Multilayered hollow container, method for manufacturing the same, and method for manufacturing recycled polyester

Abstract

A multilayer hollow container, a method for manufacturing the same, and a method for manufacturing a recycled polyester provided with a process of recovering a polyester from the aforementioned multilayer hollow container, the multilayer hollow container having: a polyester layer containing a polyester resin (X), and a polyamide layer containing a polyamide resin (Y) and a yellowing inhibitor (A), the polyamide layer being an intermediate layer, present from a ground portion to a position of 10 to 70% of a container height.

Description

Technical Field

[0001] This invention relates to multilayer hollow containers, methods for manufacturing the same, and methods for manufacturing recycled polyester. Background Technology

[0002] Containers used for holding reactive liquids such as chlorine-based bleach are mainly made of polyolefins such as polyethylene. This is because polyolefins have a molecular skeleton that is basically composed of hydrocarbons and do not have highly reactive parts within the molecule. Therefore, they can prevent deterioration caused by alkalis, hypochlorites, etc. contained in bleach.

[0003] Polyester resins, represented by polyethylene terephthalate (PET), possess excellent appearance characteristics such as transparency and gloss, as well as superior mechanical properties, aroma retention, gas barrier properties, and reusability. Therefore, polyester resins are widely used in various packaging materials such as films, sheets, and hollow containers. However, due to the presence of ester bonds, they are susceptible to hydrolysis when stored in alkaline chlorine-based bleaching agents, leading to deterioration of their mechanical properties during long-term storage.

[0004] There have also been attempts to use polyester resins with the aforementioned excellent properties in containers for chlorine-based bleach. For example, Patent Document 1 discloses a container for a chlorine-based liquid bleach composition for the purpose of improving transparency and suppressing cracking, which is formed from a resin composition containing a specific amount of polyester resin and a specific polyamide resin.

[0005] On the other hand, polyamide resins, such as poly(dimethyl adipamide), are used, particularly to improve the gas barrier properties of containers. However, yellowing due to the thermal process of polyamide-containing polyester resin compositions is more likely to occur than that of polyester alone. Therefore, yellowing occurs, especially during the recycling process of recycled container resins. This reduces the commercial value of packaging containers, and thus, research has been conducted to suppress yellowing. For example, Patent Document 2 discloses a method for manufacturing a multilayer container and recycled polyester, wherein the multilayer container comprises: a polyester resin composition layer containing a polyester resin and an amino-containing compound with yellowing-inhibiting ability, and a polyamide resin layer containing a polyamide resin.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2017 / 150109

[0009] Patent Document 2: International Publication No. 2017 / 057463 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] When reactive liquids such as chlorine bleach are contained in containers with polyester resin as the main substrate, problems such as deterioration of mechanical properties and cracking of the container, as mentioned above, occur. Although the container in Patent Document 1 can suppress cracking to some extent, it requires higher resistance to bleach and the like.

[0012] According to the manufacturing method of Patent Document 2, although the gas barrier properties and yellowing of recycled polyester are suppressed, there is room for improvement in the resistance to delamination (peel resistance) due to impact, etc., and there is a problem that a relatively large amount of yellowing inhibitor must be used.

[0013] Therefore, there is a need for containers that can maintain mechanical properties when storing bleach and other chemicals for a long period of time, and that do not delaminate when subjected to impacts, etc., and that produce recycled polyester with minimal yellowing even when the polyester used in the container is reused.

[0014] The objective of this invention is to provide: a multilayer hollow container that combines resistance to reactive liquids such as bleach, particularly crack resistance and delamination resistance, further suppresses yellowing of recycled polyester during reuse, and provides recycled polyester with suppressed color change, a method for manufacturing the same, and a method for manufacturing recycled polyester with suppressed color change.

[0015] Solution for solving the problem

[0016] In view of the above-mentioned problems, the inventors conducted in-depth research and found that: using a polyamide layer containing a yellowing inhibitor as an intermediate layer, and having a polyester layer and the intermediate layer in a specific part, a multilayer hollow container can solve the aforementioned problems, thus completing the present invention.

[0017] The present invention provides the following [1] to

[24] .

[0018] [1] A multi-layer hollow container, comprising:

[0019] A polyester layer containing polyester resin (X), and

[0020] A polyamide layer comprising polyamide resin (Y) and a yellowing inhibitor (A),

[0021] The polyamide layer is an intermediate layer, and it extends from the grounding part to a position of 10-70% of the container height.

[0022] [2] According to the multilayer hollow container described in [1] above, the aforementioned polyamide layer is substantially continuous from the grounding portion to a position of 10% of the container height.

[0023] [3] According to the multilayer hollow container described in [1] or [2] above, the polyamide resin (Y) has structural units derived from diamine and structural units derived from dicarboxylic acid, wherein the structural units derived from diamine contain more than 80 mol% structural units derived from phenylenediamine and the structural units derived from dicarboxylic acid contain more than 80 mol% structural units derived from dicarboxylic acid.

[0024] [4] The multilayer hollow container according to any one of [1] to [3] above, wherein the content of polyamide resin (Y) is 0.05 to 7.0 by mass relative to the total amount of all polyamide layers and all polyester layers.

[0025] [5] The multilayer hollow container according to any one of [1] to [4] above, wherein the polyester resin (X) has structural units derived from dicarboxylic acid and structural units derived from diol, wherein the structural units derived from dicarboxylic acid contain more than 80 mol% structural units derived from terephthalic acid and the structural units derived from diol contain more than 80 mol% structural units derived from ethylene glycol.

[0026] [6] The multilayer hollow container according to any one of [1] to [5] above, wherein the yellowing inhibitor (A) is selected from at least one of the group consisting of dyes and pigments.

[0027] [7] The multilayer hollow container according to any one of [1] to [6] above, wherein the yellowing inhibitor (A) is an anthraquinone dye.

[0028] [8] The multilayer hollow container according to any one of [1] to [7] above, wherein the content of yellowing inhibitor (A) is 1 to 30 ppm relative to the total amount of all polyamide layers and all polyester layers.

[0029] [9] The multilayer hollow container according to any one of [1] to [8] above, wherein the aforementioned polyamide layer further comprises a greening inhibitor (B).

[0030]

[10] According to the multilayer hollow container described above [9], wherein the greening inhibitor (B) is selected from at least one of the group consisting of anthraquinone dyes and azo dyes.

[0031]

[11] The multi-layer hollow container according to any one of [1] to

[10] above, wherein the multi-layer container has a 3 to 5-layer structure.

[0032]

[12] A bleaching article containing a chlorine-based liquid bleaching composition in a multi-layered hollow container as described in any one of [1] to

[11] .

[0033]

[13] According to the bleaching article described in

[12] above, the chlorine-based liquid bleaching composition contains 0.5 to 15% sodium hypochlorite by mass.

[0034]

[14] The bleaching articles according to

[12] or

[13] above, wherein the chlorine-based liquid bleaching composition contains a surfactant.

[0035]

[15] The bleaching article according to any one of

[12] to

[14] above, wherein the chlorine-based liquid bleaching composition contains an alkali agent.

[0036]

[16] A method for manufacturing a multi-layer hollow container,

[0037] The multilayer hollow container has: a polyester layer comprising polyester resin (X), and

[0038] A polyamide layer comprising polyamide resin (Y) and a yellowing inhibitor (A),

[0039] This polyamide layer is an intermediate layer, extending from the grounding portion to a position ranging from 10% to 70% of the container height.

[0040] The manufacturing method includes the following steps:

[0041] Step 1: Mix polyamide resin (Y) with yellowing inhibitor (A) to prepare a polyamide resin mixture;

[0042] Step 2 involves co-injection molding the aforementioned polyamide resin mixture with a polyester resin composition containing polyester resin (X) to obtain a multilayer preform; and,

[0043] Step 3 involves blow molding the aforementioned multi-layer preform.

[0044]

[17] According to the manufacturing method of the multilayer hollow container described above

[16] , in step 1, granular polyamide resin (Y) and yellowing inhibitor (A) are mixed at a temperature below 230°C.

[0045]

[18] In the method for manufacturing a multilayer hollow container as described in

[16] or

[17] above, in step 1, a greening inhibitor (B) is further mixed.

[0046]

[19] The method for manufacturing a multilayer hollow container according to any one of

[16] to

[18] above, wherein in step 1, polyamide resin or polyester resin is mixed with yellowing inhibitor (A) and then mixed with polyamide resin (Y).

[0047]

[20] In the method for manufacturing a multilayer hollow container as described in

[18] or

[19] above, in step 1, polyamide resin or polyester resin, yellowing inhibitor (A) and greening inhibitor (B) are mixed and then mixed with polyamide resin (Y).

[0048]

[21] A method for manufacturing recycled polyester, comprising a step of recovering polyester from a multilayer hollow container as described in any one of [1] to

[11] above.

[0049]

[22] The method for manufacturing recycled polyester according to

[21] above includes a step of removing all or part of the polyamide layer from a multilayer hollow container to recycle the aforementioned polyester.

[0050]

[23] According to the method for manufacturing recycled polyester described in

[22] above, the aforementioned multilayer hollow container is crushed and the aforementioned polyamide layer is removed by air separation.

[0051]

[24] The method for manufacturing recycled polyester according to any one of

[21] to

[23] above, wherein, after the step of recycling polyester, a step selected from one or more of the crystallization step and the solid-state polymerization step is performed.

[0052] The effects of the invention

[0053] According to the present invention, a multilayer hollow container that combines resistance to reactive liquids such as bleach, especially crack resistance and delamination resistance, further suppresses yellowing of recycled polyester during reuse, and provides recycled polyester with suppressed color change, a method for manufacturing the same, and a method for manufacturing recycled polyester with suppressed color change. Attached Figure Description

[0054] Figure 1 A side view and a perspective view are provided to illustrate one embodiment of the multi-layer container of the present invention (with a concave bottom surface).

[0055] Figure 2 A side view and a perspective view are provided to illustrate one embodiment of the multi-layer container of the present invention (with a convex bottom surface). Detailed Implementation

[0056] Multi-layer hollow container

[0057] The multilayer hollow container of the present invention comprises: a polyester layer containing polyester resin (X), and a polyamide layer containing polyamide resin (Y) and yellowing inhibitor (A), the polyamide layer being an intermediate layer, the polyamide layer being present from the ground portion to a position of 10 to 70% of the container height.

[0058] <Polyester layer>

[0059] The polyester layer contains polyester resin (X).

[0060] (Polyester resin (X))

[0061] The polyester resin (X) contained in the polyester layer is preferably a condensation polymer of dicarboxylic acid and diol, and preferably has structural units derived from dicarboxylic acid (dicarboxylic acid unit) and structural units derived from diol (diol unit).

[0062] As a dicarboxylic acid unit, structural units derived from aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids can be cited, with structural units derived from aromatic dicarboxylic acids being preferred.

[0063] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, biphenyl dicarboxylic acid, diphenyl ether-dicarboxylic acid, diphenyl sulfone-dicarboxylic acid, benzophenone-dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. From the viewpoint of cost and ease of manufacture, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid are preferred, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid are more preferred, and from the viewpoint of moldability, terephthalic acid and isophthalic acid are even more preferred, and terephthalic acid is even more preferred.

[0064] It should be noted that, as an aromatic dicarboxylic acid, an alkyl ester of an aromatic dicarboxylic acid with 1 to 4 carbon atoms can also be used.

[0065] When reusing the multilayer hollow container of the present invention, it is sometimes melt-blended with a single-layer container formed from existing polyester resin. By having units derived from terephthalic acid as dicarboxylic acid units, the multilayer hollow container of the present invention exhibits good compatibility with existing single-layer containers, resulting in good reusability.

[0066] As aromatic dicarboxylic acids, sulfophthalic acid and its metal salts can also be used. Sulfophthalic acid metal salts are the metal salts of sulfophthalic acid, and examples of metal atoms for this purpose include alkali metals and alkaline earth metals.

[0067] Specifically, sulfophthalic acid or sulfophthalic acid metal salts are represented by the following formulas (I) or (I').

[0068]

[0069] In the above formula (I'), M is a metal atom. n represents the valence of M.

[0070] Examples of metal atoms that can be M include alkali metals such as lithium, sodium, and potassium, and alkaline earth metals such as beryllium, magnesium, calcium, and strontium. Alkali metals are preferred, sodium or lithium are preferred, and sodium is more preferred. It should be noted that when n is 2 or more, M can be cross-linked with other units (e.g., other sulfophthalic acid units or sulfonyl groups in sulfophthalic acid metal salt units).

[0071] In the above equations (I) and (I'), R A This refers to substituted or unsubstituted alkyl groups, or substituted or unsubstituted aryl groups. m represents an integer from 0 to 3. It should be noted that when m is 2 or 3, each R... A Choose either the same or different.

[0072] Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-octyl, and 2-ethylhexyl. Among these, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 4 carbon atoms are more preferred.

[0073] Examples of aryl groups include phenyl and naphthyl groups. Among these, aryl groups with 6 to 12 carbon atoms are preferred, and phenyl groups are more preferred.

[0074] Examples of substituents that may be optionally present in the alkyl and aryl groups include halogen atoms such as chlorine, bromine, and iodine atoms, as well as alkyl, alkenyl, aryl, cyano, hydroxyl, nitro, alkoxy, aryloxy, acyl, amino, mercapto, alkylthio, and arylthio groups. Among these groups, those containing hydrogen atoms may optionally be further substituted by the aforementioned substituents.

[0075] As R A Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, 1-methylpropyl, 2-methylpropyl, hydroxymethyl, 1-hydroxyethyl, mercaptomethyl, methylthioethyl, phenyl, naphthyl, biphenyl, benzyl, and 4-hydroxybenzyl, with methyl, ethyl, and benzyl being preferred.

[0076] In the above equations (I) and (I'), R B It represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0077] For the preferred R A As mentioned above, however, when using sulfophthalic acid or sulfophthalic acid metal salts as polyester resin (X), m=0 is preferred, i.e., the benzene ring is not affected by R. A The units that are replaced, represented by the following formulas (Ia) or (I'a), respectively.

[0078]

[0079] In the above formula (Ia), R B R in the aforementioned equation (I)B same.

[0080] In addition, in the above formula (I'a), R B M, and n are related to R in the aforementioned equation (I'). B M and n are the same.

[0081] Furthermore, as sulfophthalic acid represented by the aforementioned formula (Ia), or as a sulfophthalic acid metal salt represented by the aforementioned formula (I'a), examples include a phthalic acid structure with two -CO- bonds at the ortho position, an isophthalic acid structure bonded at the meta position, and a terephthalic acid structure bonded at the para position, wherein the isophthalic acid structure is preferred. That is, at least one of sulfophthalic acid represented by the following formula (Ib) and a sulfophthalic acid metal salt represented by the following formula (I'b) is preferred.

[0082]

[0083] In the above formula (Ib), R B R in the aforementioned equation (I) B same.

[0084] In the above formula (I'b), R B M, and n are related to R in the aforementioned equation (I'). B M and n are the same.

[0085] The sulfonyl group in sulfoisophthalic acid or its metal salt can be at positions 2, 4, 5, or 6, but a substituted group at position 5, represented by formula (Ic) or (I'c), is preferred.

[0086]

[0087] In the above formula (Ic), R B R in the aforementioned equation (I) B same.

[0088] In the above formula (I'c), R B M and n are related to R in the aforementioned equation (I'). B M and n are the same.

[0089] In polyester resin (X), examples of sulfoisophthalic acid or sulfoisophthalic acid metal salts represented by the aforementioned formula (Ic) or formula (I'c) include 5-sulfoisophthalic acid, sodium 5-sulfoisophthalate, lithium 5-sulfoisophthalate, potassium 5-sulfoisophthalate, calcium bis(5-sulfoisophthalate), dimethyl sodium 5-sulfoisophthalate, and diethyl sodium 5-sulfoisophthalate.

[0090] When the polyester resin (X) contains structural units derived from at least one of the groups selected from sulfophthalic acid and sulfophthalic acid metal salts, it is preferable to contain at least structural units derived from sulfophthalic acid metal salts. The content of structural units derived from sulfophthalic acid and sulfophthalic acid metal salts in the polyester resin is preferably 0.01 to 15 mol% of the total dicarboxylic acid structural units, more preferably 0.03 to 10.0 mol%, further preferably 0.06 to 5.0 mol%, and even more preferably 0.08 to 2.0 mol%.

[0091] Examples of alicyclic dicarboxylic acids include cyclohexane dicarboxylic acid, norbornene dicarboxylic acid, and tricyclodecane dicarboxylic acid.

[0092] Examples of aliphatic dicarboxylic acids include malonic acid, succinic acid, adipic acid, azelaic acid, and sebacic acid.

[0093] As diol units, examples include structural units derived from aliphatic diols, structural units derived from alicyclic diols, and structural units derived from aromatic diols, with structural units derived from aliphatic diols being preferred.

[0094] Examples of aliphatic diols include ethylene glycol, 2-buten-1,4-diol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, methylpentyl glycol, and diethylene glycol. Among these, ethylene glycol is preferred.

[0095] Examples of alicyclic diols include cyclohexanediol, isosorbide, spirocyclodiol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, norbornenediol, and tricyclodecanediol.

[0096] Examples of aromatic diols include bisphenol compounds and hydroquinone compounds.

[0097] Polyester resin (X) can also have structural units derived from hydroxycarboxylic acids.

[0098] Examples of hydroxycarboxylic acids include aliphatic hydroxycarboxylic acids, alicyclic hydroxycarboxylic acids, and aromatic hydroxycarboxylic acids.

[0099] Examples of aliphatic hydroxycarboxylic acids include 10-hydroxyoctadecanoic acid, lactic acid, hydroxyacrylic acid, 2-hydroxy-2-methylpropionic acid, and hydroxybutyl acid.

[0100] Examples of alicyclic hydroxycarboxylic acids include hydroxymethylcyclohexane carboxylic acid, hydroxymethyl norbornene carboxylic acid, and hydroxymethyl tricyclodecane carboxylic acid.

[0101] Examples of aromatic hydroxycarboxylic acids include hydroxybenzoic acid, hydroxytoluic acid, hydroxynaphthoic acid, 3-(hydroxyphenyl)propionic acid, hydroxyphenylacetic acid, and 3-hydroxy-3-phenylpropionic acid.

[0102] Polyester resin (X) can also have structural units derived from monofunctional compounds and structural units derived from polyfunctional compounds.

[0103] Examples of monofunctional compounds include monocarboxylic acids and monohydric alcohols. Specifically, examples include aromatic monocarboxylic acids, aliphatic monocarboxylic acids, aromatic monohydric alcohols, aliphatic monohydric alcohols, and alicyclic monohydric alcohols.

[0104] Examples of multifunctional compounds include aromatic polycarboxylic acids, alicyclic polycarboxylic acids, aliphatic polyols, alicyclic polyols, and their esters.

[0105] The polyester resin (X) preferably has structural units derived from dicarboxylic acids and structural units derived from diols, wherein the structural units derived from dicarboxylic acids contain structural units derived from terephthalic acid, and the structural units derived from diols contain structural units derived from ethylene glycol; more preferably, it has structural units derived from dicarboxylic acids and structural units derived from diols, wherein the structural units derived from dicarboxylic acids contain at least 80 mol% of structural units derived from terephthalic acid, and the structural units derived from diols contain at least 80 mol% of structural units derived from ethylene glycol; even more preferably, it has structural units derived from dicarboxylic acids and structural units derived from diols, wherein the structural units derived from dicarboxylic acids contain at least 90 mol% of structural units derived from terephthalic acid, and the structural units derived from diols substantially contain at least 100 mol% of structural units derived from ethylene glycol.

[0106] As a specific example of polyester resin (X), polyethylene terephthalate (PET) can be cited.

[0107] Polyethylene terephthalate (PET) may also contain structural units derived from aromatic dicarboxylic acids other than terephthalic acid. Preferably, the aromatic dicarboxylic acids other than terephthalic acid are selected from one or more of isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid. These are low in cost, and the copolyester resins containing them are easy to manufacture.

[0108] Among these, isophthalic acid and naphthalenedicarboxylic acid are preferred, with isophthalic acid being more preferred. Polyethylene terephthalate containing structural units derived from isophthalic acid exhibits excellent moldability; furthermore, its slower crystallization rate enhances its ability to prevent whitening of molded articles. Additionally, polyethylene terephthalate containing structural units derived from naphthalenedicarboxylic acid raises the glass transition point of the resin, improves heat resistance, and absorbs ultraviolet light, making it suitable for manufacturing multilayer hollow containers requiring UV resistance. It should be noted that 2,6-naphthalenedicarboxylic acid is preferred as a naphthalenedicarboxylic acid component due to its ease of manufacture and high economic efficiency.

[0109] When polyethylene terephthalate contains structural units derived from aromatic dicarboxylic acids other than terephthalic acid, the proportion of the aromatic dicarboxylic acid derived from terephthalic acid is preferably 1 to 20 mol%, more preferably 1 to 10 mol%, and even more preferably 1 to 5 mol%.

[0110] It should be noted that polyester resin (X) can be used alone or in combination with two or more resins.

[0111] Polyester resin (X) can be manufactured by direct esterification or transesterification, which are known methods.

[0112] The intrinsic viscosity of the polyester resin (X) is preferably 0.5~2.0 dL / g, more preferably 0.6~1.5 dL / g. If the intrinsic viscosity is 0.5 dL / g or higher, the container has excellent mechanical properties.

[0113] It should be noted that the intrinsic viscosity was determined as follows: polyester resin was dissolved in a phenol / 1,1,2,2-tetrachloroethane (6 / 4 mass ratio) mixed solvent to prepare 0.2 g / dL, 0.4 g / dL, and 0.6 g / dL solutions, which were then measured at 25°C using an automatic viscosity measuring device (Malvern, Viscotek).

[0114] (Other ingredients)

[0115] Other components may also be present in the polyester layer. Examples of such components include heat stabilizers, light stabilizers, moisture-proof agents, waterproof agents, lubricants, and spreading agents.

[0116] The polyester layer may contain resins other than polyester resin (X) as the main component, without impairing the effects of the present invention. The content of polyester resin (X) relative to the total resin content of the polyester layer is preferably 80 to 100% by mass, more preferably 90 to 100% by mass.

[0117] <Polyamide layer>

[0118] The polyamide layer comprises polyamide resin (Y) and yellowing inhibitor (A).

[0119] By incorporating a polyamide layer, the multilayer hollow container of the present invention exhibits excellent resistance to reactive liquids such as bleach, and in particular, crack resistance. Furthermore, the use of the polyamide layer ensures good moldability and facilitates the separation and recycling of the polyester resin.

[0120] Furthermore, it is believed that by including a yellowing inhibitor (A) in the nitrogen-containing polyamide layer, which is prone to causing yellowing of recycled resin, yellowing can be effectively suppressed. In particular, it is believed that since the yellowing inhibitor remains corresponding to the amount of polyamide resin remaining in the recycled polyester resin, even when using pigments or dyes suitable as yellowing inhibitors according to the present invention, an appropriate amount of yellowing inhibitor can be included in the recycled polyester resin, resulting in recycled polyester with minimal color change, particularly colorless. Additionally, it is believed that since the polyamide layer formed in the container body with a small amount of resin contains the yellowing inhibitor (A), even a small amount of the yellowing inhibitor (A) can effectively suppress yellowing.

[0121] (Polyamide resin (Y))

[0122] Examples of polyamide resins (Y) include xylene-containing polyamide resins, nylon 6, nylon 66, nylon 666, nylon 610, nylon 11, nylon 12, and mixtures thereof. Among these, xylene-containing polyamide resins are preferred because they improve resistance to reactive liquids and facilitate separation from the polyester layer during reuse. Xylene-containing polyamide resins are preferably polyamide resins containing structural units derived from diphenylene oxide.

[0123] The xylene-containing polyamide resin is obtained by polycondensation of a diamine containing phenylenediamine and a dicarboxylic acid, and has structural units derived from phenylenediamine and structural units derived from dicarboxylic acid. For the xylene-containing polyamide resin, the diamine-derived structural units (diamine units) preferably contain 50 mol% or more of phenylenediamine-derived structural units, more preferably 70 mol% or more, further preferably 80-100 mol%, and even more preferably 90-100 mol%.

[0124] The preferred dimethylamine is m-phenylenediamine, p-phenylenediamine, or both, but m-phenylenediamine is more preferred. Furthermore, the diamine unit constituting the xylene-containing polyamide resin preferably contains 50 mol% or more of structural units derived from m-phenylenediamine, more preferably 70 mol% or more, further preferably 80-100 mol%, and even more preferably 90-100 mol%. By ensuring that the m-phenylenediamine-derived structural units in the diamine unit are within the above-mentioned range, the polyamide resin exhibits better resistance to reactive liquids.

[0125] The diamine units in polyamide resins containing xylene groups can consist only of structural units derived from phenylenediamine, but they can also contain structural units derived from diamines other than phenylenediamine. Here, examples of diamines other than phenylenediamine include ethylenediamine, tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, and 2,4,4-trimethyl-hexamethylenediamine, which are straight-chain or branched aliphatic diamines; 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)naphthane, and bis(aminomethyl)tricyclodecane, which are alicyclic diamines; and bis(4-aminophenyl)ether, p-phenylenediamine, and bis(aminomethyl)naphthalene, which are diamines with aromatic rings.

[0126] Among polyamide resins containing xylene, compounds that can form dicarboxylic acid units include α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, and dodecanoic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; other aliphatic dicarboxylic acids such as dimer acids; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, xylene dicarboxylic acid, and naphthalene dicarboxylic acid. α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms are preferred, and adipic acid and sebacic acid are more preferred. From the viewpoint of good resistance to reactive liquids, adipic acid is further preferred.

[0127] For polyamide resins containing xylene, the structural units derived from dicarboxylic acid (dicarboxylic acid units) preferably contain more than 50 mol% of structural units derived from dicarboxylic acid, more preferably more than 70 mol%, further preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%.

[0128] That is, the polyamide resin (Y) preferably has structural units derived from diamine and structural units derived from dicarboxylic acid, wherein the structural units derived from diamine contain at least 50 mol% of structural units derived from phenylenediamine and the structural units derived from dicarboxylic acid contain at least 50 mol% of structural units derived from bisaccharide; more preferably, it has structural units derived from diamine and structural units derived from dicarboxylic acid, wherein the structural units derived from diamine contain at least 80 mol% of structural units derived from phenylenediamine and the structural units derived from dicarboxylic acid contain at least 80 mol% of structural units derived from bisaccharide.

[0129] m-Phenylenediamine is preferred as the phenylenediamine.

[0130] In addition, the dicarboxylic acid unit remaining after adipic acid is preferably derived from α,ω-linear aliphatic dicarboxylic acid with 4 to 20 carbon atoms.

[0131] Furthermore, as a preferred polyamide resin containing xylene groups, examples include polyamide resins in which 70 mol% or more of the diamine units are structural units derived from phenylenediamine (preferably m-phenylenediamine), 70-99 mol% of the dicarboxylic acid units are structural units derived from acetic acid, and 1-30 mol% of the dicarboxylic acid units are structural units derived from isophthalic acid. Preferably, the aforementioned polyamide resin is a polyamide resin in which 80 mol% or more of the diamine units are structural units derived from phenylenediamine (preferably m-phenylenediamine), 80-99 mol% of the dicarboxylic acid units are structural units derived from acetic acid, and 1-20 mol% of the dicarboxylic acid units are structural units derived from isophthalic acid.

[0132] By adding isophthalic acid units as dicarboxylic acid units, the melting point is lowered, which can reduce the molding processing temperature. Therefore, thermal degradation during molding can be suppressed. In addition, the crystallization time is delayed, thereby improving stretch formability.

[0133] In addition to the aforementioned diamines and dicarboxylic acids, as components constituting xylene-containing polyamide resins, lactams such as ε-caprolactam and laurolactam, aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid, and aromatic aminocarboxylic acids such as p-aminomethylbenzoic acid may also be used as copolymerizing components, without impairing the effects of the present invention.

[0134] The xylene-containing polyamide resin is preferably manufactured by a molten polycondensation reaction (hereinafter, sometimes referred to as "melt polycondensation"). For example, it is preferably manufactured by polymerizing a nylon salt formed from a diamine and a dicarboxylic acid in the presence of water under pressure and temperature, while removing water, in the molten state. Alternatively, it can be manufactured by directly adding a diamine to a molten dicarboxylic acid and carrying out polycondensation at atmospheric pressure. In this case, to maintain the reaction system in a homogeneous liquid state, it is preferable to continuously add the diamine to the dicarboxylic acid, and during this process, raise the temperature of the reaction system to a level not lower than the melting points of the resulting oligoamide and polyamide, and allow the polycondensation to proceed. Furthermore, the xylene-containing polyamide obtained by melt polycondensation can be further subjected to solid-state polymerization as needed, thereby increasing the molecular weight.

[0135] Polyamide resins containing xylene groups are preferably polycondensed in the presence of phosphorus-containing compounds. Polycondensation of xylene-containing polyamide resins in the presence of phosphorus-containing compounds improves processing stability during melt molding and makes coloring easier to suppress.

[0136] The preferred phosphorus-containing compounds are hypophosphorous compounds and phosphorous compounds, with hypophosphorous compounds being more preferred.

[0137] The phosphorus-containing compounds are preferably organometallic salts, and more preferably alkali metal salts.

[0138] From the viewpoints of promoting polymerization and preventing discoloration, hypophosphite, metal hypophosphite, metal phenylphosphonate, ethyl hypophosphite, dimethyl phosphite, phenylmethyl phosphite, phenylphosphonate, and ethyl phenylphosphonate are examples of hypophosphite compounds, with metal hypophosphite being preferred.

[0139] Examples of metal hypophosphite salts include sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, and calcium hypophosphite, with sodium hypophosphite being a more preferred choice.

[0140] Examples of metal salts of phenylphosphonite include sodium phenylphosphonite, potassium phenylphosphonite, and lithium phenylphosphonite.

[0141] Examples of phosphorous compounds include phosphorous acid, pyrophosphorous acid, metal salts of phosphite, metal salts of ethylphosphonic acid, metal salts of phenylphosphonic acid, triethyl phosphite, triphenyl phosphite, ethylphosphonic acid, phenylphosphonic acid, and diethyl phenylphosphonic acid.

[0142] Examples of metal salts of phosphite include sodium hydrogen phosphite, sodium phosphite, potassium phosphite, and calcium phosphite.

[0143] Examples of metal salts of ethylphosphonic acid include sodium ethylphosphonate and potassium ethylphosphonate; examples of metal salts of phenylphosphonic acid include sodium phenylphosphonate, potassium phenylphosphonate, and lithium phenylphosphonate.

[0144] A compound containing phosphorus atoms may be a single type or may contain two or more types.

[0145] Furthermore, the polycondensation of xylene-containing polyamide resins is preferably carried out in the presence of phosphorus-containing compounds and alkali metal compounds. However, if a large amount of the phosphorus-containing compound is used, there is a concern that the polyamide resin may gel. Therefore, from the viewpoint of adjusting the amidation reaction rate, the coexistence of alkali metal compounds is preferred.

[0146] Examples of alkali metal compounds include alkali metal hydroxides and alkali metal acetates. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Examples of alkali metal acetates include lithium acetate, sodium acetate, potassium acetate, rubidium acetate, and cesium acetate.

[0147] When an alkali metal compound is used to polycondense polyamide resin, from the viewpoint of suppressing gel formation, the amount of alkali metal compound used is preferably 0.5 to 1, more preferably 0.55 to 0.95, and even more preferably 0.6 to 0.9.

[0148] The number-average molecular weight of the polyamide resin is appropriately selected based on the application and molding method of the multilayer hollow container. From the viewpoint of the formability and strength of the multilayer hollow container, a number-average molecular weight of 10,000 to 60,000 is preferred, and a number-average molecular weight of 11,000 to 50,000 is more preferred.

[0149] It should be noted that the number-average molecular weight of polyamide resin is calculated using the following formula (X).

[0150] Number average molecular weight = 2 × 1,000,000 / ([COOH] + [NH2]) ... (X)

[0151] (In the formula, [COOH] represents the concentration of terminal carboxyl groups in the polyamide resin (μmol / g), and [NH2] represents the concentration of terminal amino groups in the polyamide resin (μmol / g).)

[0152] Here, the terminal carboxyl group concentration is the value calculated by neutralizing and titrating benzyl alcohol containing polyamide dissolved in an aqueous sodium hydroxide solution.

[0153] In this invention, from the viewpoint of suppressing yellowing of recycled polyester, the concentration of terminal amino groups in the polyamide resin (Y) is preferably 50 μmol / g or less, more preferably 45 μmol / g or less, even more preferably 40 μmol / g or less, even more preferably 30 μmol / g or less, and even more preferably 20 μmol / g or less.

[0154] The concentration of the terminal amino group of polyamide resin (Y) is determined as follows: The polyamide resin is accurately weighed and dissolved in a phenol / ethanol = 4 / 1 volumetric solution at 20~30℃ with stirring. After complete dissolution, while stirring, the inner wall of the container is rinsed with 5mL of methanol, and then neutralized and titrated with 0.01mol / L hydrochloric acid aqueous solution to determine the concentration.

[0155] There is no particular limitation on the method for adjusting the concentration of the terminal amino group in polyamide resin (Y). The concentration of the terminal amino group can be suppressed at a lower level by adjusting the molar ratio of diamine to dicarboxylic acid to carry out polycondensation reaction, by simultaneously adding monocarboxylic acid with terminal amino group, and by carrying out polycondensation reaction with diamine and dicarboxylic acid, or by reacting with carboxylic acid with terminal amino group after polycondensation reaction.

[0156] The content of polyamide resin (Y) contained in the polyamide layer is preferably 0.05 to 7.0% by mass relative to the total amount of all polyamide layers and all polyester layers. From the viewpoint of resistance to reactive liquids and inhibition of yellowing of recycled polyester, it is more preferably 0.5 to 6.0% by mass, further preferably 1.0 to 5.0% by mass, and even more preferably 1.5 to 4.5% by mass.

[0157] It should be noted that, in this invention, "the total amount of all polyamide layers and all polyester layers" refers to the total mass of all polyamide layers and all polyester layers constituting the multilayer hollow container. In the case of multiple layers, it is their total mass.

[0158] (Yellowing Inhibitor (A))

[0159] The polyamide layer of the multilayer hollow container contains a yellowing inhibitor (A).

[0160] The content of yellowing inhibitor (A) relative to the total amount of all polyamide layers and all polyester layers is preferably 1 to 30 ppm, more preferably 1.5 to 25 ppm from the viewpoint of effectively inhibiting yellowing of recycled polyester, and even more preferably 2 to 22 ppm and 3 to 20 ppm from the viewpoint of mixing and molding properties during manufacturing.

[0161] It should be noted that in this invention, "ppm" refers to parts per million by mass.

[0162] Regarding the content of yellowing inhibitor (A), from the viewpoint of effectively suppressing yellowing of recycled polyester, it is preferably 0.001 to 1.0% by mass in the polyamide layer, more preferably 0.005 to 0.5% by mass, further preferably 0.008 to 0.1% by mass, and even more preferably 0.01 to 0.08% by mass.

[0163] As a yellowing inhibitor (A), at least one of the group consisting of dyes and pigments is preferred, and from the viewpoint of transparency, dyes are more preferred.

[0164] Blue dyes and blue pigments are preferred as dyes and pigments.

[0165] By using dyes or pigments, yellowing of the recycled polyester obtained from the multilayer hollow container of the present invention can be suppressed in extremely small quantities. Furthermore, by using dyes, it is possible to obtain recycled polyester in even smaller quantities with excellent transparency.

[0166] Examples of dyes include anthraquinone dyes, pyrazolone dyes, coumarin dyes, violet ketone dyes, methynyl dyes, and quinoline ketone dyes, with anthraquinone dyes being preferred.

[0167] Anthraquinone dyes include those in which the hydrogen atoms of the aromatic ring are replaced by aromatic amines, aliphatic amines, hydroxyl groups, and halogens. Anthraquinone dyes in which the hydrogen atoms of the aromatic ring are replaced by aromatic amines are preferred.

[0168] By using anthraquinone dyes, yellowing of recycled polyester obtained from the multilayer hollow container of the present invention can be suppressed in minute quantities.

[0169] As anthraquinone dyes, anthraquinone blue dyes are preferred.

[0170] As an anthraquinone dye, compounds represented by the following formula (1) are preferred.

[0171]

[0172] (In the formula, n represents the number of R, and each of the two n's is independently 1 to 5. Each R's independently represents an alkyl group with 1 to 4 carbon atoms. Each of the two X's independently represents a hydrogen atom or a hydroxyl group.)

[0173] In formula (1), n ​​is 1 to 5, preferably 2 to 5, more preferably 2 to 3. By making n within the aforementioned range, yellowing (Δb* value) of recycled polyester can be suppressed. Each R independently represents an alkyl group having 1 to 4 carbon atoms, preferably selected from at least one of the groups consisting of methyl and ethyl. R preferably substitutes at least the para or ortho position for the amino group, more preferably at least the ortho position, and even more preferably both the para and ortho positions. Each of the two X's independently represents a hydrogen atom or a hydroxyl group, preferably a hydrogen atom.

[0174] Examples of specific compounds represented by formula (1) include 1,4-bis[(2-ethyl-6-methylphenyl)amino]anthraquinone, Solvent Blue 97, Solvent Blue 104, Solvent Green 3, and Solvent Green 28, with 1,4-bis[(2-ethyl-6-methylphenyl)amino]anthraquinone, Solvent Blue 97, and Solvent Blue 104 being preferred.

[0175] From the viewpoint of effectively suppressing yellowing of recycled polyester, the dye content relative to the total amount of all polyamide layers and all polyester layers is preferably 1 to 30 ppm, preferably 1.5 to 25 ppm, and from the viewpoint of mixing and molding properties during manufacturing, it is more preferably 3 to 22 ppm, further preferably 8 to 20 ppm, even more preferably 4 to 15 ppm, and even more preferably 5 to 10 ppm.

[0176] It should be noted that in this invention, "ppm" refers to parts per million by mass.

[0177] From the viewpoint of effectively suppressing yellowing of recycled polyester, the dye content in the polyamide layer is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.5% by mass, even more preferably 0.008 to 0.1% by mass, and even more preferably 0.01 to 0.06% by mass.

[0178] Phthalocyanine compounds (phthalocyanine pigments) can be cited as examples of pigments.

[0179] Examples of phthalocyanine compounds include metal-free phthalocyanines and copper phthalocyanines, with copper phthalocyanines being preferred.

[0180] Examples of copper phthalocyanines include α-type copper phthalocyanine (Pigment Blue 15:1), β-type copper phthalocyanine (Pigment Blue 15:3 or 15:4), ε-type copper phthalocyanine (Pigment Blue 15:6), copper chloride phthalocyanine, and copper bromide phthalocyanine, with α-type copper phthalocyanine and β-type copper phthalocyanine being preferred.

[0181] From the viewpoint of effectively suppressing yellowing of recycled polyester, the pigment content relative to the total amount of all polyamide layers and all polyester layers is preferably 1 to 30 ppm, more preferably 1.5 to 25 ppm, and more preferably 3 to 22 ppm, and even more preferably 8 to 20 ppm, from the viewpoint of mixing and molding properties during manufacturing.

[0182] It should be noted that in this invention, "ppm" refers to parts per million by mass.

[0183] From the viewpoint of effectively suppressing yellowing of recycled polyester, the pigment content in the polyamide layer is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.5% by mass, even more preferably 0.01 to 0.1% by mass, and even more preferably 0.03 to 0.08% by mass.

[0184] Yellowing inhibitors (A) can be used alone or in combination with two or more.

[0185] Commercially available yellowing inhibitors (A) include MACROLEX Blue RR Gran (anthraquinone dye, manufactured by LANXESS), MACROLEX Blue 3R (1,4-bis[(2-ethyl-6-methylphenyl)amino]anthraquinone, anthraquinone dye, manufactured by LANXESS), Orracet Blue 690 (anthraquinone dye, manufactured by BASF Corporation), HELIOGEN BLUE K6907 (Pigment Blue 15:1, α-type copper phthalocyanine pigment, manufactured by BASF Corporation), and HELIOGEN BLUE K7090 (Pigment Blue 15:3, β-type copper phthalocyanine pigment, manufactured by BASF Corporation).

[0186] (Greening Inhibitor (B))

[0187] The polyamide layer of the multilayer hollow container preferably contains a greening inhibitor (B).

[0188] The greening inhibitor (B) suppresses the green color in the -a* direction when measured with a colorimeter when the multilayer hollow container of the present invention is reused to form recycled polyester.

[0189] The content of the greening inhibitor (B) relative to the total amount of all polyamide layers and all polyester layers is preferably 1 to 30 ppm, more preferably 1.5 to 25 ppm from the viewpoint of effectively suppressing the greening of recycled polyester, and even more preferably 2 to 22 ppm and 3 to 20 ppm from the viewpoint of mixing and molding properties during manufacturing.

[0190] It should be noted that in this invention, "ppm" refers to parts per million by mass.

[0191] Regarding the content of the greening inhibitor (B), from the viewpoint of effectively suppressing the greening of recycled polyester, the content in the polyamide layer is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.5% by mass, further preferably 0.008 to 0.1% by mass, and even more preferably 0.01 to 0.08% by mass.

[0192] The greening inhibitor (B) is preferably selected from at least one of the groups consisting of dyes and pigments, and from the point of view of transparency, dyes are more preferred.

[0193] The dye is preferably selected from at least one of the group consisting of anthraquinone dyes and azo dyes, and from the viewpoint of heat resistance, anthraquinone dyes are more preferred.

[0194] In addition, the greening inhibitor (B) is preferably a red dye, more preferably at least one of the group consisting of anthraquinone red dyes and azo red dyes, and from the viewpoint of heat resistance, anthraquinone red dyes are even more preferred.

[0195] By using anthraquinone-based red dyes and azo-based red dyes, the greening of recycled polyester obtained from the multilayer hollow container of the present invention can be suppressed in minute quantities.

[0196] As an anthraquinone dye, compounds represented by the following formula (2) are preferred.

[0197]

[0198] In formula (2), each of the two Ys independently represents a hydrogen atom or a group shown in formula (2a), and each of the two Xs independently represents a hydrogen atom or a hydroxyl group. Among them, at least one Y is a group shown in formula (2a).

[0199] In formula (2a), R represents an alkyl group having 1 to 4 carbon atoms.

[0200] In formula (2), each of the two Ys independently represents a hydrogen atom or a group shown in formula (2a). Preferably, at least one Y is a group shown in formula (2a), one Y is a group shown in formula (2a), and the remaining Y is a hydrogen atom.

[0201] In the case where each of the two X's independently represents a hydrogen atom or a hydroxyl group, but one Y's is a group represented by formula (2a), the X's bonded to the same aromatic ring is preferably a hydroxyl group.

[0202] In formula (2a), R represents an alkyl group having 1 to 4 carbon atoms, preferably selected from at least one of the groups consisting of methyl and ethyl. It should be noted that when both Ys are groups represented by formula (2a), the Rs in the two groups represented by formula (2a) may be the same or different. R is preferably para-substituted with an amino group.

[0203] Examples of specific compounds represented by formula (2) include Solvent Violet 36 and Solvent Violet 13, with Solvent Violet 36 being preferred.

[0204] Greening inhibitors (B) can be used alone or in combination with two or more.

[0205] Commercially available greening inhibitors (B) include MACROLEX Violet 3R Gran (anthraquinone dye, manufactured by LANXESS), MACROLEX Violet B Gran (anthraquinone dye, manufactured by LANXESS), MACROLEX RedViolet R Gran (Disperse Violet 31, Disperse Violet 26, Solvent Violet 59, anthraquinone dye, manufactured by LANXESS), MACROLEX Red 5B Gran (Disperse Violet 31, Disperse Violet 26, Solvent Violet 59, anthraquinone dye, manufactured by LANXESS), and MACROLEX Red B (Solvent Red 195, azo dye, manufactured by LANXESS).

[0206] In the polyamide layer of the multilayer hollow container of the present invention, the mass ratio of yellowing inhibitor (A) to greening inhibitor (B) [(A) / (B)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40.

[0207] If the aforementioned mass ratio is within this range, the color change of the recycled polyester obtained after reuse will be smaller, and in particular, polyester with excellent colorlessness can be obtained.

[0208] (Other ingredients)

[0209] Other components may also be present in the polyamide layer. Examples of such components include heat stabilizers, light stabilizers, moisture-proof agents, waterproofing agents, lubricants, and spreading agents.

[0210] The polyamide layer may also contain resins other than polyamide resin (Y) as the main component, without impairing the effects of the present invention.

[0211] In particular, when using the masterbatch method described later to mix the yellowing inhibitor (A), it is preferable to include the polyamide resin or polyester resin used in the masterbatch. In this case, the amount of polyamide resin or polyester resin used in the masterbatch relative to the total amount of polyamide layer is preferably 1 to 20% by mass, more preferably 3 to 15% by mass.

[0212] (Resin composition in the polyamide layer)

[0213] From the viewpoint of gas barrier properties, the content of polyamide resin (Y) in the polyamide layer is preferably 80 to 100% by mass, and more preferably 90 to 100% by mass, relative to the total amount of resin in the polyamide layer.

[0214] <Structure / Characteristics of Multi-Layer Hollow Containers>

[0215] The multilayer hollow container of the present invention has the following multilayer structure: a polyester layer comprising polyester resin (X), and a polyamide layer comprising polyamide resin (Y) and yellowing inhibitor (A), the polyamide layer being an intermediate layer, the polyamide layer being present from the ground portion to a position of 10 to 70% of the container height.

[0216] The multilayer hollow container of the present invention may also include resin layers other than the aforementioned polyester layer and polyamide layer. From the viewpoint of facilitating grading during reuse and improving the yellowing inhibition effect, it is preferable to have a low content of resin layers other than the aforementioned polyester layer and polyamide layer, and preferably, to have substantially no resin layers other than the aforementioned polyester layer and polyamide layer. Additionally, an adhesive layer formed of an adhesive and an inorganic layer formed of an inorganic material may be provided; however, for these, from the viewpoint of facilitating grading during reuse and improving the yellowing inhibition effect, it is preferable to have a low content of adhesive layers and inorganic layers, and preferably, to have substantially no adhesive layers and inorganic layers.

[0217] The multilayer hollow container of the present invention has a multilayer structure of at least one layer of polyamide as the intermediate layer, with three or more layers, preferably with three to five layers, more preferably with three or five layers, and even more preferably with three layers.

[0218] In the multilayer hollow container of the present invention, at least one of the middle layers is a polyamide layer, but the outermost layer is preferably a polyester layer. In addition, the innermost layer is also preferably a polyester layer, and more preferably both the outermost and innermost layers are polyester layers.

[0219] Here, "outermost layer" refers to the layer that exists on the outer surface of a multi-layered hollow container and is usually in contact with the atmosphere (air), "innermost layer" refers to the layer that exists on the inner surface of a multi-layered hollow container and is in contact with the contents, and "middle layer" refers to the layers other than the outermost and innermost layers.

[0220] If the outermost layer is a polyester layer, the impact resistance, appearance, and design of the multilayer hollow container become excellent.

[0221] Therefore, as a structure of multi-layer hollow containers, multi-layer hollow containers have a structure of 3 to 5 layers, and more preferably, the outermost and innermost layers are polyester layers.

[0222] In the case of a 3-layer structure, the preferred layer from the innermost layer is polyester layer / polyamide layer / polyester layer; in the case of a 5-layer structure, the preferred layer from the innermost layer is polyester layer / polyamide layer / polyamide layer / polyester layer / polyester layer.

[0223] In the multilayer hollow container of the present invention, the polyamide layer is an intermediate layer, which exists from the grounding part to a position of 10-70% of the container height.

[0224] The phrase "the polyamide layer exists from the grounding portion to a position of 10-70% of the container height" means that the narrowest possible range of the polyamide layer is from the grounding portion (0% of the container height) to 10% of the container height. Conversely, the widest possible range is from the grounding portion (0% of the container height) to 70% of the container height. In other words, for the multilayer hollow container of the present invention, the polyamide layer is an intermediate layer, existing from the grounding portion (0% of the container height) to at least 10% of the container height, with an upper limit of 70% of the container height.

[0225] From the viewpoint of balancing resistance to reactive liquids such as bleach and resistance to delamination, and further suppressing yellowing of recycled polyester, the polyamide layer is located at a position from the grounding part to 10-70% of the container height, preferably at 10-60% of the container height, more preferably at 10-50% of the container height, even more preferably at 10-40% of the container height, and even more preferably at 10-30% of the container height.

[0226] Figure 1 and Figure 2 The following figures illustrate representative embodiments of the multilayer container of the present invention. Figure 1 The image shows a multi-layered container with a concave bottom surface (1a is a side view, 1b is a perspective view). Figure 2 The figures show a multi-layered container with a convex bottom surface (2a is a side view, 2b is a perspective view). The various parts of the invention will be described based on these figures.

[0227] The “grounding part” is the part that contacts the horizontal surface when the multi-layer hollow container of the present invention is placed on the horizontal surface. Figure 1 Inside the container, at the lower end 14 of the main body, Figure 2 In the container, surface 24 is in contact with the horizontal plane.

[0228] "Container height" is the length of the longest vertical line that contacts the container when a vertical line is drawn from the aforementioned horizontal plane where the multi-layer hollow container is configured; that is, the distance from the ground to the upper end of the multi-layer hollow container. Figure 1 Within the container, the shortest distance is from the lower end 14 of the main body to the upper end of the neck 11. Figure 2 In the container, it is the shortest distance from the surface 24 in contact with the horizontal plane to the upper end of the neck 21.

[0229] In addition, the "main body" is the part that forms the sides of the container and becomes the main part of the container, which is the part other than the neck and bottom. Figure 1The container contains the entirety of the frustum-shaped portion 12 and the cylindrical portion 13. Figure 2 The container contains the entirety of the truncated cone portion 22 and the cylindrical portion 23.

[0230] The "bottom" is the part of the container that contacts the horizontal surface when placed on it, and the part that holds the contents along the direction of gravity when filling multiple layers of the container. Typically, when viewed from directly above, it is the part located at the bottom of the container and has the same shape as the container itself. Figure 1 The container is a concave, roughly hemispherical shape, 15. Figure 2 The container is a portion that combines the inverted frustum portion 25 and the surface 24 that contacts the horizontal surface.

[0231] The "neck" is the part that does not substantially contribute to the retention of the contents; it is the part with an opening for filling and discharging the contents. It is usually located at the top of the container and has a fitting part with the lid. Figure 1 In the container, for neck 11, Figure 2 In the container, for neck 21.

[0232] It should be noted that the terms "grounding part," "container height," "main body," and "bottom" do not include decorative parts, handles, etc., that do not affect the storage of the contents. The "neck" does not include decorative parts, etc. Furthermore, the terms "grounding part," "container height," "main body," "bottom," and "neck" do not include lids, skirts, etc., that are separately molded from and fixed to the multi-layer hollow container.

[0233] By including a polyamide layer in the aforementioned locations, both resistance to reactive liquids such as bleach and resistance to delamination can be achieved. The rationale is unclear, but the following considerations are made: In multi-layered containers, the complex shape and lower stretch ratio tend to concentrate the polyamide layer in the middle layer near the bottom surface, which is in prolonged contact with the contents, and near the lower part of the main body. This improves resistance to reactive liquids such as bleach, particularly crack resistance. Furthermore, the presence of a polyester layer in the upper part reduces the likelihood of overall container delamination (peeling).

[0234] From the viewpoint of resistance to reactive liquids such as bleach, especially considering both crack resistance and delamination resistance, and further suppressing yellowing of recycled polyester, the polyamide layer preferably exists substantially continuously from the grounding portion to a position of at least 10% of the container height, more preferably at least continuously from the grounding portion to a position of at least 10% of the container height.

[0235] Furthermore, from the viewpoint of balancing resistance to reactive liquids such as bleach, especially crack resistance and delamination resistance, and further suppressing yellowing of recycled polyester, the polyamide layer preferably comprises more than 90% of the bottom surface, more preferably more than 99% of the bottom surface, and preferably less than 100% of the bottom surface. More preferably, it comprises 100% of the bottom surface, and even more preferably, it comprises the entire bottom surface.

[0236] In particular, from the viewpoint of further improving resistance to reactive liquids, resistance to delamination, and inhibition of yellowing of recycled polyester, it is preferable that the polyamide layer exists on the entire bottom surface and is substantially continuous from the grounding portion to a position of 10% of the container height, more preferably on the entire bottom surface and is continuous from the grounding portion to a position of 10% of the container height.

[0237] "Continuously existing from the grounding part to 10% of the container height" means that the polyamide layer exists on the entire surface from the grounding part to 10% of the container height. This means that the polyamide layer must exist at any position from the outer surface to the inner surface of the container, when viewed perpendicularly to the outer surface.

[0238] The polyamide layer can be substantially continuous from the grounding portion to a position of 10-70% of the container height, or substantially continuous from the grounding portion to a position of 10-60% of the container height, or substantially continuous from the grounding portion to a position of 10-50% of the container height, or substantially continuous from the grounding portion to a position of 10-40% of the container height, or substantially continuous from the grounding portion to a position of 10-30% of the container height.

[0239] "Exists in more than 90% of the bottom surface" means that the polyamide layer exists in more than 90% of the area of ​​the bottom surface, and "exists on the entire bottom surface" means that the polyamide layer must exist at any position when viewed vertically from the outer surface to the inner surface of the bottom surface.

[0240] In the multilayer hollow container of the present invention, the ratio of the thickness (W) of the polyester layer to the thickness (S) of the polyamide layer in the portion where the polyamide layer is the intermediate layer (thickness ratio W / S) is preferably 2.5 or more and 200 or less. It should be noted that the thickness of the polyester layer refers to the average thickness; when there are multiple polyester layers in the main body, the total thickness of all multiple layers is calculated. The same applies to the thickness of the polyamide layer.

[0241] If the thickness ratio W / S is 2.5 or higher, the grading process in the manufacturing method of recycled polyester, especially in air separation and gravity separation, will facilitate the grading of polyamide resin from polyester resin, which is preferred. Furthermore, if the thickness ratio W / S is 200 or lower, the hollow container will have excellent gas barrier properties, allowing for long-term preservation of the contents.

[0242] From the viewpoint of improving the gradability in the grading process and ensuring good resistance to reactive liquids such as bleach and delamination in multi-layer hollow containers, the thickness ratio (W / S) is more preferably 3 to 50, and even more preferably 4 to 15.

[0243] Furthermore, the thickness of the main body of the multilayer hollow container (the total thickness of all layers in the main body) is preferably 100 μm to 5 mm, more preferably 150 μm to 3 mm, and even more preferably 200 μm to 2 mm. Additionally, the thickness (W) of each polyester layer is preferably 30 μm to 2 mm, more preferably 40 μm to 1 mm, and even more preferably 50 μm to 500 μm.

[0244] For the thickness (S) of the polyamide layer, each layer is preferably 1 to 200 μm, more preferably 3 to 100 μm, and even more preferably 8 to 50 μm. In this invention, by making the thickness of the polyamide layer within this range, resistance to reactive liquids such as bleach and resistance to delamination are ensured, and the polyamide layer becomes easier to grade from the polyester during the grading process.

[0245] [Bleach items]

[0246] The bleaching article of the present invention is a bleaching article in which a chlorine-based liquid bleaching composition is contained in a multi-layer hollow container of the present invention.

[0247] That is, a bleaching article comprising a chlorine-based liquid bleaching composition contained in a multi-layered hollow container, the multi-layered hollow container having: a polyester layer comprising a polyester resin (X), and a polyamide layer comprising a polyamide resin (Y) and a yellowing inhibitor (A), the polyamide layer being an intermediate layer, existing from the ground portion to a position of 10-70% of the container height. When storing and handling the chlorine-based liquid bleaching composition in the multi-layered hollow container of the present invention, by forming a structure in which the polyamide layer serving as the intermediate layer is concentrated on the bottom surface and the lower part of the main body of the multi-layered container, which is prone to cracking, a bleaching article endowed with crack resistance can be formed.

[0248] The multi-layer hollow container of the present invention has resistance to reactive liquids such as bleach and resistance to stratification. Therefore, it is preferred to contain chlorine-based liquid bleach compositions, and the method for containing chlorine-based liquid bleach compositions is preferred.

[0249] That is, the multi-layer hollow container of the present invention can be a multi-layer hollow container for chlorine-based liquid bleach compositions, the multi-layer hollow container having: a polyester layer containing polyester resin (X), and a polyamide layer containing polyamide resin (Y) and yellowing inhibitor (A), the polyamide layer being an intermediate layer existing from the ground portion to a position of 10 to 70% of the container height.

[0250] When the multi-layer hollow container of the present invention is used to store chlorine-based liquid bleach compositions, recycled polyester that balances resistance to bleach, especially crack resistance and delamination resistance, further suppresses yellowing of recycled polyester during reuse, and has no color change can be obtained.

[0251] <Chlorine-based liquid bleach composition>

[0252] The chlorine-based liquid bleach composition (hereinafter also simply referred to as "bleach composition") contained in the container of the present invention will be described.

[0253] (Bleaching ingredient)

[0254] The aforementioned bleaching composition preferably contains chlorite, hypochlorite, isocyanurate chloride, etc. as bleaching ingredients, more preferably contains hypochlorite and isocyanurate chloride as bleaching ingredients, and even more preferably contains hypochlorite as bleaching ingredient.

[0255] The aforementioned chlorites, hypochlorites, and isocyanurates are preferably metal salts, and more preferably alkali metal salts. Sodium and potassium are preferred as alkali metals, with sodium being more preferred.

[0256] Sodium hypochlorite is a particularly preferred bleaching agent.

[0257] When the aforementioned chlorine-based liquid bleaching composition contains sodium hypochlorite, the content of sodium hypochlorite is preferably 0.5 to 15% by mass, more preferably 1 to 12% by mass, even more preferably 2 to 9% by mass, and even more preferably 2 to 8% by mass.

[0258] If the sodium hypochlorite content is within the above range, good bleaching properties and storage stability are obtained.

[0259] (Alkali)

[0260] The aforementioned chlorine-based liquid bleach composition preferably contains an alkaline agent. The alkaline agent is added to improve the stability of bleaching components such as sodium hypochlorite in the bleach composition, and also to ensure a sufficient bleaching effect on the dirt.

[0261] Alkali agents include alkali metal hydroxides, alkali metal carbonates, silicates, phosphates, etc., with alkali metal hydroxides being preferred.

[0262] Sodium and potassium are preferred as alkali metals.

[0263] Sodium hydroxide and potassium hydroxide are preferred as alkali metal hydroxides, with sodium hydroxide being more preferred.

[0264] The concentration of the alkali agent in the aforementioned bleaching agent composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more. Furthermore, it is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less. When the concentration of the alkali agent is within the above range, the stability of sodium hypochlorite becomes good, and a sufficient bleaching effect is obtained.

[0265] (chelating agent)

[0266] The aforementioned bleaching agent composition may also contain chelating agents.

[0267] Chelating agents stabilize bleaching compositions by capturing heavy metals contained therein. Examples include aminophosphonic acid-N-oxide, particularly [tris(methylene)]triphosphonic acid-N-oxide, 2-phosphonobutane-1,2,4-tricarboxylate, 1-hydroxyethane-1,1-diphosphonate, and cross-linked polycarboxylate. Chelating agents can be used alone or in combination of two or more, without particular limitation.

[0268] The chelating agent content is preferably 0.1 to 30% by mass, more preferably 0.3 to 20% by mass, in the bleaching agent composition. Sufficient cleaning power is obtained by maintaining the chelating agent content within this range.

[0269] (surfactant)

[0270] The aforementioned chlorine-based liquid bleach composition preferably contains a surfactant. By containing a surfactant, the bleaching performance of articles with various surface properties is improved. Examples of surfactants include anionic surfactants, amphoteric surfactants, nonionic surfactants, and cationic surfactants, with anionic surfactants and amphoteric surfactants being preferred, and anionic surfactants being more preferred.

[0271] Examples of anionic surfactants include sulfate salts, carboxylates, sulfonates, and phosphate salts, with sulfate salts, carboxylates, and sulfonates being preferred, sulfate salts and carboxylates being more preferred, and sulfate salts being even more preferred.

[0272] Examples of sulfate salts include alkyl sulfate salts and alkyl ether sulfate salts, with alkyl ether sulfate salts being preferred.

[0273] As a specific example of alkyl ether sulfate salts, polyoxyethylene alkyl ether sulfate salts are preferred, and polyoxyethylene alkyl ether sulfate salts are more preferred.

[0274] The alkyl group of the polyoxyethylene alkyl ether sulfate salt preferably has 12 to 18 carbon atoms, more preferably 12 to 14 carbon atoms, and even more preferably 12 carbon atoms.

[0275] The average molar number of ethylene oxide groups added to the polyoxyethylene alkyl ether sulfate salt is preferably 0.5 to 10, more preferably 1 to 5.

[0276] The polyoxyethylene alkyl ether sulfate salt is preferably sodium salt, potassium salt, or triethanolamine salt, more preferably sodium salt or triethanolamine salt, and even more preferably sodium salt.

[0277] Specifically, sodium polyoxyethylene lauryl ether sulfate is preferred.

[0278] Examples of carboxylates include fatty acid salts and α-sulfonyl fatty acid ester salts.

[0279] Examples of sulfonates include alkylbenzene sulfonates, α-olefin sulfonates, and alkyl sulfonates.

[0280] Examples of phosphate salts include alkyl phosphate salts.

[0281] Examples of amphoteric surfactants include alkylamine oxides, alkyl betaines, and alkyl amino fatty acid salts, with alkylamine oxides being preferred.

[0282] Examples of nonionic surfactants include sucrose fatty acid esters, dehydrated sorbitan fatty acid esters, polyoxyethylene dehydrated sorbitan fatty acid esters, fatty acid alkanolamides, polyoxyethylene alkyl ethers, and polyoxyethylene alkylphenyl ethers.

[0283] Examples of cationic surfactants include alkyl trimethylammonium salts and dialkyl dimethylammonium salts. Cationic surfactants are primarily used to provide hygienic properties.

[0284] Among them, polyoxyalkylene alkyl ether sulfate salt and alkylamine oxide are preferred.

[0285] The surfactant can be used alone or in combination with two or more. The surfactant content in the chlorine-based liquid bleach composition is preferably 0.01 to 7.0% by mass, more preferably 0.03 to 5.0% by mass, and even more preferably 0.05 to 3.0% by mass.

[0286] (Other ingredients, etc.)

[0287] The aforementioned bleaching composition preferably contains a solvent. The solvent content in the chlorine-based liquid bleaching composition is preferably the balance of the bleaching agent, surfactant, alkali, chelating agent, and other components listed herein.

[0288] Examples of solvents included in bleaching compositions include water and water-miscible organic solvents, with water being the most preferred. The water content in chlorine-based liquid bleaching compositions is preferably 80-98% by mass, more preferably 88-98% by mass, and even more preferably 90-98% by mass. Excellent storage stability is observed when the water content is within the above range.

[0289] Examples of water-miscible organic solvents include alcohols and ethers.

[0290] The aforementioned bleaching agent composition may also contain fluorescent dyes; free radical scavengers such as BHT (butylated hydroxytoluene); abrasives / suspending agents such as calcium carbonate, silica, montmorillonite, and bentonite; and fragrances such as terpene alcohol fragrances.

[0291] The pH of the chlorine-based liquid bleach composition is preferably alkaline, and at 20°C, the pH is preferably 11-13.8, more preferably 11.3-13.7, and even more preferably 11.5-13.5. If the pH of the chlorine-based liquid bleach composition is within the above range, it is preferred from the perspective of storage stability and bleaching effect.

[0292] [Manufacturing method of multi-layer hollow containers]

[0293] The manufacturing method of the multi-layer hollow container of the present invention is as follows: the multi-layer hollow container has: a polyester layer containing polyester resin (X), and a polyamide layer containing polyamide resin (Y) and yellowing inhibitor (A), the polyamide layer being an intermediate layer, the polyamide layer existing from the ground portion to a position of 10-70% of the container height, the manufacturing method comprising the following steps: step 1, mixing polyamide resin (Y) and yellowing inhibitor (A) to prepare a polyamide resin mixture; step 2, co-injection molding the aforementioned polyamide resin mixture with a polyester resin composition containing polyester resin (X) to obtain a multi-layer preform; and step 3, blow molding the aforementioned multi-layer preform.

[0294] <Step 1 (Step for preparing polyamide resin mixture)>

[0295] In step 1, polyamide resin (Y) is mixed with yellowing inhibitor (A) to prepare a polyamide resin mixture.

[0296] Typically, to ensure that the yellowing inhibitor is distributed throughout the entire container, equipment is needed to stir, mix, or knead the yellowing inhibitor with all the resin. However, in the manufacturing method of the multilayer hollow container of the present invention, by mixing the yellowing inhibitor (A) with a small amount of polyamide resin (Y), the yellowing inhibitor can be effectively distributed throughout the entire container with small-scale and short-time mixing, resulting in excellent productivity.

[0297] The mixing method can be dry mixing or melt blending (melt mixing), but from the viewpoint of reducing the thermal process or preventing the deterioration of the resin and yellowing inhibitor, dry mixing and masterbatch melt blending are preferred. Furthermore, from the viewpoint of preventing the yellowing inhibitor from adhering to the molding machine and its surroundings in step 2 and remaining thereafter, melt blending is preferred, and from the viewpoint of reducing the thermal process or preventing the deterioration of the resin and yellowing inhibitor, masterbatch blending is preferred.

[0298] In step 1, it is preferable to mix the granular polyamide resin (Y) with the yellowing inhibitor (A) at a temperature below 230°C, more preferably at a temperature below 150°C, and even more preferably at a temperature below 100°C. Mixing at a temperature below 230°C reduces the thermal process and prevents deterioration of the resin and the yellowing inhibitor. This is believed to be because the polyamide resin can maintain its granular form, thus exhibiting less thermal deterioration. When mixing at a temperature below 230°C, dry mixing is preferred.

[0299] The yellowing inhibitor (A) suitable for use in step 1 is the same as that described in the above (yellowing inhibitor (A)) section, preferably at least one of the group consisting of dyes and pigments, more preferably an anthraquinone dye.

[0300] Furthermore, the yellowing inhibitor (A) is preferably in the form of a powder, dispersion, or solution, and more preferably in the form of a powder. By having the yellowing inhibitor (A) in these forms, it can be mixed with the polyamide resin (Y) more easily and uniformly.

[0301] By mixing granular polyamide resin (Y) with powdered yellowing inhibitor (A) at low temperature, the degradation of the resin and yellowing inhibitor can be prevented, and the yellowing inhibitor can be uniformly mixed with the resin.

[0302] In addition, in step 1, it is preferable to further mix in a greening inhibitor (B).

[0303] The greening inhibitor (B) suitable for use in step 1 is the same as that described in the above-mentioned (greening inhibitor (B)) item, preferably at least one of the group consisting of free dyes and pigments, more preferably at least one of the group consisting of free anthraquinone dyes and azo dyes, further preferably at least one of the group consisting of free anthraquinone red dyes and azo red dyes, and from the viewpoint of heat resistance, anthraquinone red dyes are even more preferred.

[0304] Furthermore, the greening inhibitor (B) is preferably in the form of a powder, dispersion, or solution, and more preferably in the form of a powder. By having the greening inhibitor (B) in these forms, it can be mixed with the polyamide resin (Y) more easily and uniformly.

[0305] Examples of mixing devices used in dry mixing include drum mixers, ribbon mixers, Henschel mixers, and Banbury internal mixers.

[0306] In step 1, the method of mixing polyamide resin (Y) and yellowing inhibitor (A) by melt blending can be the masterbatch method or the full composite method, with the masterbatch method being preferred.

[0307] The masterbatch method involves mixing a small amount of polyamide resin or polyester resin with yellowing inhibitor (A) to form a masterbatch in step 1, and then mixing it with the remaining polyamide resin (Y). Alternatively, a greening inhibitor (B) can be mixed simultaneously when obtaining the masterbatch. Specifically, in step 1, it is preferable to mix the polyamide resin or polyester resin with yellowing inhibitor (A) and then mix it with polyamide resin (Y). More preferably, in step 1, the polyamide resin or polyester resin, yellowing inhibitor (A), and greening inhibitor (B) are mixed and then mixed with polyamide resin (Y).

[0308] Polyamide resin or polyester resin is preferably used in the masterbatch. Polyamide resin is preferred for its miscibility with polyamide resin (Y), while polyester resin is preferred for its ability to suppress yellowing caused by thermal processes. It should be noted that they can also be mixed and used together.

[0309] The polyamide resin used in the masterbatch is preferably polyamide resin (Y), and more preferably the same as the balance polyamide resin (Y).

[0310] The polyester resin used in the masterbatch can be the same as the polyester resin (X) or the same as the polyester resin (X) in the polyester layer.

[0311] The amount of polyamide resin or polyester resin used in the masterbatch is preferably 1 to 20% by mass relative to the total amount of resin in the polyamide layer, and more preferably 3 to 15% by mass.

[0312] As a method for obtaining masterbatch, when compounding a yellowing inhibitor (A) with polyamide resin or polyester resin, if the melting point of the resin used in the masterbatch is set as Tm, the compounding temperature (°C) is preferably Tm+5 to Tm+60, more preferably Tm+10 to Tm+50, and even more preferably Tm+15 to Tm+40 from the viewpoint of thorough mixing. Specifically, 245 to 300°C is even more preferred, 250 to 290°C is even more preferred, and 255 to 280°C is even more preferred from the viewpoint of thorough mixing. In addition, the compounding time is preferably 10 to 600 seconds, more preferably 20 to 400 seconds, and even more preferably 30 to 300 seconds from the viewpoint of thorough mixing. Examples of apparatus used for compounding include open mixing rollers, closed Banbury mixers, kneaders, and continuous mixers (single-screw mixers, twin-screw mixers, multi-screw mixers, etc.).

[0313] In addition, as a method for mixing the masterbatch with the remaining polyamide resin (Y), dry mixing and further compounding can be mentioned, with dry mixing being preferred. Dry mixing preferably involves mixing the granules of the masterbatch with the granules of the remaining polyamide resin (Y) in a mixing device such as a drum mixer.

[0314] The full composite method is a method of mixing and blending the total amount of polyamide resin (Y) used in the polyamide layer with the yellowing inhibitor (A).

[0315] From the viewpoint of ensuring thorough mixing, the mixing temperature is preferably 245~300℃, more preferably 250~290℃, and even more preferably 255~280℃. Furthermore, from the viewpoint of ensuring thorough mixing, the mixing time is preferably 10~600 seconds, more preferably 20~400 seconds, and even more preferably 30~300 seconds. Examples of apparatus used for mixing include open-type mixing rollers, closed-type Banbury mixers, kneaders, and continuous mixers (single-screw mixers, twin-screw mixers, multi-screw mixers, etc.).

[0316] The polyamide resin mixture obtained in this process is preferably of the same composition as the aforementioned <polyamide layer>.

[0317] <Process 2 (Process for obtaining multi-layer preforms)>

[0318] In step 2, the aforementioned polyamide resin mixture is co-injected with a polyester resin composition containing polyester resin (X) to obtain a multilayer preform.

[0319] The aforementioned polyester resin composition, except for the polyester resin (X), preferably has the same composition as the aforementioned <polyester layer>.

[0320] In co-injection molding, a mixture of polyester resin and polyamide resin is extruded into a mold separately and co-injected to form a multi-layer preform.

[0321] In the case of co-injection molding of the multilayer hollow container of the present invention, by delaying the filling start time of the polyamide resin mixture compared with the filling start time of the polyester resin constituting the polyester layer, a multilayer hollow container in which the polyamide layer is concentrated on the bottom surface and the lower part of the main body can be obtained.

[0322] <Process 3 (Blow Molding Process)>

[0323] In step 3, the aforementioned multi-layer preform is blow-molded.

[0324] In the manufacturing method of the multi-layer hollow container of the present invention, it is preferable to form the multi-layer preform (multi-layer blank) obtained by step 2 by stretch blow molding.

[0325] In step 2, it is preferable to perform stretch blow molding on the multi-layer preform obtained by co-injection molding, and more preferably to perform biaxial stretch blow molding on the multi-layer preform obtained by co-injection molding. It should be noted that, as conditions for biaxial stretch blow molding, it is preferable to heat the preform at a temperature of 95~110°C, the primary blow molding pressure at 0.5~1.2 MPa, and the secondary blow molding pressure at 2.0~2.6 MPa. This results in a multi-layer hollow container with suppressed thickness and stretching unevenness and excellent strength.

[0326] [Manufacturing method of recycled polyester]

[0327] The multi-layer hollow container of the present invention, as described above, is suitable for reuse, and can be used as a raw material to manufacture recycled polyester.

[0328] The method for manufacturing recycled polyester of the present invention preferably includes a step of recovering polyester from the aforementioned multi-layer hollow container.

[0329] That is, preferably, a process for recovering polyester from a multi-layer hollow container is provided, the multi-layer hollow container having: a polyester layer containing polyester resin (X), and a polyamide layer containing polyamide resin (Y) and yellowing inhibitor (A), the polyamide layer being an intermediate layer, the polyamide layer being present from the ground portion to a position of 10 to 70% of the container height.

[0330] The preferred method for manufacturing recycled polyester from multilayer hollow containers is to remove all or part of the polyamide layer from the aforementioned multilayer hollow container, recycle the polyester constituting the polyester layer, and use this polyester as recycled polyester. It should be noted that the method for manufacturing recycled polyester from multilayer hollow containers is not limited to the above method; it can also be a method for manufacturing recycled polyester without the process of removing the polyamide resin.

[0331] The recycled polyester obtained by this manufacturing method can be used for various applications such as resin moldings and fibers.

[0332] The method for manufacturing the recycled polyester of the present invention will be described in detail below.

[0333] In this manufacturing method, the multi-layer hollow containers are typically used, but can also be unused. Examples of used multi-layer hollow containers include those temporarily circulating in the recycling market.

[0334] In this manufacturing method, firstly, when a cover is installed on a multi-layer hollow container, it is preferable to remove the cover from the multi-layer hollow container.

[0335] Next, the container is crushed, cleaned as needed, and the polyester is selectively separated as needed for recycling (recycling process).

[0336] Next, the material is granulated as needed to form pellets (granulation process).

[0337] Then, crystallization and solid-state polymerization processes (crystallization / solid-state polymerization processes) are carried out as needed.

[0338] The following describes each process.

[0339] <Recycling Process>

[0340] The recycling process involves crushing and recycling multi-layer hollow containers to recover recycled polyester.

[0341] Preferably, the multi-layer hollow container is crushed and all or part of the polyamide layer is removed, and the polyester is selectively removed. More preferably, the polyester and the polyamide resin constituting the polyamide layer are graded.

[0342] The pulverization of multi-layer hollow containers can be carried out using pulverizers such as single-screw pulverizers, twin-screw pulverizers, triple-screw pulverizers, and shredders. The pulverized material obtained can be in the form of flakes, powder, or lumps. The main body of the multi-layer hollow container is mostly thin-walled, with a thickness of a few millimeters or less; therefore, most of the pulverized material is usually in flake form. It should be noted that flake-shaped pulverized material refers to thin sheets or flat pieces with a thickness of approximately 2 millimeters or less.

[0343] Furthermore, in multi-layer hollow containers, the polyester layer and the polyamide layer are structurally integrated, but they are usually not bonded to each other. During the crushing process, the polyester and polyamide resins can be easily separated into separate pulverized particles. Additionally, by forming flakes, they can be easily separated by the airflow separated by air classification, as described later.

[0344] In this process, polyester and polyamide resin may not be completely separated. The pulverized material may be separated into a component with a relatively high polyester content and a component with a relatively low polyester content and a relatively high polyamide resin content. It should be noted that, for ease of explanation, the component with a relatively high polyester content will be referred to as polyester, and the component with a relatively high polyamide resin content will be referred to as polyamide resin.

[0345] As mentioned above, the pulverized material is graded into polyester and polyamide resins (grading process).

[0346] As a grading method, it is preferable to use specific gravity screening that utilizes the difference in specific gravity between polyester and polyamide resin.

[0347] That is, preferably, the aforementioned multi-layer hollow container is crushed and the polyamide layer is removed by air separation.

[0348] As a specific gravity screening method, wind separation can be cited as an example of screening pulverized materials based on wind force. Wind separation can be exemplified by methods such as: in a separation device that generates a rotating airflow inside, pulverized materials in contact with the airflow generated by the separation device are classified and recovered into those with a high specific gravity or small specific surface area that fall naturally due to their own weight, and those with a low specific gravity or large specific surface area that are swirled up by the airflow.

[0349] In this method, the polyester shreds fall naturally due to their own weight, while the polyamide resin shreds are rolled up, thereby allowing the polyester and polyamide resin to be graded and recycled.

[0350] In this type of air separation, the same operation can be repeated for the same pulverized material. For example, naturally falling material can be further air separated to increase the polyester content in recycled polyester.

[0351] It should be noted that the grading method is not limited to air separation. Examples include: immersing the pulverized material in a liquid such as water and grading it based on the difference in specific gravity of the pulverized material to the liquid; applying a certain vibration to the pulverized material to separate and grade pulverized materials with different specific gravities; etc.

[0352] <Granulation Process>

[0353] The recycled polyester is preferably granulated to form pellets to facilitate operations such as molding and processing.

[0354] Granulation can be performed before or after the crystallization / solid-phase polymerization process described later, but it is preferable to perform it before the crystallization / solid-phase polymerization process. By performing it before the crystallization / solid-phase polymerization process, the operability in the crystallization / solid-phase polymerization process is also improved.

[0355] In the granulation process, it is preferable to plasticize and granulate the pulverized material through melt blending. Examples of granulation equipment used for plasticizing and granulation include single-screw extruders, twin-screw extruders, and multi-screw extruders; however, any known equipment can be used. As for the shape of the granules, cylindrical, spherical, or ellipsoidal shapes are preferred.

[0356] Granulation, for example, preferably involves extruding plasticized recycled polyester into filaments, cooling them in a water bath, and then cutting them into granules in a granulator. The granules removed from the water bath are typically dried to remove any moisture adhering to their surfaces.

[0357] <Crystallization / Solid-phase Polymerization Process>

[0358] Following the aforementioned polyester recycling process, it is preferable to perform one or more processes selected from crystallization and solid-state polymerization, and more preferably both crystallization and solid-state polymerization. The crystallization / solid-state polymerization process is preferably performed on the granulated polyester, but it can also be performed on ungranulated polyester (e.g., pulverized material).

[0359] It should be noted that, in the case of both crystallization and solid-state polymerization, it is preferable to crystallize the polyester first and then carry out solid-state polymerization.

[0360] Polyester crystallization is carried out by maintaining the polyester under constant heating. Crystallization is preferably carried out by heating the polyester at, for example, 100 to 230°C. By crystallizing, the polyester is prevented from fusing together or adhering to the inner surface of the apparatus during solid-state polymerization or molding.

[0361] Solid-state polymerization is preferably carried out at a temperature above but below the melting point of the polyester for a certain period of time. By setting the temperature below the melting point, the polyester melting is prevented, for example, to prevent the polyester from adhering to the surface of the equipment and reducing operating efficiency. In addition, by setting the temperature above the melting point, polymerization proceeds at a sufficient polymerization rate, making it easier to obtain the desired physical properties.

[0362] Solid-phase polymerization can be carried out under vacuum or under a stream of inert gases such as nitrogen or argon. When carried out under vacuum, a concentration of 1.0 torr or less is preferred, more preferably 0.5 torr or less, and even more preferably 0.1 torr or less. Furthermore, whether under vacuum or under a stream of inert gases such as nitrogen or argon, it is preferable to minimize the oxygen concentration remaining in the system, preferably 300 ppm or less, more preferably 30 ppm or less. By setting the oxygen concentration to 30 ppm or less, it becomes less likely to cause appearance defects such as yellowing.

[0363] When solid-state polymerization is carried out under vacuum, it is preferable to maintain uniform heat conduction while frequently stirring or mixing the polyester. When carried out in the presence of an inactive gas, it is preferable to keep the surface of the polyester in contact with the dried gas while the gas stream is running.

[0364] Solid-phase polymerization apparatus for crystallization / solid-phase polymerization processes can include batch-type drum-type apparatus equipped with heating jackets, drying silo-type apparatus with inactive gas flow equipment, crystallization apparatuses and reactors with internal stirring blades and discharge screws, etc. It should be noted that crystallization and solid-phase polymerization are preferably carried out continuously or simultaneously within the same apparatus.

[0365] The heating time for solid-state polymerization is determined in due course depending on the apparatus and other conditions, but only for the polyester to obtain sufficient physical properties.

[0366] In solid-state polymerization, since the polyester is held at high temperatures for extended periods, the presence of impurities in the polyester can sometimes deteriorate its quality, such as color. Preferably, most of the polyamide resin is removed in the aforementioned removal process; in this case, the potential quality deterioration that occurs during solid-state polymerization is minimized.

[0367] In the method for manufacturing the recycled polyester of the present invention, steps other than those described above may also be performed. A cleaning step may also be performed to remove contents adhering to the inside of the multi-layered hollow container. Cleaning is preferably performed using a liquid rinse, such as water, an alkaline aqueous solution, or both.

[0368] Furthermore, cleaning can be performed before or after pulverizing in a multi-layered hollow container, but is preferably performed before any of the granulation, crystallization, or solid-phase polymerization processes. Alternatively, the cleaning process can be performed simultaneously with the pulverization process in a pulverizer, also known as a wet pulverizer, where cleaning and pulverization are carried out at the same time.

[0369] Alternatively, if a washing process is performed, a drying process can be performed afterward. By performing a drying process, the moisture content of the recycled polyester obtained in this method can be reduced, thus providing recycled polyester with high thermal stability and other high-quality characteristics. The drying process can be performed, for example, using air supplied by a dryer or hot air.

[0370] When the method for manufacturing recycled polyester includes a polyamide resin removal step, the polyamide resin content in the obtained recycled polyester is preferably less than 1% by mass, more preferably less than 0.8% by mass, and even more preferably less than 0.6% by mass. In this way, by reducing the polyamide resin content, the quality of the recycled polyester becomes good.

[0371] Example

[0372] The present invention will now be described in more detail with reference to examples and comparisons, but the present invention is not limited to these examples.

[0373] [raw material]

[0374] The polyester resin, yellowing inhibitor, and greening inhibitor used in the examples and comparative examples are as described below. Additionally, the polyamide resin used is from the manufacturer in Manufacturing Example 1 below.

[0375] <Polyester Resin (X1)>

[0376] Isophthalic acid copolymer polyethylene terephthalate (intrinsic viscosity: 0.83 dL / g, melting point: 248℃), trade name: BK2180, manufactured by Mitsubishi Chemical Corporation.

[0377] <Yellowing Inhibitor>

[0378] Blue RR: Solvent Blue 97 (anthraquinone dye), trade name: MACROLEX Blue RR Gran, manufactured by LANXESS.

[0379] Blue 690: Solvent Blue 104 (anthraquinone dye), trade name: Orracet Blue 690, manufactured by BASF Corporation.

[0380] <Greenification Inhibitor>

[0381] Violet 3R: Solvent Violet 36 (anthraquinone dye), trade name: MACROLEX Violet 3RGran, manufactured by LANXESS.

[0382] Red B: Solvent Red 195 (azo dye), trade name: MACROLEX Red B, manufactured by LANXESS.

[0383] <Polyamide resin (Y1)>

[0384] Manufacturing Example 1 (Manufacturing of Polyamide Resin (Y1))

[0385] In a 50-liter reaction vessel equipped with a stirrer, partial condenser, total condenser, thermometer, dropping funnel, nitrogen inlet pipe, and wire die, precisely weighed 15000 g (102.6 mol) of adipic acid, 13.06 g (123.3 mmol, equivalent to 151 ppm phosphorus concentration in polyamide) of sodium hypophosphite monohydrate (NaH2PO2·H2O), and 6.849 g (83.49 mmol, equivalent to 0.68 molar ratio to sodium hypophosphite monohydrate) were placed. After thorough nitrogen purging, the system was further heated to 170°C under a small nitrogen flow while stirring. While stirring, 13896 g (102.0 mol, equivalent to 0.994 molar ratio) of m-phenylenediamine was added dropwise, and the generated condensation water was drained from the system while the temperature was continuously increased. After the addition of m-phenylenediamine was completed, the internal temperature was maintained at 260°C, and the reaction was continued for 40 minutes. Afterward, the system was pressurized with nitrogen, and the polymer was removed from the die and granulated to obtain approximately 24 kg of polyamide.

[0386] Then, the aforementioned polyamide was added to a jacketed drum dryer equipped with a nitrogen inlet pipe, vacuum line, vacuum pump, and thermocouple for internal temperature measurement. While rotating at a certain speed, the inside of the drum dryer was fully purged with nitrogen gas of 99% by volume or higher purity. The drum dryer was then heated under the same nitrogen gas flow for approximately 150 minutes, raising the granule temperature to 150°C. At the moment the granule temperature reached 150°C, the pressure within the system was reduced to below 1 torr. The temperature was further increased, raising the granule temperature to 200°C for approximately 70 minutes, and then maintained at 200°C for 30–45 minutes. Then, nitrogen gas of 99% by volume or higher purity was introduced into the system, and cooling was performed while maintaining the rotation of the drum dryer, yielding polyamide resin (Y1). The concentration of amino-terminal groups was measured, and the result was 14.4 μmol / g.

[0387] <Polyamide resin mixture>

[0388] Manufacturing Example 2 (Manufacturing of a Dry-Mixed Polyamide Resin Blend)

[0389] Polyamide resin (Y1) and the yellowing inhibitor and greening inhibitor listed in Table 1 were added to a mixer at the mass ratios in Table 1 and dry-mixed at 25°C to prepare a polyamide resin mixture.

[0390] Manufacturing Examples 3-8 (Manufacturing of Polyamide Resin Mixtures Based on Masterbatch Method)

[0391] The masterbatch was pre-dry-blended with polyamide resin (polyamide resin (Y1)), yellowing inhibitor (Blue RR or Blue 690), and greening inhibitor (Violet 3R or Red B) at the ratios listed in Table 1. Next, the dry-blended mixture was melt-blended at 260°C using a twin-screw extruder (Toshiba Machine Co., Ltd., TEM26SX) to obtain masterbatch granules. The granules were then dried in a vacuum dryer at 150°C for 5 hours to obtain the masterbatch.

[0392] Next, the obtained masterbatch and the balance of polyamide resin (Y1) are mixed in a mass ratio as shown in Table 1, with masterbatch / balance of polyamide resin = 10 / 90, to prepare a polyamide resin mixture.

[0393] Manufacturing Example 9 (Manufacturing of Polyamide Resin Blends Based on Fully Composite Method)

[0394] Polyamide resin (Y1) and the yellowing inhibitor and greening inhibitor in Table 1 were introduced into a twin-screw extruder at the mass ratio in Table 1, and mixed and extruded at 260°C to prepare a polyamide resin mixture.

[0395] Multi-layer hollow container

[0396] Examples 1-13 and Comparative Examples 1-4 (Manufacturing of Multilayer Hollow Containers)

[0397] <Preform Forming>

[0398] An injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., model DU130CI) with two injection barrels and two sets of molds (manufactured by Kortec) was used to injection mold a three-layer preform (each preform weighing 25g) consisting of a polyester layer, a polyamide layer, and a polyester layer. Polyester resin (X1) was injected from one injection barrel, and the polyamide resin mixture obtained in Examples 2-9 (Examples 1-13 and Comparative Example 4), polyester resin (X1) (Comparative Example 1), or polyamide resin (Y1) (Comparative Examples 2 and 3) was injected from the other injection barrel. The molding conditions were as shown below, and the mass of the polyamide layer relative to the preform as a whole is recorded in Table 1. Furthermore, the position of the polyamide layer after bottle molding is also recorded in Table 1. Specifically, the position of the polyamide layer was adjusted by delaying the filling start time of the polyamide resin mixture or polyamide resin constituting the polyamide layer compared to the filling start time of the polyester resin (X1) constituting the polyester layer. The preform has the following shape: total length 95mm, outer diameter 22mm, and wall thickness 4.0mm. The forming conditions for the 3-layer preform are as follows.

[0399] In addition, in Examples 1-13 and Comparative Example 4, the adhesion degree of yellowing inhibitors and greening inhibitors to the hopper after preform molding was evaluated. The results are shown in Table 1.

[0400] Epidermal side injection barrel temperature: 285℃

[0401] Core-side injection molding barrel temperature (3 layers only): 265℃

[0402] Resin flow path temperature inside the mold: 285℃

[0403] Mold cooling water temperature: 15℃

[0404] Loop time: 40 seconds

[0405] <Bottle Forming>

[0406] Using a blow molding apparatus (EFB1000ET, Frontier Inc.), the preform obtained above was subjected to biaxial stretch blow molding to obtain a bottle (multi-layer hollow container). The bottle has a total length of 223 mm, an outer diameter of 65 mm, a body thickness of 350 μm, an internal volume of 500 mL, and a petal-shaped bottom. No shallow recesses were provided in the body. The biaxial stretch blow molding conditions are as follows.

[0407] The bottles (multi-layered hollow containers) obtained in the examples and comparative examples were used to evaluate the bleach resistance (crack resistance) and delamination resistance by conducting bleach storage tests and side impact tests. The results are shown in Table 1.

[0408] Preform heating temperature: 103℃

[0409] Pressure required for tension bar: 0.7 MPa

[0410] Single blow molding pressure: 1.1 MPa

[0411] Secondary blow molding pressure: 2.5MPa

[0412] Delay time for one blow molding cycle: 0.30 seconds

[0413] Blow molding time per cycle: 0.30 seconds

[0414] Second blow molding time: 2.0 seconds

[0415] Blow molding venting time: 0.6 seconds

[0416] Mold temperature: 30℃

[0417] [Determination Method]

[0418] <Location of the polyamide layer>

[0419] To determine the location of the polyamide in the multilayer bottles obtained in the examples and comparative examples, the multilayer bottles were cut along the stretching direction, and iodine tincture was dropped onto the cross-section to stain the polyamide layer, thus confirming the location of the polyamide layer.

[0420] It should be noted that the upper position of the polyamide layer (the height from the ground where the polyamide layer exists, expressed as a ratio when the container height is set to 100%) is set as the average value at measurement section 3.

[0421] In Table 1, the presence of a polyamide layer on the entire bottom surface is marked as "present", the presence of a polyamide layer on a portion of the bottom surface is marked as "partial", and the absence of a polyamide layer on the bottom surface is marked as "absent".

[0422] <Degree of adhesion of yellowing inhibitors>

[0423] The degree of adhesion of the yellowing inhibitor was determined by the following method and evaluated according to the following criteria.

[0424] After forming a 10kg preform in the aforementioned [preform forming] process, the degree of adhesion of the yellowing inhibitor to the hopper filled with the polyamide resin mixture is visually confirmed. The less adhesion to the hopper, the more efficiently the yellowing inhibitor is introduced into the multi-layer container.

[0425] A: It cannot be confirmed whether the yellowing inhibitor adheres to the hopper.

[0426] B: The yellowing inhibitor has been confirmed to adhere to the hopper.

[0427] <Degree of adhesion of greening inhibitors>

[0428] The degree of adhesion of the greening inhibitor was determined by the following method and evaluated according to the following criteria.

[0429] After forming a 10kg preform in the aforementioned [preform forming] process, the degree of adhesion of the green staining inhibitor to the hopper filled with the polyamide resin mixture is visually confirmed. The less adhesion to the hopper, the more efficiently the green staining inhibitor is introduced into the multi-layer container.

[0430] A: It cannot be confirmed whether the greening inhibitor adheres to the hopper.

[0431] B: The adhesion of the greening inhibitor to the hopper has been confirmed.

[0432] <Bleaching Agent Storage Test (Bleaching Agent Resistance (Crack Resistance))>

[0433] The multi-layered bottles obtained in the examples and comparative examples were filled with bleach (Kitchen Haiter (manufactured by Kao Corporation, containing sodium alkyl ether sulfate)) and stored at 40°C for 6 months. The presence or absence of cracks in the bottles during this period was used to evaluate the bleach resistance. Bottles without cracks showed excellent bleach resistance. Two bleach solutions were evaluated: a 6% concentration of hypochlorous acid (concentrated solution) and a 3% concentration of hypochlorous acid (diluted to half with water).

[0434] None: No cracks appeared after storage.

[0435] Yes: Cracks appeared after storage.

[0436] <Side Impact Test (Delamination Resistance)>

[0437] In the multilayer bottles obtained in the examples and comparative examples, 500 mL of carbon dioxide-water mixture was placed in the bottles, which had been stored at 23°C and 50% RH for one week. An impact test was then conducted using a side impact testing machine (a device that applies impact to the main body of the bottle by dropping the oscillator from a 90° angle relative to the bottle with a 3 kg hammer mounted at the front end of the oscillator). The delamination resistance of the multilayer bottles was evaluated based on the peeling observed after 30 impact tests. Less peeling indicates better delamination resistance.

[0438] A: No peeling occurred at the end of the 30 impact tests.

[0439] B: Peeling occurs at the end of 30 impact tests, with the peeling amplitude in the longitudinal direction being within 3.0 cm.

[0440] C: Peeling occurs at the end of 30 impact tests, with the peeling amplitude exceeding 3.0 cm in the longitudinal direction.

[0441] [Manufacturing of recycled polyester]

[0442] <Recycling and Granulation Process>

[0443] 10 kg of hollow multilayer containers obtained in Examples 1-13 and Comparative Examples 1-4 were crushed in a crusher with a mesh diameter of 8 mm, and the resulting flaky crushed material was recycled as recycled polyester.

[0444] The recycled polyester was extruded in a twin-screw extruder (Toshiba Machine Co., Ltd., TEM26SX) at a heater temperature of 270°C and an extrusion speed of 20 kg / h to form a filament. While being cooled in a water bath, it was simultaneously cut into granules in a granulator. It should be noted that in Examples 1-13 and Comparative Examples 2-4, air separation of the polyamide layer was not performed.

[0445] <Crystallization / Solid-phase Polymerization Process>

[0446] The granules obtained in the aforementioned granulation process were heated at 200°C under vacuum reduced to below 1 torr for 7 hours. The heat-treated granules were then removed, and their yellowness Δb*, greenness Δa*, and haze were evaluated. The results are shown in Table 1.

[0447] [Determination Method]

[0448] <Yellowness Δb *>

[0449] The yellowness Δb* of the recycled polyester granules obtained in the [manufacturing of recycled polyester] is determined according to the following method and evaluated according to the following criteria.

[0450] For the hue of the granules, based on JIS Z 8722, a colorimeter ZE-2000 (manufactured by Nippon Denshoku Kogyo, with a 12V 20W halogen lamp light source) was used. The granules were filled into a 30mmφ pool container, and the average value obtained by the reflectance method was used as the hue for measurement.

[0451] It should be noted that the b* value represents chromaticity. +b* indicates the yellow direction, and -b* indicates the blue direction. Furthermore, the smaller the absolute value of Δb*, the more suppressed the yellowing is. Additionally, a lower absolute value indicates higher chromaticity. The Δb* value represents the difference between the b* value of the samples from the examples and comparative examples below and the b* value of the polyester resin alone (the bottle of Comparative Example 1) that underwent the same treatment as the examples and comparative examples.

[0452] <Greenness Δa *>

[0453] The greenness Δa* of the recycled polyester granules obtained in the [manufacturing of recycled polyester] is determined according to the following method and evaluated according to the following criteria.

[0454] For the hue of the granules, based on JIS Z 8722, a colorimeter ZE-2000 (manufactured by Nippon Denshoku Kogyo, with a 12V 20W halogen lamp light source) was used. The granules were filled into a 30mmφ pool container, and the average value obtained by the reflectance method was used as the hue for measurement.

[0455] It should be noted that the a* value represents chromaticity. +a* indicates the red direction, and -a* indicates the green direction. Furthermore, the smaller the absolute value of Δa*, the more the greening is suppressed. Additionally, a lower absolute value indicates higher chromaticity. The Δa* value represents the difference between the a* value of the samples from the examples and comparative examples below and the a* value of the polyester resin alone (the bottle of Comparative Example 1) that underwent the same treatment as the examples and comparative examples.

[0456] <Δhaze>

[0457] The following is formed into a plate, and the Δ haze of the obtained plate is measured.

[0458] (Plate forming)

[0459] Using an injection molding machine (Sumitomo Heavy Industries, Ltd., model SE130DU-HP) equipped with an injection barrel, the recycled polyester granules obtained in the [manufacturing of recycled polyester described later] were injected and injection molded into sheets under the conditions shown below. The sheet shape is as follows: 60mm in length, 90mm in width, and 3.0mm in wall thickness. The sheet molding conditions are as follows.

[0460] Injection barrel temperature: 280℃

[0461] Mold cooling water temperature: 15℃

[0462] Loop time: 45 seconds

[0463] (Measurement and evaluation of Δ haze)

[0464] Δhaze is measured using the following method and evaluated according to the following criteria.

[0465] The haze of the aforementioned plate was measured using a haze meter COH7700 (manufactured by Nippon Denshoku Kogyo, white LED light source) based on JIS K 7136, with the average value of four measurements taken.

[0466] Δhaze represents the value obtained by subtracting the haze of the polyester resin subjected to the same treatment as in the examples and comparative examples from the haze of the samples from the examples and comparative examples. The smaller the Δhaze value, the better the transparency of the recycled polyester.

[0467] [Table 1]

[0468]

[0469] As shown in Table 1, the multilayer hollow containers of Examples 1-13 combine resistance to bleach (crack resistance) and resistance to delamination. Adding a small amount of yellowing inhibitor to the polyamide layer suppresses yellowing of the recycled polyester during reuse. Furthermore, adding a greening inhibitor to the polyamide layer also suppresses greening of the recycled polyester during reuse, while maintaining excellent transparency.

[0470] Furthermore, in the case of multilayer hollow containers as described in Examples 2 to 12, where the masterbatch method is used as the preparation method for the polyamide resin mixture constituting the polyamide layer, the yellowing inhibitor and greening inhibitor are not attached to the hopper, making them easy to manufacture and further suppressing the yellowing of recycled polyester during reuse.

[0471] Explanation of reference numerals in the attached figures

[0472] 1a, 1b: Multi-layered containers (with concave bottom)

[0473] 2a, 2b: Multi-layered containers (with convex bottom)

[0474] 11, 21: Neck

[0475] 12, 13, 22, 23: Main body

[0476] 14: Grounding part

[0477] 15: Bottom

[0478] 24: Grounding part and part of the bottom surface

[0479] 25: Part of the bottom surface

Claims

1. A multi-layer hollow container, comprising: Polyester layer containing polyester resin (X), A polyamide layer comprising polyamide resin (Y) and a yellowing inhibitor (A), Yellowing inhibitor (A) is selected from at least one of the following groups: blue dyes and blue pigments. The content of the yellowing inhibitor (A) in the polyamide layer is 0.001~1.0% by mass. The polyamide layer is an intermediate layer, and it extends from the grounding part to a position of 10-70% of the container height.

2. The multi-layer hollow container according to claim 1, wherein, The polyamide layer is substantially continuous from the grounding portion to a position at least 10% of the container height.

3. The multi-layer hollow container according to claim 1 or 2, wherein, The polyamide resin (Y) has structural units derived from diamine and structural units derived from dicarboxylic acid, wherein the structural units derived from diamine contain more than 80 mol% structural units derived from phenylenediamine and the structural units derived from dicarboxylic acid contain more than 80 mol% structural units derived from dicarboxylic acid.

4. The multi-layer hollow container according to claim 1 or 2, wherein, The content of polyamide resin (Y) is 0.05 to 7.0% by mass relative to the total amount of all polyamide layers and all polyester layers.

5. The multi-layer hollow container according to claim 1 or 2, wherein, The polyester resin (X) has structural units derived from dicarboxylic acids and structural units derived from diols, wherein the structural units derived from dicarboxylic acids contain more than 80 mol% structural units derived from terephthalic acid, and the structural units derived from diols contain more than 80 mol% structural units derived from ethylene glycol.

6. The multi-layer hollow container according to claim 1 or 2, wherein, The yellowing inhibitor (A) is an anthraquinone dye.

7. The multi-layer hollow container according to claim 1 or 2, wherein, The content of yellowing inhibitor (A) is 1 to 30 ppm relative to the total amount of all polyamide layers and all polyester layers.

8. The multi-layer hollow container according to claim 1 or 2, wherein, The polyamide layer also contains a greening inhibitor (B).

9. The multi-layer hollow container according to claim 8, wherein, The greening inhibitor (B) is selected from at least one of the groups consisting of anthraquinone dyes and azo dyes.

10. The multi-layer hollow container according to claim 1 or 2, wherein, Multi-layer containers have a structure of 3 to 5 layers.

11. A bleaching article comprising a chlorine-based liquid bleaching composition contained in a multi-layered hollow container as described in any one of claims 1 to 10.

12. The bleaching article according to claim 11, wherein, The chlorine-based liquid bleach composition contains 0.5-15% sodium hypochlorite by mass.

13. The bleaching article according to claim 11 or 12, wherein, The chlorine-based liquid bleach composition contains a surfactant.

14. The bleaching article according to claim 11 or 12, wherein, The chlorine-based liquid bleach composition contains an alkaline agent.

15. A method for manufacturing a multi-layer hollow container, The multi-layer hollow container has: a polyester layer comprising polyester resin (X), A polyamide layer comprising polyamide resin (Y) and a yellowing inhibitor (A), Yellowing inhibitor (A) is selected from at least one of the following groups: blue dyes and blue pigments. The content of the yellowing inhibitor (A) in the polyamide layer is 0.001~1.0% by mass. This polyamide layer is an intermediate layer, extending from the grounding portion to a position ranging from 10% to 70% of the container height. The manufacturing method includes the following steps: Step 1: Mix polyamide resin (Y) with yellowing inhibitor (A) to prepare a polyamide resin mixture; Step 2 involves co-injection molding the polyamide resin mixture with a polyester resin composition containing polyester resin (X) to obtain a multilayer preform; and, Step 3: Blow molding the multi-layer preform.

16. The method for manufacturing a multi-layer hollow container according to claim 15, wherein, In step 1, granular polyamide resin (Y) and yellowing inhibitor (A) are mixed at a temperature below 230°C.

17. The method for manufacturing a multi-layer hollow container according to claim 15 or 16, wherein, In step 1, the greening inhibitor (B) is further mixed.

18. The method for manufacturing a multi-layer hollow container according to claim 15 or 16, wherein, In step 1, polyamide resin or polyester resin is mixed with yellowing inhibitor (A) and then mixed with polyamide resin (Y).

19. The method for manufacturing a multi-layer hollow container according to claim 17, wherein, In step 1, polyamide resin or polyester resin, yellowing inhibitor (A) and greening inhibitor (B) are mixed and then mixed with polyamide resin (Y).

20. A method for manufacturing recycled polyester, comprising a step of recovering polyester from a multilayer hollow container according to any one of claims 1 to 10.

21. The method for manufacturing recycled polyester according to claim 20, comprising a step of removing all or part of the polyamide layer from a multilayer hollow container to recycle the polyester.

22. The method for manufacturing recycled polyester according to claim 21, wherein, After the multi-layer hollow container is crushed, the polyamide layer is removed by air separation.

23. The method for manufacturing recycled polyester according to any one of claims 20 to 22, wherein, After the polyester recycling process, one or more processes selected from the crystallization process and the solid-state polymerization process are carried out.

Images