Multilayer container and multilayer preform

Abstract

To provide a multilayer container having high sanitation performance and high environmental load reduction performance.SOLUTION: A multilayer container according to the present invention comprises a mouth part, a shoulder part, a trunk part and a bottom part, and has an inner layer and an outer layer. The inner layer is constituted of virgin polyester, and the outer layer is constituted of recycled polyester. The virgin polyester constituting the inner layer is one or more polyester selected from manganese catalyst polyester, titanium catalyst polyester, aluminum catalyst polyester, lithium catalyst polyester and germanium catalyst polyester.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-layer container and a multi-layer preform used in the manufacture of the multi-layer container. [Background technology]

[0002] Polyesters such as polyethylene terephthalate are widely used in the manufacture of containers for filling beverages and the like because they are inexpensive and have excellent mechanical properties, chemical stability, heat resistance, gas barrier properties, transparency, and the like.

[0003] The polyesters used in the manufacture of containers are either those using an antimony catalyst (hereinafter referred to as antimony-catalyzed polyester) or those using a germanium catalyst (hereinafter referred to as germanium-catalyzed polyester) as a synthesis catalyst, with antimony-catalyzed polyester being particularly widely used from a cost perspective.

[0004] Incidentally, in recent years, for the purpose of reducing the environmental burden, containers have been produced using polyester obtained by recycling used polyester containers by various methods (hereinafter referred to as recycled polyester).

[0005] However, polyester containers are not recycled for each catalyst used in polyester synthesis, so there is a high possibility that the recycled polyester will contain antimony catalysts. In addition, it is difficult to completely remove contaminants when recycling polyester containers.

[0006] Therefore, when polyester containers are repeatedly recycled, contaminants and antimony catalysts that could not be removed accumulate, raising concerns that they may leach into the contents. Furthermore, in convenience stores and the like, containers filled with the contents are placed upright and heated in a hot water heater before being sold. When the products are heated in this manner, the elution of antimony is particularly problematic. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems, and the problem it aims to solve is to provide a multi-layer container that has high hygiene and high environmental load reduction properties, in which the leaching of antimony and contaminants into the contents does not pose a problem even when the container is heated. Another object of the present invention is to provide a multi-layer preform for use in producing the multi-layer container. [Means for solving the problem]

[0008] The multi-layer container of the present invention has a mouth portion, a shoulder portion, a body portion, and a bottom portion, An inner layer and an outer layer, The inner layer is made of virgin polyester, The outer layer is made of recycled polyester, The virgin polyester constituting the inner layer is characterized in that it is one or more polyesters selected from manganese catalyzed polyesters, titanium catalyzed polyesters, aluminum catalyzed polyesters, lithium catalyzed polyesters, and germanium catalyzed polyesters.

[0009] In one embodiment, the multi-layer container of the present invention has an eluted antimony concentration of less than 6 ppb.

[0010] In one embodiment, the content of the recycled polyester is 40 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the total amount of the resin material contained in the multilayer container.

[0011] In one embodiment, the thickness of the inner layer is equal to or greater than 0.01 mm and equal to or less than 0.21 mm.

[0012] In one embodiment, the multi-layer container of the present invention is a heating container.

[0013] The multilayer preform of the present invention is a multilayer preform for producing the multilayer container described above, The container has a mouth, a body, and a bottom, An inner layer and an outer layer, The inner layer is made of virgin polyester, The outer layer is made of recycled polyester, The virgin polyester constituting the inner layer is characterized in that it is one or more polyesters selected from manganese catalyzed polyesters, titanium catalyzed polyesters, aluminum catalyzed polyesters, lithium catalyzed polyesters, and germanium catalyzed polyesters. Effect of the Invention

[0014] According to the present invention, it is possible to provide a multilayer container having high hygiene and a high reduction in the environmental load, and also to provide a multilayer preform used for producing the multilayer container. Furthermore, the multilayer container of the present invention has an inner layer made of virgin polyester and an outer layer made of recycled polyester, but it is relatively easy to adjust the thickness of each layer in a two-layer container, and the amount of recycled polyester used in the outer layer can be easily increased. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a multilayer container of the present invention. [Diagram 2] 1 is a schematic cross-sectional view showing one embodiment of a multilayer container of the present invention. [Diagram 3] FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer preform of the present invention. [Figure 4] FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer preform of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (Multilayer container) As shown in FIG. 1, the multilayer container 10 of the present invention has an inner layer 11 and an outer layer 12. Furthermore, the multilayer container 10 of the present invention may have a vapor-deposited film on the surface of the inner layer 11 (not shown).

[0017] In one embodiment, the multi-layer container 10 includes a mouth 13, a shoulder 14, a body 15, and a bottom 16. In one embodiment, the shoulder 14 is provided between the mouth 13 and the body 15, and has a shape in which the diameter gradually increases from the mouth 13 side toward the body 15 side.

[0018] In one embodiment, as shown in Figure 1 etc., mouth portion 13 includes a threaded portion 17 to which a cap is screwed, a cap 18 below threaded portion 17, and a support ring 19 below cap 18. Also, in one embodiment, as shown in Figure 1 etc., bottom portion 16 includes a depressed portion 20 located in the center and a grounding portion 21 provided around depressed portion 20. This configuration makes it possible to prevent deformation of the container due to an increase or decrease in internal pressure when heated contents are filled into the multilayer container or when the container is heated after filling. In one embodiment, the body 15 of the multi-layer container 10 includes a panel portion 22. This configuration makes it possible to prevent deformation of the container due to an increase or decrease in internal pressure when the multi-layer container is filled with heated contents or when the container is heated after filling.

[0019] The eluted antimony concentration of the multilayer container of the present invention is preferably less than 6 ppb, and more preferably less than 3 ppb. By controlling the eluted antimony concentration to less than 6 ppb, the value recommended by the U.S. Food and Drug Administration (FDA) in 21 CFR (Chapter 21 of the Code of Federal Regulations) is met, which is preferable. Depending on the type of contents to be filled in the multilayer container of the present invention, there may be cases where the contents already contain a small amount of antimony. By setting the eluted antimony concentration of the multilayer container to less than 3 ppb, the amount of antimony ultimately dissolved in the contents can be reduced. In the present invention, the "dissolved antimony concentration of the multilayer container" is measured by filling the multilayer container of the present invention with ultrapure water at 23°C, leaving it upright in an environment at 70°C for 14 days, and then measuring the water removed from the multilayer container.

[0020] The outer layer of the multilayer container of the present invention is made of recycled polyester as described below, and the content of this recycled polyester is preferably 40 parts by mass or more and 95 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of the total amount of resin material contained in the multilayer container. By setting the content of recycled polyester to 40 parts by mass or more per 100 parts by mass of the total amount of resin materials contained in the multilayer container, the environmental load of the multilayer container can be further reduced. By setting the content of recycled polyester to 95 parts by mass or less per 100 parts by mass of the total amount of resin material contained in the multilayer container, it is possible to prevent the recycled polyester from being exposed to the inner layer during the production of the multilayer container.

[0021] The volume / weight of the multilayer container of the present invention is preferably 5 mL / g or more and 50 mL / g or less, and more preferably 8 mL / g or more and 45 mL / g or less. By setting the volume / weight of the multilayer container to 5 mL / g or more, the blow moldability of the multilayer container can be improved. Furthermore, by setting the volume / weight of the multilayer container to 50 mL / g or less, the heat resistance and strength of the multilayer container can be improved.

[0022] The multilayer container of the present invention can prevent antimony and other substances from leaching into the contents even when filled with high-temperature contents or when the contents are heated after filling, and is highly hygienic, making it suitable for use as a heating container.

[0023] (Inner layer) The inner layer of the multilayer container of the present invention is characterized in that it is made of virgin polyester selected from manganese catalyzed polyester, titanium catalyzed polyester, aluminum catalyzed polyester, lithium catalyzed polyester and germanium catalyzed polyester. With such a configuration, even if recycled polyester is used for the outer layer, antimony can be prevented from eluting into the contents. In the present invention, the term "virgin polyester" refers to polyester that has not been subjected to the recycling treatment described below, that is, unused polyester.

[0024] Examples of the manganese catalyst include fatty acid manganese salts such as manganese acetate, manganese carbonate, manganese chloride, manganese acetylacetonate salts, and manganese hydroxide. Examples of the titanium catalyst include titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and tetrabenzyl titanate, titanium oxides obtained by hydrolysis of titanium alkoxides, titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanic acid-aluminum hydroxide mixtures, titanium chloride, titanium chloride-aluminum chloride mixtures, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, and titanium acetylacetonate. Examples of aluminum catalysts include aluminum trisacetylacetate, aluminum monoacetylacetonate bis(ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate. Examples of the lithium catalyst include ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium. Examples of germanium catalysts include germanium dioxide, germanium tetroxide, germanium tetramethoxide, germanium tetraethoxide, germanium tetrapropoxide, germanium tetrabutoxide, germanium tetrapentoxide, and germanium tetrahexoxide.

[0025] In the present invention, the term "polyester" refers to a copolymer of a dicarboxylic acid compound and a diol compound. Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorene acid, and ester derivatives thereof. Examples of the diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecane dimethanol, tricyclodecane ethanol, tetracyclododecane dimethanol, tetracyclododecane diethanol, decalin dimethanol, decalin diethanol, 5-cyclohexanediol ... -methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamantanediol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, and pentaerythritol. Among polyesters, polyethylene terephthalate, which is a copolymer of terephthalic acid and ethylene glycol, or modified polyethylene terephthalate in which a copolymerization monomer is added to this, is preferred.

[0026] As long as the characteristics of the present invention are not impaired, the polyester may contain monomers other than the dicarboxylic acid compound and the diol compound, but the content thereof is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 3 mol % or less, based on the total structural units.

[0027] The inner layer may contain additives, provided that they do not impair the properties of the present invention. Examples of such additives include oxygen absorbers, gas barrier resins (polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6)), plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, slip agents, mold release agents, antioxidants, ion exchange agents, acetaldehyde absorbers (e.g., AA Scavengers manufactured by Color Matrix), and colorants.

[0028] In the multilayer container 10 of the present invention, the inner layer 11 is preferably provided in a content filling region, as shown in Fig. 1. In the present invention, the "content filling region" refers to a region where the content comes into contact with the multilayer container when the multilayer container is filled with the content and placed upright. In one embodiment, the inner layer 11 is preferably provided from a position 70 mm below the upper end of the mouth portion 13 to the bottom portion 16 . More preferably, the inner layer 11 is provided from a position 15 mm below the upper end of the mouth portion 13 to the bottom portion 16. With such a configuration, the content filling area can be covered with the inner layer, and even if recycled polyester is used for the outer layer, antimony elution into the content can be effectively prevented. More preferably, in the multilayer container 10 of the present invention, the inner layer 11 is provided from the upper end of the mouth 13 to the bottom 16 as shown in Fig. 2. By using recycled polyester for the outer layer, it is possible to effectively prevent antimony from eluting into the contents even when the container is stored at a temperature of 200° C. in a vending machine or the like while lying on its side.

[0029] The thickness of the inner layer in the multi-layer container is preferably 0.01 mm or more and 0.21 mm or less, and more preferably 0.025 mm or more and 0.1 mm or less. By making the thickness of the inner layer in the multi-layer container 0.01 mm or more, it is possible to effectively prevent antimony from eluting into the contents, even when recycled polyester is used for the outer layer. Furthermore, by setting the thickness of the inner layer in the multilayer container to 0.21 mm or less, the proportion of the outer layer in the multilayer container can be increased, thereby further improving the environmental load reduction of the multilayer container.

[0030] (outer layer) The outer layer of the multilayer container of the present invention is made of recycled polyester. By adopting such a configuration, it is possible to improve the reduction of the environmental load of the multilayer container of the present invention.

[0031] In the present invention, the term "recycled polyester" refers to chemically recycled polyester or mechanically recycled polyester. Chemically recycled polyester refers to polyester obtained by breaking down polyester containers down to the monomer level and then repolymerizing them. Mechanically recycled polyester refers to polyester obtained by sorting, crushing and washing polyester containers to remove contaminants and foreign matter to obtain flakes, and then treating the flakes for a certain period of time under high temperature and reduced pressure to remove contaminants from within the resin.

[0032] The outer layer may contain additives, provided that they do not impair the properties of the present invention. Examples of such additives include oxygen absorbers, gas barrier resins (polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6)), plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, slip agents, mold release agents, antioxidants, ion exchange agents, acetaldehyde absorbers (e.g., AA Scavengers manufactured by Color Matrix), and colorants.

[0033] The thickness of the outer layer in the multi-layer container is preferably 0.04 mm or more and 0.33 mm or less, and more preferably 0.1 mm or more and 0.2 mm or less. By setting the thickness of the outer layer in the multilayer container to 0.04 mm or more, the environmental load of the multilayer container can be further reduced. Furthermore, by setting the thickness of the outer layer in the multi-layer container to 0.33 mm or less, it is possible to prevent the recycled polyester from being exposed to the inner layer side during the production of the multi-layer preform.

[0034] (evaporated film) The multilayer container of the present invention may have a vapor-deposited film on the surface of the inner layer, thereby improving the gas barrier properties of the multilayer container.

[0035] Examples of the vapor-deposited film include vapor-deposited films composed of metals such as aluminum, inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide, organic silicon compounds such as hexamethyldisiloxane, and hard carbon films such as DLC (Diamond Like Carbon) films. The hard carbon film made of DLC is also called i-carbon film or hydrogenated amorphous carbon film (aC:H), and is an amorphous carbon film mainly composed of SP3 bonds.

[0036] The thickness of the deposited film is not particularly limited, and can be, for example, 1 nm or more and 150 nm or less.

[0037] The deposition film can be formed by a conventional method, for example, physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0038] (Multi-layer preform) The multilayer preform 23 of the present invention is used for producing the multilayer container, and has an inner layer 24 and an outer layer 25 as shown in FIGS.

[0039] In one embodiment, the multi-layer preform 23 includes a mouth portion 26, a body portion 27, and a bottom portion 28, as shown in FIGS.

[0040] (Inner layer) The inner layer may be provided so as to cover the lower end of the mouth portion 26 to the bottom portion 28 as shown in Fig. 3, or may be provided so as to cover the upper end of the mouth portion 26 to the bottom portion 28 as shown in Fig. 4. Alternatively, the inner layer may be provided so as to cover the body portion 27 and the bottom portion 28 (not shown). The material constituting the inner layer has been described above, and therefore will not be described here.

[0041] The thickness of the inner layer in the multi-layer preform is preferably 0.1 mm or more and 1.2 mm or less, and more preferably 0.2 mm or more and 0.5 mm or less. By making the thickness of the inner layer in the multi-layer preform 0.1 mm or more, it is possible to effectively prevent antimony from eluting into the contents, even when recycled polyester is used for the outer layer. By setting the thickness of the inner layer in the multilayer preform to 1.2 mm or less, the proportion of the outer layer in the multilayer container can be increased, and the environmental load of the multilayer container can be further reduced.

[0042] (outer layer) The material constituting the outer layer has been described above, and therefore will not be described here.

[0043] The thickness of the outer layer in the multi-layer preform is preferably 1.2 mm or more and 3.5 mm or less, and more preferably 1.9 mm or more and 2.2 mm or less. By setting the thickness of the outer layer in the multilayer preform to 1.2 mm or more, the environmental load of the multilayer container can be further reduced. Furthermore, by setting the thickness of the outer layer in the multi-layer preform to 3.5 mm or less, it is possible to prevent the recycled polyester from being exposed to the inner layer side during the production of the multi-layer preform.

[0044] (Manufacturing method of multi-layer container) The multilayer container of the present invention can be manufactured by producing a multilayer preform by co-injection molding the materials constituting the above-mentioned inner layer and outer layer, and then blow molding the multilayer preform. The position where the inner layer is formed can be adjusted by the injection molding conditions such as the resin temperature.

[0045] The multilayer container of the present invention can also be produced by utilizing two-color molding or insert molding. Furthermore, the multilayer container of the present invention can be produced by injection molding virgin polyester into an inner mold to form an inner layer, retracting the inner mold to provide a gap between the inner mold and the inner layer, and then injection molding recycled polyester into this gap to form an outer layer. EXAMPLES

[0046] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0047] Example 1 Virgin polyester (germanium-catalyzed PET, J-125S, manufactured by Mitsui Chemicals, Inc.) and mechanically recycled polyester (NA-BT7906, manufactured by Kyoei Sangyo Co., Ltd.) were prepared. These were co-injected using an injection molding machine to create a multi-layer (two-layer, two-type) preform shown in Figure 4, which has an inner layer made of virgin polyester and an outer layer made of mechanically recycled polyester. The amount of mechanically recycled polyester used was adjusted to 80 parts by mass per 100 parts by mass of the resin material constituting the multi-layer preform. The body of the multi-layer preform had a thickness of 2.8 mm and a weight per unit area of ​​22 g.

[0048] Next, the multilayer preform was heated to 110° C. and subjected to biaxial stretch blow molding in a blow molding die to obtain a multilayer container having a capacity of 500 mL as shown in FIG.

[0049] Comparative Example 1 A single-layer preform was produced in the same manner as in Example 1, except that only the mechanically recycled polyester was used, and this was then biaxially stretched and blow molded to produce a container with a capacity of 500 mL.

[0050] Comparative Example 2 A single-layer preform was produced in the same manner as in Example 1, except that only the above virgin polyester was used, and this was then biaxially stretched and blow molded to produce a container with a capacity of 500 mL.

[0051] Comparative Example 3 A single-layer preform was produced using only virgin polyester (antimony-catalyzed PET, Shinkogosen, 5015W), and this was then biaxially stretched and blow molded to produce a single-layer container with a capacity of 500 mL.

[0052] <<Evaluation of eluted antimony concentration>> The containers obtained in the above Examples and Comparative Examples were filled with 480 mL of ultrapure water. In each container, the ultrapure water was filled from a position 28.7 mm from the top end of the mouth to the bottom. Next, the sample was placed in a hot water heater set at 70° C. and left standing upright for 14 days. After the container was left to stand, the water was removed and its antimony concentration was measured by inductively coupled plasma mass spectrometry (ICP-MS). The measurement results are summarized in Table 1.

[0053] <<Heat resistance evaluation>> The containers obtained in the above Examples and Comparative Examples were filled with 480 mL of water and then capped. It was immersed in 70°C hot water for 80 minutes. After immersion, the container was placed upright on a flat desk and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1. (Evaluation Criteria) OK: The container is upright. NG: It didn't stand upright and fell over.

[0054] <<Reduced environmental impact>> Based on the content of recycled polyester per 100 parts by mass of the total amount of the resin material contained in the containers obtained in the above Examples and Comparative Examples, the level of environmental load reduction was defined as follows. OK: Recycled polyester content is 30 parts by mass or more NG: Recycled polyester content is less than 30 parts by mass

[0055] [Table 1]

[0056] As is clear from the above table, the multilayer container of the present invention has excellent environmental load reducing properties. Furthermore, the multilayer container of the present invention has high heat resistance and can effectively reduce the concentration of eluted antimony after heating, and can therefore be suitably used as a heating container. [Explanation of symbols]

[0057] 10: multi-layer container, 11: inner layer, 12: outer layer, 13: mouth, 14: shoulder, 15: body, 16: bottom, 17: screw, 18: cap, 19: support ring, 20: recess, 21: ground contact, 22: panel, 23: multi-layer preform, 24: inner layer, 25: outer layer, 26: mouth, 27: body, 28: bottom

Claims

1. A step of manufacturing a multilayer preform by co-injecting the materials constituting the inner layer and the outer layer, A method for manufacturing a multilayer container, comprising the step of manufacturing a multilayer container by blow molding the multilayer preform, The multilayer container has the inner layer and the outer layer, The inner layer is made of virgin polyester, The outer layer is made of recycled polyester, The amount of recycled polyester is 40 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the total amount of resin material contained in the multilayer container. The virgin polyester constituting the inner layer is one or more polyesters selected from manganese catalyst polyester, titanium catalyst polyester, aluminum catalyst polyester, lithium catalyst polyester, and germanium catalyst polyester. The recycled polyester constituting the outer layer contains antimony, The thickness of the inner layer is 0.01 mm or more and 0.21 mm or less. A method for manufacturing a multilayer container, characterized by the following:

2. A method for manufacturing a multilayer container according to claim 1, wherein 480 mL of ultrapure water is filled into the multilayer container having a capacity of 500 mL, and then the container is left standing upright in a hot warmer set to 70°C for 14 days, after which the water is removed from the multilayer container, and the eluted antimony concentration, which is the amount of antimony contained in the water measured by inductively coupled plasma mass spectrometry (ICP-MS), is less than 6 ppb.

3. The method for manufacturing a multilayer container according to claim 1 or 2, wherein the multilayer container is a heating container.

4. A method for manufacturing a multilayer preform, comprising the step of producing a multilayer preform by co-injection molding the materials constituting the inner layer and the outer layer, The multilayer preform is a multilayer preform used in the method for manufacturing a multilayer container according to any one of claims 1 to 3, The multilayer preform comprises the inner layer and the outer layer, The inner layer is made of virgin polyester, The outer layer is made of recycled polyester, The amount of recycled polyester is 40 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the total amount of resin material contained in the multilayer container. The virgin polyester constituting the inner layer is one or more polyesters selected from manganese catalyst polyester, titanium catalyst polyester, aluminum catalyst polyester, lithium catalyst polyester, and germanium catalyst polyester. The recycled polyester constituting the outer layer contains antimony, A method for manufacturing a multilayer preform, characterized by the above.

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