Thermoplastic polymer foamed particle, thermoplastic polymer foamed particle molded body, and identification method for thermoplastic polymer foamed particle or thermoplastic polymer foamed particle molded body

Abstract

Provided are: thermoplastic polymer foamed particles in which it is possible to identify the foamed particles themselves; and a thermoplastic polymer foamed particle molded body that, by being formed from the identifiable thermoplastic polymer foamed particles, can be identified without ruining the aesthetics thereof. Further provided is an identification method for the thermoplastic polymer foamed particles and / or the thermoplastic polymer foamed particle molded body.　Thermoplastic polymer foamed particles (100) exhibit a light emission reaction derived from a light-emitting rare-earth element (10) through irradiation with electromagnetic waves. This thermoplastic polymer foamed particle molded body is formed through in-mold molding using the thermoplastic polymer foamed particles (100) and thereby exhibits a light emission reaction. This identification method for the thermoplastic polymer foamed particles or the thermoplastic polymer foamed particle molded body comprises: i) an electromagnetic wave irradiation step for irradiating the surfaces of the thermoplastic polymer foamed particles or the thermoplastic polymer foamed particle molded body with electromagnetic waves; and ii) a detection step for detecting, by using a detection device, a light emission reaction that is derived from a light-emitting rare-earth element and that occurs through the irradiating with the electromagnetic waves to obtain a light emission spectrum. A first method of the identification method further comprises iii-1) an identification step for observing the contrast between the light emission spectrum and a blank spectrum in which the light emission reaction derived from the light-emitting rare-earth element is not exhibited. A second method of the identification method further comprises iii-2) an identification step for comparing the light emission spectrum with a preset standard light emission spectrum in which the light emission reaction derived from the light-emitting rare-earth element is exhibited.

Description

Expanded thermoplastic polymer beads, expanded thermoplastic polymer beads molded product, and method for identifying expanded thermoplastic polymer beads or expanded thermoplastic polymer beads molded product

[0001] The present invention relates to identifiable expanded thermoplastic polymer beads, expanded thermoplastic polymer bead moldings, and a method for identifying expanded thermoplastic polymer beads or expanded thermoplastic polymer bead moldings.

[0002] Conventionally, techniques for attaching identification information to products to enable identification have been proposed from various viewpoints, such as counterfeit prevention, product management, and production history.

[0003] As a technique for providing identification information to a resin molded product, for example, Patent Document 1 discloses a technique for providing a predetermined index on the surface of a foamed resin molded product by utilizing the tip surface of a piston that closes the cavity of a raw material filling machine for foamed resin molding. Also, Patent Document 2 discloses a technique for irradiating a laser onto the surface of a molded product obtained by molding a resin composition to partially foam it, thereby forming a foaming identification part and marking it.

[0004] JP 2010-149297 WO2022 / 191310A1

[0005] However, the following problems exist when identifying expanded bead moldings formed using expanded beads. In the above-mentioned conventional technology, a visually identifiable identification mark is attached to the surface of the molding, which makes the identification mark conspicuous in appearance and causes problems from the viewpoint of aesthetics. This can result in limitations on the uses and sales destinations of the molding. Furthermore, the above-mentioned conventional technology of attaching an identification mark to the surface of the molding makes it possible to identify the expanded bead molding itself. However, it is not possible to identify the type of expanded beads used in the production of the expanded bead molding.

[0006] For example, there are cases where the manufacturer of the expanded beads is different from the manufacturer of the expanded bead molding that purchases the expanded beads and manufactures the expanded bead molding, and in such cases, it is difficult for the user of the expanded bead molding to determine whether the expanded bead molding has been manufactured using the desired expanded beads.

[0007] On the other hand, physically marking the surface of the expanded beads to make them identifiable would require special manufacturing equipment, which would be costly and therefore not practical.

[0008] The present invention has been made in consideration of the above-mentioned problems. Specifically, the present invention provides expanded thermoplastic polymer beads that are identifiable as expanded beads themselves, and also provides expanded thermoplastic polymer beads moldings that are identifiable without impairing their aesthetic appearance because they are made from the identifiable expanded thermoplastic polymer beads. Furthermore, the present invention provides a method for identifying these expanded thermoplastic polymer beads and / or expanded thermoplastic polymer beads moldings.

[0009] The expanded thermoplastic polymer particles of the present invention are characterized in that they exhibit a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves.

[0010] The expanded thermoplastic polymer bead molding of the present invention is characterized by being obtained by molding the expanded thermoplastic polymer bead of the present invention in a mold.

[0011] The method for identifying expanded thermoplastic polymer beads or expanded thermoplastic polymer bead moldings of the present invention includes at least one of the following first and second identification methods. That is, the first identification method is characterized by comprising: i) an electromagnetic wave irradiation step of irradiating the surface of expanded thermoplastic polymer beads or expanded thermoplastic polymer bead moldings with electromagnetic waves; ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element due to the electromagnetic wave irradiation with a detection device to obtain an emission spectrum; and iii-1) an identification step of comparing the emission spectrum with a blank spectrum that does not show a luminescence reaction caused by the luminescent rare earth element.

[0012] The second identification method is characterized by comprising: i) an electromagnetic wave irradiation step of irradiating electromagnetic waves onto the surface of a thermoplastic polymer foamed particle or a thermoplastic polymer foamed particle molding; ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element due to the electromagnetic wave irradiation using a detection device to obtain an emission spectrum; and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that indicates a luminescence reaction caused by the luminescent rare earth element.

[0013] The expanded thermoplastic polymer beads of the present invention exhibit a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. Therefore, the expanded thermoplastic polymer beads of the present invention can be identified by detecting this luminescent reaction. Furthermore, a thermoplastic polymer expanded bead molding obtained by molding the expanded thermoplastic polymer beads of the present invention in a mold is composed of expanded beads exhibiting the luminescent reaction. Therefore, the expanded thermoplastic polymer bead molding of the present invention exhibits a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. Detection of this luminescent reaction not only enables the expanded thermoplastic polymer bead molding to be identified, but also enables identification that the expanded thermoplastic polymer bead molding is composed of the expanded thermoplastic polymer beads of the present invention. Furthermore, a first identification method of the present invention compares the emission spectrum detected in the luminescent reaction due to the luminescent rare earth element in the expanded thermoplastic polymer beads or the expanded thermoplastic polymer bead molding with a blank spectrum that does not exhibit the luminescent reaction due to the luminescent rare earth element. This first identification method allows identification of the expanded thermoplastic polymer beads or the expanded thermoplastic polymer bead molding of the present invention. The second identification method of the present invention involves comparing an emission spectrum detected in a luminescence reaction due to a luminescent rare earth element in a thermoplastic polymer foamed bead or a thermoplastic polymer foamed bead molding with a predetermined reference emission spectrum showing a luminescence reaction due to a luminescent rare earth element, thereby making it possible to identify whether the foamed thermoplastic polymer beads or foamed thermoplastic polymer foamed bead molding of the present invention are the specified foamed thermoplastic polymer beads or the specified foamed thermoplastic polymer foamed bead molding.

[0014] FIG. 1 is a schematic cross-sectional view of a single-layer type thermoplastic polymer expanded bead which is one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a two-layer type thermoplastic polymer expanded bead which is one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a three-layer type thermoplastic polymer expanded bead which is one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a two-layer cylindrical thermoplastic polymer expanded bead which is one embodiment of the present invention, taken along the axial direction. FIG. 5 is a chart showing the emission spectrum of luminescent compound 1 used in the examples. FIG. 6 is a chart showing the emission spectrum of the expanded bead molding of Example 1 and a baseline which is the spectrum of a blank expanded bead molding. FIG. 7 is a schematic diagram of a DSC curve measured to obtain the total heat of fusion and high-temperature peak heat quantity of expanded polyolefin resin beads which are one embodiment of the present invention.

[0015] Below, we will explain the expanded thermoplastic polymer beads of the present invention (hereinafter sometimes referred to as the expanded beads of the present invention or expanded beads), the expanded thermoplastic polymer bead molding of the present invention (hereinafter sometimes referred to as the expanded bead molding or molding of the present invention), and the method for identifying the expanded thermoplastic polymer beads of the present invention or the expanded thermoplastic polymer bead molding (hereinafter sometimes simply referred to as the identification method of the present invention or identification method).

[0016] In the description of the present invention, the emission spectrum, the inherent emission spectrum of a luminescent rare earth element component, the blank spectrum not showing a luminescent reaction derived from a luminescent rare earth element, and the predetermined reference emission spectrum showing a luminescent reaction derived from a luminescent rare earth element respectively refer to the following:

[0017] The term "emission spectrum" refers to the emission spectrum of a luminescence reaction that occurs when an electromagnetic wave of a predetermined wavelength is irradiated onto a measurement target. Here, the measurement target includes molded articles such as expanded beads and expanded bead molded articles, as well as the luminescent rare earth element component itself. In the present invention, the emission spectrum is a concept composed of one or more elements selected from the overall pattern shape, the number of peaks, the wavelength at which each peak is detected, the shape of each peak, the intensity ratio between each peak, the area ratio between each peak, etc. Furthermore, the wavelength of the light emitted in the luminescence reaction is not particularly limited, and examples thereof include visible light and infrared light.

[0018] The inherent emission spectrum of a luminescent rare earth element component refers to the emission spectrum detected when the luminescent rare earth element component itself is irradiated with electromagnetic waves of a predetermined wavelength. The inherent emission spectrum varies depending on the type and combination of luminescent rare earth elements selected. Therefore, it is possible to induce a luminescence reaction that exhibits a different inherent emission spectrum by using a specific luminescent rare earth element or a combination of two or more luminescent rare earth elements. In this specification, the inherent emission spectrum of a luminescent rare earth element component may sometimes be simply referred to as the inherent emission spectrum.

[0019] A blank spectrum that does not show a luminescent reaction due to a luminescent rare earth element refers to a spectrum detected when an electromagnetic wave of a predetermined wavelength is irradiated onto a molded article that does not contain a luminescent rare earth element component and is composed of a polymer of a predetermined composition. The molded article may be an expanded bead or an expanded bead molding. Specifically, the blank spectrum that does not show a luminescent reaction due to a luminescent rare earth element is a spectrum detected when an electromagnetic wave of a predetermined wavelength is irradiated onto a molded article composed of a polymer that has the same composition as the expanded bead or expanded bead molding to be identified, except that it does not contain a luminescent rare earth element component. Furthermore, the molded article may be an expanded bead or an expanded bead molding manufactured by the same manufacturing method as the expanded bead or expanded bead molding to be identified. In this specification, a blank spectrum that does not show a luminescent reaction due to the luminescent rare earth element may sometimes be simply referred to as a blank spectrum. The blank spectrum is used in the first identification method described below.

[0020] A predetermined reference emission spectrum showing a luminescent reaction due to a luminescent rare earth element refers to an emission spectrum detected when an electromagnetic wave of a predetermined wavelength is irradiated onto a molded article containing a predetermined luminescent rare earth element component and composed of a polymer of a predetermined composition. The emission spectrum shows a luminescent reaction due to a luminescent rare earth element. The molded article may be an expanded bead or an expanded bead molding. The content of the luminescent rare earth element component in the expanded beads used to obtain the reference emission spectrum may be approximately 0.0001% by mass or more and 0.5% by mass or less. In this specification, the predetermined reference emission spectrum showing a luminescent reaction due to the luminescent rare earth element may be simply referred to as a reference emission spectrum or a predetermined reference emission spectrum. The reference emission spectrum is used in the second identification method described below. In addition, the following may describe a process of detecting a reference emission spectrum by irradiating an electromagnetic wave of a predetermined wavelength onto an expanded bead containing a predetermined luminescent rare earth element component and composed of a polymer of a predetermined composition. This step can also be carried out in the same manner by using a foamed bead molding made from the foamed beads instead of the foamed beads.

[0021] [Expanded Thermoplastic Polymer Beads] The expanded beads of the present invention are expanded thermoplastic polymer beads that exhibit a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. Specifically, the expanded beads exhibit a luminescent reaction detectable as an emission spectrum when irradiated with electromagnetic waves. The present invention is completely different from conventional techniques that physically mark expanded bead moldings; it imparts identifiability through a luminescent reaction to the expanded beads themselves that constitute the expanded bead molding. Therefore, the present invention does not impair the aesthetic appearance of the expanded bead molding itself. Furthermore, identification is possible by applying the identification method described below. The spectrum of the luminescent reaction due to the luminescent rare earth element varies depending on the type and combination of luminescent rare earth elements contained in the expanded beads and the composition of the polymer that constitutes the expanded beads. Therefore, for example, by using the second identification method described below to check whether a predetermined reference emission spectrum and the emission spectrum detected from the expanded beads to be identified show similar patterns, the expanded beads can be more precisely identified. Furthermore, when an expanded bead molding produced in a mold using the expanded beads of the present invention is irradiated with electromagnetic waves, the expanded beads of the present invention that constitute the expanded bead molding exhibit a luminescent reaction. By detecting such a luminescence reaction, the expanded bead molding can be identified as being made using the expanded beads of the present invention. Therefore, according to the present invention, it is possible to trace the expanded beads that make up the expanded bead molding from the expanded bead molding. In other words, according to the present invention, it is possible to determine, for example, information about the origin of the expanded beads that make up the expanded bead molding from the expanded bead molding. The information that can be determined, including the origin information, is information linked to a predetermined reference emission spectrum, and will be described in detail below.

[0022] The expanded beads of the present invention will be described in more detail below. In the following description, preferred numerical ranges of the present invention may be indicated as appropriate. In such cases, preferred, more preferred, and particularly preferred ranges regarding the upper and lower limits of the numerical range can be determined from all combinations of the upper and lower limits. In the following description, the expression "A to B" representing a numerical range is synonymous with "A or more and B or less," and represents a numerical range including the endpoints A and B of the numerical range.

[0023] (Thermoplastic Polymer) The expanded beads of the present invention are composed of a thermoplastic polymer. The thermoplastic polymer refers to a polymer having thermoplastic properties, and specifically includes a thermoplastic resin and a thermoplastic elastomer.

[0024] Examples of the thermoplastic resin include polyolefin resins such as polypropylene resins and polyethylene resins; polystyrene resins; polyamide resins; polyester resins; polycarbonate resins; and modified polyphenylene ether resins.

[0025] In this specification, the term "polypropylene-based resin" refers to a propylene homopolymer or a polypropylene-based copolymer containing 50% by mass or more of structural units derived from propylene. Specific examples include propylene homopolymers such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene; and propylene-based copolymers such as ethylene-propylene copolymer, butene-propylene copolymer, hexene-propylene copolymer, ethylene-propylene-butene terpolymer, and propylene-maleic anhydride copolymer. These copolymers may be, for example, random copolymers or block copolymers, but are preferably random copolymers.

[0026] In this specification, the term "polyethylene resin" refers to an ethylene homopolymer or an ethylene copolymer containing 50% by mass or more of structural units derived from ethylene. Specific examples include polyethylenes such as high-density polyethylene (PE-HD), medium-density polyethylene (PE-MD), low-density polyethylene (PE-LD), linear low-density polyethylene (PE-LLD), and linear very low-density polyethylene; and ethylene copolymers such as ethylene-vinyl acetate copolymer and ethylene-methyl methacrylate copolymer.

[0027] In this specification, the term "polyamide resin" refers to a resin having an amide bond in the molecular chain. Specific examples include homopolyamides such as nylon 6 obtained by ring-opening polymerization of ε-caprolactam and nylon 66 obtained by co-condensation polymerization of hexamethylenediamine and adipic acid, and polyamide copolymers such as polycaproamide / polyhexamethyleneadipamide copolymer (nylon 6 / 66), caprolactam / hexamethylenediaminoadipic acid / lauryllactam (nylon 6 / 66 / 12), and caprolactam / lauryllactam copolymer (nylon 6 / 12).

[0028] In this specification, the term "polyester resin" refers to a resin having an ester bond in the molecular chain. Specific examples include aliphatic polyesters such as polylactic acid, polybutylene succinate, polybutylene adipate, and polyhydroxybutyric acid; and aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate.

[0029] Examples of the thermoplastic elastomer include olefin-based thermoplastic elastomers (TPO) and urethane-based thermoplastic elastomers (TPU).

[0030] Those skilled in the art can distinguish between thermoplastic resins and thermoplastic elastomers. Thermoplastic resins typically exhibit a flexural modulus of 100 MPa or more. From the viewpoint of the moldability of the expanded beads, the flexural modulus of the thermoplastic resin is preferably 3000 MPa or less, more preferably 2000 MPa or less, even more preferably 1500 MPa or less, and particularly preferably 1200 MPa or less. On the other hand, thermoplastic elastomers exhibit rubber elasticity at room temperature and typically exhibit a flexural modulus of less than 100 MPa. The flexural modulus of a thermoplastic polymer can be determined in accordance with JIS K7171:2008. From the viewpoint of achieving an excellent balance between the moldability and physical properties of the expanded beads, the expanded beads of the present invention are preferably composed of a thermoplastic resin.

[0031] The expanded beads of the present invention may be composed of one type of thermoplastic polymer, or may be composed of two or more types of thermoplastic polymers.

[0032] From the viewpoint of obtaining a foamed bead molding obtained by in-mold molding using the foamed beads of the present invention with better shock-absorbing properties, compression recovery, and light weight, the foamed beads of the present invention preferably contain a polyolefin resin, more preferably a polypropylene resin, and the polypropylene resin preferably accounts for 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of the thermoplastic polymer constituting the foamed beads of the present invention (100% by mass).

[0033] Furthermore, from the viewpoint of contributing to the achievement of the Sustainable Development Goals (SDGs), the expanded beads of the present invention preferably contain a recycled thermoplastic polymer. Here, the recycled thermoplastic polymer broadly includes thermoplastic polymers recovered from waste products such as scraps generated at production sites during production and used films and foamed molded articles.

[0034] In recent years, there has been a social trend toward providing products made from recycled materials. Therefore, those who provide final products to the market may wish to indicate that at least a portion of the product contains recycled materials. However, in the technical field of expanded bead moldings, the manufacturer of the expanded beads may be different from the manufacturer that purchases the expanded beads and produces the expanded bead moldings. In such cases, a problem has arisen in that it is difficult for purchasers (e.g., users) of the expanded bead moldings to confirm whether the expanded beads that make up the expanded bead moldings contain expanded beads containing recycled thermoplastic polymers.

[0035] In contrast, in the expanded beads of the present invention containing a recycled thermoplastic polymer, the expanded beads or expanded bead moldings made using the expanded beads exhibit a luminescent reaction due to the luminescent rare earth element when irradiated with electromagnetic waves. Therefore, users of expanded bead moldings should be aware in advance that expanded beads containing a recycled thermoplastic polymer, which is the material used, exhibit a predetermined luminescent reaction when irradiated with electromagnetic waves. This allows the user to identify an expanded bead molding they have obtained as having been made using expanded beads containing a recycled thermoplastic polymer by irradiating the expanded bead molding with electromagnetic waves and detecting the luminescent reaction. In other words, this aspect of the present invention enables tracking of expanded beads containing a recycled thermoplastic polymer.

[0036] Examples of recycled thermoplastic polymers include thermoplastic polymers derived from recycled materials, such as post-consumer materials and pre-consumer materials. Post-consumer materials, as defined in JIS Q14021:2000, refer to materials discarded from households or materials generated by commercial, industrial, and other end-user facilities that are no longer usable for their intended purposes. Post-consumer materials include materials returned from distribution channels. Pre-consumer materials, as defined in JIS Q14021:2000, refer to materials removed from the waste stream during manufacturing processes. For example, pre-consumer materials exclude unsuitable for processing, polishing, and scrap that can be reused in the same process as their generation. In this specification, recycled materials also include unsuitable for processing, polishing, and scrap that can be reused in the same process as pre-consumer materials. Thermoplastic polymers derived from these recycled materials are generally available as pellets obtained by collecting, crushing, and / or melting these recycled materials. For example, thermoplastic resins derived from post-consumer materials can be obtained by recovering used thermoplastic resin foam molded articles used by end users, crushing and / or melting them, and pelletizing them. Alternatively, thermoplastic resins derived from post-consumer materials can be obtained by recovering thermoplastic resins from automobile shredder residue generated during the automobile disposal process, crushing and / or melting them, and pelletizing them. In this specification, automobile shredder residue (ASR) refers to "automobile shredder residue" as defined in Article 2, Paragraph 5 of the "Law Concerning Recycling, etc. of End-of-Life Automobiles" (Law No. 87 of 2002). In the present invention, expanded particles containing recycled thermoplastic polymers may be composed solely of the above-described recycled thermoplastic polymers, or may be composed of a mixture of recycled thermoplastic polymers and virgin thermoplastic polymers. In this specification, virgin thermoplastic polymers refer to new thermoplastic polymers, excluding recycled materials.The recycled thermoplastic polymer may be the same as the thermoplastic polymer described above, except that it is recycled.

[0037] When the expanded beads of the present invention are composed of a mixture of a virgin thermoplastic polymer and a recycled-derived thermoplastic polymer, the mass ratio of the virgin thermoplastic polymer to the recycled-derived thermoplastic polymer in the expanded beads (virgin thermoplastic polymer:recycled thermoplastic polymer) is preferably 97:3 to 1:99, more preferably 95:5 to 10:90, even more preferably 90:10 to 30:70, and particularly preferably 85:15 to 50:50.

[0038] The expanded beads of the present invention may contain other polymers besides the thermoplastic polymer. Examples of other polymers include thermosetting resins and rubbers. The content of other polymers in the expanded beads is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 0%, i.e., the expanded beads contain substantially only thermoplastic polymers as polymers.

[0039] (Luminescent Rare Earth Element) The expanded beads of the present invention exhibit a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. In other words, the expanded beads of the present invention contain a luminescent rare earth element together with the thermoplastic polymer described above. The expanded beads of the present invention can be identified by the luminescent reaction exhibited by irradiation with electromagnetic waves.

[0040] The luminescent reaction is derived from one or more luminescent rare earth elements selected from the group consisting of praseodymium (Pr), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and thulium (Tm). In other words, the expanded beads of the present invention may contain one or more luminescent rare earth elements selected from the group consisting of praseodymium (Pr), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and thulium (Tm). The expanded beads of the present invention more preferably contain, as a luminescent rare earth element, one or more elements selected from the group consisting of praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and thulium (Tm). In the present invention, the luminescent rare earth element may be a single element or a composite containing the luminescent rare earth element, as long as it exhibits a luminescent reaction upon at least electromagnetic wave irradiation.

[0041] It is useful to directly or indirectly recognize information about the emission spectrum exhibited by the luminescent reaction in the expanded beads of the present invention. The expanded beads of the present invention can be identified as follows based on such recognition. That is, the expanded beads of the present invention are expanded beads containing a thermoplastic polymer and a luminescent rare earth element component that emits light and exhibits a specific emission spectrum when irradiated with electromagnetic waves. The expanded beads of the present invention can be identified as those containing the luminescent rare earth element by comparing the emission spectrum detected by irradiating the expanded beads with the electromagnetic waves with a predetermined reference emission spectrum that indicates the luminescent reaction originating from the luminescent rare earth element. This identification method will be described in detail later. Here, "directly recognizing information about the emission spectrum exhibited by the luminescent reaction" refers to directly obtaining the actual light intensity and wavelength pattern of the emission spectrum. On the other hand, "indirectly recognizing the information" refers to mechanically identifying the expanded beads using a system, such as a comparison system, in which a reference emission spectrum pattern is recorded so as to be collatable.

[0042] In this specification, luminescent rare earth elements or composites containing luminescent rare earth elements may be collectively referred to as luminescent rare earth element components. Examples of luminescent rare earth element components include taggant particles, which will be described later.

[0043] In one embodiment of the present invention, the expanded beads of the present invention preferably contain taggant particles containing a luminescent rare earth element. In the present invention, the taggant particles are particulate identifiers that contain a luminescent rare earth element component and enable identification by a luminescent reaction. From the viewpoint of facilitating a stable luminescent reaction, the taggant particles are preferably a compound containing a luminescent rare earth element. However, the taggant, or identifier, is not necessarily limited to particles.

[0044] The shape of the taggant particles is not particularly limited and can take various shapes, such as spherical, oval (egg-shaped), cylindrical, prismatic, pellet-like, and granular. One embodiment of the taggant particles is a fine powder having an average particle diameter of 0.1 μm to 100 μm, preferably 1 μm to 50 μm. In this case, the fine particle taggant particles can be more uniformly dispersed in the thermoplastic polymer constituting the expanded beads, thereby improving the accuracy of detecting the luminescent reaction. The average particle diameter of the taggant particles is measured by the following method. First, the taggant particles are observed using a scanning electron microscope and an image is taken. The image is analyzed to measure the area (projected area) of the particle, and the diameter of a virtual circle having the same area as the projected area is defined as the particle diameter. This measurement is performed on 100 or more particles, and the arithmetic mean value is defined as the average particle diameter of the taggant particles.

[0045] Examples of taggant particles, which are particulate composites containing a luminescent rare earth element component, include crystalline ligands obtained by reacting a luminescent rare earth element with an unsaturated organic ligand, and crystalline ligands obtained by reacting a luminescent rare earth element, a non-luminescent rare earth element, and an unsaturated organic ligand. More specifically, the crystalline ligands are composites obtained by coordinating one or more luminescent rare earth elements to an unsaturated organic ligand. Examples of the unsaturated organic ligand include phthalates, isophthalates, terephthalates, trimesates, trimellitates, pyromellitates, and mellitates.

[0046] The taggant particle composite has the advantage that a wide variety of emission spectra can be achieved by designing the type and combination of luminescent rare earth elements used. For example, a specific emission spectrum exhibited by a molded article made of a polymer composition of a given composition containing certain taggant particles when irradiated with electromagnetic waves of a specific wavelength can be pre-associated with one or more pieces of information selected from the following: the properties of the material constituting the expanded beads, physical property information of the expanded beads, such as apparent density, production condition information, such as production lot number and production date, and source information, such as manufacturer information. The molded article is preferably expanded beads or expanded bead moldings. This allows the taggant particles to more effectively function as particulate identifiers that enable identification by luminescence reaction. Specifically, the pre-associated information can be obtained from expanded beads containing the taggant particles or their moldings using the second identification method described below.

[0047] When the crystalline ligand is irradiated with electromagnetic waves, light energy is transferred to the luminescent rare earth element via the organic ligand contained in the composite. As a result, the luminescent rare earth element becomes excited, and then a luminescence reaction occurs in which light of a predetermined wavelength, such as visible light, is emitted, and the element returns to its ground state. In order to maximize the energy of the electromagnetic waves transferred to the luminescent rare earth element via the organic ligand, it is preferable that the organic ligand has a structure that exhibits optimal absorption in the wavelength range of the electromagnetic waves selected for excitation. In other words, it is preferable that the electromagnetic waves be selected from a wavelength range that can be optimally absorbed by the organic ligand contained in the composite.

[0048] From the viewpoint of making it easier to detect the luminescent reaction due to electromagnetic wave irradiation and making it difficult to reduce the moldability of the expanded beads, the content Ctt of taggant particles in the expanded beads of the present invention is preferably 0.0001% by mass or more and 0.5% by mass or less, more preferably 0.0005% by mass or more and 0.1% by mass or less, even more preferably 0.001% by mass or more and 0.05% by mass or less, and particularly preferably 0.002% by mass or more and 0.03% by mass or less. In other words, from the viewpoint of making it easier to detect the luminescent reaction, the lower limit of the content Ctt is more preferably 0.0005% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.002% by mass or more. On the other hand, from the viewpoint of further suppressing the increase in costs due to the use of taggant particles containing expensive luminescent rare earth elements, from the viewpoint of providing expanded beads having superior moldability, and from the viewpoint of providing expanded beads having superior uniformity of cell diameter, the upper limit of the content Ctt is more preferably 0.1 mass% or less, even more preferably 0.05 mass% or less, and particularly preferably 0.03 mass% or less.

[0049] For compounds containing luminescent rare earth elements, see, for example, Japanese Patent Application Laid-Open No. 2006-249075, Japanese Patent Application Laid-Open No. 2022-187940, and US 2010 / 0207067.

[0050] (Electromagnetic Waves) The electromagnetic waves used to cause the luminescent rare earth elements to emit light may be appropriately selected depending on the type and combination of luminescent rare earth elements contained in the expanded beads. Examples of electromagnetic waves include infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays. Light rays are preferred as the electromagnetic waves because they are easy to handle and use, and ultraviolet rays are particularly preferred. In other words, taggant particles that exhibit a luminescent reaction when exposed to light are preferred in the present invention. The irradiated light may be a single wavelength or a broad wavelength having multiple wavelengths. It is particularly preferred that the expanded beads of the present invention do not exhibit a luminescent reaction when exposed to visible light but exhibit a luminescent reaction when exposed to ultraviolet light. In this case, the taggant particles composed of the luminescent rare earth elements are not visible to the naked eye when exposed to visible light, thereby preventing the aesthetic appearance of the expanded bead molding from being impaired.

[0051] (Mold of Expanded Beads) Next, the structure and shape of the expanded beads of the present invention will be described with reference to Figs. 1 to 4. The shape of the expanded beads is not particularly limited, and various shapes such as spherical, elliptical, cylindrical, and cylindrical shapes can be used. Figs. 1 to 3 are schematic cross-sectional views showing a cut surface taken through the center of a spherical expanded bead 100, and Fig. 4 is a schematic cross-sectional view taken along the axial direction of a double-layered cylindrical expanded bead 100. The structure and shape of the expanded beads of the present invention can be designed as appropriate as long as the objects and effects of the present invention are not impaired, and several desirable structures and shapes can be mentioned, as described below.

[0052] The expanded beads 100A shown in Figure 1 are spherical and single-layered. That is, the expanded beads 100A are entirely composed of an expanded layer 20, with taggant particles 10 dispersed therein. The single-layer expanded beads 100A have the advantages of being easy to manufacture and easily lightweight. However, the expanded beads of the present invention are not limited to a single-layer structure. Examples of expanded beads of the present invention having a multilayer structure are described below with reference to Figures 2 to 4.

[0053] The expanded beads 100 (100B, 100C, 100D) shown in Figures 2 to 4 have a multilayer structure including a foam layer 20 made of a thermoplastic polymer and a polymer layer 30 made of a polymer. Expanded beads with a multilayer structure are preferred because they offer various advantages, as described below. In such a multilayer structure, the ratio [Ctr / Ctt] of the content Ctr of taggant particles 10 in the polymer layer 30 to the content Ctt of taggant particles 10 in the expanded beads 100 is preferably 2 or more, more preferably 5 or more, even more preferably 10 or more, and particularly preferably 20 or more. By having a relatively high content of taggant particles 10 in the polymer layer 30, the concentration of taggant particles 10 can be locally increased in the polymer layer 30 while maintaining a low content Ctt of taggant particles 10 in the entire expanded beads 100. As a result, the probability of collision between the irradiated electromagnetic waves and the taggant particles 10 increases in the polymer layer 30 of the multilayer expanded beads 100, allowing for an efficient light-emitting reaction. Furthermore, by having a relatively large amount of taggant particles 10 present in the polymer layer 30, it is possible to prevent the taggant particles 10 from adversely affecting the foaming state of the foam layer 20, and more uniform bubbles are likely to be formed in the foam layer 20. The upper limit of the ratio [Ctr / Ctt] is preferably 100 or less, more preferably 80 or less, even more preferably 50 or less, and particularly preferably 35 or less, from the viewpoint of preventing the fusibility of the expanded beads from being impaired. In other words, the ratio [Ctr / Ctt] is preferably 2 or more and 100 or less, more preferably 5 or more and 80 or less, even more preferably 10 or more and 50 or less, and particularly preferably 20 or more and 35 or less. Regarding the expanded beads of the present invention, the taggant particle content refers to the ratio (mass %) of the mass of the taggant particles contained in the expanded beads to the mass of the expanded beads.

[0054] In addition, an embodiment in which the content Ctt of taggant particles in the multilayered expanded beads 100 is 0.0001 mass% or more and 0.5 mass% or less, and the ratio [Ctr / Ctt] of the content Ctr of taggant particles 10 in the polymer layer 30 to the content Ctt of taggant particles 10 in the expanded beads 100 is 2 or more, is excellent in that it reduces the amount of taggant particles 10 used and increases the efficiency of the luminescence reaction without hindering the expanded state of the expanded beads 100.

[0055] As described above, in the multilayer structure, it is particularly preferable that the following feature be further added to expanded beads having a ratio [Ctr / Ctt] of the content Ctr of taggant particles 10 in the polymer layer 30 to the content Ctt of taggant particles 10 in the expanded beads 100 of 2 or more. That is, from the viewpoint of making it possible to sufficiently increase the content of taggant particles 10 in the polymer layer 30 and efficiently inducing a luminescent reaction, in addition to the above feature, the mass proportion of the polymer layer 30 in the expanded beads 100 is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 8% by mass or less.

[0056] The foam layer 20 in the expanded beads 100B, 100C, and 100D may or may not contain taggant particles 10. However, from the viewpoint of maintaining a good foaming state of the foam layer 20 and improving economic efficiency by reducing the amount of taggant particles 10 used, the content of taggant particles 10 in the foam layer 20 is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.001% by mass or less, particularly preferably 0.0001% by mass or less, and most preferably 0, i.e., the foam layer 20 does not contain taggant particles 10.

[0057] Here, an example of a multilayered expanded bead 100 is an expanded bead 100B, as shown in FIG. 2, which is spherical and has a foamed layer 20 as a core layer and a polymer layer 30 as a coating layer covering the foamed layer 20, with the polymer layer 30 located on the surface of the expanded bead. Another example is an expanded bead 100C, as shown in FIG. 3, which is spherical and has a foamed layer 20 as a core layer, an outermost layer 40 provided on the surface of the expanded bead, and an intermediate polymer layer 30 located between the foamed layer 20 and the outermost layer 40. The outermost layer 40 can be made of any material, such as a foamed thermoplastic polymer or a non-foamed thermoplastic polymer. To ensure sufficient luminescence in the intermediate polymer layer 30, the outermost layer 40 is preferably a layer that is easily permeable to electromagnetic waves, and more preferably a layer that is easily permeable to ultraviolet or visible light, which are preferred as electromagnetic waves. For example, the outermost layer 40 may be made of a transparent or white polymer. Another embodiment is an expanded bead 100D, as shown in Fig. 4, which is cylindrical and has a foam layer 20 as a core layer and a polymer layer 30 as a coating layer that coats the lateral circumferential surface of the foam layer 20, with the polymer layer 30 located on the surface of the expanded bead. Fig. 4 shows an embodiment in which the polymer layer 30 is provided on the entire circumferential surface of the expanded bead 100D in the longitudinal direction, and the foam layer 20 is exposed at end faces 21 in the longitudinal direction. However, as a modified example, the expanded bead 100D may have the polymer layer 30 covering the entire foam layer 20, including the end faces 21. Note that, although not shown, the expanded bead of the present invention is not limited to an embodiment in which the polymer layer is provided on the surface side of the foam layer, and also includes an embodiment in which the polymer layer is provided closer to the center of the expanded bead than the foam layer.

[0058] 2 and 3 show an embodiment in which the polymer layer 30, which is a coating layer, covers the entire foam layer 20, but the present invention also encompasses embodiments in which the polymer layer 30 partially covers the foam layer 20, as in the case of the expanded beads 100D shown in Fig. 4, as long as the objects and effects of the present invention are not impaired. From the viewpoint of improving the detection accuracy of the luminescent reaction, the expanded beads 100 having a multilayer structure having the polymer layer 30 covering the foam layer 20 are preferably composed of the foam layer 20 and the polymer layer 30 covering 30% or more of the surface area of ​​the foam layer 20. From the same viewpoint, it is more preferable that the polymer layer 30 cover 50% or more of the surface area of ​​the foam layer 20, and even more preferable that it cover 70% or more.

[0059] In the above-described multilayer expanded beads 100, the expanded beads 100B and 100D, in particular those in which the polymer layer 30 is located on the surface of the expanded beads, can efficiently absorb the energy of the irradiated electromagnetic waves into the taggant particles 10 contained in the polymer layer 30. Therefore, the expanded beads 100B and 100D undergo a favorable luminescence reaction, and as a result, the luminescence spectrum of the luminescence reaction can be detected with high accuracy.

[0060] However, even in an embodiment in which the polymer layer 30 does not appear on the surface of the expanded beads 100, as in the expanded beads 100C, as long as the polymer layer 30 is provided in the vicinity of the surface of the multilayer expanded beads 100, the energy of the irradiated electromagnetic waves can be efficiently absorbed by the taggant particles 10 contained in the polymer layer 30, as in the expanded beads 100B and 100D. In other words, the polymer layer 30 is preferably provided on or near the surface of the multilayer expanded beads 100. The polymer layer 30 being provided in the vicinity of the surface of the multilayer expanded beads 100 means that at least a portion of the polymer layer 30 is located in a region d1 extending from the surface of the multilayer expanded beads 100 to a depth of 1000 μm toward the center, as shown in FIG. 3 , for example.

[0061] In the multilayer expanded beads 100 comprising the above-described foam layer 20 and polymer layer 30, from the viewpoint of efficiently inducing the luminescent reaction of the expanded beads 100 and improving detection accuracy, the content Ctr of taggant particles 10 in the polymer layer 30 is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and particularly preferably 0.02% by mass or more. On the other hand, from the viewpoint of not inhibiting the fusibility of the expanded beads and obtaining expanded beads with excellent moldability, the content Ctr of taggant particles 10 in the polymer layer 30 is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less. In other words, the content Ctr of taggant particles 10 in the polymer layer 30 is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.005% by mass or more and 1% by mass or less, even more preferably 0.01% by mass or more and 0.5% by mass or less, and particularly preferably 0.02% by mass or more and 0.1% by mass or less.

[0062] Furthermore, it is more preferable that the expanded beads 100 have (i) a ratio [Ctr / Ctt] of the content Ctr of taggant particles 10 in the polymer layer 30 to the content Ctt of taggant particles 10 in the expanded beads 100 having the foam layer 20 and the polymer layer 30, of 2 or more, and (ii) the content Ctr of taggant particles 10 in the polymer layer 30 is 0.001% by mass or more and 5% by mass or less. According to this embodiment, the concentration of taggant particles 10 in the polymer layer 30 can be increased while keeping the amount of taggant particles 10 used in the entire expanded beads 100 low. As a result, the expanded state of the expanded beads 100 can be maintained better, and the luminescent reaction of the expanded beads 100 can be efficiently induced, thereby improving detection accuracy. Furthermore, the expanded beads 100 of this embodiment have excellent moldability, as fusion between the expanded beads is less likely to be inhibited when producing an expanded bead molding.

[0063] Furthermore, in addition to the above (i) and (ii), the expanded beads 100 preferably have (iii) a content Ctt of taggant particles 10 in the expanded beads 100 of 0.0001% by mass or more and 0.5% by mass or less. The expanded beads 100 of this embodiment are excellent in terms of moldability, occurrence of a significant luminescence reaction, and reduction in the amount of taggant particles 10 used. Furthermore, the expanded beads 100 of this embodiment are unlikely to inhibit fusion between the expanded beads when producing an expanded bead molding, and are therefore excellent in moldability.

[0064] Furthermore, in addition to the above (i), (ii), and (iii), it is preferable that the expanded beads 100 have (iv) a polymer layer 30 located on the surface of the expanded beads 100. According to this embodiment, the concentration of taggant particles 10 in the polymer layer 30 located on the surface can be increased while keeping the amount of taggant particles 10 used in the entire expanded beads 100 small. As a result, the expanded state of the expanded beads 100 can be maintained in a good state, and the luminescent reaction of the expanded beads 100 can be made to occur more efficiently, thereby significantly improving detection accuracy. Furthermore, the expanded beads 100 of this embodiment have excellent moldability, as the fusion between the expanded beads is less likely to be inhibited when producing an expanded bead molding.

[0065] The thermoplastic polymer constituting the foam layer 20 in the multilayer expanded beads 100 can be appropriately selected from the various thermoplastic polymers used to form the thermoplastic polymer expanded beads described above. The polymer constituting the polymer layer 30 is not limited to a thermoplastic polymer. The polymer constituting the polymer layer 30 may be the same as or a different polymer from the thermoplastic polymer constituting the foam layer 20. The method for obtaining the multilayer expanded beads having the polymer layer 30 covering the foam layer 20 described above is not particularly limited. Examples of such methods include, for example, a method in which, in the production of thermoplastic polymer particles described below, polymer particles having a coating layer laminated on the surface of a core layer are obtained by co-extrusion using an extruder, and at least the core layer of the polymer particles is expanded; or a method in which single-layer expanded beads are obtained and the surface of the single-layer expanded beads is coated with a powdered polymer.

[0066] The polymer layer 30 located on the surface of the expanded beads 100 preferably has the following configuration from the viewpoint of improving the fusion properties between the expanded beads during the production of an expanded bead molding. That is, the polymer constituting the polymer layer 30 is preferably a thermoplastic polymer. Furthermore, the melting point or softening point of the polymer constituting the polymer layer 30 is preferably lower than the melting point of the thermoplastic polymer constituting the foamed layer 20. By achieving such a temperature relationship, the fusion properties between the expanded beads are less likely to be hindered even when the content of taggant particles 10 contained in the polymer layer 30 is relatively high. From this viewpoint, the melting point Tms of the thermoplastic polymer constituting the polymer layer 30 is preferably lower than the melting point Tmc of the thermoplastic polymer constituting the foamed layer 20, for example. That is, it is preferable that Tms < Tmc. From the viewpoint of sufficiently improving the fusion properties between the expanded beads even when the content of taggant particles 10 contained in the polymer layer 30 is relatively high, it is preferable that Tmc - Tms ≧ 3°C, more preferably Tmc - Tms ≧ 5°C, and even more preferably Tmc - Tms ≧ 8°C. From the viewpoint of suppressing peeling between the foam layer 20 and the polymer layer 30, it is preferable that Tmc - Tms ≦ 35°C, more preferably Tmc - Tms ≦ 20°C, and even more preferably Tmc - Tms ≦ 15°C. In other words, in the present invention, the Tmc - Tms is preferably 3°C or higher and 35°C or lower, more preferably 5°C or higher and 20°C or lower, and even more preferably 8°C or higher and 15°C or lower.

[0067] The melting point Tmc of the thermoplastic polymer constituting the foam layer 20 varies depending on the type of thermoplastic polymer constituting the foam layer 20, but is generally 100°C or higher and 250°C or lower, preferably 110°C or higher and 200°C or lower, more preferably 120°C or higher and 180°C or lower, and even more preferably 140°C or higher and 160°C or lower. The melting point Tms of the thermoplastic polymer constituting the polymer layer 30 is generally 80°C or higher and 180°C or lower, preferably 100°C or higher and 150°C or lower, and more preferably 105°C or higher and 140°C or lower. The combination of the thermoplastic polymer constituting the foam layer 20 and the thermoplastic polymer constituting the polymer layer 30 is not particularly limited, but it is preferable that the thermoplastic polymer constituting the foam layer 20 is a polyolefin-based resin and the thermoplastic polymer constituting the polymer layer 30 is a polyolefin-based resin. In this case, it is preferable that the difference [Tmc - Tms] between the melting point Tmc of the polyolefin resin constituting the foam layer and the melting point Tms of the polyolefin resin constituting the polymer layer is 3°C or more and 35°C or less.

[0068] The melting point of a thermoplastic polymer is determined in accordance with JIS K7121:1987. Specifically, the conditioning method employs "(2) Measuring the melting temperature after a certain heat treatment," and conditioning is performed at a heating rate and cooling rate of 10°C / min. The conditioned test piece is heated from 30°C to 200°C at a heating rate of 10°C / min to obtain a DSC curve, and the apex temperature of the melting peak in the DSC curve is taken as the melting point. Note that if multiple melting peaks appear in the DSC curve, the apex temperature of the melting peak with the largest area is taken as the melting point.

[0069] The polymer layer 30 may be in a foamed state or a non-foamed state. From the viewpoint of further increasing the detection accuracy of the taggant particles 10 contained in the polymer layer 30, it is preferable that the polymer layer 30 be in a substantially non-foamed state. Being in a substantially non-foamed state includes a state in which the polymer layer 30 is not foamed and does not contain any bubbles, and a state in which the bubbles have disappeared after foaming, and means that there is almost no bubble structure.

[0070] The presence of a rare earth element in the expanded beads can be confirmed by known elemental analysis methods such as inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence elemental analysis (XRF). From the viewpoints of low cost and ensuring a more reliable luminescent reaction, the content of the luminescent rare earth element in the expanded beads is preferably 0.4 ppm or more and 2000 ppm or less, more preferably 2 ppm or more and 400 ppm or less, even more preferably 4 ppm or more and 200 ppm or less, and particularly preferably 4 ppm or more and 120 ppm or less. The content of the luminescent rare earth element in the expanded beads is measured by performing inductively coupled plasma mass spectrometry (ICP-MS) on the expanded beads as a sample. From the same viewpoint, in expanded beads having a foam layer and a polymer layer, the content of the luminescent rare earth element in the polymer layer is preferably 4 ppm or more and 12,500 ppm or less, more preferably 12 ppm or more and 4,000 ppm or less, even more preferably 40 ppm or more and 1,250 ppm or less, and particularly preferably 40 ppm or more and 400 ppm or less. The content of the luminescent rare earth element in the polymer layer can be measured in the same manner as in measuring the content of the luminescent rare earth element in expanded beads, except that the polymer layer is used as the measurement sample.

[0071] Furthermore, the content of taggant particles in expanded beads can be calculated from the content of luminescent rare earth elements in the expanded beads, for example, by determining the composition of the taggant particles contained in the expanded beads in advance. Determining the composition of the taggant particles in advance means, for example, when the taggant particles are crystalline ligands obtained by reacting a luminescent rare earth element with an unsaturated organic ligand, determining the composition, i.e., the types and component ratios of the luminescent rare earth element and the unsaturated organic ligand, in advance by a method exemplified in chemical analysis.

[0072] (Carbon Particles) The expanded beads of the present invention may contain carbon particles. For example, to provide a black expanded bead molding, the expanded beads may contain carbon particles as a black pigment. The carbon particles are added, for example, to impart a black color to the expanded beads or to impart functionality, such as electrical conductivity. When carbon particles are contained, the carbon particle content (Cct) in the expanded beads is preferably 0.01% by mass or more and 15% by mass or less, more preferably 0.1% by mass or more and 12% by mass or less, even more preferably 1% by mass or more and 10% by mass or less, particularly preferably 1.5% by mass or more and 5% by mass or less, and most preferably 2% by mass or more and 4% by mass or less. In particular, when the carbon particles are a black pigment, the above numerical ranges have the following effects. That is, by having the carbon particle content (Cct) in the expanded beads be 0.01% by mass or more, it is possible to obtain an expanded bead molding with a high degree of blackness, for example, an L* value of 30 or less. A highly black expanded bead molding imparts a luxurious feel to the molding, and is therefore preferable from the perspective of aesthetics. From this viewpoint, the carbon particle content Cct is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, particularly preferably 1.5% by mass or more, and most preferably 2% by mass or more. On the other hand, in order to prevent a decrease in the detection accuracy of the luminescence reaction of the expanded beads due to the carbon particles, the carbon particle content Cct in the expanded beads is preferably 15% by mass or less. In other words, the expanded beads of the present invention, in which the carbon particle content Cct is adjusted to the above-mentioned range, are black in color but can be identified by the luminescence reaction. From this viewpoint, the carbon particle content Cct is preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 4% by mass or less.

[0073] From the viewpoint of obtaining a molded article with a high degree of blackness and enabling detection of a luminescence reaction with higher accuracy, expanded beads having a foam layer made of a thermoplastic polymer and a polymer layer covering the foam layer, in which the ratio [Ctr / Ctt] of the taggant particle content Ctr in the polymer layer to the taggant particle content Ctt in the expanded beads is 2 or more, and the carbon particle content Cct is 0.01% by mass or more and 15% by mass or less are preferred. Among these, it is more preferred that the polymer layer is provided on or near the surface of the expanded beads, and that the carbon particle content in the expanded beads is within the above-mentioned range. This provides expanded beads that have a black appearance and are easily distinguishable by a luminescence reaction.

[0074] According to studies conducted on the present invention, it was thought that, for example, when carbon particles are incorporated into expanded beads to obtain a foamed bead molding with a high degree of blackness, the carbon particles tend to absorb at least a portion of the electromagnetic waves irradiated to identify the expanded beads or the light generated by the electromagnetic wave irradiation, resulting in a decrease in the accuracy of light detection. However, according to the above-described embodiment of the present invention in which taggant particles are incorporated into the polymer layer, even when carbon particles are incorporated, the luminescence reaction of the expanded beads is prevented from being inhibited, and expanded beads that exhibit a black appearance and are easily identifiable by their luminescence reaction can be provided.

[0075] When the expanded beads of the present invention are multilayer expanded beads having a foam layer and a polymer layer, it is preferred that the carbon particles are contained in both the foam layer and the polymer layer, and that the polymer layer contains taggant particles. The content of the carbon particles in the foam layer and the polymer layer is preferably within the same range as the content of the carbon particles in the expanded beads. This provides expanded beads that are easily distinguishable by luminescence reaction and have a beautiful black appearance with reduced color unevenness.

[0076] The carbon particles used as a black pigment refer to particles containing carbon, and examples thereof include one or more materials selected from carbon black, conductive carbon, carbon nanotubes, graphene, graphite, activated carbon, etc. Among these, carbon black is preferred from the viewpoint of an excellent balance between dispersibility in polymers such as resins and cost. Examples of carbon black include channel black, roller black, furnace black, thermal black, acetylene black, and ketjen black.

[0077] The expanded beads of the present invention may contain any additives as appropriate, provided that the additives do not impair the objects and effects of the present invention. For example, the optional additives may include a flame retardant, a flame retardant assistant, a cell regulator, a lubricant, a crystal nucleating agent, a conductive filler, an antistatic agent, etc.

[0078] (Average Cell Diameter) The expanded beads of the present invention are produced by expanding raw polymer particles and have a cell structure containing a large number of cells. From the viewpoint of improving the moldability of the expanded beads, the average cell diameter of the expanded beads of the present invention is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and particularly preferably 80 μm or more. On the other hand, from the viewpoint of improving the surface smoothness of the molded article, the average cell diameter of the expanded beads of the present invention is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 180 μm or less, and preferably 150 μm or less. In other words, the cell diameter is preferably 20 μm or more and 250 μm or less, more preferably 30 μm or more and 200 μm or less, even more preferably 50 μm or more and 180 μm or less, and particularly preferably 80 μm or more and 150 μm or less.

[0079] The average cell diameter of expanded beads is determined as follows. First, an expanded bead is cut at a position that halves its volume. Next, a photograph of the cross section is taken so that the exposed cut surface is entirely within the field of view. On the photograph, four line segments are drawn from the outermost surface of the expanded bead, passing through the center, to the outermost surface on the opposite side, with the angles between adjacent line segments being equal. In other words, the line segments are drawn so that the angles between adjacent line segments are 45°. The total length L of the four line segments thus obtained is divided by the number N of all the cells touching the line segments, and the value (L / N) is taken as the average cell diameter of one expanded bead. This procedure is performed on 10 or more expanded beads, and the arithmetic average value is taken as the average cell diameter of the expanded beads.

[0080] When producing an expanded bead molding by in-mold molding using the expanded beads of the present invention, from the viewpoint of easily exhibiting excellent moldability and easily obtaining a molded body with little color unevenness, it is preferable that the average cell diameter of the expanded thermoplastic polymer beads is 20 μm or more and 250 μm or less, and that the coefficient of variation of the cell diameter is 30% or less; it is more preferable that the average cell diameter of the expanded thermoplastic polymer beads is 30 μm or more and 200 μm or less, and that the coefficient of variation of the cell diameter is 25% or less; it is even more preferable that the average cell diameter of the expanded thermoplastic polymer beads is 50 μm or more and 180 μm or less, and that the coefficient of variation of the cell diameter is 20% or less; and it is even more preferable that the average cell diameter of the expanded thermoplastic polymer beads is 80 μm or more and 150 μm or less, and that the coefficient of variation of the cell diameter is 15% or less. Expanded beads having such a preferred configuration are easily realized, for example, by expanded beads having a foamed layer made of a thermoplastic polymer and a polymer layer, in which the taggant particle content Ctt in the expanded beads is 0.0001% by mass or more and 0.5% by mass or less, and the ratio [Ctr / Ctt] of the taggant particle content Ctr in the polymer layer to the taggant particle content Ctt in the expanded beads is 2 or more. In the above-mentioned embodiment of expanded beads with high blackness, it is more preferable that the polymer layer is a coating layer that coats the foamed layer. This is because the luminescent reaction can be easily detected by providing the polymer layer, in which the taggant particles are concentrated, on the surface side of the expanded beads.

[0081] Furthermore, the expanded beads of the present invention, in which the carbon particle content Cct in the expanded beads is 0.01% by mass or more and 15% by mass or less, the average cell diameter of the expanded thermoplastic polymer beads is 20 μm or more and 250 μm or less, and the cell diameter coefficient of variation is 30% or less, have excellent moldability and are likely to produce expanded bead moldings that are black in appearance and have little color unevenness. The reason why color unevenness is easily suppressed by having a small cell diameter coefficient of variation is thought to be because the thickness of the cell film is more likely to become uniform. From this viewpoint, it is more preferable that the carbon particle content Cct in the expanded beads is 0.01% by mass or more and 15% by mass or less, the average cell diameter of the expanded thermoplastic polymer beads is 30 μm or more and 200 μm or less, and the coefficient of variation of the cell diameter is 25% or less, it is even more preferable that the average cell diameter of the expanded thermoplastic polymer beads is 50 μm or more and 180 μm or less, and the coefficient of variation of the cell diameter is 20% or less, and it is particularly preferable that the average cell diameter of the expanded thermoplastic polymer beads is 80 μm or more and 150 μm or less, and the coefficient of variation of the cell diameter is 15% or less. The expanded beads of the present invention having the above-mentioned black appearance can be easily realized, for example, by expanded beads having a carbon particle content Cct of 0.01% by mass or more and 15% by mass or less, a foamed layer made of a thermoplastic polymer, a polymer layer, a taggant particle content Ctt of 0.0001% by mass or more and 0.5% by mass or less, and a ratio [Ctr / Ctt] of the taggant particle content Ctr in the polymer layer to the taggant particle content Ctt in the expanded beads of 2 or more. In the above-mentioned embodiment of expanded beads having a high blackness, it is more preferable that the polymer layer is a coating layer that coats the foamed layer. This is because the luminescent reaction can be easily detected by providing the polymer layer, in which the taggant particles are concentrated, on the surface side of the expanded beads.

[0082] When a relatively large amount of taggant particles is blended into expanded beads to improve the detection accuracy of the luminescence reaction of expanded beads, the taggant particles may also act as nuclei for bubble formation. This can lead to a risk of impairing the expanded state of the expanded beads, resulting in, for example, an increase in the coefficient of variation of the bubble diameter. In particular, black expanded beads containing carbon particles require blending a larger amount of taggant particles, which can easily impair the expanded state of the expanded beads. In contrast, according to the above-described embodiment of the present invention, which includes a polymer layer containing taggant particles, the taggant particles can be unevenly distributed in the polymer layer within the expanded beads. Therefore, the present invention provides expanded beads that are easy to identify by luminescence reaction and do not impair the expanded state of the expanded beads.

[0083] The coefficient of variation can be calculated by dividing the standard deviation of the cell diameters of the expanded beads by the average cell diameter of the expanded beads and multiplying the result by 100. The value given by the square root of the unbiased variance is taken as the standard deviation.

[0084] (Bulk Density of Expanded Beads) The bulk density of the expanded beads of the present invention is not particularly limited, but from the viewpoint of weight reduction, it is 150 kg / m ３ It is preferable that the saturation is 100 kg / m or less. ３ More preferably, it is 50 kg / m or less. ３ From the viewpoint of the rigidity of the expanded bead molding produced using the expanded beads, the bulk density of the expanded beads is more preferably 10 kg / m or less. ３ It is preferable that the viscosity is 15 kg / m or more. ３ More preferably, it is 20 kg / m or more. ３ In other words, in the present invention, the bulk density of the expanded beads is 10 kg / m or more. ３ More than 150kg / m ３ It is preferable that the viscosity is 15 kg / m or less. ３ More than 100kg / m ３ More preferably, it is 20 kg / m or less. ３ More than 50kg / m ３ It is even more preferable that:

[0085] The bulk density of expanded beads is measured by the following method. First, the expanded beads to be measured are conditioned by standing for 24 hours or more in an environment of 23°C temperature, 50% relative humidity, and 1 atm. After conditioning, expanded beads with a mass W (g) are packed into a measuring cylinder so that they naturally accumulate, and the bottom of the measuring cylinder is lightly tapped several times against a horizontal surface to stabilize the packed height of the expanded beads in the measuring cylinder. The bulk volume V (L) of the expanded beads indicated on the measuring cylinder is read, and the mass W of the expanded beads is divided by the bulk volume V of the expanded beads (W / V), and the bulk density (kg / m) of the expanded beads is calculated by converting the unit. ３ ) can be obtained.

[0086] (High-temperature peak) The expanded beads of the present invention preferably have a crystalline structure that exhibits a high-temperature peak as described below. Expanded beads that exhibit a high-temperature peak are preferred from the viewpoint of a wider range of molding conditions under which a good expanded bead molding can be obtained. Note that the crystalline structure that exhibits a high-temperature peak can be formed when the thermoplastic polymer constituting the expanded beads is a crystalline polymer.

[0087] Here, the term "high-temperature peak" refers to a melting peak whose peak temperature appears higher than the melting peak inherent to the thermoplastic polymer in the first DSC curve (see FIG. 7 ) measured by heat flux differential scanning calorimetry based on JIS K7122-1987, in which a 1-3 mg expanded bead test piece is heated and melted from 30°C to a temperature 30°C higher than the melting end temperature at a heating rate of 10°C / min. In this specification, the melting peak inherent to the thermoplastic polymer may be referred to as "intrinsic peak a," and the melting peak whose peak temperature appears higher than "intrinsic peak a" may be referred to as "high-temperature peak b." FIG. 7 shows an example of a DSC curve of expanded beads measured by heat flux differential scanning calorimetry. Although one high-temperature peak b is shown in FIG. 7 , there may be two or more high-temperature peaks b.

[0088] The characteristic peak a is a peak generated by melting of the inherent crystals of the thermoplastic polymer that is the base material constituting the expanded beads, and is thought to be a peak that appears due to melting of the crystals that the base material constituting the expanded beads normally has. On the other hand, the high-temperature peak b is presumed to appear when secondary crystals different from the crystals that are normally present in the base material constituting the expanded beads are present. A method for obtaining expanded beads having the above-mentioned high-temperature peak b will be described later.

[0089] From the viewpoint of obtaining an expanded bead molding having an excellent balance of cushioning properties and rigidity, the heat of fusion of the high-temperature peak b of the expanded beads is preferably 5 J / g or more, more preferably 7 J / g or more, and even more preferably 10 J / g or more. Furthermore, from the viewpoint of reducing the steam pressure at which the expanded beads can be molded during in-mold molding, the heat of fusion of the high-temperature peak b is preferably 30 J / g or less, more preferably 28 J / g or less, and even more preferably 25 J / g or less. In other words, the heat of fusion of the high-temperature peak b of the expanded beads is preferably 5 J / g or more and 30 J / g or less, more preferably 7 J / g or more and 28 J / g or less, and even more preferably 10 J / g or more and 25 J / g or less. When two or more high-temperature peaks b appear, the heat of fusion of the high-temperature peaks b means the total heat of all the high-temperature peaks b. For the method of calculating the heat of fusion of the high-temperature peak b, see the description in the Examples below.

[0090] From the viewpoint of improving the fillability into a molding die, the average particle diameter of the expanded beads is preferably 0.3 mm to 8 mm, more preferably 0.5 mm to 5 mm, and even more preferably 0.8 mm to 4.5 mm. The average particle diameter of the expanded beads is determined by the following method. First, the volume-based particle size distribution of the expanded beads is converted to a number-based particle size distribution by assuming the shape of the particles as spherical, thereby obtaining the number-based particle size distribution. Then, the particle diameters based on this number-based particle size distribution are arithmetically averaged to obtain the number-based arithmetic mean particle diameter. The particle diameter refers to the diameter of a hypothetical sphere having the same volume as the particles. The volume-based particle size distribution of the expanded beads can be measured using a particle size distribution analyzer (e.g., "Militrack JPA" manufactured by Nikkiso Co., Ltd.). The number of expanded beads used for measurement may be, for example, 2,000 or more.

[0091] From the same viewpoint, the average mass of the expanded beads is preferably 0.2 mg to 5 mg, more preferably 0.5 mg to 4 mg, and even more preferably 0.8 mg to 3 mg. The average mass of the expanded beads can be determined by randomly selecting 100 or more expanded beads, measuring the mass [mg] of the expanded beads, and dividing the mass by the number of expanded beads used in the measurement.

[0092] (Method for producing expanded thermoplastic polymer beads) The expanded beads of the present invention can be produced by following a general method for producing expanded beads, except that a luminescent rare earth element is blended. A general method for producing expanded beads includes, for example, producing thermoplastic polymer beads, impregnating the thermoplastic polymer beads with a blowing agent, and then expanding the beads. An example of the method for producing expanded beads of the present invention is described below.

[0093] First, a thermoplastic polymer and a luminescent rare earth element component are fed into an extruder, melt-kneaded to prepare a molten mixture, and then the molten mixture is extruded from the extruder to produce thermoplastic polymer particles. Generally, the molten mixture extruded from the extruder is cut using a pelletizer or the like, and the mass and shape are adjusted to form small pellet-shaped thermoplastic polymer particles. The molten mixture may contain any additives as appropriate. Alternatively, the luminescent rare earth element component may be incorporated into the thermoplastic polymer before the thermoplastic polymer particles are produced.

[0094] To produce multilayered expanded beads, a core layer-forming melt-kneaded mixture and a coating layer-forming melt-kneaded mixture are prepared, and multilayered thermoplastic polymer beads are produced using a production apparatus equipped with a core layer-forming extruder, a multilayer strand-forming die attached downstream of the core layer-forming extruder, and a coating layer-forming extruder. The production apparatus is connected downstream of the polymer layer-forming extruder to a multilayer strand-forming die, allowing for lamination of the melt-kneaded mixtures for forming each layer within the die and for co-extrusion. The multilayered thermoplastic polymer beads produced as described above in the present invention include an embodiment in which the core layer is a foamed layer and the coating layer is a polymer layer coating the foamed layer, and an embodiment in which the core layer is a polymer layer and the coating layer is a foamed layer coating the polymer layer.

[0095] Next, the thermoplastic polymer particles obtained as described above, an aqueous medium, an inorganic dispersant, and other optional additives are supplied to a pressure vessel and dispersed in a dispersing step, followed by an impregnation step in which the thermoplastic polymer particles are impregnated with a blowing agent. The aqueous medium may, for example, be water. Examples of the inorganic dispersant include inorganic substances such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide, kaolin, mica, talc, and smectite. A dispersing aid, such as an anionic surfactant such as sodium dodecylbenzenesulfonate or sodium alkanesulfonate, may also be added together with the dispersant. The blowing agent may be appropriately selected from blowing agents commonly used in the production of expanded beads. Specific examples of blowing agents include inorganic physical blowing agents such as carbon dioxide, air, nitrogen, helium, argon, and water; and organic physical blowing agents such as propane, butane, hexane, cyclopentane, ethyl chloride, 1,3,3,3-tetrafluoropropene, and 1-chloro-3,3,3-trifluoropropene. Among these blowing agents, preferably, blowing agents containing an inorganic physical blowing agent such as carbon dioxide, nitrogen, or air as a main component are used, and more preferably, carbon dioxide is used. These physical blowing agents may be used alone or in combination of two or more.

[0096] When producing expanded beads exhibiting high-temperature peak b, it is advisable to adjust the temperature rise rate in the pressure vessel or maintain the temperature in the pressure vessel at a predetermined temperature for a predetermined period of time during the dispersion and / or impregnation steps. More specifically, for example, during the dispersion and / or impregnation steps, the temperature in the pressure vessel is maintained at a temperature between 20°C below the melting point of the substrate and the end temperature of the substrate for 10 to 60 minutes. The temperature in the pressure vessel is then adjusted to a temperature between 15°C below the melting point of the substrate and the end temperature of the substrate. If necessary, the temperature is maintained for another 10 to 60 minutes. This temperature adjustment adjusts the crystalline state of the thermoplastic polymer particles. The substrate refers to the thermoplastic polymer that constitutes the thermoplastic polymer particles.

[0097] Next, an expansion step is carried out in which the thermoplastic polymer particles and the aqueous medium are released into a pressure environment lower than the pressure inside the pressure vessel and expanded, thereby obtaining expanded particles having a high-temperature peak b. If the high-temperature peak b in the expanded particles is not required, the temperature adjustment inside the pressure vessel described above can be omitted as appropriate. The expansion step is not limited to the above method, and for example, expanded particles can also be obtained by removing the polymer particles impregnated with the blowing agent from the pressure vessel after the impregnation step and heating the polymer particles to expand them.

[0098] In order to further reduce the bulk density of the first-stage expanded beads obtained by the above-described expansion process, a second-stage expansion process may be further carried out. The second-stage expansion process is a process in which the first-stage expanded beads produced as described above are fed into a pressure-resistant vessel, pressurized to increase the pressure (internal pressure) within the cells of the expanded beads, and then heated to expand again. By carrying out the second-stage expansion process, expanded beads exhibiting a desired bulk density can be easily produced.

[0099] The manufacturing method of the expanded beads of the present invention is not limited to the above-described manufacturing method. For example, a melt-kneaded material not containing a luminescent rare earth element component is prepared to produce thermoplastic polymer particles, which are then expanded to obtain pre-expanded beads. The luminescent rare earth element component can then be applied to the pre-expanded beads by any application method to obtain the expanded beads of the present invention. An example of such an application method is to sprinkle the luminescent rare earth element component in particulate form on the surface of the pre-expanded beads. In this case, by slightly melting the surface of the pre-expanded beads in advance by heating, the luminescent rare earth element component in particulate form can be firmly attached to the surface. Another application method is to prepare a liquid in which the luminescent rare earth element component is dispersed, apply the liquid to the pre-expanded beads by spraying, etc., and then dry it appropriately.

[0100] [Expanded Thermoplastic Polymer Bead Molding] The expanded bead molding of the present invention is produced by molding the expanded beads of the present invention described above in a mold. The expanded bead molding of the present invention enjoys the excellent effects of the expanded beads of the present invention described above. That is, when the expanded bead molding of the present invention is irradiated with electromagnetic waves, the expanded beads constituting the expanded bead molding exhibit a luminescent reaction. As a result, the luminescent reaction can be detected from the expanded bead molding. Therefore, the expanded bead molding of the present invention can be identified by detecting the luminescent reaction.

[0101] Furthermore, the expanded beads themselves that constitute the expanded bead molding can be tracked. Specifically, the expanded bead molding or the expanded beads that constitute it can be identified by comparing whether the emission spectrum of the luminescence reaction detected from the expanded bead molding and a preset reference emission spectrum show a similar pattern. The content of taggant particles in the molding used to obtain the reference emission spectrum is generally 0.0001% by mass or more and 0.5% by mass or less. Specific examples of the molding containing taggant particles include expanded beads. Therefore, according to the present invention, it is possible to track the expanded beads that constitute the expanded bead molding from the expanded bead molding by determining the preset reference emission spectrum.

[0102] The expanded bead molding of the present invention is suitable for various applications, including, but not limited to, automobile components, packaging materials, and building materials.

[0103] The expanded bead molding of the present invention is an expanded bead molding obtained by in-mold molding of expanded beads containing a thermoplastic polymer and a luminescent rare earth element component that emits light when irradiated with electromagnetic waves and exhibits a specific emission spectrum. The expanded bead molding of the present invention can be identified as an expanded bead molding made from expanded beads containing the luminescent rare earth element by comparing the emission spectrum detected when the expanded bead molding is irradiated with the electromagnetic waves with a predetermined reference emission spectrum that indicates a luminescence reaction due to the luminescent rare earth element. Details of this identification method will be described later.

[0104] (Molded Body Density of Expanded Bead Molded Body) The molded body density of the expanded bead molded body of the present invention is 10 kg / m from the viewpoint of an excellent balance between light weight and mechanical properties such as rigidity. ３ More than 150kg / m ３ It is preferable that the viscosity is 15 kg / m or less. ３ More than 100kg / m ３ More preferably, it is 20 kg / m or less. ３ More than 50kg / m ３ The molding density of the expanded bead molding is calculated by dividing the mass of the expanded bead molding by the volume calculated based on the external dimensions of the expanded bead molding. When it is difficult to calculate the volume from the external dimensions, the volume of the expanded bead molding can be determined by a submersion method.

[0105] (L* Value of Expanded Bead Molding) The present invention can provide a black expanded bead molding by using the expanded beads of the present invention, which exhibit a significant black color. The L* value of the expanded bead molding is, for example, preferably 30 or less, more preferably 28 or less, and even more preferably 25 or less. The L* value of the expanded bead molding is the L* value of the surface of the expanded bead molding in the CIE 1976 L*a*b* color system, and can be measured with a spectrophotometer. The L* value is an index of brightness, and the lower the value, the higher the blackness and the deeper the black.

[0106] Black expanded bead moldings tend to be popular in the automotive industry because they give viewers a sense of luxury. However, black expanded bead moldings generally absorb light and are therefore considered undesirable from the perspective of detecting luminescence reactions. To address this problem, for example, a sufficiently large amount of taggant particles in the expanded beads has been considered. However, in this case, the taggant particles may act as nuclei for bubble formation, reducing the uniformity of bubbles formed within the expanded beads. Therefore, further studies have been conducted to provide an expanded bead molding that maintains a good expansion state of the expanded beads, exhibits a black color, and enables detection of luminescence reactions. As described above in the description of the expanded beads of the present invention, it has been found that it is particularly preferable to use expanded beads of the present invention that have a foam layer and a polymer layer, in which the content of taggant particles in the expanded beads (Ctt) is 0.0001% by mass or more and 0.5% by mass or less, and the ratio (Ctr / Ctt) of the content of taggant particles in the polymer layer (Ctr) to the content of taggant particles in the expanded beads (Ctt) is 2 or more. By significantly increasing the content of taggant particles in the polymer layer, it becomes easier to induce a luminescent reaction, thereby improving the accuracy of light detection. Therefore, even black foamed bead moldings can be sufficiently identified by the luminescent reaction. Furthermore, by setting the content of taggant particles in the foam layer to zero or lower than that in the polymer layer, it is possible to more reliably prevent the taggant particles from adversely affecting the foaming state of the foamed beads.

[0107] From the viewpoint of increasing the degree of blackness and more sufficiently improving the detection accuracy of the luminescent reaction, it is preferable to use expanded beads that have the foam layer and the polymer layer covering the foam layer, and it is more preferable to use expanded beads that have the foam layer and the polymer layer covering the foam layer, with the polymer layer located on the surface of the expanded beads.

[0108] [Method for producing expanded thermoplastic polymer bead moldings] The expanded bead moldings of the present invention can be obtained by in-mold molding using the expanded beads of the present invention. For example, the expanded bead moldings can be produced as follows. First, the expanded beads of the present invention are filled into a mold having a cavity corresponding to the shape of the desired expanded bead molding, and the expanded beads filled in the mold are heated with a heating medium such as steam. The expanded beads in the cavity soften by heating, undergo secondary expansion, and their surfaces melt and fuse together. This integrates the expanded beads, resulting in an expanded bead molding that matches the shape of the cavity.

[0109] [Method for Identifying Expanded Thermoplastic Polymer Beads or Expanded Thermoplastic Polymer Bead Moldings] Next, the identification method of the present invention will be described. The identification method of the present invention includes the method for identifying expanded thermoplastic polymer beads of the present invention and the method for identifying expanded thermoplastic polymer bead moldings of the present invention. Furthermore, the identification method of the present invention can identify the expanded thermoplastic polymer beads that constitute the expanded thermoplastic polymer bead moldings by identifying the expanded thermoplastic polymer bead moldings. Furthermore, because the identification method of the present invention is non-destructive, the state of the expanded beads and expanded bead moldings before and after the identification process is not changed, and they can be identified while maintaining their aesthetic appearance. The identification method of the present invention includes a first identification method that includes the following features i) and ii) and further includes at least iii-1), and a second identification method that includes the following features i) and ii) and further includes at least iii-2).

[0110] The first method for identifying expanded thermoplastic polymer beads of the present invention comprises the following steps i), ii), and iii-1): i) an electromagnetic wave irradiation step of irradiating the surface of an expanded thermoplastic polymer bead with electromagnetic waves, ii) a detection step of detecting a luminescence reaction attributable to a luminescent rare earth element caused by the electromagnetic wave irradiation with a detection device to obtain an emission spectrum, and iii-1) an identification step of comparing the emission spectrum with a blank spectrum that does not show a luminescence reaction attributable to a luminescent rare earth element.

[0111] The first method for identifying expanded thermoplastic polymer bead moldings of the present invention comprises the following steps i), ii), and iii-1): i) an electromagnetic wave irradiation step of irradiating the surface of an expanded thermoplastic polymer bead molding with electromagnetic waves, ii) a detection step of detecting a luminescence reaction attributable to a luminescent rare earth element caused by the electromagnetic wave irradiation with a detection device to obtain an emission spectrum, and iii-1) an identification step of comparing the emission spectrum with a blank spectrum that does not show a luminescence reaction attributable to a luminescent rare earth element.

[0112] By the steps i), ii), and iii-1), it is possible to determine whether or not the expanded beads or expanded bead moldings of the present invention exhibit a luminescent reaction. Whether or not the expanded beads or expanded bead moldings exhibit a luminescent reaction can be determined by the following method. Here, the method for determining whether or not the expanded bead moldings exhibit a luminescent reaction will be described. The luminescence spectrum (S) and spectrum (S ０ ) are shown in FIG. 6. First, an expanded bead molding to be identified and a blank molding having the same composition as the target molding except that it does not contain a luminescent rare earth element component are prepared. The blank molding is preferably an expanded bead molding produced in the same manner as the target molding except that it does not contain a luminescent rare earth element component. Then, they are irradiated with electromagnetic waves of a predetermined wavelength, and the emission spectrum (S) of the expanded bead molding of the present invention generated by the irradiation and the spectrum (S) of the blank molding (e.g., an expanded bead molding) are measured. ０ ) is detected. Next, for all peaks that appear in the emission spectrum (S), the wavelengths and the peak intensities I of the emission peaks at each wavelength are confirmed. In addition, the spectrum (S ０ ) intensity I ０ Then, the spectrum (S ０ ) Intensity I at each wavelength ０ The ratio of the peak intensity I at each wavelength in the emission spectrum (S) to the ０ ) are calculated. In the following description, the ratio is referred to as the ratio of peak intensities I (I / I ０ ), or simply the ratio (I / I ０The ratio of the peak intensities I obtained at each wavelength (I / I ０ ) is identified as the maximum value. ０ It can be confirmed that the higher the maximum value of the ratio (I / I), the more accurately the luminescence reaction of the foamed bead molding of the present invention is detected. ０ When the maximum value of I / I is 1.1 or more, it can be determined that a luminescence reaction has occurred in the object to be identified. ０ When the maximum value of the ratio (I / I) is less than 1.1, or when no peak appears in the emission spectrum (S), it can be determined that no luminescence reaction has occurred. ０ The ratio (I / I) is preferably 1.3 or more, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. ０ When the intensity I is within the above range, the luminescence reaction occurs more efficiently, and the detection accuracy is improved. ０ The peak intensity I is measured using the same device under the same measurement conditions.

[0113] The above-described discrimination can also be performed using expanded beads as the identification target instead of the expanded bead molding. In this case, the blank molding is preferably an expanded bead produced in the same manner as the expanded beads to be identified, except that it does not contain a luminescent rare earth element component.

[0114] The second method for identifying expanded thermoplastic polymer beads of the present invention comprises the following steps i), ii), and iii-2): i) an electromagnetic wave irradiation step of irradiating the surface of an expanded thermoplastic polymer bead with electromagnetic waves, ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element due to the electromagnetic wave irradiation with a detection device to obtain an emission spectrum, and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that indicates a luminescence reaction caused by the luminescent rare earth element.

[0115] The second method for identifying expanded thermoplastic polymer bead moldings of the present invention includes the following steps i), ii), and iii-2): i) an electromagnetic wave irradiation step of irradiating the surface of the expanded thermoplastic polymer bead molding with electromagnetic waves; ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element, resulting from the electromagnetic wave irradiation, using a detection device to obtain an emission spectrum; and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum indicating a luminescence reaction caused by the luminescent rare earth element. By including step iii-2), the second identification method described above exhibits a favorable effect in that it enables tracking of various information about the expanded beads. Examples of the various information about the expanded beads include one or more pieces of information selected from the characteristics, physical properties, production conditions, and origin of the expanded beads. The characteristics refer to the characteristics of the material constituting the expanded beads. An example of the physical properties is the apparent density of the expanded beads. Examples of the production conditions include one or more pieces of information selected from the production lot number and the date of manufacture. An example of the origin is the name of the manufacturer of the expanded beads. The occurrence of this effect will be specifically explained below.

[0116] In the second identification method of the present invention described above, the predetermined reference emission spectrum refers to the emission spectrum detected when a molded article containing a predetermined luminescent rare earth element component and composed of a polymer of a predetermined composition is irradiated with electromagnetic waves of a predetermined wavelength. That is, the reference emission spectrum is derived from a specific emission spectrum exhibited by the luminescent reaction of the predetermined luminescent rare earth element component. However, even when irradiated with electromagnetic waves of the same wavelength, the emission spectrum generated by irradiation can be influenced not only by the luminescent rare earth element component but also by the composition of the polymer constituting the expanded beads and any additives. Therefore, the reference emission spectrum is not necessarily identical to the intrinsic emission spectrum of the contained luminescent rare earth element component itself. Therefore, the predetermined reference emission spectrum is set to take into account the influence of the composition of the polymer constituting the expanded beads and any additives.

[0117] To effectively utilize step iii-2), it is advisable to link various information, including, for a reference expanded bead exhibiting a reference emission spectrum, information on the physical properties of the expanded bead, such as the properties of the material constituting the expanded bead, the apparent density, production condition information, such as the production lot number and production date, and source information, such as the manufacturer, to the reference emission spectrum. By doing so, when the second identification method is performed, light-emitting particles that exhibit an emission spectrum with a pattern similar to that of the reference emission spectrum through the comparison can be traced as having the same information as the reference expanded bead. When the object to be identified is an expanded bead molding, the comparison can be traced as having the same information as the reference expanded bead. In other words, the second identification method including step iii-2) enables more sophisticated identification.

[0118] The content of the luminescent rare earth element component, such as taggant particles, in the expanded beads used to obtain the reference emission spectrum is generally 0.0001% by mass or more and 0.5% by mass or less. When obtaining the preset reference emission spectrum, it is preferable to obtain the specific emission spectrum of the luminescent rare earth element component itself, as shown in FIG. 5 . This makes it possible to compare the peaks in the specific emission spectrum of the luminescent rare earth element component itself with the peaks in the preset reference emission spectrum. This further improves the accuracy of the identification process. The emission spectrum of the expanded beads or expanded bead molding to be identified is confirmed in a chart, such as the emission spectrum (S) in FIG. 6, where the vertical axis represents peak intensity and the horizontal axis represents wavelength. The emission spectrum (S) of expanded beads or expanded bead moldings containing a luminescent rare earth element component is judged to have a similar pattern to a reference emission spectrum (not shown) based on the concept of emission peaks consisting of one or more elements selected from the overall pattern shape, the number of peaks, the wavelengths at which each peak is detected, the shape of each peak, the intensity ratio between each peak, the area ratio between each peak, etc. The absolute value of the peak intensity does not need to be included in the elements that make up the emission spectrum. However, the reference emission spectrum and the emission spectrum to be identified are measured using the same device under the same measurement conditions.

[0119] Even if the details of the luminescent rare earth element component contained in the taggant particle are unknown, the above-mentioned detection and matching are possible by irradiating expanded beads of a predetermined composition containing the taggant particle with electromagnetic waves of a predetermined wavelength, as long as a reference expansion spectrum has been confirmed in advance. As a result, it is possible to identify the expanded beads or expanded bead moldings to be identified. Note that details of the luminescent rare earth element component refer to, for example, the type and combination of luminescent rare earth elements contained in the luminescent rare earth element component, the type of ligand that coordinates the luminescent rare earth element, and the production method thereof.

[0120] The specific means for comparing the reference emission spectrum with the detected emission spectrum is not particularly limited. For example, a detection device equipped with a program that calculates the degree of statistical agreement between the reference emission spectrum and the detected emission spectrum and automatically determines the comparison result based on the degree of agreement can be used. Alternatively, manual comparison can be performed by comparing the number and wavelength of peaks shown in the reference emission spectrum pattern with those shown in the detected emission spectrum, or by comparing the area ratios of each peak when two or more peaks are shown.

[0121] While the marking techniques of the prior art, such as those described in Patent Documents 1 and 2, allow for easy identification by visually observing the surface of a molded product, they have the potential for duplication by malicious third parties. According to the present invention, the emission spectrum pattern can be finely adjusted, for example, by selecting the type and combination of luminescent rare earth elements and the type of ligand that coordinates the luminescent rare earth elements. Therefore, the emission spectrum marking can be prevented from being duplicated by third parties. Furthermore, authenticity can be easily determined by defining a reference spectrum as the emission spectrum of an authentic product and comparing it with the emission spectrum detected from the expanded beads or expanded bead moldings to be identified.

[0122] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Table 1 shows details of the resins used in the examples and comparative examples. Tables 2 to 4 show the compositions and contents used to produce the expanded beads of each example and comparative example, as well as the evaluation results of each example and comparative example. In the tables, carbon black is represented as CB. Note that the content of each component here is the same as the amount of each component blended to produce the expanded beads. In the examples and comparative examples shown below, resin particles were prepared using a resin material as the thermoplastic polymer particles.

[0123] The luminescent compounds used in the examples and comparative examples are as follows. Luminescent compound 1 is a taggant particle containing a luminescent rare earth element, while luminescent compounds 2 and 3 are granular luminescent compounds that do not contain a luminescent rare earth element. A chart of the emission spectrum detected when luminescent compound 1 was irradiated with ultraviolet light having a wavelength of 320 nm is shown in FIG. 5. <Luminescent Compound 1> Manufactured by OLNICA; Grade name OLNICA 65013919 (a crystalline ligand obtained by reacting a luminescent rare earth element with an unsaturated organic ligand) Luminescent rare earth element contained: terbium Electromagnetic wave used: 320 nm ultraviolet light The specific emission spectrum of luminescent compound 1: exhibits peaks at 488 nm, 546 nm, 589 nm, and 622 nm. <Light-emitting compound 2> Sigma-Aldrich: 4,4-bis(2-benzoxazolyl)stilbene (BBS) Electromagnetic wave used: 320 nm ultraviolet light Intrinsic emission spectrum of light-emitting compound 2: Peaks at 430 nm, 470 nm, and 500 nm <Light-emitting compound 3> Quinacridone-based organic color pigment Electromagnetic wave used: 320 nm ultraviolet light Intrinsic emission spectrum of light-emitting compound 3: 653 nm

[0124] The following examples and comparative examples are carried out based on the first identification method of the present invention. However, in advance, expanded beads containing each luminescent compound and having the same composition as in each example and comparative example were irradiated with ultraviolet light at a wavelength of 320 nm, and the emission spectrum of the resulting luminescent reaction was detected using a detection device described below to confirm the reference emission spectrum. These reference emission spectra are not required for the detection test of the luminescent reaction in the first identification method described below. As described at the end of this example, the reference emission spectrum is used to compare the reference emission spectrum with the emission spectra of each example and comparative example when carrying out the second identification method of the present invention.

[0125] Example 1 (Preparation of Resin Particles) A ​​manufacturing apparatus was prepared, including a core layer extruder with an inner diameter of 50 mm, a multilayer strand forming die attached downstream of the core layer extruder, and a coating layer extruder with an inner diameter of 30 mm. The manufacturing apparatus was configured so that the downstream side of the coating layer extruder was connected to the multilayer strand forming die, allowing for lamination of melt-kneaded materials to form each layer within the die and co-extrusion. A virgin polypropylene-based resin (PP1) shown in Table 1 was used as the resin constituting the core layer. In addition to the resin described above, zinc borate was used as a bubble adjuster in an amount of 0.1 parts by mass per 100 parts by mass of the core layer molding material, and carbon black was used in the amount shown in Table 2. These were fed to the core layer extruder and melt-kneaded. A virgin polypropylene-based resin (PP2) shown in Table 1 was used as the resin constituting the coating layer. In addition to the resins described above, luminescent compound 1 and carbon black were used as coating layer-forming materials in the amounts shown in Table 2, and these were fed into an extruder for forming a coating layer and melt-kneaded. The melt-kneaded mixtures for forming each layer obtained by melt-kneading as described above were introduced into a die for forming a multilayer strand and merged inside the die, and a multilayer strand with a two-layer structure (coating layer / core layer) having a core layer and a coating layer covering the lateral surface of the core layer was extruded from the holes in a nozzle attached downstream of the die. The extruded strand was water-cooled in a water tank and cut using a pelletizer to obtain resin particles with an average mass of 1.0 mg per particle.

[0126] (Preparation of Expanded Beads) 1 kg of the resin particles obtained as described above was placed in a 5-L pressure vessel together with 3 L of water as an aqueous dispersion medium. Furthermore, 0.3 parts by mass of kaolin as an inorganic dispersant and 0.004 parts by mass of a surfactant (as an active ingredient) were added to the pressure vessel per 100 parts by mass of the resin particles. The surfactant used was sodium dodecylbenzenesulfonate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Neogen). Next, carbon dioxide was injected into the pressure vessel as a blowing agent, and the pressure was increased to a gauge pressure of 2.0 MPa (G). Note that the pressure indicated by (G) is the gauge pressure, i.e., the pressure value relative to atmospheric pressure. The contents of the pressure vessel were then heated at a rate of 2°C / min with stirring to the foaming temperature shown in Table 2, and the temperature was maintained for 15 minutes. This resulted in the DSC curve (endothermic curve) of the resulting expanded beads exhibiting a high-temperature peak in the heat flux differential scanning calorimetry (HSC) curve. The contents of the pressure vessel, i.e., resin particles and water, were then released under atmospheric pressure to expand the core layer, yielding expanded particles having a multilayer structure comprising a foamed layer and a non-foamed polymer coating layer, the coating layer covering the foamed layer. The expansion pressure in the pressure vessel immediately before expansion was the value shown in Table 2. The resulting expanded particles were left to cure for 24 hours in an environment of 23°C, 50% relative humidity, and 1 atm.

[0127] (Production of Expanded Bead Molded Articles) The cured expanded beads were compressed and filled into a mold having a molding cavity capable of molding a flat-plate-shaped molded article measuring 400 mm long, 300 mm wide, and 30 mm high, to a filling ratio P shown in Table 2. A metal mold was used as the mold. Compression filling is a filling method in which the expanded beads are compressed by applying pressure and filled into the mold. Steam was then supplied into the mold to heat the expanded beads, yielding a flat-plate-shaped expanded bead molded article. Heating with steam was performed as follows: First, steam was supplied into the mold with the drain valves on both sides open to perform preheating (exhaust step). Steam was then supplied from one side of the mold to heat it, and then steam was further supplied from the other side to heat it. Next, steam was supplied from both sides of the mold to heat it until the molding pressure inside the mold reached the pressure shown in Table 2. After heating, the pressure was released and the mold was cooled with water until the pressure on the molding surface of the mold reached 0.04 MPa (G), after which the mold was opened and the expanded bead molding was removed. The expanded bead molding obtained was cured in an oven at 80°C for 12 hours and then slowly cooled to room temperature to obtain an expanded bead molding.

[0128] The filling rate P is a value expressed by the following formula (1): [Formula 1] P = [a / (b × c)] × 100 (1) (where a in formula (1) is the mass (unit: kg) of the expanded beads filled in the molding die, and b is the bulk density (unit: kg / m 3 ), and c is the internal volume of the mold (unit: m 3 )

[0129] Examples 2, 3, 7 to 11, 14 and Comparative Example 1 Expanded beads and expanded bead molded articles were produced in the same manner as in Example 1, except for the changes shown in Tables 2 to 4.

[0130] Examples 4 to 6, 12, and 13 and Comparative Examples 2 and 3 A melt-kneaded mixture was prepared by melt-kneading the resins, carbon black, and luminescent compounds shown in Tables 2 to 4. The melt-kneaded mixture was then fed into a single-layer extruder to extrude strands. The extruded strands were cooled with water and cut with a pelletizer to obtain resin particles with an average mass of 1.0 mg per particle.

[0131] The resin particles obtained as described above were expanded in the same manner as in Example 1 to produce single-layer expanded particles.

[0132] Using the expanded beads obtained as described above, an expanded bead molding was produced in the same manner as in Example 1.

[0133] <Measurement of Bulk Density of Expanded Beads> The expanded beads were conditioned by standing for 24 hours in an environment of 23°C temperature, 50% relative humidity, and 1 atm. After conditioning, the expanded beads with a mass W (g) were packed into a measuring cylinder so that they would naturally pile up, and the bottom of the measuring cylinder was lightly tapped against a horizontal surface several times to stabilize the packed height of the expanded beads in the measuring cylinder. The bulk volume V (L) of the expanded beads indicated on the measuring cylinder was read, and the mass W of the expanded beads was divided by the bulk volume V of the expanded beads (W / V) and converted into units to determine the bulk density (kg / m) of the expanded beads. ３ ) was obtained.

[0134] <Measurement of Heat of Fusion of High-Temperature Peak of Expanded Beads> According to JIS K7122-1987, a 2 mg expanded bead specimen was subjected to heat flux differential scanning calorimetry, and the specimen was heated at a heating rate of 10°C / min from 30°C to a temperature 30°C higher than the end of the melting peak. A first DSC curve (see FIG. 7) was obtained by heating the expanded bead specimen at a heating rate of 10°C / min from 30°C to a temperature 30°C higher than the end of the melting peak. A line was then drawn on the DSC curve shown in FIG. 7 connecting point I, which corresponds to 80°C on the DSC curve, with point II, which corresponds to the end temperature of the melting of the expanded bead. The end temperature of the melting is the high-temperature end point of high-temperature peak b, and is the intersection of high-temperature peak b and the baseline on the DSC curve that is higher than high-temperature peak b. As shown in FIG. 7, after drawing a line connecting points I and II, a line passing through maximum point III between intrinsic peak a and high-temperature peak b and parallel to the vertical axis of the graph intersects with the line connecting points I and II, which is designated as point IV. The area enclosed by the straight line connecting points I and IV, the straight line connecting points III and IV, and the DSC curve connecting points I and III was defined as the area of ​​intrinsic peak a. The area enclosed by the straight line connecting points IV and II, the straight line connecting points III and IV, and the DSC curve connecting points III and II (shaded area) was defined as the area of ​​high-temperature peak b. The total heat of fusion of the expanded beads was calculated from the sum of the areas of intrinsic peak a and high-temperature peak b determined as described above, and the heat of fusion of high-temperature peak b was calculated from the area of ​​high-temperature peak b.

[0135] <Measurement of the average cell diameter of expanded beads and calculation of the coefficient of variation of cell diameter> First, an expanded bead was cut at a position that divided its volume in half. Next, a photograph of the cross section was taken so that the entire exposed cut surface was within the field of view. On the photograph, four line segments were drawn from the outermost surface of the expanded bead, passing through the center, to the outermost surface on the opposite side, with the same angle between adjacent line segments. That is, four line segments were drawn on the photograph so that the angle between adjacent line segments was 45°. The total length L of the four line segments thus obtained was divided by the number N of all cells contacting the line segments, and the value (L / N) was taken as the average cell diameter of one expanded bead. This procedure was performed on 20 expanded beads, and the arithmetic average value was taken as the average cell diameter of the expanded beads. In addition, the standard deviation of the cell diameter of the expanded beads was divided by the average cell diameter of the expanded beads, and the result was multiplied by 100 to determine the coefficient of variation. The value given by the square root of the unbiased variance was taken as the standard deviation.

[0136] <Measurement of Molded Article Density of Expanded Bead Molded Article> The density was calculated by dividing the mass of the expanded bead molded article by the volume calculated based on the external dimensions of the expanded bead molded article.

[0137] <Measurement of L* Value of Expanded Bead Molding> Five sites were randomly selected from the skin surface of the expanded bead molding, i.e., the surface that was in contact with the mold during in-mold molding, and the L* value of the expanded bead molding was measured using a spectrophotometer ("SE2000" manufactured by Nippon Denshoku Industries Co., Ltd.). The measurement range was 30 mmφ, and the measurement method was the reflection method. The arithmetic mean of the L* values ​​at these five measurement positions was taken as the L* value of the expanded bead molding.

[0138] <Luminescence Reaction Detection Test> In the detection test, a luminescence reaction detection test from an expanded bead molding was conducted using a spectrometer (product name: AvaSpec-2048) manufactured by AVANTES as a luminescence reaction detection device. The detection device has at least the function of detecting the emission spectrum of the luminescence reaction caused by the electromagnetic wave irradiation. Specifically, a test piece was first cut out from the expanded bead molding so that the skin surface was the detection target surface and placed in the detection device holder. Then, the detection target surface was irradiated with ultraviolet light at a wavelength of 320 nm using an ultraviolet irradiation device. The emission spectrum (S) emitted from the expanded bead molding by such irradiation was then detected. Furthermore, for each peak in the emission spectrum (S), the wavelength at which each peak was observed and the peak intensity I of each peak were recorded. The emission spectrum (S) in Example 1 is shown in FIG. 6.

[0139] (Ratio of peak intensity I (I / I ０ )) Expanded beads were produced in the same manner as in each Example and Comparative Example, except that no luminescent compound was added, and a blank expanded bead molding was produced using the expanded beads. Detection was carried out using the blank expanded bead molding in the same manner as in the luminescence reaction detection test, and the spectrum (S ０ ) was detected. Since the blank foamed bead molding does not contain any emissive compound, the spectrum (S ０ ) can also be called a "baseline" that does not show a clear emission peak. ０ ) is shown in Figure 6. The spectrum (S ０ ) intensity I ０ The spectrum (S ０ ) Intensity I at each wavelength ０ The ratio of the peak intensity I at each wavelength in the emission spectrum (S) to the ０ The ratio of the peak intensities I obtained (I / I ０The maximum value among the peak intensities I was determined. This was called the ratio of peak intensities I (I / I ０ The ratio of peak intensity I (I / I ０ When the maximum value of the peak intensity I (I / I) is 1.1 or more, it is determined that the expanded beads constituting the expanded bead molding exhibit a luminous reaction. ０ As shown in Tables 2 to 4, in all examples, the ratio of peak intensities I (I / I ０ ) was 1.1 or more, and it was confirmed that the expanded beads of the present invention could be identified as the expanded beads of the present invention by detecting a luminescence reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. ０ The wavelength of the emission peak of the emission spectrum (S) showing the maximum value of the luminescence spectrum (S) was 546 nm.

[0140] Although the luminescence reaction detection test performed in this example was based on the first identification method, such a test does not limit the method for identifying expanded beads of the present invention. For example, a predetermined reference emission spectrum is confirmed using expanded beads or expanded bead moldings containing one or more predetermined luminescent rare earth element components. A second identification method can then be employed to identify the target by comparing the emission spectrum of the expanded beads or expanded bead moldings to be identified with the predetermined reference emission spectrum. The comparison can be performed using a program that determines whether the patterns of the two emission spectra match by comparing one or more items selected from the number of peaks in the two emission spectra, the wavelengths of the peaks, the intensity ratio between each peak, and the area ratio between each peak. Using such an identification method enables more advanced identification of expanded beads or expanded bead moldings.

[0141] For example, a more advanced identification of expanded beads or expanded bead moldings using the second identification method can be performed as follows. First, expanded beads (No. 1) containing luminescent compound 1 are produced using recycled raw materials as the polypropylene-based resin. Next, the expanded beads (No. 1) are molded in a mold to produce an expanded bead molding (No. 1). Note that the expanded beads (No. 1) and the expanded bead molding (No. 1) can be produced by the same method as in Example 1, except that recycled raw materials are used as the polypropylene-based resin. Then, a test piece is cut out from the expanded bead molding (No. 1) so that the skin surface serves as the detection target surface, and ultraviolet light with a wavelength of 320 nm is irradiated onto the detection target surface. The emission spectrum emitted from the expanded bead molding (No. 1) by such irradiation is detected, and the foam spectrum is recorded in a device as a reference emission spectrum. The reference emission spectrum is then linked to information that the expanded bead molding is made of expanded beads produced using recycled polypropylene-based resin. Next, expanded beads (No. 2) containing the luminescent compound 1 are produced using recycled raw materials as the polypropylene-based resin. The expanded beads (No. 2) are then molded in a mold to produce the expanded bead molding (No. 2) to be identified. The expanded beads (No. 2) and the expanded bead molding (No. 2) are produced, for example, by the same method as in Example 1. The emission spectrum emitted from the expanded bead molding (No. 2) by such irradiation is detected, and the foam spectrum is compared with the reference emission spectrum detected as described above to confirm that the patterns of the two emission spectra match. If the patterns of the two emission spectra match as a result of the above operations, the expanded bead molding (No. 2) to be identified is identified as an expanded bead molding made of expanded beads produced using the recycled polypropylene-based resin, like the expanded beads (No. 1).

[0142]

[0143]

[0144]

[0145]

[0146] The present invention as described above encompasses the following technical concepts: (1) Expanded thermoplastic polymer beads that exhibit a luminescent reaction due to a luminescent rare earth element when irradiated with electromagnetic waves. (2) Expanded thermoplastic polymer beads as described in (1) above, wherein the expanded thermoplastic polymer beads contain taggant particles formed using the luminescent rare earth element. (3) Expanded thermoplastic polymer beads as described in (2) above, wherein the taggant particle content Ctt in the expanded thermoplastic polymer beads is 0.0001% by mass or more and 0.5% by mass or less. (4) Expanded thermoplastic polymer beads as described in (3) above, wherein the expanded thermoplastic polymer beads have a foam layer formed from a thermoplastic polymer and a polymer layer formed from a polymer, and the ratio [Ctr / Ctt] of the taggant particle content Ctr in the polymer layer to the taggant particle content Ctt in the expanded thermoplastic polymer beads is 2 or more. (5) Expanded thermoplastic polymer beads as described in (4) above, wherein the polymer layer is located on the surface of the expanded thermoplastic polymer beads. (6) The expanded thermoplastic polymer bead according to (4) or (5), wherein the content Ctr of taggant particles in the polymer layer is 0.001% by mass or more and 5% by mass or less. (7) The expanded thermoplastic polymer bead according to any one of (4) to (6), wherein the expanded thermoplastic polymer bead has a multilayer structure composed of the foam layer and the polymer layer covering 50% or more of the surface area of ​​the foam layer. (8) The expanded thermoplastic polymer bead according to any one of (1) to (7), wherein the expanded thermoplastic polymer bead has a foam layer composed of a polyolefin resin and a polymer layer composed of a polyolefin resin, and the difference [Tmc - Tms] between the melting point Tmc of the polyolefin resin constituting the foam layer and the melting point Tms of the polyolefin resin constituting the polymer layer is 3°C or more and 35°C or less. (9) The expanded thermoplastic polymer beads according to any one of (1) to (8), wherein the expanded thermoplastic polymer beads contain carbon particles and the carbon particle content Cct in the expanded thermoplastic polymer beads is 0.01% by mass or more and 15% by mass or less. (10) The expanded thermoplastic polymer beads according to any one of (1) to (9), wherein the expanded thermoplastic polymer beads are made of a polyolefin resin.(11) The expanded thermoplastic polymer beads according to any one of (1) to (10), wherein the expanded thermoplastic polymer beads contain a recycled thermoplastic polymer. (12) The expanded thermoplastic polymer beads according to any one of (1) to (11), wherein the luminescent reaction is derived from one or more luminescent rare earth elements selected from the group consisting of praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and thulium (Tm). (13) The expanded thermoplastic polymer beads according to any one of (1) to (12), wherein the average cell diameter of the expanded thermoplastic polymer beads is 30 μm or more and 200 μm or less, and the coefficient of variation of the cell diameter is 25% or less. (14) The expanded thermoplastic polymer beads according to any one of (1) to (13), wherein the content Cct of carbon particles in the expanded thermoplastic polymer beads is 0.01% by mass or more and 15% by mass or less, the average cell diameter of the expanded thermoplastic polymer beads is 30 μm or more and 200 μm or less, and the coefficient of variation of the cell diameter is 25% or less. (15) The expanded thermoplastic polymer beads according to any one of (1) to (14), wherein the expanded thermoplastic polymer beads are molded in a mold. (16) A method for identifying expanded thermoplastic polymer beads or expanded thermoplastic polymer bead moldings obtained by in-mold molding of the expanded thermoplastic polymer beads described in (1) to (14), comprising: i) an electromagnetic wave irradiation step of irradiating the surface of the expanded thermoplastic polymer beads or the expanded thermoplastic polymer bead molding with electromagnetic waves; ii) a detection step of detecting a luminescence reaction attributable to a luminescent rare earth element caused by the electromagnetic wave irradiation with a detection device to obtain an emission spectrum; and iii) at least one identification step selected from the following iii-1) and iii-2): iii-1) an identification step of comparing the emission spectrum with a blank spectrum that does not show a luminescence reaction attributable to a luminescent rare earth element; and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that shows a luminescence reaction attributable to a luminescent rare earth element.(17) Expanded thermoplastic polymer beads comprising a thermoplastic polymer and a luminescent rare earth element component that emits light when irradiated with electromagnetic waves and exhibits a specific emission spectrum, wherein the expanded beads can be identified as containing the luminescent rare earth element by comparing the emission spectrum detected when the expanded beads are irradiated with the electromagnetic waves with a predetermined reference emission spectrum that indicates a luminescent reaction attributable to the luminescent rare earth element. (18) Expanded thermoplastic polymer beads comprising a thermoplastic polymer, wherein the expanded beads can be identified as containing the luminescent rare earth element by: i) an electromagnetic wave irradiation step of irradiating the surface of the expanded beads with electromagnetic waves, ii) a detection step of detecting a luminescent reaction attributable to the luminescent rare earth element caused by the electromagnetic wave irradiation with a detection device to obtain an emission spectrum, and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that indicates a luminescent reaction attributable to the luminescent rare earth element. (19) Expanded thermoplastic polymer beads, characterized in that they are identified as expanded beads containing a luminescent rare earth element through the following steps: i) an electromagnetic wave irradiation step of irradiating the surface of the expanded beads with electromagnetic waves, ii) a detection step of detecting a luminescence reaction caused by the electromagnetic wave irradiation and attributed to a luminescent rare earth element with a detection device to obtain an emission spectrum, and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum showing a luminescence reaction attributed to the luminescent rare earth element. (20) Expanded thermoplastic polymer beads, characterized in that they are identified as expanded beads containing the luminescent rare earth element by molding expanded beads containing a thermoplastic polymer and a luminescent rare earth element component that emits light when irradiated with electromagnetic waves and exhibits a specific emission spectrum in a mold, by comparing the emission spectrum detected by irradiating the expanded bead molding with the electromagnetic waves with a predetermined reference emission spectrum showing a luminescence reaction attributed to the luminescent rare earth element.(21) An expanded bead molding obtained by molding expanded beads made of a thermoplastic polymer in a mold, characterized in that the expanded bead molding can be identified as being made of expanded beads containing a luminescent rare earth element by the following steps: i) an electromagnetic wave irradiation step of irradiating the surface of the expanded bead molding with electromagnetic waves; ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element due to the electromagnetic wave irradiation using a detection device to obtain an emission spectrum; and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that indicates a luminescence reaction caused by the luminescent rare earth element. (22) An expanded bead molding obtained by molding expanded beads made of a thermoplastic polymer in a mold, characterized in that the expanded bead molding is identified as being made of expanded beads containing a luminescent rare earth element through the following steps: i) an electromagnetic wave irradiation step of irradiating the surface of the expanded bead molding with electromagnetic waves; ii) a detection step of detecting a luminescence reaction caused by the luminescent rare earth element due to the electromagnetic wave irradiation with a detection device to obtain an emission spectrum; and iii-2) an identification step of comparing the emission spectrum with a predetermined reference emission spectrum that indicates a luminescence reaction caused by the luminescent rare earth element.

[0147] 10: taggant particle 20: foamed layer 21: end surface 30: polymer layer 40: outermost surface layer 100, 100A, 100B, 100C, 100D: expanded beads d1: region S: a chart showing the emission spectrum of the expanded bead molding of Example 1. ０ . . . A chart showing the spectrum of the foamed bead molding which is the blank of Example 1.

Claims

1. Thermoplastic polymer foam particles that exhibit a luminescent reaction derived from luminescent rare earth elements when exposed to electromagnetic waves.

2. The thermoplastic polymer foam particles according to claim 1, wherein said thermoplastic polymer foam particles contain taggant particles containing said luminescent rare earth element.

3. The thermoplastic polymer foamed beads according to claim 2, wherein the taggant particle content Ctt in the thermoplastic polymer foamed beads is 0.0001% by mass or more and 0.5% by mass or less.

4. The thermoplastic polymer foamed beads according to claim 3, which have a foamed layer composed of a thermoplastic polymer and a polymer layer composed of a polymer, and the ratio [Ctr / Ctt] of the taggant particle content Ctr in the polymer layer to the taggant particle content Ctt in the thermoplastic polymer foamed beads is 2 or more.

5. The thermoplastic polymer foam bead of claim 4, wherein said polymer layer is located on a surface of the foam bead.

6. The thermoplastic polymer expanded beads according to claim 4 or 5, wherein the content Ctr of taggant particles in the polymer layer is 0.001% by mass or more and 5% by mass or less.

7. The thermoplastic polymer foamed beads according to any one of claims 4 to 6, wherein the thermoplastic polymer foamed beads have a multilayer structure composed of the foamed layer and the polymer layer covering 50% or more of the surface area of ​​the foamed layer.

8. The thermoplastic polymer foamed particles according to any one of claims 1 to 7, which have a foamed layer made of a polyolefin resin and a polymer layer made of a polyolefin resin, and the difference [Tmc - Tms] between the melting point Tmc of the polyolefin resin constituting the foamed layer and the melting point Tms of the polyolefin resin constituting the polymer layer is 3°C or more and 35°C or less.

9. The thermoplastic polymer foam particles described in any one of claims 1 to 8, wherein the thermoplastic polymer foam particles contain carbon particles, and the carbon particle content Cct in the thermoplastic polymer foam particles is 0.01 mass% or more and 15 mass% or less.

10. The thermoplastic polymer foam particles according to any one of claims 1 to 9, wherein the thermoplastic polymer foam particles are composed of a polyolefin resin.

11. The thermoplastic polymer foam particles according to any one of claims 1 to 10, wherein the thermoplastic polymer foam particles comprise a recycled thermoplastic polymer.

12. The thermoplastic polymer foam particles according to any one of claims 1 to 11, wherein the luminescent reaction is derived from one or more luminescent rare earth elements selected from the group consisting of praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and thulium (Tm).

13. A thermoplastic polymer foamed bead described in any one of claims 1 to 12, wherein the average bubble diameter of the thermoplastic polymer foamed bead is 30 μm or more and 200 μm or less, and the coefficient of variation of the bubble diameter is 25% or less.

14. A thermoplastic polymer expanded bead molding obtained by molding the thermoplastic polymer expanded bead according to any one of claims 1 to 13 in a mold.

15. A method for identifying thermoplastic polymer foamed beads or thermoplastic polymer foamed bead moldings obtained by molding the thermoplastic polymer foamed beads in a mold according to any one of claims 1 to 13, comprising: i) an electromagnetic wave irradiation step of irradiating an electromagnetic wave to a surface of the thermoplastic polymer foamed beads or the thermoplastic polymer foamed bead molding, ii) a detection step of detecting a luminescence reaction originating from a luminescent rare earth element caused by the electromagnetic wave irradiation with a detection device to obtain an emission spectrum, and iii) at least one identification step selected from the following iii-1) and iii-2): iii-1) an identification step of comparing the emission spectrum with a blank spectrum showing no luminescence reaction originating from a luminescent rare earth element, and iii-2) an identification step of collating the emission spectrum with a predetermined reference emission spectrum showing a luminescence reaction originating from a luminescent rare earth element.

Images