Bundling method and bundle

Abstract

The objective of this invention is to provide a packaging method that can simultaneously suppress temperature rise and stacking stability of black foam at a low cost. The aforementioned objective is addressed by a packaging method using a bundle (100), which includes: a setting step in which a cover plate (2) is set on one or more layers of black foam (1) stacked on a pallet (4) to cover the main surface of its uppermost section; and a covering step in which a black stretch film (3) is used to cover the outer periphery of the side of the aforementioned black foam (1).

Description

Technical Field

[0001] This invention relates to a method for bundling foamed molded articles and to bundling materials. Background Technology

[0002] Beaded foam (foamed materials) are widely used in packaging materials, building materials, and vehicle components due to their excellent cushioning and lightweight properties, and the ability to be shaped to suit various applications. For example, beaded foam is manufactured by pre-foaming thermoplastic resin granules in a molding plant to create pre-foamed granules, which are then in-mold molded. Various shapes can be formed using molds used in in-mold molding, making beaded foam versatile in shapes ranging from block to box.

[0003] Carbon-containing beaded molded materials have superior thermal insulation properties compared to ordinary beaded molded materials, and therefore, the demand for them as residential thermal insulation materials has been increasing in recent years.

[0004] As for packaging films used in conventional methods of bundling beaded foam, Patent Document 1 discloses a packaging film with small through holes in a thermoplastic resin film containing white pigment or metal powder. Patent Document 2, as a method for bundling black beaded foam, discloses a method using white paper for bundling.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 5-262370

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-202786 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The method described in Patent Document 1 is a bundling method that uses a foam coated with a low-melting-point resin as the object and is based on bundling a non-carbon-free, i.e., non-black, bead-based foam. Therefore, for the method described in Patent Document 1, when bundling a black foam, which absorbs heat more easily than a white foam, there is a problem in suppressing the temperature rise of the foam within the bundle. Furthermore, the bundling method described in Patent Document 2 has a problem regarding the stacking stability of the bundle.

[0011] In view of the above-mentioned situation, one object of the present invention is to provide a method for bundling black foam that can simultaneously suppress the temperature rise of the black foam and maintain its stacking stability when bundling the foam.

[0012] Solution for solving the problem

[0013] That is, one aspect of the present invention includes the following configuration.

[0014] A bundling method for bundling rectangular black foam bodies formed of thermoplastic resin with a brightness index L* less than 65 into a single bundle includes: a setting step of setting a cover plate larger than the size of the black foam bodies for at least one layer of the aforementioned black foam bodies stacked on a pallet, such that it covers at least the main surface of the uppermost layer of the aforementioned black foam bodies; and a covering step of covering the outer periphery of the side of the aforementioned black foam bodies with a black stretch film while a gap is provided between the cover plate and the aforementioned black foam bodies.

[0015] A bundle comprising: a rectangular black foam body, at least one layer of which is stacked on a pallet and formed of a thermoplastic resin with a brightness index L* less than 65; a cover plate, which is disposed over the black foam body such that it covers at least the uppermost part of the main surface of the black foam body, and is larger than the black foam body; and a black stretch film, which covers the outer periphery of the cover plate and the side surface of the black foam body with a gap between it and the black foam body.

[0016] The effects of the invention

[0017] According to one aspect of the present invention, when packaging black foam, it is possible to both suppress the temperature rise of the foam and maintain its stacking stability. Attached Figure Description

[0018] Figure 1 This is a side view illustrating the schematic configuration of the bundle according to one embodiment of the present invention.

[0019] Figure 2 This is a side view illustrating the schematic configuration of the bundle according to another embodiment of the present invention.

[0020] Figure 3 It means Figure 2 The side view shows a schematic configuration of a modified example of a bundle. Detailed Implementation

[0021] The following description describes one embodiment of the present invention, but the invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope shown in the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included within the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. It should be noted that all academic and patent documents described in this specification are incorporated herein by reference. In addition, unless otherwise specified, in this specification, "A~B" indicating a numerical range means "A or more (inclusive of A and greater than A) and B or less (inclusive of B and less than B)". Furthermore, the accompanying drawings are provided for ease of understanding when referred to in conjunction with the following description and are not necessarily drawn to a fixed scale.

[0022] [1. Technical concept of the present invention]

[0023] Black-based foams, especially carbon-containing beaded foams that can act as inhibitors of radiative heat transfer, have excellent thermal insulation properties and have therefore been widely used in residential insulation materials and other applications in recent years.

[0024] When using black foam in outdoor applications such as construction sites, the foam is transported to the site in bundles and, depending on the situation, stored outdoors in these bundles until use. However, black foam readily absorbs heat, causing its surface temperature to rise. Here, simple bundles for rain or dirt protection are typically made of polyolefin bags. These bags are transparent, allowing sunlight to pass through, and sometimes the temperature inside the bundle rises abnormally. Therefore, it is evident that using polyolefin bags to bundle black foam leads to deformation due to the foam's heat absorption and melting.

[0025] As a method for packaging foam to prevent deformation caused by sunlight, the method described in Patent Document 1, which uses a thermoplastic resin film with light-shielding measures to package the foam, is an example. However, conventional packaging methods target white foam, which is less likely to absorb heat compared to black foam. When packaging black foam, the suppression of temperature rise is insufficient. Furthermore, even when using a thermoplastic resin film with light-shielding measures for packaging, the surface of the foam in contact with the thermoplastic resin film may sometimes melt and deform due to the temperature rise of the thermoplastic resin film itself.

[0026] Patent document 2 describes a method for bundling black foam using white paper. However, paper-based bundling is prone to collapse due to its lack of elasticity, and there is room for improvement in the stacking stability of the foam.

[0027] In addition, a method was proposed to block sunlight by covering the bundled foam (bundling material) with blue plastic sheeting or similar materials. However, this method is difficult to implement completely on construction sites. Furthermore, large-scale packaging using blue plastic sheeting or similar materials not only incurs high costs but also presents significant processing difficulties.

[0028] Black foam is a fragile product and is traded at a low price. Therefore, it is desirable that the packaging method for black foam is simple and low-cost, and that good stacking stability is desired to avoid damage during transportation, etc.

[0029] In view of the above situation, with the aim of providing a method for bundling black foam that can simultaneously suppress the temperature rise of the black foam and maintain stacking stability at low cost, the inventors conducted in-depth research and completed the present invention.

[0030] [2. Packaging method for black foam materials]

[0031] A method for bundling black foam according to one embodiment of the present invention is a method for bundling rectangular black foam formed of thermoplastic resin with a brightness index L* less than 65 into a single bundle. The method includes: a setting step, in which a cover plate larger than the size of the black foam is set for at least one layer of the aforementioned black foam stacked on a pallet, such that it at least covers the main surface of the uppermost layer of the aforementioned black foam; and a covering step, in which a black stretch film is used to cover the outer periphery of the cover plate and the side surface of the aforementioned black foam, with a gap between the cover plate and the black foam. Hereinafter, "the method for bundling black foam according to one embodiment of the present invention" will sometimes be referred to as "this bundling method".

[0032] According to the above configuration, in the aforementioned covering process, with a gap between the black foam and the cover plate, the outer periphery of the side of the black foam is covered by a black stretch film. Therefore, since air is trapped between the black foam and the black stretch film, the heat absorbed by the black film is difficult to transfer to the black foam. Thus, according to the above configuration, the temperature rise of the black foam can be suppressed. Furthermore, warping, deformation, or dimensional changes of the black foam that accompany such a temperature rise can be prevented.

[0033] Furthermore, according to the above configuration, both the cover plate covering the main surface of the aforementioned black foam at the top and the outer periphery of the side of the aforementioned black foam are covered by a black stretch film. Therefore, by utilizing the black stretch film, the contact between the black foam and the cover plate is maintained, thereby preventing the black foam from collapsing and achieving a bundled item with stacking stability.

[0034] As described above, based on the above configuration, when the black foam is bundled, it is possible to both suppress the temperature rise of the black foam and maintain its stacking stability.

[0035] (Stacking process)

[0036] This bundling method preferably includes a stacking process of stacking at least one layer of black foam on a pallet. The stacking process can be performed before or after the setting process described later.

[0037] In one embodiment of the present invention, the number of stacked layers of the black foam is not particularly limited as long as it is one or more layers; for example, it can be two or more layers, or four or more layers. Here, the number of layers of the black foam can also be referred to as the number of stacked black foams.

[0038] In one embodiment of the present invention, the method of stacking black foam bodies (stacking method) is not particularly limited. From the viewpoint of preventing the goods from collapsing, alternating stacking, brick stacking, rotating staggered stacking, and gap stacking are preferred.

[0039] (Setting up the process)

[0040] This bundling method includes a setting step in which a cover plate larger than the aforementioned black foam is set for at least one layer of the aforementioned black foam stacked on a pallet, such that it at least covers the main surface of the uppermost layer of the aforementioned black foam. In this specification, the cover plate set at the uppermost layer of the aforementioned stacked black foam is sometimes referred to as the uppermost (topmost) cover plate. The term "main surface" as used here refers to the surface of the black foam that primarily bears the action of the cover plate. More specifically, "main surface" refers to the upper or lower surface of the black foam when the stacking direction of the black foam is set to vertical.

[0041] In one embodiment of the present invention, the setting process may further include the step of placing a cover plate on the pallet. According to this configuration, soiling of the black foam during the bundling process can be suppressed. It should be noted that when the setting process includes the step of placing the cover plate on the pallet, it is preferable to perform the step of placing the cover plate on the pallet before the aforementioned (stacking process). That is, the black foam is preferably stacked on the cover plate after it has been placed on the pallet. In this specification, the cover plate placed on the aforementioned pallet is sometimes referred to as the lower section (pad) cover plate.

[0042] In one embodiment of the present invention, the setting process preferably further includes: a step of clamping a cover plate between the black foam bodies stacked in the stacking process. The step of clamping the cover plate between the black foam bodies can be performed before or after the setting of the upper and / or lower cover plates. In this specification, at least one cover plate clamped between the aforementioned black foam bodies is sometimes referred to as a middle (central) cover plate.

[0043] In this specification, the structure formed by the cover plate and the black foam layered on the pallet in the aforementioned (stacking process) and the aforementioned (setting process) is sometimes referred to as a laminate.

[0044] (Covering process)

[0045] This packaging method includes a covering process, in which a black stretch film is used to cover the outer periphery of the cover plate and the side of the black foam body while a gap exists between the black stretch film and the black foam body. Here, "a gap exists between the black stretch film and the black foam body" means that the black stretch film does not come into contact with the black foam body.

[0046] The covering process described in one embodiment of the present invention can also be described as follows: For the cover plate and the black foam (laminated body) stacked on the pallet in the aforementioned (stacking process) and the aforementioned (setting process), a black stretch film is wound around the cover plate such that it covers (contacts) the side-end of the cover plate, such that the entire side of the laminate is covered by at least one turn (layer), preferably two turns or more, and more preferably three turns or more, that is, the black foam is not exposed to the outside. By covering the laminate with the black stretch film at least one turn, the stacking stability of the black foam can be well achieved.

[0047] In one embodiment of the present invention, the gap between the aforementioned black foam and the black stretched film is preferably 5 mm or more. If the gap between the black foam and the black stretched film is 5 mm or more, then when the black stretched film absorbs sunlight and heats up, there is no need to worry about the black foam coming into contact with the heated black stretched film, and the temperature rise and dissolution of the black foam caused by sunlight can be more strongly suppressed.

[0048] In one embodiment of the present invention, in the covering process, in addition to using a black-based stretched film, a stretched film other than black can be used to cover the laminate. The stretched film other than black is not particularly limited; for example, a white or transparent stretched film can be used.

[0049] 〔3. Packages〕

[0050] The following is a reference. Figures 1-3 The packaging materials provided by this packaging method are described in detail below. Figure 1 This is a schematic cross-sectional view showing the bundling of a single piece of foam using this bundling method. Figure 2 This is a schematic diagram illustrating the bundling of multiple foam sheets using this bundling method. Figure 3 It means Figure 2 A side view showing a schematic configuration of a modified example of a bundle.

[0051] like Figure 1 As shown, the bundle 100 provided by this bundling method includes a black foam body 1, cover plates 2a and 2b, a black stretch film 3, and a tray 4. The cover plates 2a and 2b are plates larger than the black foam body 1 and are disposed above and below the black foam body 1. It should be noted that the bundle 100 only needs to have at least a cover plate 2a covering the upper surface of the black foam body 1.

[0052] The bundle 100 has a structure in which a black foam body 1, cover plates 2a and 2b are stacked on a pallet 4. Furthermore, a black stretch film 3 covers the outer periphery of the sides of the black foam body 1 and the cover plates 2a and 2b with a gap between it and the black foam body 1. The black stretch film 3 covers the sides in such a way that it is in contact with at least the outer periphery of the side of the cover plate 2a.

[0053] exist Figure 1In the configuration shown, the black stretch film 3 is configured such that it is separated from the side of the black foam 1, contacts the outer periphery of the side of the cover plates 2a and 2b, and covers the entire upper surface of the cover plate 2a. This improves the stacking stability of the black foam 1 in the bundle 100. Considering the stacking stability of the black foam 1, the black stretch film 3 only needs to contact the outer periphery of the side of the cover plate 2a and cover at least the edge of the upper surface of the cover plate 2a. It should be noted that in this specification, the direction in which the tray 4 is disposed in the laminated structure is referred to as the lower section, and the opposite direction is referred to as the upper section.

[0054] The bundle 100 only needs to have at least one layer of black foam material 1. For example... Figure 2 As shown, in another embodiment of the present invention, the bundle 100 provided by this bundling method is composed of two layers of black foam 1a and 1b. Figure 2 The bundle 100 shown includes black foam bodies 1a and 1b, cover plates 2c, 2d and 2e, black stretch film 3, and tray 4.

[0055] Cover plate 2c covers the upper surface of the upper section of black foam 1a. Furthermore, for the stacked black foams 1a and 1b, cover plate 2d is sandwiched between the black foams 1a and 1b. Additionally, cover plate 2e covers the lower surface of the lower section of black foam 1b. This stack of black foams 1a and 1b and cover plates 2c, 2d, and 2e is thus positioned on the support plate 4. It should be noted that... Figure 2 The bundle 100 shown only needs to have a cover plate 2c that covers at least the upper surface of the black foam 1a at the top.

[0056] The black stretch film 3 covers the outer periphery of the sides of the black foam bodies 1a and 1b and the cover plates 2c, 2d, and 2e with a gap between them. The black stretch film 3 covers the sides in such a way that it is in contact with at least the outer periphery of the side of the cover plate 2c.

[0057] exist Figure 2 In the configuration shown, the black stretch film 3 is configured such that it is separated from the sides of the black foams 1a and 1b, contacts the outer periphery of the sides of the cover plates 2c, 2d and 2e, and covers the entire upper surface of the cover plate 2c. This improves the stacking stability of the black foams 1a and 1b in the bundle 100. Considering the stacking stability of the black foams 1a and 1b, the black stretch film 3 only needs to contact the outer periphery of the sides of the cover plate 2c and cover the upper edge of the cover plate 2c.

[0058] Figure 3The bundle 100 shown does not have a cover plate sandwiched between the black foam bodies 1a and 1b. Figure 2 The structures shown are different. More specifically, in Figure 3 In the bundle 100 shown, the cover plate 2f covers the upper surface of the upper section of the black foam 1a. Additionally, the cover plate 2g covers the lower surface of the lower section of the black foam 1b. The black foams 1a and 1b are in direct contact with each other, and there is no cover plate sandwiched between them.

[0059] The bundle 100 described in one embodiment of the present invention can also be described as a bundle comprising: a rectangular black foam 1, which is at least one layer laminated on a pallet 4 and is formed of a thermoplastic resin with a brightness index L* less than 65; a cover plate 2, which is provided over the aforementioned black foam 1 such that it covers at least the uppermost part of the main surface of the aforementioned black foam 1, and is larger than the aforementioned black foam 1; and a black stretch film 3, which covers the outer periphery of the cover plate 2 and the side surface of the aforementioned black foam 1 with a gap between it and the aforementioned black foam 1.

[0060] Hereinafter, the materials of the bundle 100 constituting one embodiment of the present invention will be described in detail.

[0061] (Black foam 1)

[0062] In one embodiment of the present invention, the black foam body 1 is a black resin foam molded body with a brightness index L* less than 65. There is no particular limitation as long as it is a beaded foam molded body obtained by pre-foaming and molding foamable thermoplastic resin particles or by foaming and molding thermoplastic resin particles. The black foam body 1 can be composed of a single piece of black resin foam molded body with a brightness index L* less than 65, or it can be composed of two or more pieces of black resin foam molded body with a brightness index L* less than 65 stacked together.

[0063] The thermoplastic resins constituting foamed thermoplastic resin particles or thermoplastic foam particles are not particularly limited, but can include, for example, styrene-based resins such as polystyrene (PS), styrene-acrylonitrile copolymer (AS), styrene-(meth)acrylic acid copolymer (heat-resistant PS), styrene-(meth)acrylic ester copolymer, styrene-butadiene copolymer (HIPS), three-dimensional copolymers of N-phenylmaleimide-styrene-maleic anhydride, and their alloys with AS (IP); vinyl-based resins such as polymethyl methacrylate, polyacrylonitrile resins, and polyvinyl chloride resins; and polypropylene, polyethylene, ethylene-propylene copolymers, ethylene-propylene-butene three-dimensional copolymers, and cycloolefin resins. Polyolefin resins such as (co)polymers, and polyolefin resins for which branched or cross-linked structures have been introduced to control rheology; polyamide resins such as nylon 6, nylon 66, nylon 11, nylon 12, and MXD nylon; aromatic polyester resins such as polyethylene terephthalate, 1,3-propylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; aliphatic polyester resins such as polylactic acid; engineering plastics such as polycarbonate resins, polyphenylene ether resins (PPE), modified polyphenylene ether resins (modified PPE), polyoxymethylene resins, polyphenylene sulfide resins, aromatic polyether resins, and polyetheretherketone resins. These can be used alone or in combination of two or more types. Among these thermoplastic resins, polystyrene resins are preferred from the viewpoint of being relatively inexpensive, capable of being molded using low-pressure steam without special methods, and providing high cushioning and heat insulation properties. That is, in one embodiment of the present invention, the black foam 1 is preferably a foam formed of polystyrene foaming resin.

[0064] In one embodiment of the present invention, the method for making the brightness index L* of the black foam 1 less than 65, in other words, the method for making the beaded foam molded body formed of thermoplastic resin exhibit a black color, is not particularly limited. Examples include: methods that contain carbon in the foamed thermoplastic resin particles or thermoplastic foam particles constituting the aforementioned beaded foam molded body, and methods that contain black pigments. Among these, from the perspective of imparting excellent heat insulation properties to the black foam 1, methods that contain carbon in the foamed thermoplastic resin particles or thermoplastic foam particles are preferred. In other words, the black foam 1 described in one embodiment of the present invention preferably contains carbon.

[0065] The carbon content of the black foam 1 described in one embodiment of the present invention is not particularly limited. From the viewpoint of improving thermal insulation, it is preferably 2% or more in 100% by weight of the black foam 1, and preferably 8% or less in order to obtain good foaming and molding properties.

[0066] Carbon contained in the black foam 1 can include graphite, graphene, activated carbon, coke, carbon black, etc. Among these, graphite or carbon black is preferred from the perspective of achieving a good balance between cost and improved thermal insulation, and graphite is more preferred.

[0067] In one embodiment of the present invention, the brightness index L* of the black foam 1 is less than 65, preferably less than 60, more preferably less than 55, and even more preferably less than 50. Foam with a brightness index L* less than 65 exhibits a black or gray color. Therefore, when the black foam 1 is packaged using conventional packaging methods, it may sometimes absorb heat from sunlight, heat up, melt, or deform. On the other hand, when the black foam 1 is packaged using this packaging method, since the heating of the black foam 1 can be suppressed, even black foam 1 with a brightness index L* less than 65 can be stably packaged and stored.

[0068] In this specification, the luminance index L* refers to the value of the luminance index L* in the CIE 1976 L*a*b* color space. For example, the luminance index L* value for white is 100, and the luminance index L* value for black is 0. It should be noted that the luminance index L* in the CIE 1976 L*a*b* color space can be measured using, for example, a spectrophotometer (KONICA MINOLTA, CM-2500d, etc.), with a xenon lamp as the measurement light source and a measurement diameter set to φ8mm.

[0069] In one embodiment of the present invention, the shape of the black foam 1 is not particularly limited, and can be, for example, rectangular, triangular, hexagonal or other polygonal shapes, circular shapes, etc. Alternatively, the black foam 1 can be filled into a wooden panel such as a load-bearing wall panel. The shape of the black foam 1 can be appropriately set according to the desired application.

[0070] In one embodiment of the present invention, the expansion ratio of the black foam 1 is preferably 60 times or more. If the expansion ratio of the black foam 1 is 60 times or more, the foam can be provided at a lower cost, which is therefore economically advantageous.

[0071] When using conventional bundling methods, such as bundling with plastic straps or ropes, to bundle black foam 1 with a foaming ratio of 60 times or more, the following problem occurs: the corners of the molded part of the black foam 1 that come into contact with the plastic straps or the like deform or break. In this bundling method, since the black foam 1 does not directly contact the black stretch film 3, even with such a foam, it can be bundled without deformation or breakage.

[0072] (Covering plate 2)

[0073] As one embodiment of the present invention, the cover plate 2 is not particularly limited, but is preferably selected from at least one of the group consisting of wood board, corrugated cardboard, plastic corrugated cardboard and synthetic resin board containing foaming raw materials.

[0074] Regarding the size of the cover plate 2, it is preferred that at least one of the width and / or depth directions is larger than the external dimensions of the black foam 1, and preferably both the width and depth directions are more than 5 mm larger than the external dimensions of the black foam 1.

[0075] The thickness of the cover plate 2 is not particularly limited, but it needs to be thick enough to withstand the strength required for covering and fixing with the black stretch film 3. Specifically, a thickness of 1 mm or more is preferred, a thickness of 2 mm or more is more preferred, and a thickness of 3 mm or more is even more preferred. Alternatively, two or more cover plates 2 can be overlapped to achieve the desired thickness.

[0076] (Black stretched film 3)

[0077] In one embodiment of the present invention, the black stretched film 3 is formed from black synthetic resin.

[0078] In one embodiment of the present invention, the synthetic resin constituting the black stretch film 3 is not particularly limited, and examples include polyolefin resins, acrylic resins, and polyvinyl chloride resins. Among these synthetic resins, polyolefin resins are preferred, and polyethylene resins are particularly preferred, as they possess tensile strength at break and elongation at break that can stably cover the bundled object.

[0079] As for polyethylene-based resins, there are no particular limitations as long as they are ethylene homopolymers or copolymers with ethylene as the main component and can be used as stretched films. Polyethylene-based resins with a melt flow rate (MFR) of 0.5 g / 10 min or more and 7 g / 10 min or less, measured at 190°C and a load of 21.18 N, are particularly preferred. The lower limit of the MFR of the polyethylene-based resin is more preferably 0.7 g / 10 min or more, and particularly preferably 1.0 g / 10 min or more. Furthermore, the upper limit of the MFR of the polyethylene-based resin is more preferably 5.0 g / 10 min or less, and particularly preferably 3.0 g / 10 min or less. If the MFR of the polyethylene-based resin is 0.5 g / 10 min or more, there is no concern about excessive load on the extruder during extrusion molding, and there is no concern about problems with the dispersion of carbon black in the resin (described later). Furthermore, if the MFR is 7 g / 10 min or less, there is no concern about problems with film-forming stability during blown film molding, and there is no concern about the strength of the molded film becoming too low.

[0080] In this specification, black synthetic resin refers to a dark-colored synthetic resin exhibiting a solar absorption rate of over 90% in the wavelength region of 380–720 nm. The wavelength region of 380–720 nm is described as the visible light region, which is light that humans can perceive with the naked eye. If the light absorption rate in the visible light region is high, it will appear dark, such as black or gray.

[0081] In this specification, the solar absorbance in the wavelength region of 380–720 nm can be measured using the methods shown in (1) to (5) below: (1) Prepare a black stretched film as a test piece, and use a self-recording spectrophotometer to set the reflectance of the white alumina substrate to 100%, and measure the reflectance (spectral reflectance) at each wavelength of 1 nm in the wavelength region of 380–720 nm; (2) Use JIS (2) Calculate the values ​​obtained by multiplying the spectrophotometric reflectance measured in (1) at each wavelength by the corresponding weighting factor, and calculate the solar reflectance as a sum of these values ​​(spectral solar reflectance test method); (3) For the test piece in (1), use a self-recording spectrophotometer to measure the transmittance at each wavelength with the transmittance set to 100% in the state without the test piece installed; (4) Using JISA5759 Appendix 3, calculate the values ​​obtained by multiplying the spectrophotometric transmittance measured in (3) at each wavelength by the weighting factor, and calculate the solar transmittance as a sum of these values; (5) Furthermore, based on the obtained values ​​of solar reflectance and solar transmittance, calculate the solar absorption rate using the following formula (1):

[0082] (Solar absorption rate) = 100% - (Solar reflectance) - (Solar transmittance) ... (1).

[0083] In one embodiment of the present invention, the method for making the black-based stretched film 3 black is not particularly limited, and a method of blending pigments into the synthetic resin constituting the black-based stretched film 3 can be cited as an example. As pigments, by blending black pigments such as carbon black and aniline black, the black-based stretched film 3 can be made black, that is, the solar absorption rate of the black-based stretched film 3 in the wavelength region of 380 nm to 720 nm can be 90% or more. From the viewpoint of cost and processability, carbon black is particularly preferred as a black pigment.

[0084] The content of pigment (black pigment) relative to the synthetic resin is affected by the thickness of the film and the desired light-blocking performance, and therefore cannot be generalized. It is preferably 3.0 to 15.0 parts by weight relative to 100 parts by weight of the synthetic resin. In particular, the lower limit is preferably 5.0 parts by weight or more, more preferably 6.0 parts by weight or more. Furthermore, the upper limit is preferably 12.0 parts by weight or less, more preferably 10.0 parts by weight or less. If the pigment content is 3.0 parts by weight or more, the total light transmittance is low, suppressing the decrease in solar absorption rate. Therefore, even when exposed to sunlight, excessive temperature rise of the foam can be suppressed. Furthermore, if the pigment content is 15.0 parts by weight or less, it does not affect the damage resistance and flexibility of the synthetic resin. Therefore, there is no concern about the deterioration of formability due to the decrease in strength and elongation of the black stretched film 3, and consequently, there is no concern about the lightweight properties deteriorating with increasing cost and specific gravity.

[0085] In one embodiment of the present invention, the method of manufacturing the pigment is not particularly limited, and pigments manufactured by known methods such as furnace process, tank process, and acetylene process can be used. From the viewpoint of availability, pigments manufactured by oil furnace process are preferred. In addition, from the viewpoint of ensuring good dispersibility in the black stretched film 3, the average particle size of the pigment is preferably 10 μm or less.

[0086] The black stretched film 3 according to one embodiment of the present invention can be easily manufactured by forming a resin mixture containing the above-mentioned synthetic resin and pigment using a known forming method. To obtain a homogeneous film, it is preferable to: before forming, use a mixing mill such as a single-screw extruder, twin-screw extruder, Banbury mixer, Brabender mixer, open mill rolls, or kneader to mix the aforementioned resin mixture in a heated molten state (melt mixing). The forming method for the aforementioned melt-mixed mixture is not particularly limited; examples include film-forming methods such as air-blown film forming and T-die film forming. Air-blown film forming is particularly convenient and economical, and is therefore preferred.

[0087] In one embodiment of the present invention, the thickness of the black stretch film 3 is preferably 10 μm to 250 μm, more preferably 20 μm to 150 μm, and even more preferably 25 μm to 100 μm. If the thickness of the black stretch film 3 is 10 μm or more, it can sufficiently absorb light in the visible light region, and therefore tends to stably exhibit a dark color. If the thickness of the black stretch film 3 is 250 μm or less, the processability of the bundling operation can be well maintained, and there is no concern about an excessive increase in cost.

[0088] In one embodiment of the present invention, the black stretched film 3 preferably has a longitudinal stretch ratio (hereinafter also referred to as elongation) of at least 250% or more, and the stretch ratio based on coaxial stretching or successive biaxial stretching is at least 250% in the longitudinal direction and at least 150% in the transverse direction. In this specification, the stretch ratio of the black stretched film 3 is a value measured according to ASTM-D-882 by the following method: using a tensile compression testing machine (manufactured by Shimadzu Corporation), the black stretched film 3, with a width of 1 cm and a chuck spacing of 10 cm, is stretched vertically at a speed of 300 mm / min, and the elongation at break (%) is measured as the stretch ratio (%). It should be noted that the stretch ratio of the black stretched film 3 is measured in an atmosphere of 23°C and 50% RH.

[0089] Furthermore, in one embodiment of the present invention, the tensile breaking strength (hereinafter also referred to as elongation strength) of the black stretched film 3 is preferably 30 MPa or more in the longitudinal direction and 15 MPa or more in the transverse direction. In this specification, the tensile breaking strength of the black stretched film 3 is a value measured according to ASTM-D-882 by the following method: using a tensile compression testing machine (manufactured by Shimadzu Corporation), the black stretched film 3, with a width of 1 cm and a chuck spacing of 10 cm, is stretched vertically at a speed of 300 mm / min, and the strength (MPa) at break is measured as the tensile breaking strength (MPa). It should be noted that the tensile breaking strength of the black stretched film 3 is measured in an atmosphere of 23°C and 50% RH.

[0090] The black stretch film 3 described in one embodiment of the present invention has the above-mentioned elongation and elongation strength, so when the black foam 1 is wound on the pallet 4 from the cover plate 2, the film breakage or workability deterioration can be prevented.

[0091] Furthermore, the black stretch film 3 described in one embodiment of the present invention preferably has a vent. In this bundling method, when the side wall of the black foam 1 placed on the tray 4 is covered with the black stretch film 3, a gap is provided between the black foam 1 and the black stretch film 3. Here, when the black stretch film 3 has a vent, external air circulates through the aforementioned vent, thereby suppressing the temperature rise of the space forming the aforementioned gap. As a result, the temperature rise (e.g., surface temperature) of the covered black foam 1 can be further suppressed.

[0092] The shape of the vent in the black stretch film 3 is not particularly limited, but from the perspective of suppressing the breakage of the black stretch film 3 caused by stretching, the hole shape formed by a circle (e.g., a perfect circle or an ellipse) is preferred.

[0093] There is no particular limitation on the aperture (diameter) of the vent in the black stretch film 3. However, from the perspective of preventing breakage caused by stretching of the black stretch film 3 and suppressing contamination of the black foam 1 by dust and other contaminants through ventilation, it is preferred to be 0.2 mm to 5.0 mm.

[0094] The opening ratio of the vents in the black stretched film 3 is not particularly limited, but is preferably 1% to 20% per unit area. If the opening ratio of the vents in the black stretched film 3 is within the above range, it is possible to ensure adequate ventilation while suppressing the temperature rise of the covered black foam 1 and preventing contamination of the aforementioned black foam 1 caused by dust and other contaminants that accompany the entry of outside air through the vents.

[0095] As a black stretched film 3 with vents, a film with pre-set vents can be used, or a film without vents can be formed by perforating a film without vents using known methods such as hot needle or punching. Furthermore, the arrangement pattern of the vent holes is not particularly limited; they can be arranged side-by-side or staggered.

[0096] In this bundling method, the black foam 1 (and the cover plate 2) can be covered by a single-layer film formed of a black stretched film 3, or by a multi-layer film comprising one or more black stretched films 3 and optional other films. For example, a multi-layer film can be formed by further covering (winding) the outer periphery of the black stretched film 3, which covers the outer periphery of the sides of the cover plate 2 and the black foam 1, with other films, and then using this multi-layer film to cover the black foam 1 (and the cover plate 2). It should be noted that "multi-layer" in multi-layer film means that the multi-layer film comprises two or more types of films.

[0097] In one embodiment of the present invention, when the cover plate 2 and the black foam 1 are covered by a multilayer film, at least one layer of the multilayer film needs to be a black stretched film 3. That is, the multilayer film can be a multilayer film containing one or more black stretched films 3 and one or more other films, or it can be a multilayer film formed only by two or more black stretched films 3 without other films. There are no particular limitations on the other films that can be included in the multilayer film; transparent films, white films, etc., can be used. These other films can be used individually or in combination of two or more.

[0098] In one embodiment of the present invention, when the multilayer film includes other films, these other films can be described as films that cover the outer periphery of the sides of the cover plate 2 and the black foam 1 together with the black stretched film 3. The other films may cover the entire side of the black stretched film 3 with only one layer, or with two or more layers. From the perspective of reducing the cost of the black stretched film, it is preferable to use other films to cover the black stretched film 3 with two or more layers.

[0099] (Pattern 4)

[0100] The tray 4 serves as the base portion when the aforementioned black foam 1 and the aforementioned cover plate 2 are stacked. In one embodiment of the present invention, the tray 4 can be made of wood or synthetic resin. Furthermore, the shape of the tray 4 is not particularly limited; for example, it can be rectangular.

[0101] In one embodiment of the present invention, the size of the tray 4 is not particularly limited, and examples include a tray with a width of 1100mm × length of 1100mm × thickness of 125mm and a tray with a width of 1000mm × length of 1200mm × thickness of 150mm.

[0102] One embodiment of the present invention may be configured as follows.

[0103] [1] A bundling method for bundling a rectangular black foam body formed of thermoplastic resin with a brightness index L* less than 65 into a single bundle, comprising: a setting step, wherein a cover plate larger than the size of the black foam body is set for at least one layer of the aforementioned black foam body stacked on a pallet, such that it covers at least the main surface of the uppermost layer of the aforementioned black foam body; and a covering step, wherein a black stretch film is used to cover the outer periphery of the cover plate and the side surface of the aforementioned black foam body with a gap between the cover plate and the black foam body.

[0104] [2] According to the bundling method described in [1], the aforementioned setting process includes the process of placing a cover plate on the aforementioned pallet, wherein the aforementioned black foam is stacked on the aforementioned cover plate after being placed on the aforementioned pallet.

[0105] [3] According to the bundling method described in [1] or [2], the thickness of the aforementioned black stretch film is 10 to 250 μm, and the solar absorption rate of the aforementioned black stretch film in the visible light region of 380 to 720 nm is more than 90%.

[0106] [4] The bundling method according to any one of [1] to [3], wherein the aforementioned black stretch film comprises 100 parts by weight of polyolefin resin and 3 to 15 parts by weight of carbon black.

[0107] [5] The bundling method according to any one of [1] to [4], wherein the aforementioned black stretch film has a vent.

[0108] [6] According to the bundling method described in [5], the opening ratio of the vent per unit area of ​​the aforementioned black stretch film is 1% to 20%.

[0109] [7] The bundling method according to any one of [1] to [6], wherein the aforementioned cover plate is composed of at least one selected from the group consisting of wood board, corrugated cardboard, plastic corrugated cardboard and synthetic resin board, and the thickness of the aforementioned cover plate is 1 mm or more.

[0110] [8] The bundling method according to any one of [1] to [7], wherein the aforementioned setting step includes: a step of clamping the aforementioned cover plate between the stacked black foam bodies.

[0111] [9] The bundling method according to any one of [1] to [8], wherein the gap between the aforementioned black stretch film and the aforementioned black foam is set to 5 mm or more.

[0112]

[10] A bundle comprising: a rectangular black foam body, which is at least one layered on a pallet and is formed of a thermoplastic resin with a brightness index L* less than 65; a cover plate which is provided over the black foam body to at least cover the main surface of the uppermost part of the black foam body, and is larger than the black foam body; and a black stretch film which covers the outer periphery of the cover plate and the side surface of the black foam body with a gap between it and the black foam body.

[0113] Example

[0114] Examples, comparative examples and reference examples are listed below, but the present invention is not limited to them.

[0115] 〔Material〕

[0116] The following shows the materials used in the embodiments, comparative examples, and reference examples.

[0117] (Foamed body)

[0118] Foam A: Black bead-polymer polystyrene resin foam (expansion ratio 80 times, brightness index 48, dimensions: width 909mm × length 1818mm × thickness 50mm)

[0119] Foam B: White bead-grown polystyrene resin foam (expansion ratio 80 times, brightness index 91, dimensions: width 909mm × length 1818mm × thickness 50mm)

[0120] (Covering plate)

[0121] Covering Panel A: Wooden covering panel (Dimensions: Width 1000mm × Length 1920mm × Thickness 10mm)

[0122] Covering board B: Plastic corrugated cardboard (size: 1000mm width × 1920mm length × 14mm thickness, TECCELL T14-3200 manufactured by Gifu Plastics Industries Co., Ltd.)

[0123] (Stretched film)

[0124] Black stretched film: DIA STRETCH FILM COLOR STRETCH FILM BA (Black)

[0125] Model: TK-30420BLACK

[0126] Thickness 20μm × Width 500mm × (Length 300m)

[0127] Solar absorption rate: 95%, manufactured by Sihua Cheng Industrial Co., Ltd.

[0128] Transparent Stretch Film: DIA STRETCH FILM

[0129] Model: TK-30000

[0130] Thickness 20μm × Width 500mm × (Length 300m)

[0131] Solar absorption rate: 0%, manufactured by Sihua Cheng Industrial Co., Ltd.

[0132] (Pattern)

[0133] Pallet: Wooden pallet (Dimensions: Width 1100mm × Length 2000mm × Thickness 150mm)

[0134] [Measurement Method]

[0135] The evaluation methods implemented in the embodiments, comparative examples, and reference examples are described below.

[0136] (Sunlight absorption rate)

[0137] The solar absorption rate of the stretched film was measured according to the following methods (1) to (5): (1) As a test piece, a black stretched film was prepared. Using a self-recording spectrophotometer, the reflectance of the white alumina substrate was set to 100%, and the reflectance (spectral reflectance) at each wavelength of 1 nm was measured in the wavelength range of 380 to 720 nm; (2) Using Appendix 3 of JISA 5759, the values ​​obtained by multiplying the spectral reflectance at each wavelength measured in (1) by the corresponding weighting factor at each wavelength were calculated, and the solar reflectance was calculated as the sum of these values ​​(spectral solar reflectance test method); (3) For the test piece in (1), using a self-recording spectrophotometer, the transmittance in the state without the test piece was set to 100%, and the transmittance at each wavelength was measured (spectral transmittance); (4) Using JIS Appendix 3 of A5759 calculates the values ​​obtained by multiplying the spectral transmittance at each wavelength measured in (3) by the weighting factor at each wavelength, and calculates the solar transmittance as a sum of these values; (5) further, based on the obtained values ​​of solar reflectance and solar transmittance, the solar absorption rate is calculated using the following formula (1):

[0138] (Solar absorption rate) = 100% - (Solar reflectance) - (Solar transmittance) ... (1).

[0139] (Stacking stability)

[0140] Visually assess the condition of the bundles during a 3-minute period of forklift handling and movement, and evaluate the stacking stability of the bundles according to the following criteria.

[0141] 〇: No problems such as cargo collapse occurred;

[0142] ×: If problems such as cargo collapse occur, the bundled items need to be repacked.

[0143] (Exposure test)

[0144] Outdoor exposure tests were conducted as follows. The bundles prepared in the various embodiments, comparative examples, and reference examples were placed outdoors for exposure from August 10th to August 17th, 2020. During this period, the average temperature was 31.4°C, the minimum temperature was 24.7°C, and the maximum temperature was 40.5°C.

[0145] In the exposure test, the temperature of the foam in the package was measured using the following mechanical materials and thermocouples every 15 minutes, and the highest temperature reached by the foam during the exposure period was taken as the highest surface temperature.

[0146] Thermocouple: K Thermocouple, ESCO EA742HD-32

[0147] Temperature recorder: Graphtec midi LOGGER GL840 (20-point)

[0148] After exposure, the foam was removed from the bundle and the surface properties / shape and appearance of the foam were evaluated using the following methods.

[0149] (Evaluation of the surface properties / shape of the bundled foam)

[0150] Visually inspect the foam after the exposure test and evaluate the surface properties / shape of the foam according to the following criteria;

[0151] 〇 (Good): No abnormalities were observed in the beads that make up the foam.

[0152] × (Defect): Visible hypertrophy and / or melting of the beads that make up the foam.

[0153] (Appearance of the bundled foam)

[0154] Visually inspect the foam after the exposure test and evaluate its appearance according to the following criteria;

[0155] 〇 (Good): No dirt was observed on the surface of the foam.

[0156] × (Defective): Visible dirt on the surface of the foam.

[0157] [Example 1]

[0158] Four segments of foam body A (lower segment foam body A) are stacked on top of a cover plate A (lower segment foam body A) placed on a pallet. Then, another cover plate A (central cover plate A) is placed on top of the lower segment foam body A. Subsequently, four more segments of foam body A (upper segment foam body A) are stacked on top of the central cover plate A, and another cover plate A (upper segment cover plate A) is placed on top of it (the stacking order is from bottom to top: polypropylene pallet / lower segment (pad) cover plate A / lower segment foam body A (4 segments) / middle segment (central) cover plate A / upper segment foam body A (4 segments) / upper segment (topmost) cover plate A). Next, a thermocouple is attached approximately to the center (length / thickness direction) of the side of the upper segment foam body A along its length. Subsequently, the side of the laminate formed by the aforementioned foam A and cover plate A is covered from the side of the aforementioned pallet in the vertical direction (height) by wrapping the side wall of the aforementioned laminate three times with a black stretch film (winding it in such a way that it becomes three layers in the same location), thus obtaining a bundle. Stacking stability tests and outdoor exposure tests were performed on the bundle, the highest surface temperature was measured, and the stacking stability, surface properties / shape of the bundled foam, and appearance of the bundled foam were evaluated. The results are shown in Table 1.

[0159] [Example 2]

[0160] Instead of using three turns of black stretch film, the black stretch film was wrapped around the sidewall of the laminate once (to form one layer in the same area) to cover it. Then, a transparent stretch film was wrapped around it twice from above (to form two layers in the same area). Otherwise, the package was obtained using the same method as in Example 1, and its properties were measured / evaluated. The results are shown in Table 1.

[0161] [Example 3]

[0162] Cover plate B was used instead of cover plate A as the cover plate. Otherwise, the bundles were obtained using the same method as in Example 1, and the properties of each item were measured / evaluated. The results are shown in Table 1.

[0163] [Example 4]

[0164] A perforation process was performed on the black stretched film using a heat gun to form vents (pore diameter φ1mm, staggered arrangement, opening ratio 5%). Otherwise, the bundled material was obtained using the same method as in Example 1, and the various properties were measured / evaluated. The results are shown in Table 1.

[0165] [Comparative Example 1]

[0166] Instead of using a black stretch film, a transparent stretch film was used to cover the sidewalls of the laminate by wrapping it three times (so that it forms three layers in the same location). Otherwise, the bundle was obtained using the same method as in Example 1, and the physical properties were measured / evaluated. The results are shown in Table 1.

[0167] [Comparative Example 2]

[0168] Without using a stretch film (not covering the laminate), the bundles were obtained using the same method as in Example 1, and their properties were measured / evaluated. The results are shown in Table 1. It should be noted that dust-induced fouling was observed on the surface of the foam after the exposure test.

[0169] [Comparative Example 3]

[0170] Without using cover plate A (lower cover plate, middle cover plate, and upper cover plate), the bundles were obtained using the same method as in Example 1, and their properties were measured / evaluated. The results are shown in Table 1.

[0171] [Reference Example 1]

[0172] A laminated foam B was used instead of foam A, and the black stretch film was used instead of foam B. The sidewalls of the laminate were covered by wrapping the transparent stretch film around the foam three times (so that it forms three layers in the same location). Otherwise, the package was obtained using the same method as in Example 1, and the physical properties were measured / evaluated. The results are shown in Table 1.

[0173] [Reference Example 2]

[0174] Layered foam B was used instead of foam A. Otherwise, the bundled material was obtained using the same method as in Example 1, and its properties were measured / evaluated. The results are shown in Table 1.

[0175] [Table 1]

[0176]

[0177] 〔Summarize〕

[0178] Based on Table 1, the following information is clearly available:

[0179] (1) Based on the comparison between Examples 1 to 4 and Comparative Example 1, compared with the case of wrapping with a transparent stretch film used in the past, the present wrapping method can suppress the enlargement of the beads constituting the wrapped foam and the deterioration of the surface properties and shape of the foam, such as the surface melting of the foam, by using a black stretch film for wrapping.

[0180] (2) Based on the comparison between Examples 1 to 4 and Comparative Example 2, without using a stretch film for bundling, the stacking stability of the bundled items was poor, and under simulated placement, the surface of the foam was covered with dirt and had a poor appearance.

[0181] (3) According to the comparison between Examples 1 to 4 and Comparative Example 3, without the cover plate, the black stretch film is in direct contact with the foam inside the bundle. As a result, the foam heats up, the beads become enlarged, and the surface properties and shape of the foam are poor.

[0182] (4) Based on the results of Reference Examples 1 and 2, when the foam is white (not a black foam), even if it is wrapped with a transparent stretch film, the foam will not deform or cause other problems. However, the wrapping method of this application can also be used to wrap it appropriately.

[0183] Industrial availability

[0184] According to one embodiment of the present invention, a method for packaging black-based foam can be provided that achieves both suppression of temperature rise and stacking stability of the black-based foam at low cost. The black-based foam is suitable for applications such as residential insulation materials.

[0185] Explanation of reference numerals in the attached figures

[0186] 1. 1a, 1b Black foam

[0187] 2a~2g Cover plate

[0188] 3 Black Stretch Film

[0189] 4 pallets

[0190] 100 bales.

Claims

1. A bundling method comprising bundling a rectangular black foam formed of thermoplastic resin with a brightness index L* less than 65 into a single bundle, comprising: In the setting process, for at least two layers of the black foam stacked on a pallet, a cover plate larger than the size of the black foam is provided such that it at least covers the main surface of the uppermost layer of the black foam. The cover plate is also clamped between the stacked black foam layers. In the covering process, with a gap between the cover plate and the black foam body, a black stretch film is used to cover the outer periphery of the side of the cover plate and the black foam body. The synthetic resin constituting the black stretched film is a polyolefin resin, an acrylic resin, or a polyvinyl chloride resin. The black-based stretchable film has a tensile breaking strength of more than 30 MPa in the longitudinal direction and more than 15 MPa in the transverse direction.

2. A bundling method, comprising bundling rectangular black foam formed of thermoplastic resin with a brightness index L* less than 65 into a single bundle, comprising: In the setting process, for at least one layer of the black foam stacked on the pallet, a cover plate larger than the size of the black foam is set such that it at least covers the main surface of the uppermost layer of the black foam. as well as In the covering process, with a gap between the cover plate and the black foam body, a black stretch film is used to cover the outer periphery of the side of the cover plate and the black foam body, and the gap between the black stretch film and the black foam body is set to be 5mm or more. The synthetic resin constituting the black stretched film is a polyolefin resin, an acrylic resin, or a polyvinyl chloride resin.

3. The bundling method according to claim 1 or 2, wherein, The setting process includes the process of placing a cover plate on the tray. The black foam is stacked on the cover plate after being placed on the tray.

4. The bundling method according to claim 1 or 2, wherein, The thickness of the black stretched film is 10~250μm, and the solar absorption rate of the black stretched film in the visible light region of 380~720nm is more than 90%.

5. The bundling method according to claim 1 or 2, wherein, The black stretched film comprises 100 parts by weight of polyolefin resin and 3-15 parts by weight of carbon black.

6. The bundling method according to claim 1 or 2, wherein, The black stretched film has a vent.

7. The bundling method according to claim 5, wherein, The opening ratio of the vents per unit area of ​​the black stretched film is 1% to 20%.

8. The bundling method according to claim 1 or 2, wherein, The cover plate is composed of at least one material selected from the group consisting of wood panels, corrugated cardboard, plastic corrugated cardboard, and synthetic resin panels. The thickness of the cover plate is 1 mm or more.

9. A bundle, comprising: A rectangular black foam, which is stacked in at least two layers on a pallet and is formed of a thermoplastic resin with a brightness index L* less than 65; A cover plate, which is provided to cover at least the main surface of the uppermost section of the black foam, and is also provided to clamp the stacked black foams, and is larger than the black foams; and A black stretch film, with a gap between it and the black foam, covers the outer periphery of the cover plate and the side of the black foam. The synthetic resin constituting the black stretched film is a polyolefin resin, an acrylic resin, or a polyvinyl chloride resin. The black-based stretchable film has a tensile breaking strength of more than 30 MPa in the longitudinal direction and more than 15 MPa in the transverse direction.

10. A bundle, comprising: A rectangular black foam, which is stacked in at least one layer on a pallet and is formed of a thermoplastic resin with a brightness index L* less than 65; A cover plate, which is provided over the black foam body in such a way as to at least cover the main surface of the uppermost section of the black foam body, and is larger in size than the black foam body; and A black stretch film covers the outer periphery of the cover plate and the side of the black foam body, with a gap between the black stretch film and the black foam body, and the gap between the black stretch film and the black foam body is more than 5 mm. The synthetic resin constituting the black stretched film is a polyolefin resin, an acrylic resin, or a polyvinyl chloride resin.

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