, and more preferably is composed mainly of polyethylene terephthalate.

The aromatic polyester resin (X) may contain structural units derived from a bifunctional compound such as a dicarboxylic acid other than terephthalic acid, or a diol other than ethylene glycol.
Examples of the dicarboxylic acid other than terephthalic acid include sulfophthalic acid, metal salts of sulfophthalic acid, and aromatic dicarboxylic acids other than terephthalic acid.
Preferred aromatic dicarboxylic acids other than terephthalic acid are isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid.
As the diol other than ethylene glycol, neopentyl glycol and cyclohexanedimethanol are preferred.

Furthermore, the aromatic polyester resin (X) may contain structural units derived from a monofunctional compound such as a monocarboxylic acid or a monoalcohol, and may contain structural units derived from a polyfunctional compound having at least three ester-forming groups selected from a carboxy group and a hydroxy group.

The aromatic polyester resin (X) can be produced by a known direct esterification method or transesterification method. The polycondensation catalyst used in the production of the aromatic polyester resin (X) can be an antimony compound, a germanium compound, an aluminum compound, or the like.
The aromatic polyester resin (X) may also contain recycled polyester, or may be a mixture of two or more resins.

The intrinsic viscosity of the aromatic polyester resin (X) is not particularly limited, but is preferably 0.5 to 2.0 dL/g, more 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 container can exhibit the mechanical properties required as a structure.
The intrinsic viscosity was measured by dissolving the polyester resin to be measured in a mixed solvent of phenol/1,1,2,2-tetrachloroethane (=6/4 mass ratio) to prepare 0.2, 0.4, and 0.6 g/dL solutions, and measuring the intrinsic viscosity at 25° C. using an automatic viscosity measuring device (Viscotek, manufactured by Malvern Instruments).

The content of the aromatic polyester resin (X) in the polyester resin layer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The upper limit may be 100% by mass.

[Polyglycolic acid resin layer]
The polyglycolic acid-based resin layer constituting the multilayer container of the present invention contains polyglycolic acid (Y). The polyglycolic acid (Y) is obtained by molding a multilayer container with resins constituting other layers using raw material polyglycolic acid (Y0) before the formation of the polyglycolic acid-based resin layer.
<Polyglycolic acid (Y)>
Polyglycolic acid (Y) is a polymer of glycolic acid and contains [—O—CH ₂ —CO—] derived from glycolic acid as a constituent unit.
The proportion of the structural units is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, with the upper limit being 100% by mass.
Examples of structural units other than the above-mentioned structural units include [-O-(CH ₂ ) _n -O-CO-(CH ₂ ) _m -CO-] (wherein n = 1 to 10, m = 0 to 10), [-O-CH((CH ₂ ) _j H)-CO-] (wherein j = 1 to 10), [-O-(CR ¹ R ² ) _k -CO-] (wherein R ¹ and R ² are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and k = 2 to 10), [-O-CH ₂ -CH ₂ -CH ₂ -O-CO-] and [-O-CH ₂ -O-CH ₂ -CH ₂ -]. By selecting and combining these structural units, the melting point, molecular weight, viscosity, etc. of polyglycolic acid (Y) can be adjusted.

Here, the raw material polyglycolic acid (Y0) before forming the polyglycolic acid-based resin layer, which is the raw material of polyglycolic acid (Y), can be produced by a known method. For example, condensation polymerization of glycolic acid or an ester of glycolic acid, ring-opening polymerization of glycolide, etc. can be mentioned. As described above, polyglycolic acid (Y) is obtained by molding a multilayer container with the resin that constitutes the other layers using the raw material polyglycolic acid (Y0) obtained by the condensation polymerization or ring-opening polymerization as the raw material.

The content of polyglycolic acid (Y) in the polyglycolic acid-based resin layer is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Also, it is preferably 100% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and even more preferably 85% by mass or less. When the content of polyglycolic acid (Y) is within the above range, the delamination resistance of the resulting container can be improved, and the moldability can be improved.

The dispersity (hereinafter referred to as "dispersity B") (Mw _B /Mn _B ) of the polyglycolic acid (Y) in the polyglycolic acid-based resin layer is 1.5 to 8.0. The dispersity B is preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more, and is preferably 7.5 or less, more preferably 6.5 or less, and even more preferably 6.0 or less.
On the other hand, the ratio of dispersity B to dispersity A (hereinafter referred to as "dispersity A") (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) before forming the polyglycolic acid-based resin layer (dispersity B/dispersity A) is 1.1 to 2.5. The ratio of dispersity B to dispersity A (dispersity B/dispersity A) is preferably 1.2 or more, more preferably 1.3 or more, even more preferably 1.5 or more, and preferably 2.4 or less, more preferably 2.2 or less, even more preferably 2.0 or less.
The dispersity A is preferably 1.0 or more, more preferably 1.1 or more, even more preferably 1.2 or more, still more preferably 1.5 or more, and is preferably 8.0 or less, more preferably 7.5 or less, even more preferably 7.0 or less, still more preferably 5.0 or less, and still more preferably 3.0 or less.
The dispersity means the value (Mw/Mn) obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn). The weight average molecular weight (Mw) and the number average molecular weight (Mn) can be measured by GPC under the conditions described in the examples below.
It is preferable that the dispersity B is in the above range because excellent delamination resistance can be obtained due to the hydrolysis property of polyglycolic acid. It is also preferable that the ratio of the dispersity B to the dispersity A (dispersity B/dispersity A) is in the above range because it is possible to achieve both good container moldability and excellent delamination resistance.

The polyglycolic acid-based resin layer constituting the multilayer container of the present invention may contain a resin other than polyglycolic acid (Y), or may be composed only of polyglycolic acid (Y). An example of a resin other than polyglycolic acid (Y) that may be contained in the polyglycolic acid-based resin layer is polyamide resin (Z). By containing polyamide resin (Z), the obtained multilayer container maintains high oxygen barrier properties and is also excellent in heat resistance.
The mass ratio [(Y)/(Z)] of the polyglycolic acid (Y) to the polyamide resin (Z) in the polyglycolic acid-based resin layer is preferably 50/50 to 95/5, more preferably 60/40 to 95/5, and even more preferably 70/30 to 90/10. By setting the ratio of the polyglycolic acid (Y) to the polyamide resin (Z) within the above range, the obtained multilayer container maintains high oxygen barrier properties and also has excellent heat resistance.

<Polyamide resin (Z)>
The polyamide resin (Z) has a constitutional unit derived from a diamine (hereinafter also referred to as a diamine unit) and a constitutional unit derived from a dicarboxylic acid (hereinafter also referred to as a dicarboxylic acid unit). As a diamine which is a compound constituting the diamine unit of the polyamide resin (Z), xylylenediamine is preferable. As a dicarboxylic acid which is a compound constituting the dicarboxylic acid unit of the polyamide resin (Z), an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms is preferable.
The polyamide resin (Z) preferably contains a polyamide resin (Z-1) in which 70 mol % or more of the diamine units are structural units derived from xylylenediamine and 70 mol % or more of the dicarboxylic acid units are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms.

The polyamide resin (Z-1) contains 70 mol% or more of structural units derived from xylylenediamine in the diamine units. The content of the structural units derived from xylylenediamine in the diamine units in the polyamide resin (Z-1) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. By making 70 mol% or more of the diamine units be structural units derived from xylylenediamine, it is possible to impart high gas barrier properties to the multilayer container of the present invention.
The xylylenediamine may be any of ortho-, meta-, and para-xylylenediamine, but from the viewpoints of oxygen barrier properties and moldability, meta-xylylenediamine is preferred.

The polyamide resin (Z-1) contains 70 mol% or more of structural units derived from α,ω-straight-chain aliphatic dicarboxylic acids having 4 to 20 carbon atoms in the dicarboxylic acid units. The content of structural units derived from α,ω-straight-chain aliphatic dicarboxylic acids having 4 to 20 carbon atoms in the dicarboxylic acid units in the polyamide resin (Z-1) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. By making 70 mol% or more of the dicarboxylic acid units structural units derived from α,ω-straight-chain aliphatic dicarboxylic acids having 4 to 20 carbon atoms, the colorlessness and adhesiveness of the resulting multilayer container can be efficiently improved.

Examples of α,ω-straight-chain aliphatic dicarboxylic acids having 4 to 20 carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, and 1,12-dodecanedicarboxylic acid, with adipic acid and sebacic acid being preferred, and adipic acid being more preferred. These α,ω-straight-chain aliphatic dicarboxylic acids may be used alone or in combination of two or more.

The combination of diamine units and dicarboxylic acid units in the polyamide resin (Z-1) preferably has diamine-derived structural units containing 80 mol % or more of structural units derived from xylylenediamine, and dicarboxylic acid units containing 80 mol % or more of structural units derived from adipic acid.
The proportion of the polyamide resin (Z-1) in the polyamide resin (Z) is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The upper limit is 100% by mass or less, and the polyamide resin (Z) may consist only of the polyamide resin (Z-1).

Among the compounds constituting the diamine units of polyamide resin (Z), diamines other than xylylenediamine include diamines having an aromatic ring structure, aliphatic diamines, and diamines having an alicyclic structure. Aliphatic diamines are preferred because they are easily available and have improved colorlessness and adhesion.

Examples of the aliphatic diamine include tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, 2-methyl-1,5-pentanediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, and 5-methylnonamethylenediamine.
Examples of diamines having an alicyclic structure include 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine, and aminoethylpiperazine.
Incidentally, polyamines having a valence of three or more, such as bis(hexamethylene)triamine, and monoamines, such as butylamine, hexylamine, and octylamine, may also be used within the scope of the present invention.

As with polyamide resin (Z), diamines other than xylylenediamine constituting the diamine units of polyamide resin (Z-1) can also include diamines having an aromatic ring structure, aliphatic diamines, and diamines having an alicyclic structure.

Among the compounds that can constitute the dicarboxylic acid unit of the polyamide resin (Z), examples of compounds other than α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms include dicarboxylic acids having an alicyclic structure such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, decalindicarboxylic acid, norbornanedicarboxylic acid, tricyclodecanedicarboxylic acid, pentacyclododecanedicarboxylic acid, isophoronedicarboxylic acid, and 3,9-bis(2-carboxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane; and dicarboxylic acids having an aromatic ring structure such as terephthalic acid, isophthalic acid, phthalic acid, orthophthalic acid, 2-methylterephthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetralindicarboxylic acid.
In addition, polycarboxylic acids having three or more valences, such as trimellitic acid, trimesic acid, pyromellitic acid, and tricarballylic acid, may be used as long as the effects of the present invention are not impaired, and monocarboxylic acids may also be used.

In addition to the above-mentioned diamine units and dicarboxylic acid units, the units constituting the polyamide resin (Z) may also include structural units derived from aminocarboxylic acids, etc., within the scope of the invention, so long as the effects of the invention are not impaired. Specific examples of such structural units include structural units derived from aliphatic aminocarboxylic acids and structural units derived from aromatic aminocarboxylic acids.

Compounds constituting the dicarboxylic acid, polycarboxylic acid and monocarboxylic acid used in the dicarboxylic acid unit include anhydrides and short-chain alkyl esters. Specific examples of short-chain alkyl esters include those having 1 to 3 carbon atoms, i.e., methyl esters, ethyl esters, propyl esters and isopropyl esters, with methyl esters being preferred. Compounds constituting structural units derived from aminocarboxylic acids include lactams, which are anhydrides.

Compounds other than α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms that can constitute the dicarboxylic acid units of polyamide resin (Z-1) include dicarboxylic acids having an alicyclic structure similar to those of polyamide resin (Z) and dicarboxylic acids having an aromatic ring structure.

Specific examples of the polyamide resin (Z-1) in the present invention include polyamide MXD6 (polymetaxylylene adipamide), polyamide MXD10 (polymetaxylylene sebacamide), polyamide MXD6I (isophthalic acid copolymerized polymetaxylylene adipamide), etc., and from the viewpoints of availability, gas barrier properties, and colorlessness, polyamide MXD6 or polyamide MXD10 is preferred, and polyamide MXD6 is more preferred. These polyamide resins may be used alone or in combination of two or more types.

(Method for producing polyamide resin (Z))
A preferred method for producing polyamide resin (Z) is described below, which also includes a preferred method for producing polyamide resin (Z-1). That is, polyamide resin (Z-1) is preferably produced by the same method as polyamide resin (Z).
The polyamide resin (Z) is preferably produced by a melt polycondensation method.
The melt polycondensation method is preferably a method of directly adding diamine to molten dicarboxylic acid and polycondensing it. In this case, in order to keep the reaction system in a homogeneous liquid state, it is preferable to continuously add diamine to dicarboxylic acid and to proceed with polycondensation while increasing the temperature of the reaction system so that the reaction temperature does not fall below the melting points of the oligoamide and polyamide produced.

It is preferable to add a phosphorus atom-containing compound to the polycondensation reaction system of the polyamide resin (Z) in order to obtain the effect of accelerating the amidation reaction and the effect of preventing coloration during the polycondensation reaction.
As the phosphorus atom-containing compound, metal hypophosphites such as sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, and calcium hypophosphite are preferred, and sodium hypophosphite is more preferred, because they have a high effect of promoting the amidation reaction and also have an excellent effect of preventing discoloration.

The amount of the phosphorus atom-containing compound added to the polycondensation reaction system of the polyamide resin (Z) is preferably 1 to 500 ppm, more preferably 5 to 450 ppm, and even more preferably 10 to 400 ppm, calculated as the phosphorus atom concentration in the polyamide resin (Z). By setting the amount of the phosphorus atom-containing compound to be within the above range, coloration of the polyamide during the polycondensation reaction can be prevented and gelation of the polyamide can be suppressed, so that the appearance of the resulting container can be maintained in a good condition.
In addition, an alkali metal compound and/or an alkaline earth metal compound may be added in combination with the phosphorus atom-containing compound to the polycondensation reaction system of the polyamide resin (Z).

The polyamide resin (Z) obtained by the melt polycondensation method is preferably pelletized and then dried before use, and more preferably subjected to solid-phase polymerization in order to further increase the degree of polymerization.
The solid-state polymerization is preferably carried out by heating the pellets under reduced pressure.

(Characteristics of polyamide resin (Z))
The relative viscosity of the polyamide resin (Z) is preferably 1.5 to 4.2, more preferably 1.6 to 4.0, even more preferably 1.7 to 3.8, and still more preferably 1.9 to 3.0.
By setting the relative viscosity of the polyamide resin (Z) within the above range, the molding processability is stable, and a container with a good appearance can be obtained.
In the present invention, the relative viscosity of the polyamide resin (Z) is measured by the following method. Specifically, 0.2 g of the polyamide resin is precisely weighed and dissolved in 20 mL of 96% by mass sulfuric acid at 20 to 30° C. with stirring. After complete dissolution, 5 mL of the solution is quickly taken in a Cannon-Fenske viscometer, and the solution is left in a thermostatic bath at 25° C. for 10 minutes, after which the drop time (t 0 ) of the solution is measured. The drop time (t ₀ ) of 96% by mass sulfuric acid is also measured in the same manner. The relative viscosity of the polyamide resin is calculated from the measured values of t and t ₀ according to the following formula.
Relative viscosity = t/ _t0

The content of the polyamide resin (Z) in the polyglycolic acid resin layer is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.
When the content of polyamide resin (Z) is 5% by mass or more, oxygen permeability can be sufficiently suppressed and thermal stability can be improved, and when the content is 50% by mass or less, the delamination resistance of the resulting container can be improved.

[Other ingredients]
Examples of other components contained in the polyester resin layer and the polyglycolic acid resin layer constituting the multilayer container of the present invention include recycling aids.

The recycling aid is a compound that has the effect of suppressing yellowing in the recycling step when obtaining recycled polyester, and as the recycling aid, an aldehyde scavenger is preferable.
The recycling aid is preferably a compound that has the ability to suppress yellowing of the polyester resin and contains an amino group, and more specifically, it is more preferably at least one compound selected from the group consisting of anthranilamide, anthranilic acid, and nylon 6I/6T.

In addition to the above components, the polyester resin layer and the polyglycolic acid resin layer may contain additives such as colorants, oxygen absorbers, heat stabilizers, light stabilizers, moisture-proofing agents, waterproofing agents, lubricants, and spreading agents.

[Multi-layer container]
The multilayer container of the present invention is preferably a hollow container, and when the multilayer container is a hollow container, at least the body portion has a multilayer laminate structure.
The multilayer container of the present invention preferably has a 2- to 5-layer structure, more preferably a 2-, 3- or 5-layer structure, even more preferably a 3- or 5-layer structure, and even more preferably a 3-layer structure.
Specifically, from the outside of the container, it is preferably a two-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer are laminated in this order, a three-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order, or a five-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order.

The multilayer container of the present invention may have other layers in addition to the polyester resin layer and the polyglycolic acid resin layer. Examples of other layers include an adhesive layer that contains an adhesive resin and is interposed between the polyester resin layer and the polyglycolic acid resin layer. However, from the viewpoint of improving moldability and separability during recycling, it is preferable that the container does not include an adhesive layer.

The multilayer container of the present invention may be a peelable laminate container in which the inner layer undergoes volume reduction and deformation with a decrease in the content without causing deformation of the outermost layer, and thus interlayer peeling is possible.
In the case of the above-mentioned peelable laminate container, it is preferable that the multilayer container has an outside air inlet hole for introducing outside air between the polyester-based resin layer and the polyglycolic acid-based resin layer, so that peeling between the layers can occur due to volume reduction deformation.
Due to this function, the contents are prevented from coming into direct contact with air until they are completely used up, thereby preventing oxidation of the contents.
In the case of the above-mentioned peelable laminate container, it is particularly preferable that the container has a two-layer structure in which a polyester resin layer/a polyglycolic acid resin layer are laminated in this order from the outside.
The position of the air inlet is not particularly limited, but it is preferably provided at the container mouth of the outer layer or at the container bottom. The air inlet may be formed by hollowing out only the outer layer after the multilayer container is molded, or may be formed simultaneously when the multilayer container is molded. When the air inlet is formed simultaneously when the multilayer container is molded, for example, the gap between the layers of the seal portion formed at the container bottom during blow molding may be used as the air inlet.

The thickness of the polyglycolic acid resin layer of the multilayer container of the present invention is preferably 1% or more of the total thickness, more preferably 2% or more, and even more preferably 5% or more. It is preferably 15% or less, more preferably 13% or less, and even more preferably 12% or less. If the thickness of the mixed resin layer is within the above range, sufficient oxygen barrier properties are obtained and it is economical.

The polyglycolic acid-based resin layer does not have to be laminated on the bottom or neck of the multi-layer container, and it is preferable that the mixed resin layer is present in the above-mentioned thickness and position over at least a part of the body, preferably the central part of the body, and more preferably 50% or more of the length of the body.
From the viewpoint of balancing delamination resistance and oxygen barrier properties, it is preferable that the mixed resin layer extends from the bottom of a support ring of the preform described below to a position about 20 to 40 mm from the center of the injection gate of the preform.

The total thickness of the multilayer container is preferably 50 to 500 μm, more preferably 100 to 450 μm, and even more preferably 200 to 400 μm. The total thickness of the multilayer container refers to the average value of the total thickness of all layers (resin layers) in the body of the multilayer container.
From the viewpoints of oxygen barrier property, thermal stability, delamination resistance, and production, the capacity of the multilayer container is preferably 30 to 3,000 mL, more preferably 50 to 2,000 mL, even more preferably 100 to 1,500 mL, still more preferably 200 to 1,000 mL, and even more preferably 200 to 600 mL.

The multilayer container of the present invention is more preferably a liquid packaging container in which the interior of the hollow container is filled with a liquid, and even more preferably a beverage packaging container. Examples of the liquid to be filled inside include beverages such as water, carbonated water, oxygenated water, hydrogenated water, milk, dairy products, juice, coffee, coffee drinks, carbonated soft drinks, tea, and alcoholic drinks; liquid seasonings such as sauces, soy sauce, syrup, mirin, and dressings; chemical products such as pesticides and insecticides; pharmaceuticals; and detergents. In particular, beverages and carbonated beverages that are prone to deterioration in the presence of oxygen, such as beer, wine, coffee, coffee drinks, fruit juice, carbonated soft drinks, carbonated water, and tea, are preferred.

The multilayer container of the present invention also has excellent oxygen barrier properties, and the oxygen barrier properties (mL/bottle·day·0.21 atm) of the container measured in accordance with ASTM D3985 are preferably 0.040 or less, more preferably 0.035 or less, and even more preferably 0.030 or less. The oxygen barrier properties are values based on the containers produced in the examples, i.e., containers having an internal volume of 500 mL (surface area: 0.04 ^m2 , average body thickness: 0.35 mm).

[Method of manufacturing multi-layer container]
As described above, the multilayer container of the present invention is a multilayer container having a polyester resin layer containing an aromatic polyester resin (X) and a polyglycolic acid resin layer containing polyglycolic acid (Y), in which the polyglycolic acid (Y) contained in the polyglycolic acid resin layer has a dispersity B (Mw _B /Mn _B ) of 1.5 to 8.0 and the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) before the polyglycolic acid resin layer is formed (dispersity B/dispersity A) is 1.1 to 2.5. There are no limitations on the production method, but it is preferable to produce the multilayer container by the following method.
That is, a preferred method for producing a multilayer container of the present invention is a method for producing a multilayer container comprising the following steps 1 and 2:
The polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer in the multilayer container obtained in step 2 has a dispersity B (Mw _B /Mn _B ) of 1.5 to 8.0, and the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) used in step 1 (dispersity B/dispersity A) is 1.1 to 2.5.
Step 1: A step of supplying a polyester-based resin containing an aromatic polyester resin (X), and raw material polyglycolic acid (Y0) or a polyglycolic acid-based resin mixture obtained by mixing raw material polyglycolic acid (Y0) with another resin to a molding machine to form a multilayer preform having a polyester-based resin layer and a polyglycolic acid-based resin layer. Step 2: A step of blow molding the multilayer preform obtained in step 1 to obtain a multilayer container having a polyester-based resin layer containing an aromatic polyester resin (X) and a polyglycolic acid-based resin layer containing polyglycolic acid (Y). It is more preferable to store the multilayer preform obtained in step 1 until the moisture content reaches 5,000 to 25,000 ppm, and then subject it to step 2.
Each step will be described below.

<Step 1>
Step 1 is a step of supplying a polyester-based resin containing an aromatic polyester resin (X), and raw material polyglycolic acid (Y0) or a polyglycolic acid-based resin mixture obtained by mixing raw material polyglycolic acid (Y0) with another resin to a molding machine, and forming a multilayer preform having a polyester-based resin layer and a polyglycolic acid-based resin layer.

In this step 1, it is preferable that the raw material polyglycolic acid (Y0) supplied to the injection molding machine has the structural units explained in the above section <Polyglycolic acid (Y)> and is obtained by the method explained in the same section.
The dispersity A ( _MwA / _MnA ) of the raw material polyglycolic acid (Y0) supplied to the injection molding machine in step 1 is preferably 1.0 or more, more preferably 1.1 or more, even more preferably 1.2 or more, still more preferably 1.5 or more, and preferably 8.0 or less, more preferably 7.5 or less, even more preferably 7.0 or less, still more preferably 5.0 or less, and still more preferably 3.0 or less.

In this step, when a resin other than the raw material polyglycolic acid (Y0) is used as a raw material for the polyglycolic acid-based resin layer, it is preferable to mix the raw material polyglycolic acid (Y0) with the other resin to prepare a polyglycolic acid-based resin mixture in advance before molding the preform.
Here, it is preferable that the other resin used in the polyglycolic acid resin mixture in step 1 is a polyamide resin (Z).More preferably, the other resin is a polyamide resin (Z), and the polyamide resin (Z) contains a structural unit derived from a diamine and a structural unit derived from a dicarboxylic acid, and more preferably contains a polyamide resin (Z-1) in which 70 mol % or more of the structural units derived from the diamine are structural units derived from xylylenediamine, and 70 mol % or more of the structural units derived from the dicarboxylic acid are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms.
The polyamide resin (Z) and the polyamide resin (Z-1) are preferably those described above in the section [Polyglycolic acid resin layer].

The mixing may be dry blending or melt blending (melt kneading). That is, the components may be dry blended to prepare a mixed resin, or the components may be melt blended to prepare a mixed resin. Among these, dry blending is preferred from the viewpoint of reducing the thermal history. Here, dry blending means mechanically mixing in the form of powder or pellets. For mixing, it is preferable to use a mixing device such as a tumbler mixer, ribbon mixer, Henschel mixer, or Banbury mixer. Alternatively, when subjecting to molding processing, a predetermined amount of other resin, preferably polyamide resin (Z), may be supplied by a feeder other than the feeder for supplying the raw material polyglycolic acid (Y0), to prepare a mixed resin immediately before molding the parison.
In addition, when the raw material polyglycolic acid (Y0) and other resins are melt-kneaded, the temperature in the melt-kneading is not particularly limited, but from the viewpoint of the resin being sufficiently melted and sufficiently kneaded, it is preferably 240 to 280 ° C, more preferably 245 to 270 ° C, and even more preferably 250 to 265 ° C. In addition, the time for melt-kneading is not particularly limited, but from the viewpoint of the resin being uniformly mixed, it is preferably 10 to 600 seconds, more preferably 20 to 400 seconds, and even more preferably 30 to 300 seconds. The device used for melt-kneading is not particularly limited, but examples thereof include an open-type mixing roll, a non-open-type Banbury mixer, a kneader, a continuous kneader (a single-shaft kneader, a twin-shaft kneader, a multi-shaft kneader, etc.), and the like.
Also, in the case where other resins or other components are mixed into the polyester resin layer or the polyglycolic acid resin layer, it is preferable to carry out the above-mentioned conditions.

Next, the resin constituting the polyester-based resin layer is extruded from a first extruder, and the resin constituting the polyglycolic acid-based resin layer is extruded from a second extruder to form a parison (multilayer preform). More specifically, this is preferably a process of forming a multilayer preform by extrusion molding, co-injection molding, compression molding, or the like.
In the extrusion molding, the resin constituting the polyester layer and the resin constituting the mixed resin layer are co-extruded to form a multi-layer preform.
In the co-injection molding, the resin constituting the polyester-based resin layer and the resin constituting the polyglycolic acid-based resin layer are each extruded into a mold and co-injected to form a multi-layer preform.
In compression molding, the resin constituting the polyglycolic acid-based resin layer in a molten state is intermittently extruded into an extrusion flow path in which the resin constituting the polyester-based resin layer in a molten state flows, and the resin constituting the polyester-based resin layer surrounding substantially the entire extruded resin constituting the mixed resin layer is extruded from the extrusion port of the extrusion flow path, and is supplied to an appropriate molding die as a molten resin molding material, and then compression molded to form a multilayer preform.
Among these, coinjection molding is preferred from the viewpoint of productivity.

<Moisture content adjustment process>
In this step, the multi-layer preform obtained in step 1 is stored until the moisture content of the multi-layer preform becomes 5,000 to 25,000 ppm, and then the multi-layer preform is subjected to step 2.
The moisture content can be measured by the method described in the Examples, and "ppm" in this specification means "ppm by mass."
This step is an optional step, but it is preferable to provide this step in order to adjust the dispersity B (Mw _B /Mn _B ) of the polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer of the multilayer container of the present invention to 1.5 to 8.0 and to adjust the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) before the polyglycolic acid-based resin layer is formed (dispersity B/dispersity A) to 1.1 to 2.5.

Specifically, there may be mentioned (1) a method of storing the preform obtained in the above process under high humidity, and (2) a method of immersing the preform obtained in the above process in water, and (1) a method of storing the preform obtained in the above process under high humidity is preferred.
(1) As a specific method for storing the preform obtained in the above process under high humidity, a method of storing the preform obtained in the above process in an environment of 15 to 35°C and a relative humidity of 45 to 65% for 5 to 20 days, or a method of storing the preform obtained in the above process in an environment of 36 to 50°C and a relative humidity of 75 to 95% for 10 to 40 days is preferable, and a method of storing the preform obtained in the above process in an environment of 15 to 35°C and a relative humidity of 45 to 65% for 5 to 20 days is more preferable.
In the method of storing the preform obtained in the above process for 5 to 20 days under an environment of 15 to 35°C and a relative humidity of 45 to 65%, the temperature is preferably 20 to 30°C, the relative humidity is preferably 45 to 55%, and the storage period is preferably 6 to 10 days.
In the method of storing the preform obtained in the above process for 10 to 40 days under an environment of 36 to 50° C. and a relative humidity of 75 to 95%, the temperature is preferably 36 to 45° C., the relative humidity is preferably 75 to 85%, and the storage period is preferably 12 to 20 days.
(2) A specific method for immersing the preform obtained in the above step in water includes storing the preform obtained in the above step for 0.5 to 30 hours in a water tank containing water at 15 to 35° C. In this method, the water temperature is preferably 20 to 30° C., and the storage time is preferably 3 to 10 hours.

<Step 2>
Step 2 is a step of blow molding the multilayer preform obtained in step 1 to obtain a multilayer container having a polyester-based resin layer containing the aromatic polyester resin (X) and a polyglycolic acid-based resin layer containing the polyglycolic acid (Y).
When the moisture content adjusting step is provided, in this step, the multilayer preform obtained in the moisture content adjusting step is blow molded to obtain a multilayer container having a polyester-based resin layer containing the aromatic polyester resin (X) and a polyglycolic acid-based resin layer containing the polyglycolic acid (Y).

The polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer in the multilayer container obtained in this step has a dispersity B (Mw _B /Mn _B ) of 1.5 to 8.0, and the ratio of the dispersity B to the dispersity A (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0) used in step 1 (dispersity B/dispersity A) is 1.1 to 2.5.

The dispersity B is preferably 2.0 or more, more preferably 2.5 or more, even more preferably 3.0 or more, and is preferably 7.5 or less, more preferably 6.5 or less, even more preferably 6.0 or less.
In addition, the ratio of the dispersity B to the dispersity A (dispersity B/dispersity A) is preferably 1.2 or more, more preferably 1.3 or more, even more preferably 1.5 or more, and is preferably 2.4 or less, more preferably 2.2 or less, even more preferably 2.0 or less.
It is preferable that the dispersity B is in the above range because excellent delamination resistance can be obtained due to the hydrolysis property of polyglycolic acid. It is also preferable that the ratio of the dispersity B to the dispersity A (dispersity B/dispersity A) is in the above range because it is possible to achieve both good container moldability and excellent delamination resistance.

The blow molding method in this step is selected appropriately taking into consideration the structure of the molded product, etc. Specifically, the preform can be obtained by injecting a molten resin or resin composition from an injection molding machine into a mold to produce a preform, which is then stretched by blowing (injection blow molding, injection stretch blow molding).
Alternatively, the plastic can be obtained by extruding a molten resin or resin composition from an extrusion molding machine into a mold to obtain a parison, which is then blown in the mold (direct blow molding).
The multi-layer container of the present invention is preferably produced by injection blow molding.

The multi-layer container of the present invention is preferably produced by biaxially stretching and blow molding a preform.
The multilayer container of the present invention may be formed by cold parison molding or hot parison molding. Cold parison (two-stage molding) molding is a molding method in which the preform after injection molding is cooled to room temperature, stored, and then reheated in another device and supplied to blow molding. On the other hand, hot parison molding (one-stage molding) is a blow molding method in which the parison is preheated at the time of injection molding and temperature controlled before blowing without being completely cooled to room temperature. In hot parison molding, in many cases, an injection molding machine, a temperature control zone, and a blow molding machine are provided in the same molding machine unit, and preform injection molding and blow molding are performed.

A first embodiment of the method for producing a multilayer container of the present invention is an embodiment in which molding is performed by cold parison molding.
Hereinafter, a description will be given with reference to Fig. 1. Fig. 1 is a conceptual schematic diagram showing each step of cold parison molding. However, it goes without saying that the first embodiment is not limited to the configuration shown in Fig. 1.
In Fig. 1, first, a preform 1 is heated (Fig. 1(1)). The heating is performed by an infrared heater 2 or the like.
Next, the heated preform 1 is subjected to biaxial stretch blow molding. That is, it is placed in a mold 3 (FIG. 1(2)) and is blow molded while being stretched by a stretch rod 4 (FIGS. 1(3) and 1(4)).
For example, the preform may be stretched in the axial direction by mechanical means such as by pressing the surface of the preform with a core rod insert after heating it, and then blown with high-pressure air, usually at 2 to 4 MPa, to stretch it laterally, thereby forming a blow molded product.
In order to improve the heat resistance of the container, a blow molding method that increases the crystallinity or reduces residual distortion may be combined. For example, there is a method (single blow molding) in which the surface of a multilayer preform is heated and then blow molded in a mold at a temperature above the glass transition point.
Furthermore, it may be so-called double blow molding, which comprises a primary blow molding step in which the preform is biaxially stretched and blow molded to a size larger than the final shape, a step in which this primary blow molded product is heated and thermally shrunk to form a secondary intermediate molded product, and finally a secondary blow molding step in which this secondary intermediate molded product is blow molded into the final container shape.
After the blow molding, the mold 3 is removed, and a multi-layer container 5 is obtained (FIG. 1(5)).

In cold parison molding, the parison temperature before blow molding is determined in consideration of the glass transition temperature (Tg) of the resin constituting the multilayer container of the present invention. Before blow molding means, for example, the time immediately before blowing after passing through a preheating zone.
The parison temperature is preferably a temperature exceeding the glass transition temperature (Tg _max ) of the resin having the highest glass transition temperature among the resins constituting the multilayer container of the present invention, and more preferably in the temperature range of (Tg _max + 0.1)°C to (Tg _max + 50)°C.
Moreover, the difference between the glass transition temperature (Tg _min ) of the resin having the lowest glass transition temperature among the resins constituting the multilayer container of the present invention and the above Tg _max is preferably 40° C. or less, more preferably 30° C. or less. By setting it in such a range, the blow moldability tends to be further improved.
Furthermore, when at least one of the resins constituting the multilayer container of the present invention is a crystalline resin, it is preferable that there is a large difference between the lowest crystallization temperature (Tc _min ) of the crystalline resins and the glass transition temperature (Tg _max ) of the resin having the highest glass transition temperature among the resins constituting the multilayer container of the present invention.
Specifically, Tc _min -Tg _max is preferably 5°C or higher, and more preferably 10°C or higher.
The upper limit of Tc _min -Tg _max is practically 100° C. By setting it in such a range, the blow moldability tends to be further improved.

The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to these examples.

The resins used in the examples and comparative examples are as follows.
<Polyester resin (X)>
PET: polyethylene terephthalate (intrinsic viscosity: 0.83 dL/g), product name: BK2180, manufactured by Mitsubishi Chemical Corporation (melting point 248°C)
<Raw material polyglycolic acid (Y0)>
PGA1: Polyglycolic acid (dispersity (Mw/Mn): 2.0, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA2: Polyglycolic acid (dispersity (Mw/Mn): 2.5, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA3: Polyglycolic acid (dispersity (Mw/Mn): 4.5, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA4: Polyglycolic acid (dispersity (Mw/Mn): 6.0, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA5: Polyglycolic acid (dispersity (Mw/Mn): 3.5, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA6: Polyglycolic acid (dispersity (Mw/Mn): 8.0, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
PGA7: Polyglycolic acid (dispersity (Mw/Mn): 3.0, glass transition temperature: 38°C, melting point: 221°C, crystallization temperature: 91°C)
<Polyamide resin (Z)>
MXD6: Poly(metaxylylene adipamide) (relative viscosity: 2.7, melting point = 237°C), product name: MX nylon S6007, manufactured by Mitsubishi Gas Chemical Company, Inc., corresponds to polyamide resin (Z-1)

[Measurement and evaluation method]
<Dispersion degree of polyglycolic acid>
The dispersibility of polyglycolic acid was measured as follows.
The molecular weight was calculated from the weight average molecular weight (Mw) and number average molecular weight (Mn) determined by gel permeation chromatography (GPC) measurement using a gel permeation chromatograph "HLC-8320GPC" (manufactured by Tosoh Corporation).
The above molecular weight is a PMMA-equivalent value calculated from a calibration curve using standard polymethyl methacrylate (PMMA). Two "TSKgel Super HM-H" columns were used as the measurement columns, and hexafluoroisopropanol (HFIP) with a sodium trifluoroacetate concentration of 10 mmol/L was used as the solvent. The polyglycolic acid concentration was 0.02 mass%, the column temperature was 40° C., the flow rate was 0.3 mL/min, and the refractive index detector (RI) was used. The calibration curve was prepared by dissolving six levels of standard PMMA in HFIP and measuring.
In Table 1, the dispersity A is the dispersity (Mw _A /Mn _A ) of the raw material polyglycolic acid (Y0), and the dispersity B (Mw _B /Mn _B ) is the dispersity of the polyglycolic acid contained in the polyglycolic acid-based resin layer after molding.
In Examples 5 and 6, the dispersity of polyglycolic acid in a resin composition consisting of polyglycolic acid and MXD6 is shown.

<Measurement of moisture content>
The moisture content was measured by the following method.
Using a moisture meter CA200 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and a sample charger VA-236S, 0.5 g of a sample for measurement was cut out from the preform, the set temperature was melting point -5°C, the waiting time until the start of detection was 0 seconds, the measurement time was 30 minutes, and the moisture content was measured by the Karl Fischer method. As a blank, the moisture content was measured under the same conditions for a sample of 0 g. The moisture content of the sample was calculated by the following formula.
Moisture content (ppm) = [(moisture content of sample) - (moisture content of blank)] / (mass of sample)

<Blow moldability>
The blow moldability was evaluated according to the following criteria when a bottle was blow molded under the following molding conditions in the method described in <Production of Multilayer Bottles> below. Appearance defects were whitening and surface deformation.
In addition, for Comparative Examples 1 and 2, which were rated C in the blow moldability according to the following criteria, the primary blow pressure was changed to obtain bottles for evaluation of delamination resistance.

(Evaluation criteria)
A: None of the bottles have any defects in appearance, and blow molding is possible under the molding conditions below. B: Less than 30% of the bottles have defects in appearance, and blow molding is difficult under the molding conditions below, but blow molding is possible by changing the preform heating temperature. C: More than 30% of the bottles have defects in appearance, and blow molding is difficult even if the preform heating temperature is changed. D: Bursts occur, and blow molding is difficult.

(Molding condition)
Preform heating temperature: 100°C
Primary blow pressure: 0.9 MPa
Secondary blow pressure: 2.5 MPa
Primary blow delay time: 0.30 sec
First blow time: 0.30 sec
Secondary blow time: 2.0 sec
Blow exhaust time: 0.6 sec
Mold temperature: 30°C

<Delamination resistance>
The measurement was carried out based on the measurement method according to ASTM D2463-95B. The multi-layer bottles of the examples and comparative examples were filled with 500 g of water, capped, and then stored for one day in an environment of 23°C and 50% RH, and then a drop test was carried out from a height of 1 m to measure the number of times that delamination occurred at the bottom of the bottle (the number of tests until the polyester-based resin layer and the polyglycolic acid-based resin layer peeled off), and the delamination resistance was evaluated according to the following criteria.
A: 40 or more tests before peeling B: 20 or more tests but less than 40 tests before peeling C: Less than 20 tests before peeling

Example 1
<Preform manufacturing>
PET (BK2180) as the resin for the polyester resin layer and PGA1 as the resin for the polyglycolic acid resin layer were put into the hopper of an injection blow molding machine, and a multi-layer hot runner mold was used to inject the resin under the conditions shown below to fill the cavity, thereby obtaining a preform (25 g) having a three-layer structure of polyester resin layer/polyglycolic acid resin layer/polyester resin layer. The thickness of each layer was adjusted to 5:1:5. The shape of the preform was 92 mm in total length, 22 mm in outer diameter, and 3.9 mm in thickness.
Skin side injection cylinder temperature: 285°C
Core side injection cylinder temperature: 250°C
Resin flow path temperature in mold: 290°C
Mold cooling water temperature: 15°C

<Adjusting the moisture content of the preform>
The obtained preform was stored in an environment of 23° C. and 50% RH for 14 days.

<Production of multi-layer bottles>
The preform produced by the above-mentioned manufacturing method was used to mold a multi-layer bottle.
Specifically, the obtained preform was biaxially stretched and blow molded using a biaxially stretched blow molding machine (manufactured by Frontier Co., Ltd., model EFB1000ET) to obtain a petaloid-type multi-layer bottle (three-layer structure). The total length of the bottle was 223 mm, the outer diameter was 65 mm, the internal volume was 500 mL (surface area: 0.04 ^m2 , average thickness of the body: 0.35 mm), and the bottom was petaloid-shaped. No dimples were provided on the body. The biaxially stretched blow molding conditions were as shown below. The neck area and bottom of the obtained multi-layer bottle were formed only from a polyester-based resin layer.
The multi-layer bottle thus obtained was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.
Preform heating temperature: 100°C
Primary blow pressure: 0.9 MPa
Secondary blow pressure: 2.5 MPa
Primary blow delay time: 0.30 sec
First blow time: 0.30 sec
Secondary blow time: 2.0 sec
Blow exhaust time: 0.6 sec
Mold temperature: 30°C

Example 2
A multi-layer bottle was molded in the same manner as in Example 1, except that PGA1 was changed to PGA2. The obtained multi-layer bottle was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

Example 3
A multi-layer bottle was molded in the same manner as in Example 1, except that PGA1 was changed to PGA3 and the preform heating temperature was changed to 98° C. among the biaxial stretch blow molding conditions for producing the multi-layer bottle. The above-mentioned measurements and evaluations were carried out on the obtained multi-layer bottle. The results are shown in Table 1.

Example 4
A multi-layer bottle was molded in the same manner as in Example 1, except that PGA1 was changed to PGA4 and the preform heating temperature was changed to 98° C. among the biaxial stretch blow molding conditions for producing the multi-layer bottle. The above-mentioned measurements and evaluations were carried out on the obtained multi-layer bottle. The results are shown in Table 1.

Example 5
<Preform manufacturing>
For the polyglycolic acid-based resin layer, PGA2 and polyamide resin (MXD6) were placed in a tumbler so that the mass ratio (PGA2/MXD6) was 70/30, and dry blended. PET (BK2180) was used as the resin for the polyester-based resin layer. The materials for each layer were the same as in Example 1 to obtain a preform (25 g). The thickness of each layer and the shape of the preform were also the same as in Example 1.
<Adjusting the moisture content of the preform>
The obtained preform was stored in an environment of 23° C. and 50% RH for 14 days, and the moisture content of the preform was adjusted to 13,000 ppm.

<Production of multi-layer bottles>
Using the preform produced by the above manufacturing method, a bottle was molded in the same manner as in Example 1.
The multi-layer bottle thus obtained was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

Example 6
A multi-layer bottle was molded in the same manner as in Example 5, except that PGA2 was changed to PGA5. The obtained multi-layer bottle was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

Comparative Example 1
A multi-layer bottle was molded in the same manner as in Example 1, except that PGA1 was changed to PGA6, and among the biaxial stretch blow molding conditions for producing the multi-layer bottle, the primary blow pressure was set to 0.6 MPa, and the preform heating temperature was set to 96° C. The obtained multi-layer bottle was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

Comparative Example 2
A multi-layer bottle was molded in the same manner as in Example 1, except that PGA1 was changed to PGA7, the period for adjusting the moisture content of the preform was changed from 14 days to 28 days, and among the biaxial stretch blow molding conditions for producing the multi-layer bottle, the primary blow pressure was set to 0.6 MPa and the preform heating temperature was set to 96° C. The obtained multi-layer bottle was subjected to the above-mentioned measurements and evaluations. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 6, which met the requirements of the present invention, multilayer containers were obtained that had excellent blow moldability and also excellent delamination resistance.

According to the present invention, a multi-layer container with excellent moldability and excellent delamination resistance can be obtained. Therefore, it can be particularly suitably used as a container for storing beverages, liquid seasonings, liquid chemicals, etc.

1 Preform 2 Infrared heater 3 Mold 4 Stretch rod 5 Multilayer container

Claims (8)

a polyester-based resin layer containing an aromatic polyester resin (X);
A multi-layer container having a polyglycolic acid-based resin layer containing polyglycolic acid (Y),
the polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer has a dispersity B ( _Mw / _Mn ) of 3.5 to 7.0 , the raw material polyglycolic acid (Y0) before the polyglycolic acid-based resin layer is formed has a dispersity A ( _Mw /Mn ₎ of 2.0 to 6.0, and the ratio of dispersity B to dispersity A (dispersity B/dispersity A) is 1.2 to 1.8 ; and the multilayer container has a three-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order from the outside of the container . the polyglycolic acid-based resin layer further contains a polyamide resin (Z),
the polyamide resin (Z) comprises a polyamide resin (Z-1) having a constitutional unit derived from a diamine and a constitutional unit derived from a dicarboxylic acid, in which 70 mol % or more of the constitutional units derived from the diamine are constitutional units derived from xylylenediamine, and 70 mol % or more of the constitutional units derived from the dicarboxylic acid are constitutional units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms;
2. The multilayer container according to claim 1, wherein the mass ratio [(Y)/(Z)] of the polyglycolic acid (Y) to the polyamide resin (Z) in the polyglycolic acid-based resin layer is 60/40 to 90/10 . The multilayer container according to claim 1 or 2, wherein the aromatic polyester resin (X) has a constituent unit derived from a dicarboxylic acid and a constituent unit derived from a diol, and 90 mol % or more of the constituent units derived from the dicarboxylic acid are constituent units derived from terephthalic acid, and 90 mol % or more of the constituent units derived from the diol are constituent units derived from ethylene glycol. 4. The multilayer container according to claim 1 , wherein the thickness of all layers of the multilayer container is 200 to 400 μm . The multilayer container according to any one of claims 1 to 4 , which has a capacity of 200 to 600 mL. A method for producing a multilayer container comprising the following steps 1 and 2:
A method for producing a multilayer container, wherein the polyglycolic acid (Y) contained in the polyglycolic acid-based resin layer in the multilayer container obtained in step 2 has a dispersity B ( _Mw / _Mn ) of 3.5 to 7.0 , the raw material polyglycolic acid (Y0) used in step 1 has a dispersity A ( _Mw / _Mn ) of 2.0 to 6.0, and the ratio of dispersity B to dispersity A (dispersity B/dispersity A) is 1.2 to 1.8 , and the multilayer container has a three-layer structure in which a polyester-based resin layer/a polyglycolic acid-based resin layer/a polyester-based resin layer are laminated in this order from the outside of the container .
Step 1: A step of feeding a polyester-based resin containing an aromatic polyester resin (X) and raw material polyglycolic acid (Y0) or a polyglycolic acid-based resin mixture obtained by mixing raw material polyglycolic acid (Y0) with another resin to a molding machine to form a multilayer preform having a polyester-based resin layer and a polyglycolic acid-based resin layer. Step 2: A step of blow molding the multilayer preform obtained in step 1 to obtain a multilayer container having a polyester-based resin layer containing an aromatic polyester resin (X) and a polyglycolic acid-based resin layer containing polyglycolic acid (Y). 7. The method for producing a multilayer container according to claim 6 , wherein the multilayer preform obtained in step 1 is stored until the moisture content of the multilayer preform reaches 5,000 to 25,000 ppm, and then is subjected to step 2. the other resin used in the polyglycolic acid-based resin mixture in step 1 is a polyamide resin (Z), and the mass ratio of the polyglycolic acid (Y) to the polyamide resin (Z) [(Y)/(Z)] is 60/40 to 90/10;
The method for producing a multilayer container according to claim 6 or 7, wherein the polyamide resin (Z) contains a polyamide resin (Z-1) having a constitutional unit derived from a diamine and a constitutional unit derived from a dicarboxylic acid, in which 70 mol % or more of the constitutional units derived from the diamine are constitutional units derived from xylylenediamine, and 70 mol % or more of the constitutional units derived from the dicarboxylic acid are constitutional units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms.