Resin molded article and electric apparatus

Abstract

Disclosed is a resin molded article which uses a recycled acrylonitrile butadiene styrene (ABS) resin as a starting material, wherein the content ratio of methyl methacrylate (MMA) is 10 ppm or less.

Description

Resin molded products and electrical equipment

[0001] The present disclosure relates to a resin molded product made from recycled ABS (acrylonitrile butadiene styrene) resin, and an electrical device incorporating the resin molded product.

[0002] Conventional recycled ABS (acrylonitrile butadiene styrene) resin molded products are made from ABS (acrylonitrile butadiene styrene) resin obtained by sorting collected mixed plastics at a recycling plant, etc. As a method for sorting mixed plastics, for example, a method is known in which the collected mixed plastics are irradiated with near-infrared light, the reflected light is detected, and the ABS (acrylonitrile butadiene styrene) resin is identified, and the ABS (acrylonitrile butadiene styrene) resin is separated by ejecting pulsed air (see, for example, Patent Document 1).

[0003] JP 2013-238524 A

[0004] However, conventionally, ABS (acrylonitrile butadiene styrene) resin obtained from recycled mixed plastics as described above contains materials other than ABS (acrylonitrile butadiene styrene) resin, such as other resins. Here, before molding the ABS (acrylonitrile butadiene styrene) resin, a process of removing moisture by drying is performed to reduce molding defects such as silver streaks. However, the above-mentioned materials in the recycled ABS (acrylonitrile butadiene styrene) resin obtained by recycling reduce the drying efficiency, resulting in problems such as a long drying time and increased energy consumption due to drying.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a resin molded product made from recycled ABS (acrylonitrile butadiene styrene) resin, which suppresses molding defects and reduces the time required for drying, and an electrical device equipped with the resin molded product.

[0006] The resin molded article according to the present disclosure is made from recycled ABS (acrylonitrile butadiene styrene) resin and has an MMA (methyl methacrylate) content of 10 ppm or less.

[0007] The resin molded article according to the present disclosure is made from recycled ABS (acrylonitrile butadiene styrene) resin, and has a cyclopentane content of 12 ppm or less and a carbon dioxide content of 75 ppm or less.

[0008] The electrical device according to the present disclosure includes the resin molded product.

[0009] The resin molded product and electrical device according to the present disclosure can reduce molding defects and drying time.

[0010] 1 is a diagram showing the relationship between the moisture removal rate and the MMA content of recycled ABS resin; 2 is a diagram showing the correlation between the MMA content, the drying time of recycled ABS resin, and the occurrence of silver streak defects; 3 is a diagram showing the correlation between the cyclopentane and carbon dioxide contents, the drying time of recycled ABS resin, and the occurrence of silver streak defects; 4 is a diagram showing the correlation between the MMA, cyclopentane, and carbon dioxide contents, the drying time of ABS resin, and the occurrence of silver streak defects; 5 is a diagram showing the detection frequency of materials to be removed detected from plastic flakes for each transmittance of visible light at a wavelength of 580 nm; and 6 is a diagram showing the detection frequency of materials originating from refrigerator inner boxes for each brightness.

[0011] Embodiment 1. A resin molded product according to embodiment 1 will be described below with reference to the drawings. First, a method for manufacturing the resin molded product will be described. In Japan, electrical appliances used in households are collected from consumers or businesses and dismantled in accordance with the Home Appliance Recycling Law. The four types of home appliances subject to the Home Appliance Recycling Law include air conditioners, televisions, refrigerators, and washing machines. The parts obtained by dismantling are finely crushed into flakes approximately 5 mm square and sorted by material, such as metal or plastic. The sorted and collected mixed plastics are sieved to uniformize the size, and then metals are removed and collected as mixed plastics.

[0012] Mixed plastics are further sorted based on differences in specific gravity or electrostatic charge tendency, and are classified into high-purity types such as PP (polypropylene), PS (polystyrene), ABS (acrylonitrile butadiene styrene), and other plastics. However, the resins obtained after sorting may contain a few percent of other resins. From an industrial perspective, ABS (acrylonitrile butadiene styrene) resin containing 4% or more of other resins is considered recycled ABS (acrylonitrile butadiene styrene) resin. In the following, ABS (acrylonitrile butadiene styrene) may also be referred to as ABS.

[0013] For example, when the proportion of other resins in a certain batch of ABS resin flakes was investigated, the following results were obtained: 2.00% PMMA (polymethyl methacrylate), 0.83% PA (polyamide), 0.75% AS (acrylonitrile styrene), 0.21% MS (methyl methacrylate-styrene copolymer), 0.21% MBS (methyl methacrylate-butadiene styrene copolymer), and 0.17% MABS (methyl methacrylate-acrylonitrile butadiene styrene). Of these, PMMA (polymethyl methacrylate) is used in LCD TVs and washing machines, while PA is used in all four types of home appliances. Furthermore, white ABS may contain ABS from the inner box of a refrigerator, and cyclopentane or carbon dioxide, a blowing agent for urethane foam in refrigerators, may adhere to the white ABS. In the following, PMMA (polymethyl methacrylate) may also be referred to as PMMA.

[0014] Furthermore, in order to increase the purity of the ABS resin, a separation process using near-infrared rays or a separation process based on brightness may be used. Note that compounds in the recycled ABS resin can be separated and their purity investigated by high performance liquid chromatography (HPLC) analysis using a solvent such as THF (tetrahydrofuran).

[0015] The sorted ABS resin flakes are extruded in an extruder at an extrusion temperature of 230°C to 260°C and cut into pellets using a hot cutter. The resulting ABS resin pellets are dried and then molded at a molding temperature of 230°C to 260°C to form molded resin products. Hereinafter, the above-mentioned process of obtaining molded resin products from the recovered mixed plastics may also be referred to as the recycling process.

[0016] The following describes a method for analyzing the content of MMA (methyl methacrylate), cyclopentane, and carbon dioxide in molded recycled ABS resin. In this embodiment, gas chromatography-mass spectrometry (GC / MS) analysis is performed, using the static headspace method. Approximately 0.1 g of recycled ABS resin cut into approximately 1 mm to 4 mm squares is sampled and placed in a 12.7 ml headspace vial and sealed. Note that hereinafter, MMA (methyl methacrylate) may also be referred to as MMA.

[0017] Each sealed sample was heated on a 240°C hot plate for approximately 30 minutes, and 0.1 ml of gas was collected from the headspace vial using a gas-tight syringe for analysis. The peak area values ​​of the ion chromatogram were converted to hexane volume values, and a semi-quantitative analysis was performed on the amount of gas detected per gram of sample. Details of the analytical equipment and measurement conditions are as follows: <Analytical equipment> GC / MS: JMS-K9 UltraQuad GC / MS (manufactured by JEOL) <Measurement conditions> Column: HP-VOC 60 m x 0.2 mm x 1.12 μm (manufactured by Agilent Technologies) Column temperature increase conditions: 35°C, 10 min → 6°C / min → 251°C (After maintaining the initial temperature of 35°C for 10 minutes, increase the temperature at a rate of 6°C / min to 251°C) Injection port: 1 ml / min, constant flow rate control, split ratio 20

[0018] The amount of gas detected per 1 g of sample converted to a hexane volume value is 22.4 L / mol under standard conditions, and by utilizing this, the mass percentage of each of MMA, cyclopentane, and carbon dioxide contained in the ABS resin molded product is calculated. The calculation method is shown below.

[0019] Let y (g / mol) be the molecular weight of the gas of interest, such as MMA. Also, let x (μL / g) be the converted hexane volume value of the detected gas amount per 1 g of sample. In this case, the number of moles of the gas contained in x (μL / g) is expressed by the following formula 1:

[0020]

[0021] Therefore, when the amount of gas in the sample is converted into a mass % concentration, the formula 2 is obtained.

[0022] For example, if we focus on MMA, its molecular weight y is 100 g / mol, and the hexane volume value x of the detected gas amount per 1 g of sample is 1.4 μL / g, the amount of MMA gas in the sample will be approximately 7 ppm. The gas amounts of other substances in the sample can also be obtained in a similar manner.

[0023] The drying time for recycled ABS resin will be explained below. Figure 1 shows the relationship between the moisture removal rate and the MMA content of recycled ABS resin. The moisture removal rate can be calculated by dividing the difference between the amount of water vapor generated from a sample after a 3-hour drying treatment and the amount of water vapor generated from a sample that has not been dried by the time.

[0024] When the sample contained 16 ppm of MMA, the water removal rate was 50.7 μL / (g hr), which was significantly lower than the water removal rate of 110 μL / (g hr) when the sample contained 0 ppm of MMA. When the sample contained 10 ppm of MMA, the water removal rate was 99.0 μL / (g hr), which was closer to the water removal rate of 110 μL / (g hr) when the sample contained 0 ppm of MMA than when the sample contained 16 ppm of MMA. When the sample contained 7 ppm of MMA, the water removal rate was 108 μL / (g hr), which was almost the same as when the sample contained 0 ppm of MMA.

[0025] FIG. 2 shows the correlation between the MMA content, the drying time of the recycled ABS resin, and the occurrence of silver streak defects. In FIG. 2, "○" indicates that no silver streak defects occurred, and "×" indicates that silver streak defects occurred. The same applies to "○" and "×" in the following figures. Here, if PMMA is not selectively removed, as in the conventional method, the MMA content in the recycled ABS resin will be 16 ppm or more. Conventional recycled ABS resins have an MMA content of 16 ppm or more. As shown in FIG. 2, when the MMA content is 16 ppm or more, silver streak defects occur when the drying time is less than 6 hours. In other words, to prevent silver streak defects, conventional recycled ABS resins require a drying time of 6 hours or more.

[0026] On the other hand, when the MMA content is 10 ppm, silver streak defects can be suppressed by drying for 3 hours, which is the drying time before molding for general recycled ABS resin.Furthermore, when the MMA content is 7 ppm, silver streak defects can be suppressed by drying for 2 hours, which is shorter than the drying time for general recycled ABS resin and is the same as for 100% pure virgin ABS resin.

[0027] By selectively removing PMMA, it is possible to produce molded products from recycled ABS resin with an MMA content of 10 ppm or less. As mentioned above, a 10 ppm or less MMA content reduces the drying time from the conventional 6 hours required for drying recycled ABS resin to 3 hours while suppressing silver streak defects. Furthermore, the reduction in drying time reduces electricity costs and carbon dioxide emissions. Specifically, the electricity used can be reduced by approximately 20.9 kW, resulting in a savings of approximately 1,755 yen in electricity costs. Furthermore, the carbon dioxide emissions generated by power generation can be reduced by 28 kg.

[0028] Embodiment 2. A resin molded product according to embodiment 2 will be described below. The recycling process, analysis method, and calculation method in embodiment 2 are the same as those in embodiment 1. The recycled ABS resin according to embodiment 2 has a cyclopentane content of 12 ppm or less and a carbon dioxide content of 75 ppm or less.

[0029] Figure 3 shows the correlation between the cyclopentane and carbon dioxide contents, the drying time of the recycled ABS resin, and the occurrence of silver streak defects. If the recycled ABS resin is not treated to remove carbon dioxide and cyclopentane, as in the conventional method, the carbon dioxide content will be 125 ppm or more, and the cyclopentane content will be 20 ppm or more. As shown in Figure 3, the drying time required for conventional recycled ABS resin to prevent silver streak defects will be 6 hours or more.

[0030] On the other hand, if the cyclopentane content is 12 ppm or less and the carbon dioxide content is 75 ppm or less, it is possible to suppress silver streak defects by drying for 3 hours, which is the drying time before molding of typical recycled ABS resin.

[0031] Embodiment 3. A resin molded product according to embodiment 3 will be described below. The recycling process, analysis method, and calculation method in embodiment 3 are the same as those in embodiment 1. The recycled ABS resin according to embodiment 3 has an MMA content of 10 ppm or less, as in embodiment 1, and further has a cyclopentane content of 12 ppm or less and a carbon dioxide content of 75 ppm or less, as in embodiment 2.

[0032] 4 is a graph showing the correlation between the content of each of MMA, cyclopentane, and carbon dioxide, the drying time of ABS resin, and the occurrence of silver streaks. As shown in FIG. 4, by combining the first and second embodiments, that is, by setting the content of MMA in the recycled ABS resin to 10 ppm or less, the content of cyclopentane to 12 ppm or less, and the content of carbon dioxide to 75 ppm or less, it is possible to suppress the occurrence of silver streaks even after two hours of drying.

[0033] Embodiment 4. In the following, Embodiment 4 describes a method for removing PMMA from recycled ABS resin. The recycling process, analysis method, and calculation method in Embodiment 4 are the same as those in Embodiment 1. The recycled ABS resin in Embodiment 4 is made from plastic flakes, from which materials with a visible light transmittance of 10% or more at a wavelength of 580 nm have been removed during a process of recovering and sorting ABS resin from the plastic flakes. This is described in detail below. Figure 5 is a graph showing the detection frequency of materials to be removed from plastic flakes for each transmittance of visible light at a wavelength of 580 nm. Here, PMMA is used as the material to be removed. The horizontal axis in Figure 5 represents transmittance, and the vertical axis on the left represents the detection frequency of the material to be removed at each transmittance. The line graph in Figure 5 shows the cumulative percentage of the material to be removed at each transmittance in the recycled ABS resin, with the vertical axis on the right representing this cumulative percentage [%].

[0034] The details of the analytical device and measurement conditions in the fourth embodiment are as follows: <Device> Spectrophotometer (Shimadzu UVmin-1240) <Measurement conditions> Wavelength: 580 nm

[0035] As shown in Figure 5, if PMMA is not selectively removed, the MMA content is 16 ppm or more. To reduce the MMA content from 16 ppm to 10 ppm or less, it is necessary to remove 37.5% or more of PMMA. The transmittance of PMMA is distributed in a high range compared to the transmittance of other materials in the raw plastic flakes. Therefore, in embodiment 4, materials with higher transmittance are removed from the plastic flakes in order. To remove 37.5% or more of PMMA from the high transmittance side, it is sufficient to remove materials from the plastic flakes with a transmittance of 12% or more when irradiated with visible light at a wavelength of 580 nm. Removing PMMA with a transmittance of 12% or more makes it possible to reduce the MMA content to 10 ppm or less. Furthermore, removing materials with a transmittance of 10% or more reduces the MMA content to 7 ppm or less.

[0036] Embodiment 5. In the following, Embodiment 5 describes a method for removing materials originating from refrigerator inner boxes from recycled ABS resin. The recycling process, analysis method, and calculation method in Embodiment 5 are the same as those in Embodiment 1. The recycled ABS resin molded product according to Embodiment 5 is a molded product made from plastic flakes, from which materials with a lightness L* of 90 or higher in the L*a*b* color space, where L* is lightness, a* is chromaticity in the red-green direction, and b* is chromaticity in the yellow-blue direction, have been removed. The L*a*b* color space refers to the color space adopted by the International Commission on Illumination (CIE) in 1976 and adopted in JIS Z 8781-4. The recycled ABS resin molded product according to Embodiment 5 is described in detail below.

[0037] FIG. 6 is a diagram showing the detection frequency of materials originating from the inner box of a refrigerator for each lightness level. Note that urethane adheres to the inner box of a refrigerator, and this urethane is a cause of cyclopentane and carbon dioxide generation. In the fifth embodiment, the materials to be removed are cyclopentane, carbon dioxide, and the like. Here, the horizontal axis in FIG. 6 represents lightness L*, and the vertical axis on the left represents the detection frequency of the materials originating from the inner box at each lightness L*. The line graph in FIG. 6 shows the cumulative proportion of the materials originating from the inner box at each lightness L* in the recycled ABS resin, and the vertical axis on the right represents this cumulative proportion [%].

[0038] Details of the analysis device and measurement conditions in the fifth embodiment are as follows: <Device> Spectrophotometer (CM-700d manufactured by Konica Minolta) <Measurement conditions> Observation light source: D65 Observation conditions: 10° field of view Measurement method: SCE method

[0039] If the materials from the inner boxes were not removed, the cyclopentane content of the entire plastic flakes would be 20 ppm or more, and the carbon dioxide content would be 120 ppm or more, with the materials from the inner boxes accounting for approximately 40% of the recycled ABS flakes. To reduce the cyclopentane content of the entire plastic flakes to 12 ppm or less and the carbon dioxide content to 75 ppm or less, it is necessary to remove 40% or more of the cyclopentane and carbon dioxide from the entire plastic flakes. Specifically, it is necessary to remove 37.5% or more of the materials from the inner boxes.

[0040] Here, the lightness L* of the material from the inner box is distributed in a higher range compared to other materials, so it is sufficient to remove materials with higher lightness L* from the plastic flakes. More specifically, by removing materials with a lightness L* of 90 or higher in the L*a*b* color space, it is possible to reduce the cyclopentane content to 12 ppm or less and the carbon dioxide content to 75 ppm or less. When the cyclopentane content in the resin molded product is 12 ppm or less and the carbon dioxide content is 75 ppm or less, silver streak defects can be suppressed by drying for 3 hours, which is the drying time typically required before molding recycled ABS resin.

[0041] Sixth Embodiment A resin molded product according to the sixth embodiment will be described below. The recycling process, analysis method, and calculation method in the sixth embodiment are the same as those in the first embodiment. The recycled ABS resin molded product according to the sixth embodiment is made from plastic flakes whose surfaces have been polished to a depth of 40 μm or more in a process of recovering and sorting ABS resin from the plastic flakes.

[0042] As described above, if urethane is not removed from the plastic flakes originating from the inner boxes, the cyclopentane content will be 20 ppm or more and the carbon dioxide content will be 120 ppm or more. In order to reduce the cyclopentane content to 12 ppm or less and the carbon dioxide content to 75 ppm or less, it is necessary to remove 37.5% or more of the urethane adhering to the plastic flakes originating from the inner boxes.

[0043] Here, urethane adheres to the surface of the plastic flakes to an average thickness of 124 μm. To remove 37.5% or more of the urethane, the surfaces of the plastic flakes must be polished to a depth of approximately 40 μm or more. By polishing both sides of the plastic flakes to a depth of approximately 40 μm or more during the process of collecting and sorting them from home appliance recycling plants, urethane can be removed from the plastic flakes originating from the inner boxes. If the cyclopentane content in molded products made from recycled ABS resin is 12 ppm or less and the carbon dioxide content is 75 ppm or less, silver streak defects can be suppressed by drying for three hours, which is the typical drying time for recycled ABS resin before molding.

[0044] Embodiment 7. An electrical device according to embodiment 7 will be described below. The electrical device according to embodiment 7 is equipped with a molded product made of recycled ABS resin according to embodiments 1 to 6. The recycled ABS resin according to embodiments 1 to 6 satisfies both or one of the following conditions: a first condition that the MMA content is 10 ppm or less; and a second condition that the cyclopentane content is 15 ppm or less and a carbon dioxide content is 75 ppm or less. This allows for a reduction in drying time. This reduces energy consumption and manufacturing time in the manufacture of electrical devices. This makes it possible to provide electrical devices at lower costs. Furthermore, the use of recycled materials in the resin parts of electrical devices increases, contributing to a circular economy.

[0045] The effects of the resin molded products according to embodiments 1 to 6 and the electrical device according to embodiment 7 are described below. The resin molded product according to embodiment 1 is made from recycled ABS resin and has an MMA content of 10 ppm or less. This makes it possible to reduce drying time while suppressing silver streak defects. This therefore contributes to energy savings and reduced carbon dioxide emissions.

[0046] The resin molded product according to the second embodiment is made from recycled ABS resin and has a cyclopentane content of 12 ppm or less and a carbon dioxide content of 75 ppm or less, which makes it possible to reduce the drying time while suppressing silver streak defects.

[0047] The resin molded product according to the third embodiment is made from recycled ABS resin and has an MMA content of 10 ppm or less, a cyclopentane content of 12 ppm or less, and a carbon dioxide content of 75 ppm or less, which makes it possible to further shorten the drying time while suppressing silver streak defects.

[0048] The recycled ABS resin in the resin molded product according to the fourth embodiment is made from plastic flakes left after removing materials that have a visible light transmittance of 10% or more at a wavelength of 580 nm. This allows the MMA content to be reduced to 7 ppm or less. This reduces silver streak defects and shortens drying time.

[0049] The recycled ABS resin in the resin molded product according to the fifth embodiment is made from plastic flakes remaining after removing materials with a lightness L* of 90 or higher in the L*a*b* color space, where L* is lightness, a* is chromaticity from red to green, and b* is chromaticity from yellow to blue. This makes it possible to keep the cyclopentane content at 12 ppm or less and the carbon dioxide content at 75 ppm or less. This makes it possible to suppress silver streak defects and shorten drying time.

[0050] The recycled ABS resin in the resin molded product according to the sixth embodiment is made from plastic flakes whose surfaces have been polished to a depth of 40 μm or more. This reduces the cyclopentane and carbon dioxide contents in the recycled ABS resin molded product, shortening the drying time and suppressing silver streak defects.

[0051] The electrical device according to the seventh embodiment is equipped with a resin molded product according to any one of the first to sixth embodiments. The resin molded products according to the first to sixth embodiments satisfy both or one of the first condition that the MMA content is 10 ppm or less and the second condition that the cyclopentane content is 15 ppm or less and the carbon dioxide content is 75 ppm or less, thereby enabling a reduction in drying time. This reduces energy consumption in the manufacture of electrical devices and enables more rapid manufacture of electrical devices. This makes it possible to provide electrical devices at lower costs. Furthermore, this improves the recycling rate of parts in electrical devices, contributing to a circular economy.

[0052] Although the first to seventh embodiments have been described above, the contents of the present disclosure are not limited to the above-described embodiments and include conceivable equivalents. Furthermore, the configurations described in the first to seventh embodiments and their variations can be combined with each other.

Claims

1. Resin molded products made from recycled ABS (acrylonitrile butadiene styrene) resin with an MMA (methyl methacrylate) content of 10 ppm or less.

2. The resin molded product according to claim 1, wherein the cyclopentane content is 12 ppm or less and the carbon dioxide content is 75 ppm or less.

3. A resin molded product made from recycled ABS (acrylonitrile butadiene styrene) resin, with a cyclopentane content of 12 ppm or less and a carbon dioxide content of 75 ppm or less.

4. The resin molded product according to claim 1 or 2, wherein the recycled ABS (acrylonitrile butadiene styrene) resin is made from plastic flakes remaining after removal of materials that have a visible light transmittance of 10% or more at a wavelength of 580 nm.

5. The resin molded product according to claim 2 or 3, wherein the recycled ABS (acrylonitrile butadiene styrene) resin is made from plastic flakes remaining after removal of materials with a lightness L* of 90 or more in the L*a*b* color space, where L* is lightness, a* is chromaticity in the red to green direction, and b* is chromaticity in the yellow to blue direction.

6. The resin molded product according to claim 2 or 3, wherein the recycled ABS (acrylonitrile butadiene styrene) resin is made from plastic flakes whose surfaces have been polished to a depth of 40 μm or more.

7. An electrical device equipped with the resin molded product according to any one of claims 1 to 6.

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