Polyester container and polyester preform

Abstract

To provide a polyester container that has a reduced yellow tint and can easily remove bluing agents when mechanically recycled.SOLUTION: The present invention provides a polyester container comprising mechanical recycled polyester and bluing agents. The content of the bluing agents is 0.0001% or more and 0.00125% or less by mass relative to the content of the mechanical recycled polyester.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polyester container and a polyester preform. [Background technology]

[0002] In recent years, attempts have been made to recycle plastic products in order to reduce the environmental load. For example, polyester containers such as used PET bottles have been recycled. Recycled polyesters obtained by recycling polyester containers are used in various products. As such recycled polyesters, chemically recycled polyesters and mechanically recycled polyesters are known.

[0003] Chemically recycled polyester is polyester obtained by chemically decomposing used polyester containers back to monomer units, purifying them, and repolymerizing them. Therefore, chemically recycled polyester has physical properties and characteristics comparable to those of virgin polyester. However, chemically recycled polyester has a problem in that the recycling cost is high. Here, virgin polyester is polyester produced by a conventional method from dicarboxylic acids and diols made from petroleum and the like.

[0004] On the other hand, mechanically recycled polyester is polyester obtained by crushing and washing used polyester containers to remove contaminants and foreign matter, obtaining flakes, and further treating the flakes at high temperature and reduced pressure for a certain period of time to remove contaminants inside the resin, or by pelletizing the washed flakes and further treating the pellets at high temperature and reduced pressure for a certain period of time to remove contaminants inside the resin. Mechanical recycling can obtain recycled polyester without chemical decomposition, so the recycling cost is cheaper than chemical recycling. Therefore, from the viewpoint of cost, it is desirable to use mechanically recycled polyester as the recycled polyester.

[0005] When flakes and pellets made of mechanically recycled polyester are used to manufacture polyester containers, slight amounts of impurities remaining in the flakes and pellets may cause yellowing of the polyester containers after molding. In order to reduce the yellowish tinge of the resin caused by yellowing and make it transparent, Patent Document 1 proposes using pigments such as optical brighteners and blue pigments in molded articles obtained from resin compositions containing recycled polyester. Such additives such as optical brighteners and blue pigments that reduce the yellowish tinge of the resin and make it transparent are generally called bluing agents (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-359914 A [Patent Document 2] JP 2001-166101 A Summary of the Invention [Problem to be solved by the invention]

[0007] Since flakes and pellets made of mechanically recycled polyester are used for various containers, it is desirable that the additives used in the polyester container before mechanical recycling are not left in the flakes and pellets. From this viewpoint, when a polyester container containing a bluing agent is mechanically recycled, it is desirable that the bluing agent is removed from the flakes and pellets made of the mechanically recycled polyester obtained.

[0008] The present inventors have recently discovered that when a polyester container containing a pigment as a bluing agent is mechanically recycled, the bluing agent cannot be removed.

[0009] Accordingly, an object of the present invention is to provide a polyester container which has a reduced yellowing and from which a bluing agent can be easily removed when the polyester container is mechanically recycled. Another object of the present invention is to provide a polyester preform for use in the manufacture of the polyester container. [Means for solving the problem]

[0010] The present inventors have found that the above problems can be solved by using a specific dye as a bluing agent.

[0011] Accordingly, the present invention provides a polyester container comprising mechanically recycled polyester and a bluing agent, The polyester container has a content of the bluing agent of 0.0001% by mass or more and 0.00125% by mass or less relative to a content of the mechanically recycled polyester.

[0012] In the polyester container according to the present invention, the bluing agent may be an anthraquinone-based bluing agent.

[0013] In the polyester container according to the present invention, the content of the mechanically recycled polyester relative to the total polyester constituting the polyester container may be 95% by mass or more.

[0014] The polyester container according to the present invention has a mouth, a neck, a shoulder, a body, and a bottom, The thickness of the body may be not less than 0.05 mm and not more than 0.54 mm.

[0015] In the polyester container according to the present invention, the content may be a colorless and transparent liquid.

[0016] In the polyester container according to the present invention, the L of the mechanically recycled polyester is * a * b *b in color system * The value may be +3.0 or greater.

[0017] The present invention relates to a polyester preform used in the production of the polyester container. Effect of the Invention

[0018] According to the present invention, it is possible to provide a polyester container which has a reduced yellowish color and from which a bluing agent can be easily removed during mechanical recycling. According to the present invention, a polyester preform for use in producing the polyester container can be provided. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic half-sectional view showing one embodiment of a polyester container according to the present invention. [Diagram 2] FIG. 1 is a schematic half-sectional view showing one embodiment of a polyester preform according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [Polyester container] The polyester container according to the present invention comprises mechanically recycled polyester and a bluing agent. In this specification, a "polyester container" is a container containing polyester as a main component. In this specification, a "main component" means a component that accounts for more than 50% by mass of the whole. The content of polyester in a polyester container is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more.

[0021] In this specification, the term "container" refers to a molded body that contains an article. Examples of the container include molded bodies such as compression molded bodies, injection molded bodies, blow molded bodies, and thermoformed bodies. Specific examples of the container include bottles, vials, cups, trays, and packs.

[0022] In this specification, the term "polyester" refers to a polymer that is polymerized through ester bonds. Such polyesters are usually obtained by polycondensation of a dicarboxylic acid compound and a diol compound. Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorene acid, and ester derivatives thereof. Examples of the diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecanediethanol, decalindimethanol, decalindiethanol, and 5-methylol-5-ethyl -2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamantanediol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, pentaerythritol, and bis-β-hydroxyethyl terephthalate (BHET). In the polyester container according to the present invention, the polyester is preferably polyethylene terephthalate or a modified polyethylene terephthalate obtained by polymerizing a raw material monomer of polyethylene terephthalate with a copolymerizable monomer, and particularly preferably polyethylene terephthalate.

[0023] As long as the characteristics of the present invention are not impaired, the polyester may contain monomers other than the dicarboxylic acid compound and the diol compound, but the content thereof is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 3 mol % or less, based on the total structural units.

[0024] The mechanically recycled polyester and the blueing agent contained in the polyester container according to the present invention will be described below.

[0025] <Mechanically recycled polyester> In this specification, "mechanically recycled polyester" refers to polyester obtained by crushing and washing used polyester containers to remove contaminants and foreign matter, obtaining flakes, further treating the flakes at high temperature and reduced pressure for a certain period of time to remove contaminants inside the resin, and pelletizing the flakes, or by pelletizing the washed flakes and then further treating the pellets at high temperature and reduced pressure for a certain period of time to remove contaminants inside the resin. The mechanically recycled polyester contained in the polyester container according to the present invention is preferably mechanically recycled polyethylene terephthalate.

[0026] The flakes and pellets made of the mechanically recycled polyester contain a small amount of impurities. These impurities are inevitable impurities that cannot be completely removed even when treated at high temperature and reduced pressure for a certain period of time. In the production of polyester containers, the flakes and pellets are melted, and if there are trace impurities in the flakes and pellets, the polyester will turn yellow due to the heat generated during melting. Therefore, the mechanically recycled polyester contained in the polyester container according to the present invention has a yellowish color. The polyester container according to the present invention can reduce the yellowish color of the polyester container by containing a bluing agent in a specific range described below. Such a polyester container with reduced yellowish color is particularly suitable when the content is a colorless and transparent liquid. The colorless and transparent liquid is not particularly limited, and examples thereof include drinking water.

[0027] In the polyester container according to the present invention, the L of mechanically recycled polyester * a * b * b in color system * The value may be +3.0 or more, +4.0 or more, or +4.5 or more. On the other hand, the L * a * b* b in color system * The value may be less than or equal to +20.0, less than or equal to +10.0, or less than or equal to +7.0. In this specification, the L of mechanically recycled polyester * a * b * b in color system * Values ​​are measured in accordance with JIS Z8722:2009. Specifically, mechanically recycled polyester having an arbitrary shape is freeze-pulverized to prepare a powder, and this powder is measured by reflected light using a spectrophotometer. The measurement conditions are SCE (specular reflected light excluded), 10° field of view, and D65 light source. As the spectrophotometer, for example, CMS-35SP manufactured by Murakami Color Research Laboratory Co., Ltd. can be used.

[0028] In the polyester container according to the present invention, the content of the mechanically recycled polyester relative to the total polyester constituting the polyester container is preferably 95% by mass or more, more preferably 97% by mass or more, even more preferably 99% by mass or more, and particularly preferably 99.9% by mass or more, thereby making it possible to obtain a polyester container with a reduced environmental load. The polyester container according to the present invention may contain polyesters such as virgin polyester and chemically recycled polyester in addition to mechanically recycled polyester.

[0029] <Bluing agent> In this specification, the term "bluing agent" refers to an additive that absorbs light in the wavelength range of, for example, orange to yellow within the visible light range, and adjusts the hue. In this specification, the "visible light region" refers to the region from 380 nm to 780 nm.

[0030] The bluing agent contained in the polyester container according to the present invention is a dye having a vaporization temperature of 230° C. or less at 15 mbar. By using such a dye as the bluing agent, the bluing agent can be easily removed when the polyester container is mechanically recycled. This is because, in mechanical recycling, when the flakes or pellets are treated at high temperature and reduced pressure for a certain period of time, the bluing agent can be easily removed together with contaminants inside the resin. From the viewpoint of easier removal of the bluing agent from the flakes or pellets, the vaporization temperature of the dye used as the bluing agent is preferably 225° C. or less, more preferably 220° C. or less, at 15 mbar. On the other hand, the vaporization temperature of the dye used as the bluing agent at 1013.25 mbar (atmospheric pressure) is preferably 300° C. or higher, and more preferably 350° C. or higher. By using a dye with a vaporization temperature equal to or higher than this, the amount of dye released into the atmosphere during the production of a polyester container can be reduced, and the content of the bluing agent in the polyester container after molding can be easily adjusted.

[0031] In the polyester container according to the present invention, the content of the bluing agent relative to the mechanically recycled polyester is 0.0001% by mass or more and 0.00125% by mass or less. If the content of the bluing agent is in this range, the yellowness of the polyester container can be reduced and the polyester container can be made transparent. Furthermore, by setting the content of the bluing agent in this range, the bluing agent can be easily removed when the polyester container according to the present invention is mechanically recycled. The content of the bluing agent is preferably 0.00025% by mass or more, more preferably 0.0004% by mass or more, while the content of the bluing agent is preferably 0.001% by mass or less, more preferably 0.0008% by mass or less.

[0032] The bluing agent contained in the polyester container according to the present invention preferably has a maximum absorption peak in the wavelength region of 500 nm or more and 650 nm or less in the visible light region. By using a bluing agent having a maximum absorption peak in such a wavelength region, the yellowish color of the polyester container can be efficiently reduced. More preferably, the bluing agent has a maximum absorption peak in the wavelength region of 550 nm or more and 600 nm or less in the visible light region. In this specification, the maximum absorption peak can be measured, for example, by an SPD-M20A (photodiode array detector) manufactured by Shimadzu Corporation. As a solvent for dissolving the bluing agent, for example, acetonitrile can be used.

[0033] Examples of the bluing agent include dyes such as anthraquinone-based bluing agents and indigo-based bluing agents.

[0034] The anthraquinone-based bluing agent has the formula (1): [ka] The anthraquinone-based bluing agent is preferably a bluing agent having an anthraquinone ring represented by the formula (2): [ka] [In formula (2), X 1 OH, NHR 1 or NR 1 R 2 represents X 2 NHR 3 or NR 3 R 4 R 1 , R 2 , R 3 and R 4 each independently represents a linear or branched alkyl group having from 1 to 6 carbon atoms, or a phenyl group substituted with a linear or branched alkyl group having from 1 to 6 carbon atoms. The compound having the general formula represented by the formula (2) is 1and X 2 may be the same or different. The compound represented by formula (2) is preferably 1 and X 2 At least one of the X in the formula has a phenyl group substituted with a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably, 1 Or X 2 has a phenyl group substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms.

[0035] More preferred examples of the anthraquinone-based bluing agent include the compounds represented by formulae (3) to (5). [ka]

[0036] Indigo-based bluing agents are bluing agents containing indoxyl or thioindoxyl.

[0037] From the viewpoints of heat resistance and solubility (dispersibility), the bluing agent contained in the polyester container according to the present invention is preferably an anthraquinone-based bluing agent, more preferably at least one type of bluing agent having a structure represented by formula (1), even more preferably at least one type of bluing agent having a structure represented by formula (2), even more preferably at least one type of bluing agent selected from the group consisting of compounds represented by formulas (3) to (5), and particularly preferably the bluing agent represented by formula (3).

[0038] The bluing agent may be used alone or in combination of two or more. In addition, in the production of the polyester container according to the present invention, the bluing agent may be used together with an oil component in order to disperse well in the polyester container. Examples of the oil component include ester compounds such as glycerol diacetyl monooleate. In one embodiment, the bluing agent can be added to the polyester container by using a masterbatch that includes the bluing agent and a polyester, which may include the oil component described above. In one embodiment, the bluing agent may be added during the pelletizing process of the flakes in mechanical recycling.

[0039] Hereinafter, one embodiment of the structure of the polyester container according to the present invention will be described with reference to FIG.

[0040] Fig. 1 is a schematic half-sectional view showing one embodiment of a polyester container 10 according to the present invention. As shown in Fig. 1, the polyester container 10 includes a mouth portion 11, a neck portion 12, a shoulder portion 13, a body portion 14, and a bottom portion 15.

[0041] In one embodiment, the mouth portion 11 includes a threaded portion 16 to which a cap is screwed, a cap 17 below the threaded portion 16, and a support ring 18 below the cap 17, as shown in FIG.

[0042] 1, the neck 12 is located between the support ring 18 and the shoulder 13, and has a generally cylindrical shape with a generally uniform diameter. In one embodiment, the shoulder 13 has a cylindrical shape whose diameter gradually increases from the neck 12 side toward the body 14 side.

[0043] In one embodiment, the body 14 is located between the shoulder 13 and the bottom 15 as shown in Fig. 1. Also, in one embodiment, the body 14 has a panel portion 21 that is recessed inward as shown in Fig. 1. This configuration makes it possible to prevent deformation of the polyester container due to an increase or decrease in internal pressure when the polyester container is filled with heated contents or when the polyester container is heated after being filled with contents.

[0044] 1, bottom 15 has a centrally located recessed portion 19 and a grounding portion 20 provided around recessed portion 19, and is connected to body 14 at grounding portion 20. This configuration can prevent deformation of the polyester container due to an increase or decrease in internal pressure when the polyester container is filled with heated contents or when the polyester container is heated after being filled with contents. In one embodiment, the "bottom" refers to the part inside from the part that touches the ground when the polyester container is placed on its own.

[0045] The polyester container according to the present invention has a reduced yellowish color, so that the thickness of the polyester container can be increased. This is because, even if the thickness of the polyester container is increased, the color of the contents is unlikely to change when the contents are visually observed from the outside of the polyester container. Therefore, the polyester container according to the present invention can improve the strength of the polyester container while suppressing the influence of the color on the contents. The cross-sectional thickness of the body of the polyester container is preferably 0.05 mm or more, more preferably 0.1 mm or more. On the other hand, from the viewpoint of reducing the amount of polyester containers used, the cross-sectional thickness of the body of the polyester container is preferably 0.54 mm or less, and more preferably 0.5 mm or less. The cross-sectional thickness of the body of the polyester container refers to the location where the thickness is the thinnest.

[0046] In the polyester container according to the present invention, the ratio of volume to mass (volume / mass) is preferably 5 mL / g or more, more preferably 8 mL / g or more, from the viewpoint of moldability of the polyester container. On the other hand, from the viewpoint of the strength of the polyester container, the volume / mass is preferably 50 mL / g or less, and more preferably 45 mL / g or less.

[0047] The polyester container according to the present invention may have a single layer structure or a multi-layer structure of two or more layers. When the polyester container has a multi-layer structure, each layer may have the same composition or different compositions.

[0048] In one embodiment, the polyester container may have a vapor-deposited film on its surface. This can improve the gas barrier properties of the polyester container. The vapor-deposited film may be located on the inner surface or the outer surface of the polyester container, but is preferably located on the inner surface.

[0049] Examples of the vapor-deposited film include vapor-deposited films composed of metals such as aluminum, inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide, organic silicon compounds such as hexamethyldisiloxane, and hard carbon films such as DLC (Diamond Like Carbon) films. In addition, the hard carbon film made of DLC is also called i-carbon film or hydrogenated amorphous carbon film (aC:H), and is a hard carbon film. 3 It is an amorphous carbon film that is mainly composed of bonds.

[0050] The thickness of the deposited film is not particularly limited, and can be, for example, 1 nm or more and 150 nm or less.

[0051] The deposition film can be formed by a conventional method, for example, physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. The thickness of the vapor-deposited layer can be measured, for example, at the body of a polyester container, and refers to the location where the thickness is the thinnest.

[0052] [Polyester preform] In this specification, the term "polyester preform" refers to a preform prior to blow molding into a polyester container. The polyester preform according to the present invention is used for producing the polyester container according to the present invention. Therefore, the polyester preform according to the present invention contains a mechanically recycled polyester and a bluing agent. By configuring the polyester preform in this way, the polyester container according to the present invention can be produced. The mechanically recycled polyester and the bluing agent contained in the polyester preform according to the present invention may be the same as those used in the polyester container according to the present invention.

[0053] Hereinafter, one embodiment of the structure of the polyester preform according to the present invention will be described with reference to FIG.

[0054] Fig. 2 is a schematic half-sectional view showing one embodiment of a polyester preform 30 according to the present invention. As shown in Fig. 2, the polyester preform 30 includes a mouth portion 31, a body portion 32 connected to the mouth portion 31, and a bottom portion 33 connected to the body portion 32. Of these, the mouth portion 31 corresponds to the mouth portion 11 of the polyester container 10 and has substantially the same shape as the mouth portion 11. The body portion 32 corresponds to the neck portion 12, the shoulder portion 13, and the body portion 14 of the polyester container 10 and has a substantially cylindrical shape. The bottom portion 33 corresponds to the bottom portion 15 of the polyester container 10 and has a substantially hemispherical shape.

[0055] The mouth 31 includes a threaded portion 34 that corresponds to the threaded portion 16 of the polyester container 10 to which a cap (not shown) is screwed, a cap 35 that is provided below the threaded portion 34 and corresponds to the cap 17 of the polyester container 10, and a support ring 36 that is provided below the cap 35 and corresponds to the support ring 18 of the polyester container 10. The shape of the mouth 31 may be any conventional shape.

[0056] The cross-sectional thickness of the body of the polyester preform according to the present invention is preferably 1.3 mm or more, more preferably 1.7 mm or more, while the cross-sectional thickness of the body of the polyester preform is preferably 4.7 mm or less, more preferably 4.0 mm or less. The polyester container according to the present invention can be produced by controlling the cross-sectional thickness of the body of the polyester preform to fall within the above range. The cross-sectional thickness of the body of the polyester preform refers to the location where the thickness is the thinnest.

[0057] The present invention includes the following embodiments. [1] A polyester container comprising mechanically recycled polyester and a bluing agent, The content of the bluing agent relative to the content of the mechanically recycled polyester is 0.0001% by mass or more and 0.00125% by mass or less, 1. A polyester container, wherein the bluing agent is a dye having a vaporization temperature of less than or equal to 230° C. at 15 mbar. [2] The polyester container according to [1], wherein the bluing agent is an anthraquinone-based bluing agent. [3] The polyester container according to [1] or [2], wherein the content of the mechanically recycled polyester relative to the total amount of polyester constituting the polyester container is 95 mass% or more. [4] A container having a mouth, a neck, a shoulder, a body, and a bottom; The polyester container according to any one of [1] to [3], wherein the thickness of the body is 0.05 mm or more and 0.54 mm or less. [5] The polyester container according to any one of [1] to [4], wherein the content is a colorless, transparent liquid. [6] The mechanically recycled polyester, L * a * b * b in color system * The polyester container according to any one of [1] to [5], wherein the value is +3.0 or more. [7] A polyester preform used for producing the polyester container according to any one of [1] to [6]. EXAMPLES

[0058] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0059] [Example 1] Pellet A made of mechanically recycled polyester and pellet B made of a polyethylene terephthalate master batch containing an anthraquinone-based bluing agent having the structure of formula (3) were prepared. The vaporization temperature of the bluing agent was 215° C. at 15 mbar. First, a mixture was obtained by dry blending 97 parts by mass of pellet A and 3 parts by mass of pellet B. The content of the bluing agent relative to the mechanically recycled polyester in the obtained mixture was 0.0005% by mass. Next, the obtained mixture was melted and the molten material was injected using an injection molding machine to produce the polyester preform shown in Figure 2. The body of the polyester preform had a thickness of 3.5 mm and a basis weight of 22 g.

[0060] Next, the polyester preform was heated to 110°C and subjected to biaxial stretch blow molding in a blow molding die to produce a polyester container with a capacity of 500 mL as shown in Figure 1. The cross-sectional thickness of the body of the polyester container was 0.32 mm.

[0061] [Example 2] A polyester preform shown in Fig. 2 was produced in the same manner as in Example 1, except that pellets A and B were dry blended so that the content of the bluing agent in the mechanically recycled polyester was 0.00035% by mass. The body of the polyester preform had a thickness of 3.5 mm and a basis weight of 22 g.

[0062] Next, a polyester container was produced from the polyester preform in the same manner as in Example 1. The cross-sectional thickness of the body of the polyester container was 0.32 mm.

[0063] [Example 3] A polyester preform shown in Fig. 2 was produced in the same manner as in Example 1, except that pellets A and B were dry blended so that the content of the bluing agent in the mechanically recycled polyester was 0.0002% by mass. The body of the polyester preform had a thickness of 3.5 mm and a basis weight of 22 g.

[0064] Next, a polyester container was produced from the polyester preform in the same manner as in Example 1. The cross-sectional thickness of the body of the polyester container was 0.32 mm.

[0065] [Comparative Example 1] A polyester preform shown in Fig. 2 was produced in the same manner as in Example 1, except that only pellet A was used. The body of the polyester preform had a thickness of 3.5 mm and a basis weight of 22 g.

[0066] Next, a polyester container was produced from the polyester preform in the same manner as in Example 1. The cross-sectional thickness of the body of the polyester container was 0.32 mm.

[0067] [Comparative Example 2] Pellet C was prepared, which was made of a polyethylene terephthalate master batch containing a cobalt-based pigment (cobalt blue) as a bluing agent. A polyester preform shown in Fig. 2 was produced in the same manner as in Example 1, except that pellets A and C were dry blended so that the content of the bluing agent in the mechanically recycled polyester was 0.0005% by mass. The body of the polyester preform had a thickness of 3.5 mm and a basis weight of 22 g.

[0068] Next, a polyester container was produced from the polyester preform in the same manner as in Example 1. The cross-sectional thickness of the body of the polyester container was 0.32 mm.

[0069] <<Color measurement>> The mouths of the polyester containers prepared in the Examples and Comparative Examples were cut into small pieces, and the samples were pre-cooled for 10 minutes under liquid nitrogen using a freeze grinder (6870 model Freezer / Mill, manufactured by SPEX Co., Ltd.), and then freeze-ground for 10 minutes under liquid nitrogen to obtain powder. The powder was then measured for L under reflected light using a spectrophotometer (CMS-35SP, manufactured by Murakami Color Research Laboratory Co., Ltd.). * a * b * L in color space * Value, a * value and b * The values ​​were measured under the conditions of SCE (specular reflection excluded), 10° viewing angle, and D65 light source. The measurements were performed in accordance with JIS Z8722:2009. The measurement results are shown in Table 1.

[0070] <<Measurement of bluing agent content>> The polyester containers produced in the examples and comparative examples were crushed to obtain flakes. The flakes were then treated at 230°C and 15 mbar for 2 hours. The content of the bluing agent in the treated flakes was measured by LC-MS (maxis impact, manufactured by Bruker Japan) in the examples, and by ICP-AES (ICPE-9820, manufactured by Shimadzu Corporation) in comparative example 2. The measurement results are shown in Table 1.

[0071] [Table 1]

[0072] It is seen that the polyester container according to the present invention has a reduced yellowish color, and further, that the bluing agent can be easily removed from the polyester container according to the present invention by the treatment under high temperature and reduced pressure carried out in mechanical recycling. [Explanation of symbols]

[0073] 10: Polyester container 11: Mouth 12: Neck 13:Shoulder 14: Torso 15: Bottom 16: Screw part 17: Turnip 18: Support ring 19: Depression 20: Grounding part 21: Panel section 30: Polyester preform 31: Mouth 32: Torso 33: Bottom 34: Screw part 35: Turnip 36: Support ring

Claims

1. A polyester container comprising mechanically recycled polyester and a bluing agent, A polyester container, wherein the content of the bluing agent relative to the content of the mechanically recycled polyester is 0.0001% by mass or more and 0.00125% by mass or less.

2. 2. The polyester container according to claim 1, wherein the bluing agent is an anthraquinone-based bluing agent.

3. 3. The polyester container according to claim 1, wherein a content of the mechanically recycled polyester relative to the total amount of polyester constituting the polyester container is 95 mass% or more.

4. The container has a mouth, a neck, a shoulder, a body, and a bottom, The polyester container according to any one of claims 1 to 3, wherein the thickness of the body portion is 0.05 mm or more and 0.54 mm or less.

5. The polyester container according to any one of claims 1 to 4, wherein the content is a colorless and transparent liquid.

6. The mechanically recycled polyester, L ＊ a ＊ b ＊ b in color system ＊ The polyester container according to any one of claims 1 to 5, wherein the value is +3.0 or more.

7. A polyester preform used for producing the polyester container according to any one of claims 1 to 6.

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