JP2008260208A - Sorting method of recycled plastic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sorting method of a recycled plastic material with high speed and high recycling efficiency by detecting and removing plastic containing bromine (Br) having concentration exceeding a predetermined concentration from recovered plastic 8. <P>SOLUTION: The sorting method of the recycled plastic material for sorting the material used for manufacturing the recycled plastic from plastic waste materials 1 is equipped with (a) the step of sorting the material except plastic from the plastic waste materials 1 and obtains desired recovered plastic 8, and (b) the step of detecting and removes the plastic containing bromine having the predetermined concentration or more from the recovered plastic 8 obtained by the step (a). The sorting method is characterized in that it sorts the recycled plastic material with high speed and high recycling efficiency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for selecting a recycled plastic material that can be reused from recovered plastic waste material of waste home appliances, and more particularly to a method for selecting a recycled plastic material that detects and removes plastic containing bromine at a certain concentration or higher.

  In recent years, household appliances such as air conditioners, televisions, refrigerators, and washing machines have been provided at a high penetration rate in ordinary households in Japan, and the amount of disposal of these household appliances tends to increase year by year as the spread of the household appliances progresses. Constituent members of home appliances account for a large proportion of plastic members. From the viewpoints of legal regulations concerning the protection of the global environment such as the Home Appliance Recycling Law and effective use of materials, the promotion of recycling of plastic members has become an important issue.

  Plastic recycling can be classified into three categories: material recycling, chemical recycling, and thermal recycling. Among these, material recycling is a recycling method for returning to the same plastic again, and it is an excellent recycling method with the least burden on the environment. In order to carry out material recycling, it is necessary to recycle high-quality plastics, and plastic members in which various types of materials are mixed must be separated for each material and then processed again. In order to use as recycled plastics, the recycled plastics do not contain a hazardous substance regulated by the RoHS Directive (Restriction of the use of ceramics, industrial and electrical equipment), etc. exceeding the threshold. Need to guarantee.

  Hazardous substances targeted by the RoHS Directive are cadmium, lead, hexavalent chromium, mercury, two types of bromine (Br) flame retardants (polybrominated biphenyls (PBBs), polybrominated diphenyl ethers). : PBDEs)). The threshold values of the contents regulated for each substance are 100 ppm for cadmium, 1000 ppm for lead, hexavalent chromium and mercury. Further, PBBs and PBDEs, which are brominated flame retardants, have a threshold of 1000 ppm. If the concentration of Br contained in these is less than 300 ppm, PBBs and PBDEs do not exceed 1000 ppm. However, if even a small amount of plastic containing Br having a concentration exceeding 1 wt% is mixed, the Br concentration of recycled plastics recycled using these as raw materials will exceed 300 ppm, which is a detailed information for confirming the content of PBBs and PBDEs. Since analysis is required, it is desirable that plastic containing Br having a concentration of more than 1 wt% is not mixed in waste plastic that is a raw material of recycled plastic.

  In the conventional method of producing recycled plastic from waste plastic waste recovered from household electrical appliances, in order to sort out high-purity plastic materials, sorting is performed based on the difference in specific gravity composed of dry sorting means and wet sorting means. (For example, refer to Patent Document 1). Further, in a plastic sorting apparatus containing a flame retardant, in order to sort plastic containing a flame retardant material, X-rays or characteristic X-rays generated from the plastic are irradiated by irradiating the plastic with an electron beam. The type and presence / absence of the flame retardant are determined based on the wavelength and energy, and the plastic is sorted (for example, see Patent Document 2).

JP 2006-159052 A JP 2004-219366 A

  In Patent Document 1, plastics are selected only by specific gravity. For plastics after material selection, such as polypropylene (PP), materials with a purity exceeding 99% can be selected, but there is no consideration of hazardous substances regulated by the RoHS directive etc., thus preventing contamination. In particular, with regard to Br, several plastics containing more than 1 wt% of Br are mixed in every 1000 pieces. If Br is derived from PBBs or PBDEs, the threshold regulated by the RoHS directive is set. There is a problem of exceeding.

  Moreover, in patent document 2, since it takes tens of seconds to several minutes to measure the presence / absence determination of a flame retardant-specific element, there is a problem that a large amount of plastic cannot be selected. In addition, since sorting is performed only by the presence or absence of flame retardant-specific elements, even if the content is less than 1/10 of the threshold regulated by the RoHS directive, etc., it is sorted out, so the recycling efficiency is poor. There is also a problem of becoming.

  The present invention has been made in order to solve these problems, and by detecting and removing a plastic containing Br having a concentration of more than 1 wt% from the recovered plastic waste material, the recycled plastic material has a high speed and a high recycling efficiency. The object is to provide a sorting method.

  In order to solve the above-mentioned problems, a recycled plastic material sorting method according to the present invention is a recycled plastic material sorting method for sorting materials used for the production of recycled plastics from plastic waste materials, and (a) from plastic waste materials other than plastics Selecting a material and obtaining a desired recovered plastic; and (b) detecting and removing a plastic containing Br of a predetermined concentration or more from the recovered plastic obtained in step (a). Features.

  The present invention, as described in claim 1, in order to obtain a desired recovered plastic, the material other than the plastic is selected from the plastic waste material, and then the recovered plastic obtained by the selection is more than a predetermined concentration, That is, by detecting and removing a plastic containing Br having a concentration exceeding 1 wt%, it is possible to provide a method for selecting a recycled plastic material with high speed and high recycling efficiency.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a recycled plastic sorting step in an embodiment of the present invention. The plastic waste material 1 is obtained through a conventional waste home appliance processing method. The conventional disposal method of waste home appliances is to disassemble collected used refrigerators, washing machines, air conditioners, etc., and to disassemble large metal parts such as compressors, heat exchangers, motors, cases in refrigerators, washing machines The large plastic molded parts such as a water tank, the control board, and the remaining members from which the cords are removed are roughly crushed into a few centimeters to several tens of centimeters by a crusher. The magnetic separator removes magnetic metals such as iron, the eddy current separator removes weak magnetic metals such as aluminum, copper, and stainless steel. When the metal wire is removed, the last remaining one becomes the plastic waste material 1. The plastic waste 1 is mainly composed of plastics such as polypropylene (Polypropylene: PP), polystyrene (Polystyrene: PS), acrylonitrile-butadiene-styrene (Acrylonitrile butadiene styrene: ABS). Foreign substances such as film materials such as seals, foams, metal pieces, metal wires, etc. used for type indications that could not be removed sufficiently due to the above.

  In the fine crushing step 101, the plastic waste material 1 is finely crushed by using a crushing device. The size of the crushed material is preferably 5 mm square or more and 20 mm square or less.

  In the fine crushing step 101, since the time taken for crushing can be shortened by making the crushed material 5 mm square or more, melting and thermal deterioration of the plastic can be prevented. Further, in the subsequent high concentration Br detection step 106, the target plastic is sufficiently large with respect to the X-ray irradiation region (1 mmφ), so that the target plastic can be reliably irradiated. It becomes possible to reliably detect a plastic containing high concentration Br. In addition, by making the crushed material 20 mm or less, the metal, the film-like substance 4, the foam 5 and the like can be sufficiently separated from the plastic member, so that the sorting accuracy in the next and subsequent steps is improved.

  In the magnetic sorting process 102, the magnetic metal 2 such as iron is sorted and removed, and in the eddy current sorting process 103, the weak magnetic metal 3 such as aluminum, copper, and stainless steel is sorted and removed.

  In the wind sorting step 104, lightweight foreign matters such as the film-like substance 4 and the foam 5 are sorted and removed. Further, heavy foreign matters such as metal pieces and metal wires 6 that could not be removed in the magnetic force sorting step 102 and the eddy current sorting step 103 are separated.

  By performing the magnetic force sorting step 102, the eddy current sorting step 103, and the wind force sorting step 104, it is possible to sort and remove foreign objects of metals from the plastic waste material 1 that has undergone the crushing step 101. It can be recovered and reused as a valuable resource. Further, in the wet specific gravity sorting step 105 as a subsequent step, members such as the film-like substance 4, the foam 5, the metal piece / the metal wire 6, which are difficult to be removed due to the adhesion of bubbles and the influence of water flow are removed. Therefore, the sorting accuracy in the wet specific gravity sorting step 105 is improved.

  In the wet specific gravity sorting step 105, the plastic obtained through the above steps is sorted for each material. For example, when sorting and collecting PP, sorting is performed using a liquid having a specific gravity greater than PP and smaller than PS or ABS. Since the specific gravity of PP is 0.9 to 0.91, the specific gravity of PS is 1.04 to 1.06, and the specific gravity of ABS is 1.05 to 1.1, it is necessary to select and collect PP from PS and ABS. It is preferable to use water having a specific gravity of 1. When PS and ABS contained in the remaining PP that have been separated and collected are separated and collected, they can be separated from polyvinyl chloride (PVC), other plastics, and foreign matter, which have a higher specific gravity than PS and ABS. A possible liquid may be used. For example, a saline solution having a specific gravity adjusted to 1.1 to 1.2 is preferable. For the collection, a mesh having a size that does not allow the plastic waste material 1 to pass through is used and dried after the collection.

  By doing this, it is possible to sort plastics with a small specific gravity and plastics with a large specific gravity against the specific gravity of the liquid used for sorting and collection, and to separate other foreign substances, so that it is possible to sort plastic materials with high purity. It becomes possible. The purity of the material of the recovered plastic 8 obtained by the wet specific gravity sorting step 105 was as high as 99% or more for PP.

  In addition, as a wet specific gravity sorting method, a method combining liquid cyclone sorting and flotation / sink sorting is preferable. This combination can prevent plastics having a large specific gravity from being mixed due to the overlap of plastics, air bubbles, and water flow, and can improve the sorting accuracy.

  FIG. 2 is a diagram showing the Br content of recovered PP obtained after material selection in the embodiment of the present invention. When the harmful substances contained in the recovered PP were examined, cadmium, chromium and mercury were not detected. Moreover, although lead was detected from some plastics, the concentration was 100 ppm or less, which was less than 1/10 of the threshold value of the RoHS directive, and was a satisfactory level. However, although the concentration of Br was less than 100 ppm even though it was not detected or detected for most plastics, Br having a concentration exceeding 1 wt% was detected at a ratio of 3 to 5 per 1000 pieces. As described above, if plastics with a very small Br concentration exceeding 1 wt% are mixed, the Br concentration in recycled plastics recycled from these materials exceeds 300 ppm, and this Br becomes PBBs or PBDEs. When it comes from, it exceeds the threshold defined by the RoHS directive and becomes non-compliant with RoHS. The reason why there is a plastic having a Br concentration exceeding 1 wt% will be described below.

  Bromine-based compounds added to plastics include brominated flame retardants for adding flame retardancy. Brominated flame retardants are generally widely used because of their high flame retardant efficiency, and usually 10 to 15 wt% is added to plastics. Since a specific bromine flame retardant has a specific gravity of 1.8 or more, the specific gravity of PP exceeds 1 when the amount added to the plastic exceeds 10 wt%. Therefore, when wet specific gravity sorting is performed with water, it exceeds 10 wt%. PP added with a flame retardant sinks and can be selected from PP containing no brominated flame retardant. However, when the amount of brominated flame retardant added is less than 10 wt%, the specific gravity of PP added with brominated flame retardant may not exceed 1, and when wet specific gravity sorting is performed with water, brominated flame retardant May not be sorted out from PP that does not contain. Even if the amount of brominated flame retardant added is 5 wt%, the concentration of Br contained in recycled plastic will surely exceed 1 wt%. Therefore, only plastic sorting by wet specific gravity sorting is regulated by the RoHS directive. It is difficult to meet the threshold.

  Therefore, in order to examine the content of PBBs and PBDEs, the recycled plastic obtained by the conventional method requires time-consuming, cost, and skillful inspections such as solvent extraction-gas chromatography mass spectrometry. In addition, when PBBs or PBDEs are detected, the entire lot is discarded and the recycling efficiency is significantly deteriorated. On the other hand, when the plastic containing Br having a concentration exceeding 1 wt% is removed from the recovered plastic, the concentration of Br contained in the recycled plastic does not exceed 100 ppm and satisfies the RoHS directive standard.

  From the above, in the process of selecting the plastic waste material 1 for each material, if a process of detecting and removing a plastic member containing Br at a concentration of more than 1 wt% is added, high purity that satisfies the standard of the RoHS directive It is possible to obtain a stable and efficient plastic.

  In the high concentration Br detection step 106, when the recovered plastic 8 contains a high concentration Br exceeding 1 wt%, it is detected, and the high concentration Br-containing plastic 9 is removed. As a detection method, the recovered plastic 8 is irradiated with X-rays, and among the fluorescent X-rays generated from the recovered plastic 8, 11.91 keV BrKα rays, 13.29 keV BrKβ rays, and Compton scattered rays of the X-ray tube target material are used. It is preferable to use an energy dispersive X-ray fluorescence analysis method in which the intensity energy of each 19.39 keV RhKαC ray is detected by a semiconductor detector. A method for determining whether the concentration of Br contained in the recovered plastic 8 exceeds 1 wt% will be described below.

  First, a standard sample containing 1 wt% Br is prepared. For example, decabromodiphenyl ether (DeBDE), which is a Br-containing material, is added to PP containing no impurities so as to have a Br concentration of 1 wt%, followed by kneading and molding. Next, fluorescent X-ray measurement was performed on the standard sample under predetermined conditions, and the detected 11.91 keV BrKα ray, 13.29 keV BrKβ ray, and the Compton scattered ray of the X-ray tube target material of 19.39 keV. The intensity of the RhKαC line was measured. From the measurement results, “the intensity ratio of BrKα line and RhKαC line” and “the intensity ratio of BrKβ line and RhKαC line” are calculated, and each value is stored as a standard value in the memory of the data processing unit. Thus, by using the ratio of the intensity of BrKα ray and BrKβ ray to the intensity of RhKαC ray, correction of the shape and thickness of the measurement sample as generally used in the X-ray fluorescence analysis corresponding to the RoHS directive Can be performed. In addition, by measuring two spectra of BrKα ray and BrKβ ray, it is possible to avoid erroneous determination due to the overlap of fluorescent X-rays of coexisting elements.

  The strength of BrKα ray, BrKβ ray, and RhKαC ray was measured for the recovered plastic 8 that is the object of evaluation under the same conditions as the standard sample, and the “ratio of intensity between BrKα ray and RhKαC ray” and “BrKβ ray” The ratio of the intensity ratio between the RhKαC line and the value of the standard sample stored in the memory in advance is compared. When both values exceed the standard sample value, the Br concentration exceeds 1 wt%. Was determined to be a “plastic containing”.

  In the high-concentration Br detection step 106, the shorter the Br detection time, the larger the number of objects that can be measured, but the detection sensitivity becomes worse and the detectable concentration is limited. Therefore, it is necessary to adjust the detection time so that only PP containing 1 wt% Br is detected. 3 and 4 are diagrams showing an X-ray spectrum of a Br-containing plastic in an embodiment of the present invention. FIG. 3 is a PP containing 1 wt% Br when the detection time is 0.1 seconds, and FIG. 4 is a PP containing 100 ppm Br when the detection time is 0.1 seconds. . From both figures, the spectrum can be confirmed only for PP containing 1 wt% Br by using energy dispersive X-ray fluorescence analysis with a detection time of 0.1 seconds. In addition, although the detection time of Br in the embodiment of the present invention is 0.1 seconds, it may be a time in which only PP containing Br exceeding 1 wt% can be detected.

  5 and 6 are configuration diagrams of a system for sorting out the Br-containing plastic in the embodiment of the present invention. In both figures, the collected plastic 8 is conveyed in the conveyance direction 302 by a conveyance device 301 such as a belt conveyor. The transport device 301 includes an X-ray generation device 303 that irradiates primary X-rays 304 in a direction perpendicular to the transport direction 302, and a detection device 306 that detects fluorescent X-rays 305 at a position facing the X-ray generation device 303. Is provided. The detection result of the detection device 306 is transmitted to the data processing unit 308 via the communication unit 307. If the data processing unit 308 determines that the high-concentration Br-containing plastic 9 has been detected, the high-concentration Br-containing plastic 9 is blown off by the high-pressure air 312 of the air gun 309 and removed. The high-concentration Br-containing plastic 9 blown off is collected in a collection container 310 disposed at a position opposite to the air gun 309, and the other collection plastic 8 is collected in a collection container 311 as plastic that complies with the RoHS directive.

  It is preferable that the conveying device 301 conveys the collected plastics 8 of 5 to 20 mm square arranged at intervals of 20 to 25 mm at a speed of 50 mm / sec. This is because even if the size of the recovered plastic 8 obtained through the material selection step by carrying it at a speed of 50 mm / sec is the smallest 5 mm square, the primary X-ray 304 is 0.1% from the X-ray generator 303. This is because, since irradiation can be performed for seconds, Br can be reliably detected during conveyance at a constant speed without stopping the conveyance device 301, so that conveyance and sorting can be performed simultaneously and efficiency is high. Further, by irradiating the primary X-rays 304 irradiated from the X-ray generator 303 from obliquely above in the direction perpendicular to the conveying direction of the recovered plastic 8, the primary X-rays 304 irradiated on the surface of the recovered plastic 8 are obtained. The adjacent recovered plastic 8 is not irradiated. Therefore, the fluorescent X-ray 305 is not generated from the adjacent recovered plastic 8, and the plastic that does not contain the high concentration Br is prevented from being erroneously removed.

  When the recycled plastic is manufactured using an injection molding machine using the high-purity RoHS-compliant plastic 10 obtained from the above process as a raw material, and the harmful substances of the recycled plastic are evaluated by fluorescent X-ray analysis, cadmium, chromium, mercury Was not detected. Moreover, although lead and Br were detected, both were less than 100 ppm and sufficiently smaller than the threshold value, and it was confirmed that the product complies with the RoHS directive.

  The method for sorting recycled plastic according to the embodiment of the present invention includes at least a fine crushing step 101, a wind sorting step 104, a wet specific gravity sorting step 105, a high concentration Br detection step 106, and a high concentration Br-containing plastic removal step 107. Preferably it is. Further, for example, an electrostatic sorting step or the like may be added.

  From the above, it is possible to prevent contamination of PBBs and PBDEs exceeding the threshold regulated by the RoHS Directive by providing a process for detecting and removing plastic containing high concentration Br exceeding 1 wt% from the recovered plastic 8. This makes it possible to obtain a recycled plastic 10 that complies with the RoHS directive. In addition, since only the plastic containing Br exceeding 1 wt% needs to be detected, the detection time can be reduced to 1/1000 or less of the conventional one, and it is possible to sort a large amount of plastics together with speeding up the detection time. Become.

It is a figure which shows the selection process of the recycled plastic in embodiment of this invention. It is a figure which shows the bromine content of collection | recovery PP obtained after the material selection in embodiment of this invention. It is a figure which shows the X-ray spectrum of the bromine containing plastic in embodiment of this invention. It is a figure which shows the X-ray spectrum of the bromine containing plastic in embodiment of this invention. It is a lineblock diagram of a system which sorts out bromine content plastics in an embodiment of the present invention. It is a lineblock diagram of a system which sorts out bromine content plastics in an embodiment of the present invention.

Explanation of symbols

  1 Plastic waste, 2 Magnetic metal, 3 Weak magnetic metal, 4 Film-like material, 5 Foam, 6 Metal piece / metal wire, 7 Heavy density plastic, 8 Recovered plastic, 9 High concentration Br-containing plastic, 10 High purity RoHS compatible Plastic, 101 Fine grinding process, 102 Magnetic sorting process, 103 Eddy current sorting process, 104 Wind power sorting process, 105 Wet specific gravity sorting process, 106 High density Br detection process, 107 High density Br containing plastic removal process, 301 Conveying device, 302 Transport direction, 303 X-ray generator, 304 primary X-ray, 305 fluorescent X-ray, 306 detector, 307 communication means, 308 data processing unit, 309 air gun, 310 high-concentration Br-containing plastic recovery container, 311 high-purity RoHS compatible plastic Recovery container, 312 high pressure air.

Claims (5)

A recycled plastic material sorting method for sorting materials used in the production of recycled plastic from plastic waste,
(A) selecting a material other than plastic from the plastic waste material to obtain a desired recovered plastic;
(B) detecting and removing plastic containing bromine at a predetermined concentration or more from the recovered plastic obtained by the step (a);
A method for sorting recycled plastic material, comprising: The step (a)
(C) selecting the magnetic metal and other than the magnetic metal by magnetic force, and removing the magnetic metal;
(D) selecting the weak magnetic metal remaining after the step (c) and other than the weak magnetic metal by eddy current, and removing the weak magnetic metal;
(E) The step of selecting the plastic remaining after the step (d) and the non-plastic material by wind power, and removing the non-plastic material;
The recycled plastic material sorting method according to claim 1, comprising: The step (a)
(F) using the specific gravity of the plastic remaining after the step (e), further comprising the step of obtaining the recovered plastic by selecting and removing the plastic having a predetermined specific gravity or more with a liquid, The recycled plastic material selection method according to claim 2. The step (b)
(G) obtaining a standard value for comparison in advance using a sample containing bromine at the predetermined concentration;
(H) detecting a plastic containing bromine having a predetermined concentration or more using the standard value;
The recycled plastic material sorting method according to claim 1, comprising:   The recycled plastic material sorting method according to claim 1, wherein the predetermined concentration is 1 wt%.

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