Resin sorting method, resin sorting device, and resin recycling method

Abstract

To provide a resin sorting method, resin sorting device, and resin recycling method, which enable accurate sorting of resin molded products.SOLUTION: A resin sorting method is provided, comprising measuring birefringence or in-plane retardation of a resin molded product, and sorting the resin molded product based on information obtained form a result of measurement of the birefringence or in-plane retardation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a resin separation method, a resin separation device, and a resin recycling method. [Background technology]

[0002] Polymethyl(meth)acrylate (PMMA or PMA), a polymer of methyl(meth)acrylate (MMA or MA), has excellent transparency and weather resistance. Therefore, polymethyl(meth)acrylate is widely used as a material for components constituting splash guards installed in restaurants and offices, automobile parts, signboards, display devices, resin substrates for pinball games, etc.

[0003] In response to the recent rise in resource prices and growing awareness of environmental issues, products (molded articles) containing polymethyl(meth)acrylate used for the various applications described above are being collected and recycled.

[0004] Methods for recycling polymethyl(meth)acrylate include, for example, material recycling, in which the recovered molded bodies are subjected to a molding process again to produce new molded bodies; chemical recycling, in which the recovered molded bodies are heat-treated to thermally decompose (depolymerize) the polymethyl(meth)acrylate to recover the methyl(meth)acrylate, and new molded bodies are produced using the recovered methyl(meth)acrylate (sometimes referred to as recycled polymethyl(meth)acrylate); and thermal recycling, in which the recovered molded bodies are burned as fuel and the combustion energy is used directly as a heat source and further to generate electricity.

[0005] Usually, the recovered compacts are subjected to pretreatment such as washing before being recycled. For example, a method including (A) a step of selectively removing metals from pulverized foreign matter using a metal detector, (B) a step of measuring the brightness of the pulverized foreign matter by irradiating it with light and selectively removing foreign matter with low brightness, (C) a washing step, and (D) a step of sorting by specific gravity is known as an example of such pretreatment (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-307436 A Summary of the Invention [Problem to be solved by the invention]

[0007] It is preferable to select a method for recycling the collected molded body that is appropriate for the type of molded body. For example, poly(methyl (meth)acrylate) can be recovered as a monomer in high yield by heating and pyrolyzing it at a relatively low temperature of about 300°C to 500°C. For this reason, poly(methyl (meth)acrylate) is suitable for recycling by chemical recycling. On the other hand, as a method for recycling an extrusion molded product made of poly(methyl (meth)acrylate), there are cases where material recycling is preferably selected from the viewpoint of saving energy consumption. However, if cast moldings made of polymethyl(meth)acrylate or moldings made of other resins are mixed into the recovered extrusion moldings made of polymethyl(meth)acrylate, this may cause whitening or defects in the moldings obtained after material recycling. Conventional recovery systems may not be able to accurately separate extrusion molded articles made of polymethyl(meth)acrylate from other resin molded articles (particularly cast molded articles made of polymethyl(meth)acrylate). An object of the present disclosure is to provide a resin sorting method capable of accurately sorting resin molded bodies, a resin sorting device capable of accurately sorting resin molded bodies, and a resin recycling method capable of accurately sorting resin molded bodies. [Means for solving the problem]

[0008] Means for solving the above problems include the following embodiments. <1> A step of measuring the birefringence or in-plane retardation of a resin molded product; and a step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation. <2> The information is based on the birefringence value of the resin molded body, which is 1×10 6 The result of comparing the multiplied value X with a threshold Y, <1> A method for separating a resin according to claim 1. <3> The threshold Y includes a threshold Y1 selected within the range of 10±5; <2> A method for separating a resin according to claim 1. <4> Separating resin molded bodies having a value X less than a threshold value Y1 for chemical recycling; <3> A method for separating a resin according to claim 1. <5> Separating resin molded bodies having a value X equal to or greater than a threshold value Y1 for material recycling; <3> A method for separating a resin according to claim 1. <6> The threshold Y includes a threshold Y2 selected from a range of 50 or more. <2> ~ <5> 13. A method for separating a resin according to claim 12. <7> Further comprising a step of measuring the thickness of the resin molded body; <1> ~ <6> 13. A method for separating a resin according to claim 12. <8> The thickness of the resin molded body is 0.1 mm or more and 10 mm or less. <1> ~ <7> 13. A method for separating a resin according to claim 12. <9> The method further includes a step of separating a resin molded body whose birefringence or in-plane retardation is to be measured from a resin molded body other than the resin molded body before or after measuring the birefringence or in-plane retardation of the resin molded body. <1> ~ <8> 13. A method for separating a resin according to claim 12. <10> The resin molding is transparent. <1> ~ <9> 13. A method for separating a resin according to claim 12. <11> The resin molded body contains a colorant. <1> ~ <10> 13. A method for separating a resin according to claim 12. <12> The resin molded body is a splash prevention plate, <1> ~ <11> 13. A method for separating a resin according to claim 12. <13> The birefringence or in-plane retardation of the resin molded product is measured by the crossed Nicol method. <1> ~ <12> 13. A method for separating a resin according to claim 12. <14> A measurement unit for measuring birefringence or in-plane retardation of a resin molded body; a sorting section that sorts the resin molded bodies based on information obtained from the measurement results of the birefringence or the in-plane retardation. <15> A step of measuring the birefringence or in-plane retardation of a resin molded product; A step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation; and recycling the resin molded bodies after separation. <16> The recycling process includes chemical recycling. <15> A method for recycling the resin described in claim 1. <17> The recycling process includes material recycling. <15> A method for recycling the resin described in claim 1. Effect of the Invention

[0009] According to the present disclosure, there are provided a resin sorting method capable of accurately sorting resin molded bodies, a resin sorting device capable of accurately sorting resin molded bodies, and a resin recycling method capable of accurately sorting resin molded bodies. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram illustrating a schematic configuration of a resin separation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <How to separate resin> The method for separating resins disclosed herein comprises the steps of: A step of measuring the birefringence or in-plane retardation of a resin molded product; and a step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation.

[0012] In the above method, information obtained from the measurement results of birefringence or in-plane retardation of the resin molded body is used as an index for separating the resin molded body. Therefore, the above method allows separation based on differences in the molecular weight, orientation state, etc. of the resin. For example, the above method allows separation of an extrusion molded body containing polymethyl(meth)acrylate from a cast molded body containing polymethyl(meth)acrylate. Hereinafter, the step of measuring the birefringence or in-plane retardation of the resin molded body is also referred to as "step 1", and the step of sorting the resin molded body based on the information obtained from the measurement result of the in-plane retardation is also referred to as "step 2".

[0013] (Process 1) In this step, the birefringence or in-plane retardation of the resin molded product is measured. In the present disclosure, the birefringence of a resin molded body is a value expressed by nx-ny, where nx is the principal refractive index in the in-plane direction of the resin molded body, and ny is the refractive index in the in-plane direction perpendicular to the direction showing the principal refractive index. The in-plane retardation of a resin molded body is a value obtained by multiplying the birefringence by the thickness d of the resin molded body. The relationship between the birefringence and the in-plane retardation of a resin molded body is expressed by the following formula. In-plane phase difference=(nx-ny)×d

[0014] The birefringence or in-plane retardation of the resin molded body is measured by irradiating the resin molded body with light. The measurement can be performed by any suitable method among known measurement methods. Examples of measuring devices include "RETS-100" manufactured by Otsuka Electronics Co., Ltd., "KOBRA-WPR" and "PAM-UHR100" manufactured by Oji Scientific Instruments Co., Ltd., and "WPA-100", a two-dimensional birefringence evaluation system manufactured by Photonics Lattice Co., Ltd. In the examples described below, measurements are performed using "WPA-100", a two-dimensional birefringence evaluation system manufactured by Photonics Lattice Co., Ltd.

[0015] The wavelength of light used to measure the birefringence or in-plane retardation of a resin molded product is not particularly limited, and can be selected from the wavelength range of 400 nm to 1000 nm in the visible light region to the near infrared light region depending on the visible light transmittance and other factors of the resin molded product. For example, visible light may be used when the resin molded body is transparent, and near infrared light may be used when the resin molded body is opaque. Here, "the resin molded body is transparent" refers to a transmittance of 30% or more at a wavelength of 550 nm. Also, "the resin molded body is opaque" refers to a transmittance of less than 30% at a wavelength of 550 nm. The resin molded body may be colorless and transparent, or may be colored. Whether the resin molded body is transparent or opaque, it may be colorless or colored.

[0016] When the resin molding is colorless and transparent, the wavelength of the light used for the measurement can be selected from the range of 400 nm to 1000 nm, and preferably from the range of 450 nm to 650 nm. If the resin molding has a thickness within the range described below and the measurement wavelength is within this range, the predetermined value X does not change significantly, and the resin molding can be classified using the desired threshold value Y. When the resin molded body is colorless and opaque, the wavelength of the light used for the measurement can be selected from the range of 800 nm to 1000 nm, and preferably from the range of 850 nm to 950 nm. If the resin molded body has a thickness within the range described below and the measurement wavelength is within this range, the predetermined value X does not change significantly, and the resin molded body can be classified using the desired threshold value Y.

[0017] When the resin molded body is colored and transparent, visible light or near infrared light can be used to measure the birefringence or in-plane retardation. When the resin molded body is orange to red, the wavelength of the light used for the measurement can be selected from the range of 600 nm to 1000 nm, preferably from the range of 600 nm to 700 nm. When the resin molded body is green to yellow, the wavelength of the light used for the measurement can be selected from the range of 500 nm to 600 nm. When the resin molded body is purple to blue, the wavelength of the light used for the measurement can be selected from the range of 400 nm to 500 nm. When the resin molded body is gray to black, it is preferable to use near infrared light to measure the birefringence or in-plane retardation. The wavelength of the near infrared light used for the measurement can be selected from the range of 800 nm to 1000 nm, preferably from the range of 850 nm to 950 nm. If the resin molding is within the thickness range described below and the measurement wavelength is within this range, the predetermined value X does not change significantly, and the resin molding can be separated using the desired threshold value Y.

[0018] When the resin molded body is colored and opaque, it is preferable to use near infrared rays for measuring the birefringence or in-plane retardation. The wavelength of the light used for the measurement can be selected from the range of 800 nm to 1000 nm, and is preferably selected from the range of 850 nm to 950 nm. If the resin molded body is in the thickness range described below and the measurement wavelength is in this range, the predetermined value X does not change significantly, and the resin molded body can be classified using the desired threshold value Y.

[0019] The device for measuring the birefringence or in-plane retardation of the resin molded product is not particularly limited, and a known device can be used. The method for measuring the birefringence or in-plane retardation of the resin molded body may be the crossed Nicol method. In the crossed Nicol method, the measurement target is sandwiched between two polarizing plates that are arranged so that their orientation main axes (easy transmission axes) are perpendicular to each other to form a dark field, and light is transmitted through the plate. If the measurement target has birefringence, transmitted light is observed. This transmitted light exhibits coloration, and different colors are observed depending on the magnitude of the in-plane retardation (the product of birefringence and thickness). By comparing the color of this transmitted light with a polarized color chart, the in-plane retardation value of the measurement target can be estimated.

[0020] In Step 1, the method for measuring the birefringence or in-plane retardation of the resin molded body is not particularly limited. For example, the thickness of the resin molded body conveyed by a belt conveyor or the like may be continuously measured, or the thickness of the stationary resin molded body may be measured.

[0021] (Step 2) In this step, the resin molded body is sorted based on the information obtained from the measurement results of the birefringence or in-plane retardation. In the present disclosure, "information obtained from the measurement results of birefringence or in-plane retardation" means the measured value of the birefringence or in-plane retardation measured in Step 1, or a value obtained by processing the measured value.

[0022] The smaller the value of the birefringence of the resin molded body, the smaller the orientation of the molecules in the resin molded body tends to be. Therefore, it is possible to determine whether the resin molded body is a molded body with a relatively small molecular orientation (such as a cast molded body) or a molded body with a relatively large molecular orientation (such as an extrusion molded body, an injection molded body, a blow molded body, etc.) based on the magnitude of the birefringence of the resin molded body.

[0023] In one embodiment, the information obtained from the measurement results of the birefringence or in-plane retardation of the resin molded body may include the result of comparing the value X obtained by multiplying the birefringence value of the resin molded body by 1×10 6 with a threshold value Y. The number of threshold values Y for comparison with the value X of the resin molded body is not particularly limited. By setting one threshold value Y, the resin molded body can be sorted into those with a value X less than the threshold value Y and those with a value X greater than or equal to the threshold value Y. By setting two threshold values Y1 and Y2 (Y1 < Y2), the resin molded body can be sorted into those with a value X less than the threshold value Y1, those with a value X exceeding the threshold value Y2, and those with a value X in the middle between the threshold value Y1 and the threshold value Y2. The threshold value Y may be set to three or more for performing a desired sorting.

[0024] The value of the threshold value Y for comparison with the value X of the resin molded body is not particularly limited. In some embodiments, threshold Y may include a threshold Y1 selected from within the range of 10±5, and may include a threshold Y2 selected from within the range of 50 or greater.

[0025] When the value X of the resin molded body is less than the threshold value Y1, the resin molded body may be separated for chemical recycling. When the value X of the resin molded body is equal to or greater than the threshold value Y1, the resin molded body may be separated for material recycling.

[0026] There is no particular limitation on the method for separating the resin molded bodies in step 2. For example, the resin molded bodies transported by a belt conveyer or the like may be separated continuously, or the resin molded bodies at rest may be separated.

[0027] (Step 3) The method of the present disclosure may further include a step of measuring the thickness of the resin molded body (hereinafter also referred to as step 3). There is no particular limitation on the method for measuring the thickness of the resin molded body in step 3. For example, the thickness of the resin molded body transported by a belt conveyer or the like may be continuously measured, or the thickness of a stationary resin molded body may be measured.

[0028] (Step 4) The method of the present disclosure may further include a step (hereinafter also referred to as step 4 or preliminary separation step) of separating the resin molded body whose birefringence or in-plane retardation is to be measured from resin molded bodies other than the resin molded body (hereinafter also referred to as other resin molded bodies). Step 4 may be performed before step 1, or after step 2 or step 3. From the viewpoint of separation efficiency, it is preferable to perform step 4 before step 1.

[0029] The type of the other resin molded product is not particularly limited and can be selected according to the purpose of the preliminary sorting. For example, a resin molded product containing a resin different from the resin contained in the resin molded product whose birefringence or in-plane retardation is to be measured, a resin molded product not satisfying a predetermined standard, etc. can be mentioned. The predetermined criteria include the degree of contamination by foreign matter, the degree of damage, and the shape of the resin molded body.

[0030] In this specification, a resin molded product containing a different type of resin means a resin molded product containing a different type of resin from the resin molded product desired to be separated (i.e., the resin molded product whose birefringence or in-plane retardation is to be measured).

[0031] The other resin molded articles separated in step 4 may be discarded or may be used for material recycling, thermal recycling, or the like.

[0032] By carrying out step 4, the accuracy and efficiency of separating the resin molded bodies carried out in steps 1 and 2 can be further improved. Step 4 may be, for example, a step of separating molded articles containing polymethyl(meth)acrylate and a different type of resin.

[0033] There are no particular limitations on the method for identifying the resin molded products to be separated in step 4. For example, a method capable of identifying differences in resin types, such as analysis using infrared spectroscopy, or a method capable of detecting foreign matter, can be used. There is no particular limitation on the method for separating the resin molded bodies to be separated in step 4. For example, a specific resin molded body may be separated from resin molded bodies being transported by a belt conveyer or the like, or a specific resin molded body may be separated from stationary resin molded bodies.

[0034] In the method of the present disclosure, the material of the resin molded body to be subjected to steps 1 and 2 is not particularly limited. Specific examples of materials for the resin molded body include polymethyl(meth)acrylate, polycarbonate (PC), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylonitrile / butadiene / styrene resin (ABS), polyamide (PA), polyvinyl acetate (PVA), polyurethane (PI), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), epoxy resin, phenol resin, urea resin, etc. The resin molded product may contain one type of resin or two or more types of resin.

[0035] From the viewpoint of compatibility with the method of the present disclosure, the resin to be subjected to steps 1 and 2 preferably contains polymethyl methacrylate (PMMA) or polymethyl acrylate (PMA), and more preferably contains polymethyl methacrylate (PMMA). In this specification, polymethyl methacrylate may be a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate with other monomers copolymerizable with methyl methacrylate, such as methyl acrylate, ethyl acrylate, and butyl acrylate.

[0036] In the method of the present disclosure, the shape of the resin molded article to be subjected to steps 1 and 2 is not particularly limited. From the viewpoint of compatibility with the method of the present disclosure, the resin molded body to be subjected to steps 1 and 2 is preferably a resin molded body having a thickness of 0.1 mm or more. The resin molded body may be a molded body before crushing or a molded body after crushing. The molded body before crushing is preferably in a sheet shape, but may be in any other shape. The molded body after crushing is preferably one having a longest side or diameter of more than 10 cm.

[0037] From the viewpoint of accurately separating the resin molded bodies, the thickness of the resin molded bodies to be subjected to steps 1 and 2 is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. That is, the thickness of the resin molded bodies can be in the range of 0.1 mm to 10 mm, preferably 0.1 mm to 8 mm, and more preferably 0.1 mm to 6 mm.

[0038] From the viewpoint of compatibility with the method of the present disclosure, the resin molded product to be subjected to steps 1 and 2 is preferably transparent. The resin molded body may or may not contain a colorant. The resin molded body may contain materials other than resin, such as metal, glass, semiconductor, carbon, etc., to the extent that the implementation of steps 1 and 2 is not hindered.

[0039] The source of the resin molded body in the method of the present disclosure is not particularly limited, and may be a used product or an unused product. In some embodiments, the source of the molded resin may be a splash guard. Each step in the method of the present disclosure may be independently performed either automatically or manually.

[0040] <Resin separation equipment> The resin fractionation device of the present disclosure comprises: A measurement unit for measuring birefringence or in-plane retardation of a resin molded body; and a sorting section that sorts the resin molded bodies based on information obtained from the measurement results of the birefringence or the in-plane retardation.

[0041] FIG. 1 shows a schematic configuration of a resin separation device. The resin separation device 1 shown in FIG. 1 includes a measurement unit 2 that measures the birefringence or in-plane retardation of a resin molded body, and a separation unit 3 that separates the resin molded body based on information obtained from the measurement results of the birefringence or in-plane retardation.

[0042] The above-mentioned device utilizes information obtained from the measurement results of birefringence or in-plane retardation of the resin molded body as an index for classifying the resin molded body, and therefore, the device makes it possible to classify the resin molded body based on differences in molecular weight, orientation state, etc. For example, the above-mentioned device can be used to separate molded articles (cast molded articles, etc.) that commonly contain polymethyl(meth)acrylate but have relatively low molecular orientation from molded articles (extrusion molded articles, injection molded articles, blow molded articles, etc.) that have relatively high molecular orientation.

[0043] In the above-mentioned device, the measurement section and the separation section may operate continuously or not continuously. In the examples described later, the measurement section and the separation section operate not continuously, specifically, the resin molded body is placed on a sample table, measured, and manually separated. From the viewpoint of efficiency of the separation work, it is preferable that the measurement section and the separation section operate continuously. For example, it is preferable to continuously perform the measurement of birefringence or in-plane retardation of the resin molded body transported in the device by a belt conveyor or the like, and the separation of the resin molded body.

[0044] (Measurement part) In the measurement section, the birefringence or in-plane retardation of the resin molded article is measured. The details and preferred aspects of the method for measuring the birefringence or in-plane retardation of a resin molded body in the measurement section are the same as the details and preferred aspects of the method for measuring the birefringence or in-plane retardation of a resin molded body in the above-mentioned resin fractionation method.

[0045] (Thickness measurement section) The device of the present disclosure may further include a thickness measuring unit that measures the thickness of the resin molded body. The details and preferred aspects of the method for measuring the thickness of the resin molded body in the thickness measuring section are the same as the details and preferred aspects of the method for measuring the thickness of the resin molded body in the above-mentioned resin fractionation method.

[0046] (Reserve Sorting Department) The device of the present disclosure may further include a preliminary sorting section that sorts a resin molded article whose birefringence or in-plane retardation is to be measured from a resin molded article other than the resin molded article. The details of the method for identifying and pre-sorting the resin molded bodies to be sorted in the preliminary sorting section, as well as preferred embodiments, are the same as the details of the method for identifying and pre-sorting the resin molded bodies to be sorted in the resin sorting method described above, as well as preferred embodiments.

[0047] The device of the present disclosure may have a storage section for storing the resin molded bodies after sorting or pre-sorting, a transport section for transporting the resin molded bodies, and the like, as necessary.

[0048] <Recycling methods for resin> The resin recycling method of the present disclosure includes: A step of measuring the birefringence or in-plane retardation of a resin molded product; A step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation; and recycling the resin molded bodies after separation.

[0049] In the above method, information obtained from the measurement results of birefringence or in-plane retardation of the resin molded body is used as an index for separating the resin molded body. Therefore, the above method makes it possible to separate the resin molded body based on differences in molecular weight, orientation state, etc. For example, the above method makes it possible to separate an extrusion molded body containing polymethyl(meth)acrylate from a cast molded body containing polymethyl(meth)acrylate.

[0050] In the above method, the details of the step of measuring the birefringence or in-plane retardation of the resin molded body and the step of separating the resin molded body, as well as preferred embodiments thereof, are the same as the details of steps 1 and 2 in the above-mentioned resin separation method, as well as preferred embodiments thereof. The above method may include at least one of step 3 and step 4 in the above-mentioned resin fractionation method.

[0051] The method for recycling the resin molded articles after separation is not particularly limited. For example, there is material recycling, in which the separated resin molded bodies are subjected to a molding process again to produce new molded bodies, chemical recycling, in which the separated resin molded bodies are thermally decomposed to obtain monomers to produce new molded bodies, and thermal recycling, in which the separated resin molded bodies are used as fuel.

[0052] In one embodiment, the resin molded product after fractionation includes at least one selected from the group consisting of an extrusion molded product, an injection molded product, or a blow molded product containing polymethyl(meth)acrylate, and a cast molded product containing polymethyl(meth)acrylate. When the resin molded article after separation is an extrusion molded article, an injection molded article or a blow molded article containing polymethyl(meth)acrylate, the method for recycling the extrusion molded article containing polymethyl(meth)acrylate may be material recycling. When the separated resin molded article is a cast molded article containing polymethyl(meth)acrylate, the method for recycling the cast molded article containing polymethyl(meth)acrylate may be chemical recycling. The separated resin molded articles may be subjected to treatments such as crushing and washing before being recycled. EXAMPLES

[0053] Hereinafter, embodiments of the present disclosure will be described based on examples. The following examples are not intended to limit the present disclosure.

[0054] (Test 1) The in-plane retardation of resin molded bodies 1 to 7 shown in Table 1 was measured using a two-dimensional birefringence evaluation system WPA100L manufactured by Photonics Lattice. The measurement was performed manually by placing the resin molded body on a sample stage. The measured in-plane retardation was divided by the thickness of the resin molded body to calculate the birefringence. A factor of 1×10 was applied to the obtained birefringence value. 6 The value X was calculated by multiplying by Next, the resin moldings 1 to 7 were classified by comparing the value X with a threshold value Y. Two threshold values ​​Y were set, Y1 being 10 and Y2 being 50, and the resin moldings were classified into those with an X value of less than 10 (classification 1), those with an X value of 10 or more and less than 50 (classification 2), and those with an X value of 50 or more (classification 3).

[0055] [Table 1]

[0056] As shown in Table 1, the birefringence values ​​of resin molded bodies 1 to 3 made only of PMMA were 1×10 6 The value of X obtained by multiplying by is smaller than the values ​​of X for the resin molded bodies 4 and 5 containing a resin other than PMMA and the resin molded bodies 6 and 7 consisting only of a resin other than PMMA. The above results show that it is possible to distinguish between resin moldings made only of PMMA and other resin moldings based on the size of X of the resin molding.

[0057] Furthermore, the value of X of the resin molded body 2, which is a cast molded body of PMMA, is smaller than the values ​​of X of the resin molded bodies 1 and 3, which are extrusion molded bodies of PMMA. The above results show that PMMA cast moldings and PMMA extrusion moldings can be distinguished based on the size of X of the resin molding.

[0058] The separated resin molded products having a value X less than the threshold value Y1 of 10 can be used for, for example, chemical recycling. The separated resin moldings having a value X equal to or greater than the threshold value Y1 of 10 can be used for material recycling, for example.

[0059] (Test 2) The polarization color was investigated when resin molded bodies 1 to 7 were placed between two polarizing plates arranged with their main orientation axes perpendicular to each other. As a result, no polarization color was observed (no light was transmitted) in resin molded body 2, which was a cast molding of PMMA, and the other resin molded bodies were colored as shown in Table 1. The above results show that the in-plane retardation value of a resin molding can be estimated from the polarized color observed by the crossed Nicol method, and that the resin molding can be classified in the same manner as in Test 1. [Explanation of symbols]

[0060] 1: Resin sorting device 2: Measuring part 3: Sorting department

Claims

1. A step of measuring the birefringence or in-plane retardation of a resin molded product; and a step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation.

2. The information is based on the birefringence value of the resin molded body by 1×10 ６ The resin fractionation method according to claim 1 , further comprising a comparison result between the value X multiplied by the above and a threshold value Y.

3. The method for separating resins according to claim 2 , wherein the threshold value Y includes a threshold value Y1 selected within the range of 10±5.

4. The method for separating resins according to claim 3, wherein resin molded products having a value X less than the threshold value Y1 are separated for chemical recycling.

5. 4. The method for separating resins according to claim 3, wherein a resin molded product having a value X equal to or greater than the threshold value Y1 is separated for material recycling.

6. The method for separating resins according to claim 2 , wherein the threshold value Y includes a threshold value Y2 selected from a range of 50 or more.

7. The method for separating resins according to claim 1 or 2, further comprising a step of measuring a thickness of the resin molded body.

8. 3. The method for separating a resin according to claim 1 or 2, wherein the resin molded body has a thickness of 0.1 mm or more and 10 mm or less.

9. 3. The resin separation method according to claim 1 or 2, further comprising a step of separating a resin molded body whose birefringence or in-plane retardation is to be measured from a resin molded body other than the resin molded body before or after measuring the birefringence or in-plane retardation of the resin molded body.

10. The method for separating resins according to claim 1 or 2, wherein the resin molded product is transparent.

11. The method for separating a resin according to claim 1 or 2, wherein the resin molded product contains a colorant.

12. The method for separating resins according to claim 1 or 2, wherein the resin molded article is a splash guard plate.

13. 3. The method for separating a resin according to claim 1, wherein the birefringence or in-plane retardation of the resin molded product is measured by a crossed Nicol method.

14. A measurement unit for measuring birefringence or in-plane retardation of a resin molded body; a sorting section that sorts the resin molded bodies based on information obtained from the measurement results of the birefringence or the in-plane retardation.

15. A step of measuring the birefringence or in-plane retardation of a resin molded product; A step of classifying the resin molded body based on information obtained from the measurement result of the birefringence or the in-plane retardation; and recycling the resin molded bodies after separation.

16. The method for recycling a resin according to claim 15, wherein the recycling step includes chemical recycling.

17. The method for recycling a resin according to claim 15, wherein the recycling step includes material recycling.

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