JP2000202828A - Method for recycling waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover plastic bottles efficiently from waste plastics. SOLUTION: Mixed waste plastics 2 are sorted into solid plastics 2a, lightweight plastics 2b, and small-sized plastics 2c sieved to have a prescribed size or below by an oscillation-repulsion type selector 1. Metals are removed from the solid plastics 2a in a metal selection process 4. Next, the solid plastics 2a' from which metals were removed are sorted into are solid plastics 2a" and lightweight plastics 2d in a wind force selection process 5 in the first stage. Next, the solid plastics 2a" are sorted into bottles 2e and the other heavy objects 2f in a wind force selection process in the second stage to recover the bottles 2e. The recovered bottles 2e are sorted by material in a bottle selection process 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention recovers solid plastics without containing foreign matter in order to reuse plastic wastes (hereinafter referred to as "waste plastics") discharged from general households as resources. It relates to a method of recycling waste plastic.

[0002]

2. Description of the Related Art Many methods for reusing waste plastic discharged from ordinary households have been studied.

As a means for reusing waste plastic, for example, a method of regenerating plastic by converting it into oil has been known. However, in this case, PVC (polyvinyl chloride)
It is necessary to remove chlorine contained in PVDC (polyvinylidene chloride) and the like in advance.

[0004] Also, as a means for recycling waste plastic, a method of using it as a reducing agent for a blast furnace in an ironworks has been developed. However, also in this case, it is necessary to remove chlorine-containing plastics such as PVC and PVDC before use in order to prevent the furnace from being corroded by hydrogen chloride gas.

For example, Japanese Patent Application Laid-Open No. Hei 10-225930 (Japanese Patent Application No. 9-30597) has been proposed as a conventional technique for recycling waste plastic (hereinafter referred to as "prior art 1").

As shown in FIG. 4, in prior art 1, a waste plastic is taken out of a bag by a bag breaking machine 9, and a solid plastic (solid plastic) such as a plastic bottle and a film are removed by a rocking repulsion sorter 1. It is a method of separating into lightweight plastics such as trays and the like and residues.

[0007] The light-weight plastic after separation is used in a crusher 1
5. In a wet separation step including the mixing tank 16 and the separation tank 17, after crushing, the mixture is separated into a chlorine-containing plastic and a chlorine-free plastic.

[0008] After removing metals from the solid plastic by the magnetic separator 10, usually, the alignment device 11, the sensor 12,
The chlorine-containing plastic is separated and removed by the dry sorting process including the information processing device 13 and the sorting device 14,
Solid plastics containing no chlorine are removed.

[0009] According to Prior Art 1, PET in solid plastics, which was conventionally difficult with a wet specific gravity separation method,
(Polyethylene terephthalate) plastic bottles and chlorine-containing plastics (such as PVC) can be separated, and chlorine-containing plastics can be removed efficiently.

As a dry type sorting means for determining useful plastics such as PET by judging the material of a solid plastic separated by a repulsion type sorting machine or for removing a chlorine-containing plastic, for example, JP-A-9-8976
No. 8 proposes an apparatus and the like that sorts bottle-based plastics discharged from homes by material according to the difference in absorption wavelength of near-infrared rays.

[0011]

In order to sort materials by such an optical bottle sorter,
It is desirable to reduce the amount of foreign substances as much as possible and to increase the ratio of bottles before supplying waste plastic to the apparatus.

[0012] However, in the case of general waste collected from general households as plastic-based waste, the quality of the waste is greatly influenced by the form of collection and regional characteristics. Waste plastic in a mixed state collected as general waste (garbage) is divided into solid (solid) plastics, lightweight plastics, and small-diameter plastics sieved into smaller diameters equal to or less than a predetermined value by a rocking repulsion sorter. Is separated into

[0013] Among them, those which are classified as solid plastics are mainly plastic bottles, but in addition, small amounts of films, papers, toys, etc.
Dolls, beverage cans, gas cartridges, kitchen waste, etc. are included. Conventionally, in order to remove these, sorting is usually performed manually, but it is hard work in a bad environment, and improvement of the work is desired.

Accordingly, an object of the present invention is to provide a method for recycling waste plastics, which can efficiently and without human intervention separate plastic bottles from solid plastics separated by a rocking repulsion sorter. To provide.

[0015]

According to the first aspect of the present invention,
The waste plastic in the mixed state was separated by a rocking repulsion sorter into a solid plastic, a lightweight plastic, and a waste plastic recycling method for separating into a small-diameter plastic sieved to a small diameter equal to or less than a predetermined value. The solid plastic is subjected to metal sorting to remove metal,
Next, the solid plastic from which the metal has been removed is subjected to a first-stage wind separation to separate and remove the lightweight plastic mixed in the solid plastic, and then the second-stage wind separation is applied to the solid plastic from which the lightweight plastic has been separated and removed. The present invention is characterized in that bottles are separated from heavy objects other than bottles by performing sorting, and thus the bottles are collected.

According to a second aspect of the present invention, the wind speed in the first stage is set to 4 to 8 m / s,
It is characterized in that the wind speed of the wind power selection in the stage is regulated to 10 to 12 m / s.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for recycling waste plastic according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the mixed waste plastic 2 collected as general waste (garbage) is charged into a bag breaking machine 9 as required, and is taken out of the bag. It is put into the type sorter 1. The rocking repulsion sorter 1
A form sorting type that separates waste plastic into two types, a film type and a solid type (solid plastic), and a three-type sorting type used in the present embodiment that simultaneously sieves through holes provided in a screen. is there. In the present embodiment, it is classified into three types using a three-type sorting type.

As shown in FIG. 1, a waste plastic 2 in a mixed state is put into a swinging repulsion type sorter 1, and a solid plastic 2a mainly composed of bottle plastic is provided on a heavy material side.
However, film-based and tray-based plastics are selected as lightweight plastics 2b on the lightweight side. Further, the small-diameter plastic 2c is sorted out by the sieving effect of the sieve holes set on the repulsion plate.

The separated lightweight plastic 2b is sent to a chlorine-containing plastic removing step 3. As a method for removing the chlorine-containing plastic from the lightweight plastic 2b, for example, a wet specific gravity separation process as shown in FIG. 3 is used. As shown in FIG. 3, the wet specific gravity separation step is a method of removing chlorine-containing plastic by utilizing a difference in specific gravity of plastic, and sedimenting chlorine-containing plastic (PVC and PVDC) having a higher specific gravity than water into water. Only the float is reused as raw material plastic. PE
T has almost the same specific gravity as PVC and PVDC (1.
3 to 1.4) and is discharged together with the chlorine-containing plastic. However, most of the PET is sold in the market as bottles, so it is collected on the solid plastic side. Therefore, in this wet specific gravity separation step, PET is hardly discharged as sediment. Further, PS (polystyrene) has a slightly higher specific gravity than water (about 1.1), but has a large specific gravity difference between PVC and PVDC, so that it can be sufficiently recovered by wet separation using a specific gravity liquid.

The small-diameter plastic 2c is sieved by a hole provided in a screen of a swing repulsion sorter. In the case of applying the repulsion type sorting machine to general waste, the diameter or the representative size of the sieve hole for sieving is optimally about 20 to 50 mm based on experience. Here, the small-diameter plastic 2c sieved with the sieve pore diameter includes metals such as bolts and nuts, glass pieces, ceramic pieces, earth and sand, plastic pieces, and the like. Be disposed of.

The solid plastic 2a is subjected to a metal sorting step 4
Removes metals. In the metal separation step 4, a magnetic separator is used in many cases, and almost 100% of iron is recovered. Also, by using an eddy current type metal sorter,
Non-magnetic metals such as aluminum and copper can be recovered in addition to irons.

FIG. 2 is an explanatory diagram showing a wind separator according to an embodiment of the present invention. In FIG. 2, 18 is a rotary feeder, 19 is a sirocco fan, and 20 is a partition plate. As shown in FIG. 1, from the solid plastic 2a ′ from which the metal has been removed, the solid plastic 2a ′ is subjected to a first-stage wind separation (primary wind separation step 5) using the wind separator 8 shown in FIG. Lightweight objects 2d such as film trays mixed in are removed. The wind speed in the primary wind separation step 5 for separating the light-weight material 2d such as a film tray is preferably 4 to 8 m / s.

Further, the solid plastic 2a ″ from which the light-weight material 2d such as a film tray has been removed is subjected to the second-stage wind separation (secondary wind-selection step 6) to reduce the weight of the light-weight-side bottles 2e and the weight. Since the heavy objects 2f other than the bottles on the object side are separated into toys, shoes, and other contaminants, the bottles can be collected. The wind speed in the secondary wind separation step 6 for separation is preferably 10 to 12 m / s.

Next, the bottles collected in the secondary wind sorting step 6 are separated for each material in a bottle sorting step 7 by a known plastic material judging device. As a method for removing the chlorine-containing plastic from the bottles, for example, a method for determining the material of the plastic based on the wavelength of the near-infrared spectrum can be used.

[0026]

Next, an embodiment of the present invention will be described.

According to the process of the present invention shown in FIG. 1, 1000 kg of mixed waste plastic collected as general waste (garbage) is separated into solid plastic, lightweight plastic, and small-diameter plastic (small-diameter material). The breakdown of solid plastics, lightweight plastics and small-diameter items that have been sorted out includes film trays, bottle plastics, other solid plastics,
The survey was divided into paper cloth, metal, and others. Table 1 shows the results.

[0028]

[Table 1] As shown in Table 1, about 20% of bottle-based plastic (200 kg:
About 85% (168 kg: see B) of that was recovered by the rocking repulsion sorter on the solid plastic side. The rest was recovered on the lightweight plastic side.

Forty selected by the rocking repulsion type sorter
1 kg (see C) of solid plastic is further divided into film tray, bottle plastic, other solid plastic, paper cloth, metal, and others by metal sorting process, primary wind sorting, and secondary wind sorting. Was sorted out. Table 2 shows the results. At this time, the wind speed of the primary wind sorting is 6.5 m / s, and the wind speed of the secondary wind sorting is 11 m / s
Met.

[0030]

[Table 2] As shown in Table 2, the 129 kg (see D) of the bottle-based plastic which is sorted by the secondary wind sorting on the lightweight side is 75% or more of the total weight of 171 kg (see E), and the secondary wind sorting is performed. Of D / (D + F) also exceeded 85%. In addition, the sorted plastic bottle has no foreign matter, and the near infrared ray type plastic material judging device can be aligned and sorted without any problem without manual selection.

[0031]

As described above, according to the present invention, solid plastics can be separated from waste plastics with high accuracy, and the accuracy of pretreatment for material separation of solid plastics by an optical bottle sorter. Is improved,
High-precision material separation becomes possible, and since no labor is required for removing foreign substances, labor saving can be achieved, and thus a useful effect is brought about.

[Brief description of the drawings]

FIG. 1 is a process chart according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a wind power sorter according to the embodiment of the present invention.

FIG. 3 is a process diagram showing a wet specific gravity separation process according to the embodiment of the present invention.

FIG. 4 is a process chart showing an example of a conventional method of recycling waste plastic.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Swinging repulsion sorter 2 Waste plastic 2a Solid plastic 2a 'Solid plastic from which metal was removed 2a''Solid plastic from which lightweight materials such as film trays were removed 2b Film-based plastics 2c Small diameter plastics 2d Film trays etc. 2e Bottles 2f Weight other than bottles 3 Chlorine-containing plastic removal process 4 Metal sorting process 5 Primary wind sorting process 6 Secondary wind sorting process 7 Bottle sorting process 8 Wind sorting machine 9 Bag breaker 10 Magnetic separator REFERENCE SIGNS LIST 11 Normal alignment device 12 Sensor 13 Information processing device 14 Sorting device 15 Crusher 16 Mixing tank 17 Separation tank 18 Rotary feeder 19 Sirocco fan 20 Partition plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 105: 26 (72) Inventor Shigeki Yamazaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Co., Ltd. (72) Inventor Teruo Tachifuku 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. In-house (72) Inventor Toshiro Takuwa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. (reference) 4D004 AA07 AA08 AB03 AC05 BA07 CA08 CA09 CA10 CB02 DA03 DA20 4D021 AA01 AB01 EA10 4F201 AA50 AD03 AD05 AG07 AH55 AR08 BA04 BC01 BC12 BC25 BC37 BP09 BP26 BP31 BQ44 4F301 AA11 AA16 BA01 BF26 BF32

Claims (2)

[Claims] 1. A method of recycling waste plastic in which mixed waste plastic is separated by a repulsion sorter into a solid plastic, a lightweight plastic, and a small-diameter plastic sieved to a small diameter of a predetermined value or less. In the above, the separated solid plastic is subjected to metal sorting to remove metal, and then the solid plastic from which metal has been removed is subjected to a first-stage wind sorting to separate and remove lightweight plastic mixed in the solid plastic. Then, the solid plastic from which the light-weight plastic has been separated and removed is subjected to a second-stage wind separation to separate bottles and heavy materials other than bottles, and thus the bottles are collected. How to recycle waste plastic. 2. The waste plastic according to claim 1, wherein the wind speed of the wind power sorting in the first stage is set to 4 to 8 m / s, and the wind speed of the wind power sorting in the second stage is set to 10 to 12 m / s. Recycling method.