Method for detecting foreign matter in colored recycled resin

Abstract

To provide a foreign body detection method that easily detects foreign bodies contained in colored recycled resin.SOLUTION: Provided is a method for detecting foreign bodies contained in colored recycled resin, comprising: a colored sheet creation step of creating a colored sheet S2 made of colored recycled resin; an inspection sheet creation step of creating an inspection sheet S3 by heat-pressing the created colored sheet S2 and a pair of uncolored sheets S1 made of uncolored resin so as to mix the colored recycled resin with the uncolored resin in a state of sandwiching the colored sheet S2 between the pair of uncolored sheets S1; and a foreign body detection step of detecting foreign bodies contained in the inspection sheet S3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a foreign matter detection method for detecting foreign matters contained in a colored recycled resin.

Background Art

[0002] Conventionally, resin recycling has been carried out on resin molded products such as thermoplastic resins. Such recycled resins are called recycled resins and are used when producing other products. However, foreign matters may be present in recycled resins due to surface treatment or usage patterns of molded products before recycling. Since such foreign matters deteriorate the characteristics of the product, it is important to know the degree of their inclusion. From this perspective, for example, Patent Document 1 discloses a method of pressing and flattening a recycled resin into a sheet shape to detect foreign matters mixed in the recycled resin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, for example, when the recycled resin is a colored resin (colored recycled resin), it is difficult to identify such foreign matters even if they are mixed in the colored recycled resin. In particular, it is difficult to detect foreign matters contained in a colored recycled resin colored with a so-called dark color such as black.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a foreign matter detection method that can easily detect foreign matters contained in a colored recycled resin. [Means for solving the problem]

[0006] In view of the above issues, the method for detecting foreign matter in a colored recycled resin according to the present invention is a method for detecting foreign matter contained in a colored recycled resin, and is characterized by comprising: a colored sheet manufacturing step of manufacturing a colored sheet made of the colored recycled resin; an inspection sheet manufacturing step of manufacturing an inspection sheet by sandwiching the manufactured colored sheet between a pair of uncolored sheets made of uncolored resin and heat-pressing the colored sheet and the pair of uncolored sheets so as to mix the colored recycled resin and the uncolored resin; and a foreign matter detection step of detecting the foreign matter contained in the inspection sheet. [Effects of the Invention]

[0007] According to the present invention, it becomes easier to detect foreign matter contained in colored recycled resin. [Brief explanation of the drawing]

[0008] [Figure 1] (a) is a schematic diagram illustrating the process of manufacturing a colored sheet in the foreign object detection method according to this embodiment, and (b) is a schematic diagram illustrating the process of manufacturing an inspection sheet. [Figure 2] (a) is a photograph showing the results of observing the test sheet, and (b) is a photograph showing the results of observing the colored sheet. [Modes for carrying out the invention]

[0009] A method for detecting foreign matter in colored recycled resin according to an embodiment of the present invention will be described below with reference to Figures 1 and 2.

[0010] [Process for manufacturing colored sheets] In this process, first, as shown in Figure 1(a), colored recycled resin pellets P2 are prepared. These pellets P2 are particles produced by crushing or melting and granulating resin molded products, for example, used in vehicle dashboards. The colored recycled resin may be a material recycled after consumption, i.e., PCR (Post-Consumer recycled) material. Alternatively, the colored recycled resin may be a material recycled from waste materials generated in the manufacturing process, PIR (Post-Industrial Recycled) material.

[0011] Pellet P2 is a resin that has been colored by incorporating colorants or pigments into a thermoplastic resin such as polypropylene resin or polyethylene resin. The colored recycled resin is preferably a so-called dark color, such as black, dark blue, gray, or burnt brown. To ensure stable quality, such pellets P2 are produced from the same resin molded product, and their quality is controlled by grade and other criteria as a single rod.

[0012] A colored sheet S2 is produced by hot-pressing pellets P2 made from such colored recycled resin. For example, if the pellets P2 are made of polypropylene resin, the mold temperature during hot-pressing is set to 200°C, and about 4 to 10 pellets (about 0.1g) of P2 are weighed and hot-pressed for 1 minute. This allows for the production of a colored sheet S2 with a thickness of about 100 μm.

[0013] Similarly, uncolored resin pellets P1 are prepared. Pellet P1 consists of unused resin particles and is made of the same type of thermoplastic resin as pellet P2 (for example, polypropylene resin). Therefore, pellet P1 has the inherent color of the resin (for example, white or transparent). A pair of uncolored sheets S1, S1 are produced by heating and pressing these pellets P1 in the same manner as the colored sheet S2 was produced.

[0014] [Process for manufacturing inspection sheets] As shown in Figure 1(b), in this step, the prepared colored sheet S2 is sandwiched between a pair of uncolored sheets S1, S1 made of uncolored resin, and the colored recycled resin and the pair of uncolored sheets S1, S1 are heat-pressed to mix the colored recycled resin and the uncolored resin, thereby producing an inspection sheet S3. The heat-pressing conditions for the inspection sheet S3 may be the same as the heat-pressing conditions used when producing the colored sheet S2, for example.

[0015] Furthermore, the thickness of each uncolored sheet S1 and colored sheet S2 is not particularly limited, as long as the color of the inspection sheet S3 becomes lighter (diluted) than the color of the colored sheet S2 due to the uniform mixing of the colored recycled resin and the uncolored resin.

[0016] [Foreign object detection process] In this step, foreign matter C contained in the inspection sheet S3 is detected. In this embodiment, the color of the inspection sheet S3 is lighter than the colored color of the colored sheet S2, so the color of the foreign matter contained in the colored sheet S2 is clearly reflected on the surface of the inspection sheet S3. In this way, foreign matter C contained in the colored recycled resin can be confirmed. In particular, when the color of the colored recycled resin and the color of the foreign matter C are similar in hue, the lighter the color of the inspection sheet S3, the easier it becomes to detect the foreign matter C contained in the colored recycled resin.

[0017] Figure 2(a) is a photograph showing the results of observing the inspection sheet, and Figure 2(b) is a photograph showing the results of observing the colored sheet. As shown in Figure 2(a), when the fabricated circular inspection sheet S3 was observed, foreign matter C could be confirmed in the inspection sheet S3. However, as shown in Figure 2(b), when the fabricated circular colored sheet S2 was observed, it was difficult to distinguish foreign matter C because the color of the colored recycled resin in the colored sheet S2 was similar to the color of foreign matter C. In addition, multiple voids B were observed in the colored sheet S2.

[0018] Furthermore, in the foreign matter detection process, the proportion of foreign matter C present may be determined by performing a binarization process on images captured by an imaging device on both sides of the inspection sheet S3 and calculating the total area ratio of foreign matter C to the area of ​​the inspection sheet S3. In addition, the grade of the colored recycled resin pellets P2 may be set according to the determined proportion of foreign matter C. [Explanation of Symbols]

[0019] S1: Uncolored sheet, S2: Colored sheet, S3: Inspection sheet, C: Foreign matter

Claims

[Claim 1] A method for detecting foreign matter contained in colored recycled resin, A colored sheet manufacturing process for producing a colored sheet made from the aforementioned colored recycled resin, A test sheet manufacturing process involves sandwiching a prepared colored sheet between a pair of uncolored sheets made of uncolored resin, and then heat-pressing the colored recycled resin and the pair of uncolored sheets so that the colored recycled resin and the uncolored resin are mixed, thereby producing a test sheet. A foreign matter detection step for detecting the foreign matter contained in the inspection sheet, A method for detecting foreign matter in colored recycled resin, characterized by including [a specific component].

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