Identification method and identification device for resin molding, and recycling method for resin molding, manufacturing method for regenerated methyl methacrylate, manufacturing method for methacrylic resin and manufacturing method for methacrylic resin molding

Abstract

To provide an identification method capable of easily identifying a resin molding and a recycling method for resin molding using the identification method.SOLUTION: There are provided: an identification method for resin molding that comprises arranging a resin molding between a first polarizer and a second polarizer having a transmission axis in a different direction from the first polarizer, passing light through the first polarizer, the resin molding and the second polarizer in this order, and identifying the manufacturing method for resin molding and / or the kind of the material resin based on the retardation of transmitted light; and a recycling method for rein molding that uses the identification method.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for identifying a resin molded body, a recycling method for a resin molded body, a method for producing recycled methyl methacrylate, a method for producing a methacrylic resin, and a method for producing a methacrylic resin molded body.

Background Art

[0002] Recycling methods for making new products using waste plastics are roughly classified into material recycling and chemical recycling. Material recycling is a recycling method in which waste plastics are reused as the material resin of a new product, and chemical recycling is a recycling method in which waste plastics are chemically converted into other substances, and new products are made using the obtained substances as raw materials. Since these recycling methods can cyclically utilize limited resources, they can reduce resource consumption and the amount of landfill for waste, and contribute to reducing the environmental load.

[0003] In such recycling of waste plastics, it is required to separate waste plastics according to the type or material of the material resin. By separating waste plastics, an appropriate recycling method can be selected according to the type or material of the material resin. If waste plastics can be separated and recycled by an appropriate method, problems in the recycling process caused by the mixing of waste plastics of different types of material resins or different materials formed by different manufacturing methods can be prevented. In addition, by separating waste plastics of different types and materials, recycling materials and raw materials can be obtained from waste plastics of the same type and material, and as a result, the quality of new products obtained after recycling can be improved.

[0004] Patent Documents 1 to 3 describe methods for identifying the resin type of the material of a plastic bottle using polarization.

[0005] Non-Patent Document 1 describes a method for discriminating between a cast plate manufactured by a casting method and an extruded plate manufactured by an extrusion method for the purpose of recycling an acrylic resin plate. It is disclosed that by distinguishing between the cast plate and the extruded plate, a recycling method suitable for each can be selected. In the discrimination, a metal solid heated to a certain temperature is pushed into the surface of the acrylic resin plate with a certain load, and the amount of pushing and the deformation state are observed to simply perform the discrimination.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the method described in Non-Patent Document 1, since it is necessary to press a metal solid heated to a certain temperature into an acrylic resin plate, it can only be applied to an acrylic resin plate with sufficient thickness, and there are limitations on the objects to be discriminated. Further, in order to obtain the pressing amount and deformation state serving as discrimination criteria, it is necessary to perform pressing that satisfies various conditions such as the temperature, load, and pressing time during the pressing of the metal solid before discrimination. It is a complicated discrimination method in that such a pressing process is carried out before discrimination. Furthermore, in observing the pressing amount, it is necessary to discriminate a difference in a minute pressing amount (a difference on the order of mm), and further, in observing the deformation state, it is necessary to discriminate a minute region visually or by the tactile sensation of a fingertip. Therefore, there is room for improvement also from the viewpoint of the discrimination method (ease of discrimination, accuracy, reproducibility, etc.).

[0009] In the discrimination between a cast plate and an extruded plate, since their material resins have different physical properties due to the difference in the manufacturing method even if the types are the same, it is important to apply a recycling method suitable for each. Since the material resin of the cast plate has a relatively large molecular weight and is difficult to melt compared to the extruded plate, it is difficult to perform material recycling. On the other hand, since the material resin of the extruded plate has a relatively small molecular weight and is easy to melt compared to the cast plate, material recycling is suitable. Therefore, in material recycling, there is a problem that the recycling process becomes difficult when waste materials of the extruded plate and waste materials of the cast plate are mixed. In order to solve this problem, it is important to discriminate and separate the waste materials of the cast plate and the waste materials of the extruded plate before the recycling process, which has a great influence on the subsequent recycling process. However, it is difficult to discriminate between a cast plate and an extruded plate having the same type of material resin by the difference in the chemical structure such as the composition, main chain, and functional group of the material resin, and in order to discriminate the difference in the manufacturing method, it was necessary to adopt a complicated method as described above. Furthermore, in the recycling process, if waste materials of resin molded articles made of different types of material resins are mixed, it may be difficult to obtain desired recycled materials or raw materials. For example, if the recycling process is carried out with waste materials of extrusion plates made of different types of material resins mixed, a recycled material containing different types of resins is obtained, and as a result, the purity and quality of the required recycled resin products may be reduced.

[0010] An object of the present invention is to solve the problems in view of the above circumstances, and to provide an identification method and an identification device capable of easily identifying a resin molded article. Another object of the present invention is to provide a recycling method for resin molded articles that identifies and separates resin molded articles using the above identification method.

Means for Solving the Problems

[0011] The present invention includes the following aspects. [1] A resin molded article is disposed between a first polarizer and a second polarizer having a transmission axis direction different from that of the first polarizer, Light is passed through in the order of the first polarizer, the resin molded article, and the second polarizer, An identification method for a resin molded article that identifies the manufacturing method and / or the type of material resin of the resin molded article based on the retardation of the transmitted light. [2] The identification method for a resin molded article according to [1], which identifies the manufacturing method of the resin molded article. [3] The identification method for a resin molded article according to [2], which identifies a casting method and an extrusion method as the manufacturing method of the resin molded article. [4] The identification method for a resin molded article according to [1], which identifies the type of material resin of the resin molded article. [5] The identification method for a resin molded article according to [4], which identifies at least one selected from (meth)acrylic polymers, aromatic resins, polycarbonate resins, and polyester resins as the type of material resin of the resin molded article. [6] The identification method for a resin molded article according to any one of [1] to [5], which performs identification by observing the polarization color of the transmitted light. [7] The method for identifying a resin molded body according to [6], wherein the second polarizer is arranged such that the transmission axis of the second polarizer is substantially perpendicular to the transmission axis of the first polarizer. [8] The method for identifying a resin molded body according to [6] or [7], wherein an optical path difference plate is arranged between the resin molded body and the second polarizer, and the polarization color of the transmitted light passing through the first polarizer, the resin molded body, the optical path difference plate, and the second polarizer in this order is visually observed for identification. [9] The method for identifying a resin molded body according to [8], wherein the optical path difference plate is a sensitive color plate. Method for identifying a resin molded body.

[10] The method for identifying a resin molded body according to any one of [6] to [9], wherein identification is performed by comparing with the polarization color of a resin molded body whose manufacturing method or type of material resin is known.

[11] Determining an identification criterion based on the retardation value corresponding to the polarization color of a resin molded body whose manufacturing method or type of material resin is known, observing the polarization color of the resin molded body to be identified, and comparing the retardation value corresponding to the observed polarization color with the identification criterion for identification. The method for identifying a resin molded body according to any one of [6] to [9].

[12] The method for identifying a resin molded body according to any one of [1] to [5], wherein identification is performed by comparing with the retardation of a resin molded body whose manufacturing method or type of material resin is known.

[13] Determining an identification criterion based on the retardation value of a resin molded body whose manufacturing method or type of material resin is known, measuring the retardation of the resin molded body to be identified, and comparing the obtained retardation value with the identification criterion for identification. The method for identifying a resin molded body according to any one of [1] to [5].

[14] The method for identifying a resin molded body according to any one of [1] to

[13] , which identifies a cast plate formed of an acrylic resin and an extruded plate formed of an acrylic resin.

[15] The method for identifying a resin molded body according to any one of [1] to

[14] , which identifies the type of the material resin of the resin molded body as an acrylic resin, and distinguishes between a resin molded body formed of an acrylic resin and a resin molded body formed of a resin other than an acrylic resin. The method for identifying a resin molded article according to any one of [1] to

[15] , wherein the light incident on the first polarizer is white light.

[17] An identification device used for the identification method according to any one of [1] to

[16] , comprising a light source, a first polarizer provided on the optical path of the light source, a second polarizer provided on the optical path of the light source and having a transmission axis direction different from that of the first polarizer, and an arrangement means for arranging a resin molded article to be identified provided between the first polarizer and the second polarizer. An identification device for a resin molded article, configured to pass the light from the light source through the first polarizer, the resin molded article, and the second polarizer in this order so that the retardation of the transmitted light can be measured or the polarization color can be observed.

[18] A light source, a first polarizer provided on the optical path of the light source, a second polarizer provided on the optical path of the light source and having a transmission axis direction different from that of the first polarizer, and an arrangement means for arranging a resin molded article to be identified provided between the first polarizer and the second polarizer. An identification device for a resin molded article, used to identify the manufacturing method of the resin molded article or the type of the material resin based on the retardation of the transmitted light that has passed through the first polarizer, the resin molded article, and the second polarizer in this order.

[19] Comprising imaging means for imaging the transmitted light, The identification device for a resin molded article according to

[17] or

[18] , having a configuration in which the transmitted light is imaged by the imaging means to measure the retardation.

[20] Comprising an optical path difference plate disposed between the arrangement member and the second polarizer, and having a configuration in which the polarization color of the transmitted light can be visually observed. The identification device for a resin molded article according to

[17] or

[18] .

[21] The identification device for a resin molded article according to

[20] , wherein the optical path difference plate is a sensitive color plate.

[22] The identification device for a resin molded article according to any one of

[17] to

[21] , wherein the light source is a white light source.

[23] The second polarizer is arranged or movable such that the transmission axis of the second polarizer is substantially perpendicular to the transmission axis of the first polarizer, and is provided to be substantially perpendicular, the resin molded body identification device according to any one of

[17] to

[22] .

[24] A method for recycling resin molded bodies, comprising: a step of identifying resin molded bodies having different manufacturing methods or types of material resins by the identification method according to any one of [1] to

[16] ; and a step of separating the identified resin molded bodies.

[25] The resin molded body includes a cast plate and an extruded plate formed of the same type of material resin. In the identification step, it is identified whether the resin molded body is formed by a casting method or an extrusion method. The method for recycling resin molded bodies according to

[24] , wherein, in the separation step, the resin molded body identified as being formed by a casting method and the resin molded body identified as being formed by an extrusion method are separated.

[26] The method for recycling resin molded bodies according to

[25] , wherein the resin molded body includes a cast plate formed of an acrylic resin and an extruded plate formed of an acrylic resin.

[27] The resin molded body includes a resin molded body formed of an acrylic resin and a resin molded body formed of a resin other than the acrylic resin. In the identification step, it is identified whether the resin molded body is a resin molded body formed of an acrylic resin. The method for recycling resin molded bodies according to

[25] , wherein, in the separation step, the resin molded body identified as being a resin molded body formed of an acrylic resin and the resin molded body identified as not being a resin molded body formed of an acrylic resin are separated.

[28] The method for recycling resin molded bodies according to

[25] or

[26] , having a step of materially recycling the separated extruded plate.

[29] The method for recycling resin molded bodies according to

[25] or

[26] , having a step of chemically recycling the separated cast plate. A method for producing recycled methyl methacrylate, characterized by obtaining methyl methacrylate by the recycling method described in

[30]

[29] . A method for producing a methacrylic resin, characterized by obtaining methyl methacrylate by the method for producing recycled methyl methacrylate described in

[31]

[30] , and then radically polymerizing the obtained methyl methacrylate. A method for producing a methacrylic resin molded article, characterized by obtaining a methacrylic resin by the method for producing a methacrylic resin described in

[32]

[31] , and then molding the obtained methacrylic resin or a methacrylic resin composition containing the methacrylic resin.

Effects of the Invention

[0012] According to an embodiment of the present invention, an identification method and an identification device capable of easily identifying a resin molded article can be provided. Further, according to another embodiment of the present invention, a recycling method for resin molded articles that performs identification and separation of resin molded articles using the above identification method can be provided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described.

[0015] <Identification Method of Resin Molded Article> The method for identifying a resin molded body according to an embodiment of the present invention arranges a resin molded body between a first polarizer and a second polarizer having a transmission axis direction different from that of the first polarizer, and passes light in the order of the first polarizer, the resin molded body, and the second polarizer, and identifies the manufacturing method of the resin molded body and / or the type of the material resin based on the retardation of the transmitted light.

[0016] According to the identification method according to an embodiment of the present invention and according to the identification device according to another embodiment described later, the manufacturing method of the resin molded body and the type of the material resin can be identified, and based on this identification, resin molded bodies having different manufacturing methods and / or types of material resins can be identified. The identified resin molded body can select a suitable recycling method according to its manufacturing method and the type of the material resin.

[0017] Examples of resin molded bodies include a cast plate manufactured by a casting method and an extrusion plate manufactured by an extrusion method. In particular, when they are formed of the same type of resin, as described above, it is not easy to distinguish between the two, but according to the identification method and the identification device according to an embodiment of the present invention, they can be easily distinguished. Further, when the types of the material resins are different for resin molded bodies manufactured by the same manufacturing method, the types of the material resins can be easily identified.

[0018] When light (white light) from a light source passes through the first polarizer, it is converted into polarized light. When this polarized light passes through the resin molded body, it becomes a different polarization state, and retardation (R) occurs. The polarized light in this different polarization state is passed through the second polarizer, and the retardation peculiar to the resin molded body can be measured from the transmitted light. Further, since the degree of the different polarization states after passing through the resin molded body also depends on the wavelength, a polarization color corresponding to the retardation can be seen. The retardation (R) generated when passing through a sample (resin molded body) is a physical quantity indicating the optical path difference between two specific polarizations after passing through the sample, and is also called the optical path difference, and can be expressed by the following formula in a rectangular coordinate system of x-axis, y-axis, and z-axis that are orthogonal to each other. When the retardation (R) (optical path difference) is multiplied by 2π / λ, it becomes a phase difference (birefringence phase difference) (λ: wavelength).

[0019]

Number

[0020] The resin molded body can be identified by measuring the retardation of the resin molded body and comparing it with the retardation of a resin molded body whose manufacturing method or type of material resin is known as a reference. For example, the retardation of the resin molded body to be identified whose manufacturing method or type of material resin is known is measured in advance, identification criteria are determined based on this pre-measured retardation, and the resin molded body to be identified can be identified in light of this. Also, the resin molded body can be identified by observing the polarization color of the resin molded body and comparing it with the polarization color of a resin molded body whose manufacturing method or type of material resin is known as a reference. For example, the polarization color of the resin molded body to be identified whose manufacturing method or type of material resin is known is observed in advance, identification criteria are determined based on this pre-observed polarization color, and the resin molded body to be identified can be identified in light of this.

[0021] When identifying a resin molded body by observing the polarization color, it is preferable to arrange the second polarizer so that the transmission axis of the second polarizer is substantially perpendicular or as close as possible to being perpendicular to the transmission axis of the first polarizer. It is more preferable to arrange it so that the angle formed by the transmission axis of the first polarizer and the transmission axis of the second polarizer is 90° ± 2°, and it is particularly preferable to arrange it so that the angle is 90° ± 1°. When the resin molded body is not arranged, when the transmission axes of the first polarizer and the second polarizer are perpendicular, the polarized light converted from white light passing through the first polarizer is blocked by the second polarizer, and the closer the arrangement is to perpendicular, the greater the amount of light blocked. On the other hand, when arranged in parallel, the amount of light passing through the second polarizer is maximized. When the resin molded body is arranged, when the polarized light from the first polarizer passes through the resin molded body and becomes a different polarization state, that is, when retardation occurs, even if the transmission axes of the first polarizer and the second polarizer are perpendicular, the polarized light in the different state is not blocked by the second polarizer and passes through the second polarizer, and the transmitted light can be observed. This transmitted light passing through the second polarizer has a retardation peculiar to the measured resin molded body, and by measuring the retardation of this transmitted light or by observing the polarization color, the resin molded body can be identified. The closer the transmission axis of the first polarizer and the transmission axis of the second polarizer are to being perpendicular, the greater the amount of light peculiar to the resin molded body in the light passing through the second polarizer. In the case of a perpendicular arrangement, almost only the light having a peculiar retardation can be observed.

[0022] Also, when visually observing the polarization color of the light passing through the second polarizer, it is preferable to arrange an optical path difference plate between the resin molded body and the second polarizer. By arranging the optical path difference plate, identification by polarization color becomes easier even visually. As the optical path difference plate, those having a retardation (optical path difference) of 520 to 560 nm close to the wavelength of green light are preferable. Since the optimal retardation (optical path difference) depends on the color temperature of the light source, those having a retardation (optical path difference) corresponding to the color temperature of the light source can be selected. For example, an optical path difference plate with a retardation (optical path difference) of about 530 to 550 nm, called a sensitive color plate, can be used. When the retardation (optical path difference) corresponds to the wavelength of green light, the change in the retardation (optical path difference) causes a reddish or bluish tint, so the color difference can be easily confirmed with the naked eye. By arranging an optical path difference plate having a retardation (optical path difference) close to the wavelength of green light such as a sensitive color plate, even if the retardation (optical path difference) of the resin molded body is small, the difference in polarization color can be easily confirmed visually, and identification can be easily performed with high accuracy.

[0023] In the identification by polarization color, the observed polarization color is compared with the polarization color of a reference image prepared in advance (the polarization color observed in advance for the resin molded body to be identified whose manufacturing method or type of material resin is known) and the color tone to identify the manufacturing method and the type of material resin. Also, as another collation method for identification, based on a polarization color chart showing the relationship between polarization color and retardation, the observed polarization color is converted into a retardation value, and this retardation value is compared with an identification criterion prepared in advance (for example, whether it is within a numerically defined range of retardation as an identification criterion) to identify the manufacturing method and the type of material resin. This identification criterion can be determined based on the retardation value obtained by converting the polarization color observed in advance for the resin molded body to be identified whose manufacturing method or type of material resin is known based on the same polarization color chart, or the retardation value measured by an identification device described later can also be used. By quantifying the polarization color in this way for identification, the accuracy of identification can be improved, and it also becomes easy to automate the identification.

[0024] The polarization color chart is a graph with retardation on the vertical axis and the thickness of the sample on the horizontal axis, colored according to the colors observed at each retardation. This polarization color chart is also called an interference color chart. Since the polarization color does not change if the retardation is constant, the color is constant in the horizontal axis direction of the polarization color chart. As such a polarization color chart, the Michel-Levy Color Chart can be used (see Nesse, W.D., 1991, Introduction to Optical Mineralogy, 2nd edition).

[0025] According to the polarization color chart, as shown in the examples described later, since the polarization color varies depending on the difference in the manufacturing method of the resin molded body (casting method, extrusion method), and since the polarization color may vary depending on the type of the material resin of the resin molded body, the manufacturing method of the resin molded body and the type of the material resin can be identified by observing the polarization color of the resin molded body.

[0026] When visually observing the polarization color, for example, the resin molded body can be identified using an identification device described with reference to FIG. 1 below. Instead of visually observing the polarization color, the resin molded body can be identified using an identification device that images the light passing through the second polarizer with a color camera. For example, the resin molded body can be identified using an identification device described with reference to FIG. 2 below.

[0027] Thus, according to the identification method according to the embodiment of the present invention, even for resin molded bodies formed from the same type of resin, it is possible to identify whether they are manufactured by the casting method or the extrusion method.

[0028] The extrusion method is a method of obtaining a molded article by extruding a material resin (or a resin composition in which a resin material and other components such as additives are mixed) as a molding material. When molding an acrylic resin plate, an acrylic resin (or a resin composition in which an acrylic resin and other components such as additives are mixed) is prepared, pelletized, supplied to an extruder, heated and melted, extruded, passed between rolls, and cut after cooling to obtain a plate-like body.

[0029] The casting method is a method of obtaining a resin molded article by putting a polymerizable composition into a mold and polymerizing it. The casting method is not particularly limited. For example, the cell casting method in which a polymerizable composition is injected into a mold composed of two inorganic glass plates or metal plates (SUS plates) sealed with a gasket such as a soft resin tube around the periphery and heated, or an endless belt (for example, two stainless steel endless belts polished on one side) that advances at the same speed in the same direction and a space sealed with a gasket are used as a mold, and a resin molded article is obtained by continuously injecting and heating a polymerizable composition from the upstream and polymerizing it continuously by the continuous casting method. The interval of the voids of the mold is appropriately adjusted so as to obtain a resin plate having a desired thickness, but generally it can be set to 1 to 30 mm. As the polymerizable composition used in the manufacturing method of the casting method, a liquid monomer mixture containing one or more monomers, a polymerization initiator, and, if necessary, an additive component can be used, and further, a viscous liquid (syrup) containing a polymer obtained by previously polymerizing a monomer can be used to adjust the viscosity. In the preparation of the syrup, there are a method of dissolving a separately prepared polymer in a monomer mixture, and a method of polymerizing a part of the monomer mixture to form a polymer and, if necessary, mixing one or more monomers selected from the monomers and the additive.

[0030] Further, according to the identification method according to the embodiment of the present invention, even for resin molded articles manufactured by the same manufacturing method, the type of the material resin of the resin molded article can be identified. For example, (meth)acrylic polymers (resins mainly composed of methyl (meth)acrylate units), aromatic resins (such as styrenic resins like MS, AS, ABS, etc.), polycarbonate resins (PC), and polyester resins (PET, PETG, etc.) can be respectively identified and distinguished. Note that "(meth)acrylic" means "acrylic" and / or "methacrylic".

[0031] For example, resin molded articles formed from resins with significantly different main chain structures (resins with different types of bonds contained in the main chain), such as (meth)acrylic polymers, polycarbonate resins, and polyester resins, can be respectively identified and distinguished.

[0032] (Meta)acrylic polymers have a carbon-carbon bond as the main chain and are polymers mainly composed of methyl (meth)acrylate units, including acrylic resins and other (meth)acrylic acid ester (co)polymers. The phrase "mainly composed of methyl (meth)acrylate units" means that the content of methyl (meth)acrylate units is 50% by mass or more. Also, from the perspective of ease of identification, the content of methyl (meth)acrylate units in the (meth)acrylic polymer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and can even be 100% by mass. When the (meth)acrylic polymer is a copolymer, as other monomers copolymerizable with methyl (meth)acrylate, (meth)acrylic acid esters are preferred, such as methyl (meth)acrylate (methyl acrylate when the main component is methyl methacrylate), ethyl (meth)acrylate, t-butyl (meth)acrylate, i-butyl (meth)acrylate, n-butyl (meth)acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and methyl acrylate and ethyl acrylate are preferred. Further, as other monomers copolymerizable with methyl (meth)acrylate, there are unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, itaconic acid, acid anhydrides such as maleic anhydride, itaconic anhydride, maleimide derivatives such as N-phenylmaleimide, N-cyclohexylmaleimide, vinyl esters such as vinyl acetate, vinyl benzoate, vinyl chloride, vinylidene chloride and their derivatives, nitrogen-containing monomers such as methacrylamide, acrylonitrile, epoxy group-containing monomers such as glycidyl (meth)acrylate, and aromatic vinyl compounds such as styrene, α-methylstyrene. Other monomers copolymerizable with methyl (meth)acrylate may be used alone or in combination of two or more. The acrylic resin is a resin having methyl methacrylate (MMA) units as the main component (the content of MMA units is 50% by mass or more), and the content of MMA units is preferably 85% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and can also be 100% by mass. When the acrylic resin is a copolymer, examples of other monomers copolymerizable with MMA include other monomers copolymerizable with the above-mentioned methyl (meth)acrylate, and one kind may be used alone or two or more kinds may be used in combination. The (meth)acrylic polymer as the object to be identified preferably does not contain an aromatic group and more preferably does not contain an aromatic group and an unsaturated group from the viewpoint of clearly distinguishing it from aromatic resins.

[0033] The polycarbonate resin is a polymer having a carbonate bond (-O-R-O-CO-) in the repeating unit of the main chain (R is a divalent group such as a bisphenol group), and examples thereof include those produced using bisphenol A and phosgene.

[0034] The polyester resin is a polymer having an ester bond (-CO-O-) in the repeating unit of the main chain, and examples thereof include polyethylene terephthalate (PET) and glycol-modified polyethylene terephthalate (PETG).

[0035] Also, even for resin moldings formed of polymers having a similar main chain structure, a resin molding formed of an acrylic resin containing no aromatic group and unsaturated bond such as PMMA and a resin molding formed of an aromatic resin containing an aromatic group (or further an unsaturated bond) such as styrene-based resins (e.g., MS, AS, ABS) can be identified and distinguished from each other. From the viewpoint of identification, the aromatic resin preferably has a content of units containing an aromatic group of 10% by mass or more, more preferably 30% by mass or more. A styrenic resin is a resin containing units derived from styrene or / and styrene derivatives (aromatic vinyl compounds) (hereinafter referred to as "styrenic units") (the content of styrenic units is 10% by mass or more), and the content of styrenic units is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 90% by mass or more, and can also be 100% by mass. Note that MS represents a methyl methacrylate-styrene copolymer resin, acrylonitrile-styrene copolymer resin, and ABS represents an acrylonitrile-butadiene-styrene copolymer resin.

[0036] <Resin Molded Body Identification Device> The resin molded body identification device according to another embodiment of the present invention includes a light source, a first polarizer provided on the optical path of the light source, a second polarizer provided on the optical path of the light source and having a different transmission axis direction from that of the first polarizer, and an arrangement means for arranging the resin molded body to be identified provided between the first polarizer and the second polarizer. It is characterized by being used to identify the manufacturing method or the type of the material resin of the resin molded body based on the retardation of the transmitted light that has passed through the first polarizer, the resin molded body, and the second polarizer in this order.

[0037] FIG. 1 is a schematic diagram showing the configuration of an example of the identification device according to an embodiment of the present invention. The identification device shown in FIG. 1 includes a light emitting device (white light source) 11, a first polarizing plate 12, a stage (not shown) for arranging a sample (resin molded body) 13, an optical path difference plate (sensitive color plate) 14, and a second polarizing plate 15, and these are arranged on the optical path. The upward arrow in the figure indicates the traveling direction of light, and the downward arrow indicates the observation direction (line of sight). The stage for arranging the sample can be formed of a transparent material that allows light to pass through. This stage may be movable, and when it is movable, a plurality of samples can be continuously measured. The identification device of this example can be configured by using a commercially available strain inspector. For example, the product name: Strain Eye LSM-8400LE manufactured by Lucio Co., Ltd. can be used.

[0038] The light-emitting device 11 includes a white light source such as a fluorescent lamp or a white LED, and is formed to emit white light from the upper surface in a surface-emitting manner. A first polarizing plate 12 is provided above the light-emitting device 11, and a stage (not shown) for arranging a sample (resin molded body) 13 is provided above the first polarizing plate 12, and the sample (resin molded body) 13 is arranged on this stage. Above the sample (resin molded body) 13 arranged on the stage, a second polarizing plate 15 is provided, and the transmission axis direction of the first polarizing plate and the transmission axis direction of the second polarizing plate are installed perpendicular to each other. A sensitive color plate is installed as the optical path difference plate 14 on the lower surface side of the second polarizing plate 15. The white light emitted from the light-emitting device 11 passes through the first polarizing plate 12 and is converted into polarized light, and this polarized light passes through the sample (resin molded body) 13. The polarized light that has passed through the sample 13 passes through the optical path difference plate 14 and the second polarizing plate 15, and the polarized color of the transmitted light can be observed from the upper surface side (light exit surface side) of the second polarizing plate 15. The observed polarized color is compared with the polarized color of a reference image prepared in advance (the polarized color observed in advance for a resin molded body to be identified whose manufacturing method or type of material resin is known) and the hue, so that the manufacturing method and the type of material resin can be identified.

[0039] FIG. 2 is a schematic diagram showing the configuration of another example of the identification device according to the embodiment of the present invention. The identification device shown in FIG. 2 includes a white light source (RGB-LED) 21, a first polarizing plate 22, a stage (not shown) for arranging a sample (resin molded body) 23, a second polarizing plate 24, and a color camera (CCD camera) 25, and these are arranged on the optical path. The rightward arrow in the figure indicates the traveling direction of light, and the leftward arrow indicates the photographing direction by the color camera 24. The stage for arranging the sample can be formed of a transparent material that can pass light. Further, this stage may be movable, and when it is movable, a plurality of samples can be continuously measured. The identification device in this example can be configured by using a commercially available strain inspection device. For example, product names: fully automatic strain eye LSM-9100W and LSM-9100WS manufactured by Lucio Co., Ltd. can be used.

[0040] The white light source 21 is preferably an LED light source capable of emitting white light, and more preferably a high-brightness RGB-LED. The white light emitted from the white light source 21 passes through the first polarizing plate 22 and is converted into polarized light, and this polarized light passes through the sample (resin molded body) 13. The polarized light that has passed through the sample 23 passes through the second polarizing plate 24 and is imaged by the color camera 25, and the retardation can be obtained from the captured image. The first polarizing plate 22 and the second polarizing plate 24 are rotatable within a plane perpendicular to the optical axis, and can be photographed at a plurality of rotation angles. The result of the entire field of view can be obtained by image processing. Measure in advance the retardation of the resin molded body to be identified whose manufacturing method or type of material resin is known, determine the identification criteria based on the measured retardation in advance, and the resin molded body to be identified can be identified in light of this.

[0041] By the above identification method and by the identification method using the above identification device, the resin molded bodies identified can be sorted, for example, as follows, and then a recycling process can be performed in order to perform a recycling method suitable for each of them.

[0042] <Recycling method of resin molded body> The recycling method of the resin molded body according to another embodiment of the present invention includes a step of identifying resin molded bodies of different manufacturing methods or types of material resins by the above identification method, and a step of sorting the identified resin molded bodies.

[0043] When the objects to be sorted include a cast plate and an extruded plate formed of the same type of material resin, the step of sorting the cast plate and the extruded plate can be included. By the identification method according to the above-described embodiment of the present invention, it is possible to identify whether the resin molded body is formed by a casting method or an extrusion method, and to distinguish and sort the resin molded body identified as being formed by the casting method from the resin molded body identified as being formed by the extrusion method. Preferably, when the cast plate and the extruded plate formed of acrylic resin as the resin of the same tree species are included in the sorting target, according to the recycling method of the present embodiment, the cast plate of acrylic resin and the extruded plate of acrylic resin can be accurately and simply sorted.

[0044] In addition, when the sorting target includes resin molded bodies made of resin materials of different types, the step of sorting resin molded bodies made of resin materials of different types can be included.

[0045] When the sorting target includes at least one resin molded body formed of different types of material resins, for example, (meth)acrylic polymers (resins mainly composed of (meth)acrylate units), aromatic resins (for example, styrene resins such as MS, AS, ABS, etc.), polycarbonate resins (PC), polyester resins (PET, PETG, etc.), the type of the material resin of each resin molded body can be identified by the identification method according to the above-described embodiment of the present invention, and the identified resin molded bodies can be distinguished from each other and sorted. In addition, from the viewpoint of ease of identification, the content of the material resin as the main component in the resin composition constituting the resin molded body is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0046] In addition, when the sorting target includes at least one resin molded body formed of any of the above material resins and other resin molded bodies formed of a material resin other than the material resin forming the resin molded body, the resin molded body identified as the resin molded body and the other resin molded body identified as not being the resin molded body can be distinguished and sorted. For example, when the sorting target includes a resin molded body formed of acrylic resin and a resin molded body formed of a resin other than acrylic resin, the resin molded body identified as having a material resin of acrylic resin and the resin molded body identified as not having a material resin of acrylic resin can be distinguished and sorted.

[0047] The separated extrusion plates are preferably subjected to a recycling process by material recycling. Since the extrusion plates are manufactured by an extrusion method and a resin suitable for the extrusion method is used as the material resin, their molecular weight is relatively low and they melt moderately, making them easy to mold. Therefore, they are suitable for material recycling, which is a recycling method that reuses waste plastic as the material resin for new products. In material recycling, the separated resin molded articles are crushed into flakes after removing impurities as necessary (and then washed and separated as necessary), and further melted into pellets by a granulator as necessary, and provided as the material for new products.

[0048] On the other hand, the separated cast plates are preferably subjected to a recycling process by chemical recycling or thermal recycling. Since the cast plates are manufactured by a casting method and the material resin is a resin suitable for the casting method, their molecular weight is relatively high and many of them are difficult to mold. In particular, acrylic resin cast plates are not suitable for material recycling. Therefore, the cast plates are preferably subjected to a recycling process by chemical recycling, which is a recycling method that chemically converts waste plastic into other substances and uses the obtained substances as raw materials to make new products, or thermal recycling, which is a recycling method that recovers energy by incineration.

[0049] <Chemical Recycling Method of Resin Molded Article / Manufacturing Method of Recycled MMA> As a chemical recycling method for obtaining methyl methacrylate (MMA) in particular, a method such as thermal decomposition of waste materials that has been conventionally practiced can be used to generate a methyl methacrylate-containing gas (MMA gas), and this MMA gas can be cooled to recover MMA as a liquid. A process of returning the vapor obtained by heating and boiling the condensate of this MMA gas to the condensation process again, or a purification process of the recovered MMA such as a distillation process or a crystallization process may be carried out. In particular, it is preferable to apply the chemical recycling method disclosed in Japanese Patent Application Laid-Open No. 2023-147696. For example, a resin molded body such as an acrylic resin molded body is thermally decomposed (for example, thermally decomposed at 300 to 500°C) to generate MMA gas, and high-boiling components (for example, components having a boiling point of 300°C or higher) are separated from the MMA gas using a condenser (condensation temperature is, for example, 140 to 210°C), and then a method including a step of recovering MMA can be applied.

[0050] As the condenser, a cooling tower used for normal condensation separation can be used. There are no particular restrictions on the configuration and operating conditions of the condenser. However, for example, after subjecting the MMA gas to condensation separation treatment as follows, MMA can be recovered. For example, two condensers can be used as the condenser. High-boiling components are removed from the MMA gas in the first condenser in the front stage, and the gas mainly composed of MMA from which the high-boiling components have been removed is introduced into the second condenser in the rear stage, cooled, and MMA is recovered as a liquid. The first condenser is not particularly limited, but usually a spray tower is used. In the case of a spray tower, the gas (condensable vapor) and the cooling medium may flow in parallel (the flow is in the same direction) or in countercurrent (the flow is in the opposite direction). Also, the operating conditions of the first condenser, the flow rate and pressure of the MMA gas introduced into the condenser may be appropriately determined according to known methods. The condensation temperature is preferably 140 to 210°C, more preferably 160 to 180°C. As the cooling medium, in the case of a spray tower, usually the condensate of the condensed gas is used, but it is not limited thereto. The second condenser is not particularly limited, but a spray tower or various heat exchangers can be used. The gas mainly composed of MMA from which high-boiling components have been removed and introduced into the second condenser can substantially collect all of the MMA by cooling it preferably to about 30 to 55 °C, more preferably to about 35 to 50 °C. The obtained MMA (recycled MMA) can be used in the production of methacrylic resins.

[0051] <Method for producing a methacrylic resin using MMA obtained by a chemical recycling method> The method for producing a methacrylic resin according to an embodiment of the present invention is a method for producing a methacrylic resin by radical polymerization of recycled MMA (recycled MMA) obtained by the recycling method of the embodiment of the present invention. In the method for producing a methacrylic resin according to an embodiment of the present invention, MMA alone may be homopolymerized, or other monomers such as (meth)acrylic acid esters other than MMA may be copolymerized with MMA. In particular, it is preferable to apply the method for producing a methacrylic resin disclosed in JP-A-2023-147696.

[0052] The (meth)acrylic acid ester other than MMA is not particularly limited as long as it is a (meth)acrylic acid ester copolymerizable with MMA, but (meth)alkyl acrylate esters having 1 to 5 carbon atoms in the alkyl group are preferred. For example, methyl acrylate, (meth)ethyl acrylate, (meth)n-propyl acrylate, (meth)isopropyl acrylate, (meth)n-butyl acrylate, (meth)isobutyl acrylate, (meth)sec-butyl acrylate, (meth)t-butyl acrylate and other (meth)acrylic acid esters can be mentioned. These (meth)acrylic acid esters may be used alone or in combination of two or more. Among them, methyl acrylate and ethyl acrylate are more preferable because they are excellent in copolymerizability with MMA and the resulting methacrylic resin has excellent heat resistance and thermal decomposition resistance.

[0053] In addition to the above alkyl (meth)acrylates, monomers of the following a) to g) (hereinafter abbreviated as "other monomers") may be used as long as they do not impair the performance of the methacrylic resin. a)(Meth)acrylic acid esters having a hydrocarbon group with 6 or more carbon atoms such as n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, lauryl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, 2-naphthyl (meth)acrylate, phenoxymethyl (meth)acrylate. b) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride. c) Aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p-methoxystyrene, p-acetoxystyrene, α-vinylnaphthalene, 2-vinylfluorene. d) Unsaturated nitrile compounds such as acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, vinylidene cyanide. e) Ethylenically unsaturated ether compounds such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, ethyl allyl ether. f) Vinyl halide compounds such as vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene. g) Aliphatic conjugated diene compounds such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadienes, linear and side-chain conjugated hexadienes.

[0054] The lower limit of the content of MMA in the monomer raw material used for the production of the methacrylic resin is preferably 80.0% by mass or more, more preferably 90.0% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98.0% by mass or more based on the total mass of the monomer raw material, since the heat resistance of the resulting methacrylic resin is good. On the other hand, the upper limit of the content of MMA in the monomer raw material is not particularly limited, and is preferably 99.8% by mass or less, more preferably 99.5% by mass or less, still more preferably 99.0% by mass or less based on the total mass of the monomer raw material, since the thermal decomposition resistance of the resulting methacrylic resin is good. It may be 100% by mass of MMA.

[0055] The initiator used for radical polymerization is not particularly limited. For example, azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2-2'-azobis(2-methylpropane), 1,1-azobis(cyclohexanecarbonitrile), dimethyl-2,2'-azobisisobutyrate; organic peroxides such as benzoyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxybenzoate, t-hexylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyacetate, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyethylhexanoate, 1,1,2-trimethylpropylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxynonanoate, 1,1,2-trimethylpropylperoxy-isononanoate, di-t-butyl peroxide, di-t-hexyl peroxide, lauroyl peroxide, dilauroyl peroxide; persulfate compounds such as potassium persulfate; redox polymerization initiators and the like. These polymerization initiators may be used alone or in combination of two or more. Among these polymerization initiators, azo compounds and organic peroxides are preferred because of their excellent storage stability and reactivity with MMA.

[0056] The amount of the radical polymerization initiator used in the monomer raw material is preferably 0.0001% by mass or more and 1.0% by mass or less, more preferably 0.001% by mass or more and 0.1% by mass or less, based on 100% by mass of the total mass of the monomer raw material. When the content of the radical polymerization initiator is 0.0001% by mass or more, the reactivity of the raw material monomer is excellent. Further, when the content of the radical polymerization initiator is 1% by mass or less, the heat decomposition resistance of the obtained methacrylic resin is good.

[0057] In an embodiment of the present invention, a chain transfer agent may be used to adjust the mass average molecular weight of the methacrylic resin. Examples of the chain transfer agent include mercaptan compounds such as n-butyl mercaptan, isobutyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, and n-dodecyl mercaptan; α-methylstyrene dimer; terpinolene and the like. These chain transfer agents may be used alone or in combination of two or more. Among these chain transfer agents, mercaptan compounds are preferred, and alkyl mercaptan compounds are more preferred because of their excellent reactivity with MMA.

[0058] The content of the chain transfer agent in the monomer raw material is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 1.0% by mass or less, based on 100% by mass of the total mass of the monomer raw material. When the content of the chain transfer agent is 0.01% by mass or more, the heat decomposition resistance of the methacrylic resin is good. Further, when the content of the chain transfer agent is 10% by mass or less, the mechanical properties of the obtained methacrylic resin are good.

[0059] The method for producing the methacrylic resin is not particularly limited, and examples thereof include bulk polymerization method, suspension polymerization method, emulsion polymerization method, solution polymerization method and the like. Among these polymerization methods, from the viewpoint of excellent productivity, the methacrylic resin is preferably produced by the bulk polymerization method or the suspension polymerization method, and more preferably produced by bulk polymerization.

[0060] The radical polymerization temperature may be appropriately set according to the type of monomer used, the type of radical polymerization initiator, etc. Generally, the polymerization temperature is preferably 125 to 210°C, more preferably 130 to 180°C. When the polymerization temperature is 125°C or higher, the acceleration of the polymerization rate due to the gel effect becomes large, and the productivity of the methacrylic resin is excellent. Further, when the polymerization temperature is 210°C or lower, the decomposition of the methacrylic resin can be suppressed, and the methacrylic resin is excellent in transparency, mechanical properties, heat resistance, and thermal decomposition resistance.

[0061] The mass average molecular weight of the produced methacrylic resin is preferably 20,000 to 200,000, more preferably 50,000 to 150,000. When the mass average molecular weight of the methacrylic resin is at least the lower limit value, the mechanical properties of the obtained molded body tend to be excellent, and when it is at most the upper limit value, the fluidity during melt molding tends to be excellent.

[0062] In this specification, the mass average molecular weight is a value measured using gel permeation chromatography with standard polystyrene as a standard sample.

[0063] An additive may be further added to the methacrylic resin obtained by the method for producing a methacrylic resin according to an embodiment of the present invention. Examples of the additive include lubricants, ultraviolet absorbers, heat stabilizers, colorants, antistatic agents, and the like. These additives may be used alone or in combination of two or more. The addition amount of the additive can be appropriately adjusted according to the use of the methacrylic resin, the type of the additive, etc.

[0064] <Method for producing a methacrylic resin molded body> By molding the methacrylic resin obtained by the method for producing a methacrylic resin according to an embodiment of the present invention or a methacrylic resin composition containing this methacrylic resin, a methacrylic resin molded article can be obtained. Examples of the molding method include injection molding, extrusion molding, compression molding, and the like. Further, the obtained methacrylic resin molded article may be further subjected to secondary molding such as pressure-air molding or vacuum molding. The obtained methacrylic resin molded article can be used for optical materials, vehicle parts, lighting materials, building materials, and the like.

[0065] When the difference in the type of the material resin is identified and the separated resin molded article is an extrusion plate, material recycling can be performed for each type of the material resin. When the difference in the type of the material resin is identified and the separated resin molded article is a cast plate, chemical recycling can be performed for each type of the material resin. By performing a recycling process for each type of the material resin, a recycled material or raw material that can provide a high-quality product can be obtained.

Example

[0066] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

[0067] (Example 1) A commercially available strain checker (product name: Strain Eye LSM-8400LE, manufactured by Lucio Co., Ltd.) was used so as to have the configuration of the identification device shown in FIG. 1, and the polarization colors of various resin molded articles (thickness: 3 mm) were observed. A sensitive color plate (530 nm) was used as the optical path difference plate. The following products were used as the resin molded articles. Sample 1 (PMMA cast plate): manufactured by Mitsubishi Chemical Corporation, product name "Acrylite L" Sample 2 (PMMA extrusion plate): manufactured by Kuraray Co., Ltd., product name "Comoglas P" Sample 3 (MS extrusion plate): manufactured by JSP Corporation, product name "Acriace UV" Sample 4 (PC extrusion plate): manufactured by Sumitomo Bakelite Co., Ltd., product name "Polycaice ECD100UU" Sample 5 (PETG extruded sheet): manufactured by Sumitomo Bakelite Co., Ltd., product name "Sunloid Pet Ace EPG100" In addition, the retardation (optical path difference) (R) corresponding to the observed polarization color was determined using a polarization color chart. The polarization color chart used was the Michel-Levy Color Chart (see Nesse, W.D., 1991, Introduction to Optical Mineralogy, 2nd edition). Table 1 shows the polarization colors observed for each resin molded body and the retardation (optical path difference) (R) corresponding to the polarization colors. Note that in Table 1, "R" SE " indicates the numerical value on the vertical axis of the polarization color chart corresponding to the observed polarization color, and "R" indicates the value obtained by subtracting the optical path difference (530 nm) of the sensitive color plate from that numerical value (R SE ) (the actual retardation value).

[0068]

Table 1

[0069] Comparing Sample 1 and Sample 2, as shown in Table 1, even when the types of the material resins are the same, the polarization colors and retardation (R) are different due to the difference in the manufacturing methods (casting method, extrusion method) of the resin molded bodies. In addition, comparing Samples 2 to 5 with each other, as shown in Table 1, even when the manufacturing methods are the same, the polarization colors and retardation (R) are different due to the difference in the types of the material resins (acrylic resin, MS, PC, PETG) of the resin molded bodies. From these results, according to the embodiment of the present invention, it can be seen that the manufacturing method and the type of the material resin of the resin molded body can be identified by observing the polarization color of the resin molded body.

[0070] In addition, if the discrimination criteria are determined in advance as in the example shown below, the polarization color of the resin molded body to be discriminated is observed, the polarization color is quantified based on the polarization color chart, and the obtained numerical value is compared with the numerical value range of the discrimination criteria for discrimination. <Discrimination criterion example 1> R ≤ 30 nm: The material resin is an acrylic resin and the manufacturing method is the casting method. 50 nm ≤ R ≤ 100 nm: The material resin is an acrylic resin and the manufacturing method is the extrusion method. 150 nm ≤ R: The material resin is a resin other than acrylic resin and the manufacturing method is the extrusion method.

[0071] <Identification result according to Identification criterion example 1> In the case of Sample 1, since R obtained from the observed polarized color is 0, in light of the above identification criteria, it can be identified that the material resin is an acrylic resin and the manufacturing method is the casting method. In the case of Sample 2, since R obtained from the observed polarized color is 70, in light of the above identification criteria, it can be identified that the material resin is an acrylic resin and the manufacturing method is the extrusion method. In the case of Sample 3, since R obtained from the observed polarized color is 370, in light of the above identification criteria, it can be identified that the material resin is a resin other than acrylic resin and the manufacturing method is the extrusion method. In the case of Sample 4, since R obtained from the observed polarized color is 470, in light of the above identification criteria, it can be identified that the material resin is a resin other than acrylic resin and the manufacturing method is the extrusion method. In the case of Sample 5, since R obtained from the observed polarized color is 820, in light of the above identification criteria, it can be identified that the material resin is a resin other than acrylic resin and the manufacturing method is the extrusion method. Thus, according to the above identification criteria, it is possible to identify whether the resin molded body is made by the casting method or the extrusion method, and further, it is possible to identify whether the material resin of the resin molded body classified as the extrusion method is an acrylic resin or another resin.

[0072] If the identification criteria are determined in advance as in the following examples, it is possible to further identify the material resin of the resin molded body to be identified. <Identification criterion example 2> R ≤ 30 nm: The material resin is an acrylic resin and the manufacturing method is the casting method. 50 nm ≤ R ≤ 100 nm: The material resin is an acrylic resin and the manufacturing method is the extrusion method. 350 nm ≤ R ≤ 400 nm: The material resin is MS resin and the manufacturing method is the extrusion method. 450 nm ≤ R ≤ 500 nm: The material resin is polycarbonate resin and the manufacturing method is the extrusion method. 800 nm ≤ R ≤ 850 nm: The material resin is polyester resin and the manufacturing method is the extrusion method.

[0073] <Identification result according to Identification criterion example 2> In the case of Sample 1, since R obtained from the observed polarized color is 0, in light of the above identification criteria, it can be identified that the material resin is acrylic resin and the manufacturing method is the casting method. In the case of Sample 2, since R obtained from the observed polarized color is 70, in light of the above identification criteria, it can be identified that the material resin is acrylic resin and the manufacturing method is the extrusion method. In the case of Sample 3, since R obtained from the observed polarized color is 370, in light of the above identification criteria, it can be identified that the material resin is MS resin and the manufacturing method is the extrusion method. In the case of Sample 4, since R obtained from the observed polarized color is 470, in light of the above identification criteria, it can be identified that the material resin is polycarbonate resin and the manufacturing method is the extrusion method. In the case of Sample 5, since R obtained from the observed polarized color is 820, in light of the above identification criteria, it can be identified that the material resin is polyester resin and the manufacturing method is the extrusion method. Thus, according to the above Identification criterion example 2, it is possible to identify whether the resin molded body is of the casting method or the extrusion method. Furthermore, it is possible to identify whether the material resin of the resin molded body classified as the extrusion method is acrylic resin, styrene-acrylic resin, polycarbonate resin, or polyester resin.

Explanation of symbols

[0074] 11 Light-emitting device (light source) 12 First polarizing plate 13 Sample (resin molded body) 14 Birefringence plate (sensitive color plate) 15 Second polarizing plate 21 RGB-LED light source 22 First polarizing plate 23 Sample (resin molded body) 24 Second polarizing plate 25 Color camera

Claims

1. A resin molded body is disposed between a first polarizer and a second polarizer having a transmission axis direction different from that of the first polarizer, and light is passed through the first polarizer, the resin molded body, and the second polarizer in this order, and a method for identifying a resin molded body, which identifies the manufacturing method of the resin molded body and / or the type of the material resin based on the retardation of the transmitted light.

2. The method for identifying a resin molded body according to claim 1, which identifies the manufacturing method of the resin molded body.

3. The method for identifying a resin molded body according to claim 2, which identifies a casting method and an extrusion method as the manufacturing method of the resin molded body.

4. The method for identifying a resin molded body according to claim 1, which identifies the type of the material resin of the resin molded body.

5. The method for identifying a resin molded body according to claim 4, which identifies at least one selected from (meth)acrylic polymers, aromatic resins, polycarbonate resins, and polyester resins as the type of the material resin of the resin molded body.

6. The method for identifying a resin molded body according to claim 1, which performs identification by observing the polarization color of the transmitted light.

7. The method for identifying a resin molded body according to claim 6, wherein the second polarizer is disposed such that the transmission axis of the second polarizer is substantially perpendicular to the transmission axis of the first polarizer.

8. An optical path difference plate is disposed between the resin molded body and the second polarizer, and identification is performed by visually observing the polarization color of the transmitted light that has passed through the first polarizer, the resin molded body, the optical path difference plate, and the second polarizer in this order. The method for identifying a resin molded body according to claim 6.

9. The method for identifying a resin molded body according to claim 8, wherein the optical path difference plate is a sensitive color plate. A method for identifying a resin molded body.

10. The method for identifying a resin molded body according to claim 6, which performs identification in comparison with the polarization color of a resin molded body whose manufacturing method or type of material resin is known.

11. An identification criterion is determined based on the retardation value corresponding to the polarization color of a resin molded body whose manufacturing method or type of material resin is known, the polarization color of the resin molded body to be identified is observed, and identification is performed by comparing the retardation value corresponding to the observed polarization color with the identification criterion. The method for identifying a resin molded body according to claim 6.

12. The method for identifying a resin molded body according to claim 1, which performs identification in comparison with the retardation of a resin molded body whose manufacturing method or type of material resin is known.

13. Determine the identification criteria based on the retardation value of a resin molded body whose manufacturing method or type of material resin is known, Measure the retardation of the resin molded body to be identified, and perform identification by comparing the obtained retardation value with the said identification criteria. The method for identifying a resin molded body according to claim 1.

14. The method for identifying a resin molded body according to claim 1, which identifies a cast plate formed of an acrylic resin and an extruded plate formed of an acrylic resin.

15. As the type of material resin of the resin molded body, identify an acrylic resin, and distinguish a resin molded body formed of an acrylic resin from a resin molded body formed of a resin other than acrylic resin. The method for identifying a resin molded body according to claim 1.

16. The light incident on the first polarizer is white light. The method for identifying a resin molded body according to claim 1.

17. An identification device used in the identification method according to claim 1, Comprising a light source, a first polarizer provided on the optical path of the light source, a second polarizer provided on the optical path of the light source and having a transmission axis direction different from that of the first polarizer, and an arrangement means for arranging the resin molded body to be identified provided between the first polarizer and the second polarizer. The light from the light source is passed through the first polarizer, the resin molded body, and the second polarizer in this order, and is configured to measure the retardation of the passed light or observe the polarization color. An identification device for a resin molded body.

18. Comprising a light source, a first polarizer provided on the optical path of the light source, a second polarizer provided on the optical path of the light source and having a transmission axis direction different from that of the first polarizer, and an arrangement means for arranging the resin molded body to be identified provided between the first polarizer and the second polarizer. An identification device for a resin molded body, which is used to identify the manufacturing method or type of material resin of the resin molded body based on the retardation of the passed light that has passed through the first polarizer, the resin molded body, and the second polarizer in this order.

19. Comprising imaging means for imaging the passed light, The identification device for a resin molded body according to claim 17 or 18, which is configured to image the passed light by the imaging means and measure the retardation.

20. Comprising an optical path difference plate disposed between the arrangement member and the second polarizer, and having a configuration that allows the polarization color of the passed light to be visually observed. The identification device for a resin molded body according to claim 17 or 18.

21. The resin molded body identification device according to claim 20, wherein the optical path difference plate is a sensitive color plate.

22. The resin molded body identification device according to claim 17 or 18, wherein the light source is a white light source.

23. The resin molded body identification device according to claim 17 or 18, wherein the second polarizer is arranged or movable so that the transmission axis of the second polarizer is substantially perpendicular to the transmission axis of the first polarizer and is provided so as to be substantially perpendicular.

24. A resin molded body recycling method including a step of identifying resin molded bodies having different manufacturing methods or types of material resins by the identification method according to any one of claims 1 to 16, and a step of separating the identified resin molded bodies.

25. The resin molded body includes a cast plate and an extruded plate formed of the same type of material resin, in the identification step, identifying whether the resin molded body is formed by a casting method or an extrusion method, The resin molded body recycling method according to claim 24, wherein, in the separation step, the resin molded body identified as being formed by a casting method and the resin molded body identified as being formed by an extrusion method are separated.

26. The resin molded body recycling method according to claim 25, wherein the resin molded body includes a cast plate formed of an acrylic resin and an extruded plate formed of an acrylic resin.

27. The resin molded body includes a resin molded body formed of an acrylic resin and a resin molded body formed of a resin other than an acrylic resin, in the identification step, identifying whether the resin molded body is a resin molded body formed of an acrylic resin, The resin molded body recycling method according to claim 25, wherein, in the separation step, the resin molded body identified as being a resin molded body formed of an acrylic resin and the resin molded body identified as not being a resin molded body formed of an acrylic resin are separated.

28. The resin molded body recycling method according to claim 25, comprising a step of materially recycling the separated extruded plate.

29. The resin molded body recycling method according to claim 25, comprising a step of chemically recycling the separated cast plate.

30. A method for producing recycled methyl methacrylate, characterized by obtaining methyl methacrylate by the recycling method according to claim 29.

31. A method for producing a methacrylic resin, comprising: obtaining methyl methacrylate by the method for producing regenerated methyl methacrylate according to claim 30, and then subjecting the obtained methyl methacrylate to radical polymerization.

32. A method for producing a methacrylic resin molded article, comprising: obtaining a methacrylic resin by the method for producing a methacrylic resin according to claim 31, and then molding the obtained methacrylic resin or a methacrylic resin composition containing the methacrylic resin.

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