JP2004025734A - Method for regeneration treatment of plastic and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the regeneration treatment of a plastic capable of efficiently producing pellets becoming a raw material without lowering the quality of a plastic product, and an apparatus therefor. <P>SOLUTION: The plastic is ground into a small piece state and the obtained small piece like ground material is heated and melted to be molded into a small granular state. The obtained small piece-like molded article is processed into a particulate state and the obtained particulates are subjected to extrusion molding to be formed into a pellet state. The plastics treated by this method are, for example, plastic wastes in which various plastic material are mixed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for reprocessing plastic. Here, the plastics to be treated are various plastic materials forming films, sheets, containers, packaging, and the like. This is plastic waste (hereinafter referred to as "waste plastic") in which various plastics such as food containers and packaging materials that are discharged and collected are mixed.
[0002]
[Prior art]
Generally, such waste plastics are collected as non-burnable waste, but from the viewpoint of shortage of waste disposal sites and effective use of resources, there is a demand for the development of technology to recycle waste plastic as new plastic materials. ing. In the field of such technology, as a method of recycling plastics, the recovered waste plastics are manually separated into the same material as much as possible, then crushed to the extent that they can be easily transported, and then heated and melted with an extruder or the like to form A method for obtaining a desired plastic molded product is known.
[0003]
Plastics include olefin-based plastics such as polyethylene (PE) and polypropylene (PP), styrene-based plastics such as polystyrene (PS), and vinyl-based plastics such as polyvinyl chloride (PVC). Sorting includes removing non-plastic materials such as aluminum foil and paper pieces, as well as plastics other than the desired plastic. That is, it is desirable to remove as much foreign matter as possible, such as plastic, aluminum foil, and paper pieces other than the desired plastic.
[0004]
For example, waste plastics having a specific gravity higher than water settle in water, and those having a specific gravity lower than water use the property of floating on water, so that plastic (PVC, PET, etc.) having a higher specific gravity than water can be used. It can be separated and recovered from plastics (PP, PE, etc.) having a lower specific gravity. However, foreign substances such as aluminum foil and paper pieces with air bubbles may adhere to or become entangled with plastics having a low specific gravity, float on the water surface, and be collected together with those plastics. In that case, foreign materials such as aluminum foil and paper chips are mixed in the collected waste plastic.
[0005]
A great deal of labor and cost is required to remove small foreign matters such as aluminum foil and paper chips mixed in the waste plastic. For this reason, conventionally, without removing these, the waste plastic has been put into an extruder as it is and extruded, for example, to be formed into a lump such as a plate, a rod, a column, or a block, or a sheet. Such a molded product is limited to a specific use that does not cause any particular problem even if foreign materials (for example, relatively large aluminum foil or paper) in which the materials do not melt with each other are mixed therein. And reused.
[0006]
[Problems to be solved by the invention]
Its main use is as a material for molded articles such as pallets, piles, blocks, rods, flowerpots, etc., but it is desired to expand the use without limiting the use as a product. In order to expand this application, it is necessary to use pelletized material as an easy-to-use molding raw material, but in the production of pellets, aluminum foil and paper chips mixed in waste plastic remain without being removed Causes quality deterioration. In particular, if aluminum foil, paper, or the like having a relatively large size is contained in the pellet, the performance of a product formed using the pellet may be reduced.
[0007]
If a screen is installed in the extruder, foreign substances such as aluminum foil can be removed from the waste plastic. However, if a relatively large amount of foreign matter is mixed in the screen, the screen often becomes clogged and the flowability of the melt deteriorates, reducing the amount of extrusion.Therefore, the machine must be stopped and the screen replaced each time. As a result, the operation rate of the machine is remarkably reduced, which causes a problem in production efficiency.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for recycling plastic, which can efficiently produce pellets as raw materials without deteriorating the quality of plastic products.
[0009]
[Means for Solving the Problems]
In the method of the present invention, the plastic is pulverized into small pieces, the obtained small pulverized material is heated and melted to form small particles, and the obtained small particle molded product is processed into fine particles to obtain a fine particle. A plastic recycling method characterized by extruding the obtained fine particles into pellets.
[0010]
The method of the present invention is suitable for reclaiming waste plastic in which various plastic materials are mixed.
[0011]
The apparatus of the present invention comprises means for pulverizing plastic into small pieces, means for heating and melting the obtained small pulverized material to form small particles, and processing the obtained small-grained molded product into fine particles. A plastic recycling processing apparatus comprising: means for processing; and means for extruding the obtained fine particles into pellets.
[0012]
In the apparatus of the present invention, the crushing means is, for example, for crushing the plastic into fluff or flake. Further, in the embodiment of the present invention, the molding means heat-melts and extrudes the plastic processed into small pieces, and extrudes the plastic into small particles. The powder mill and the extruding means for processing into a fine powder are extruders for extruding the molded product processed into the fine powder into pellets.
[0013]
According to the present invention, even if foreign substances such as aluminum foil and paper pieces are mixed in the plastic to be processed, these foreign substances are pulverized together with the plastic, formed into small particles, and then processed into fine particles, Finally, it is extruded into a pellet. In this series of steps, the foreign matter is also processed into fine particles, so that the foreign matter does not hinder the fluidity of the plastic and does not cause clogging of the screen as in the conventional case. Therefore, plastic pellets can be efficiently produced.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing the configuration of an apparatus for carrying out the plastic recycling treatment method of the present invention divided into means for each step.
[0015]
The plastic recycling apparatus 1 according to the embodiment includes a pulverizing step 4 for pulverizing a plastic 2 to be processed including various plastic materials such as collected waste plastics, aluminum foil, and foreign matters such as paper chips into small pieces, and discharging the plastics. And a granulator 8 for heating and melting the fluff or flake plastic supplied from the screw press 6 on the side and extruding the plastic into small granules, and converting the obtained small granules into fine granules. It includes a powder mill 10 for processing and an extruder 12 for extruding the obtained fine particles into pellets.
[0016]
In the pulverizing step 4, for example, a main substance among foreign substances such as plastics other than a desired plastic is manually removed from the collected waste plastic and then pulverized into small pieces. In the illustrated example, the crusher 14, the hand separator 16, the first specific gravity separator 18, the crusher 20, and the second specific gravity separator 22, which are sequentially arranged along the processing flow of the plastic 2, perform the crushing process. 4 is performed.
[0017]
The crusher 14 crushes the plastic 2 such as waste plastic in which various plastics such as collected films, sheets, containers, and packaging are mixed.
[0018]
The hand sorter 16 is configured so that foreign substances such as plastics, aluminum foil, and paper pieces other than the target plastic can be manually removed from the plastics 2 crushed by the crusher 14. Providing a place for coarse separation work where manual sorting is performed.
[0019]
The first specific gravity separator 18 uses a property that a substance having a specific gravity higher than water sediments in water and a substance having a specific gravity lower than water floats on water, thereby using plastic (PVC, PET, etc.) having a specific gravity higher than water. It separates and removes aluminum foil and paper pieces, and collects plastics (PP, PE, etc.) having a lower specific gravity than water.
[0020]
The crusher 20 crushes the plastic 2 collected by the first specific gravity separator 18 further finely.
[0021]
The second specific gravity separator 22 is composed of a foreign material that cannot be separated by the first specific gravity separator 18 from the plastics 2 crushed by the crusher 20, for example, an aluminum foil that has air bubbles or adheres to or entangles with the target plastic. , For separating paper pieces.
[0022]
The small-sized plastic separated by the second specific gravity separator 22 may be directly guided to the granulator 8 of the present apparatus, but it is preferable that the plastic is pressed by the screw press 6 and then guided to the granulator 8. If the plastic 2 contains a large amount of water, bubbles may be generated or the physical properties may be reduced due to the influence of the water. Therefore, the plastic 2 is sufficiently dehydrated before being guided to the granulator 8 and then guided to the granulator 8. It is preferable to do so.
[0023]
The granulator 8 heats and melts the small pieces of plastic supplied from the pulverizing step 4 and extrudes them into small grains. For example, the granulator 8 heats and melts and extrudes fluff or flake shaped plastics. It is composed of an extruder that granulates into granules.
[0024]
When the granulator 8 performs the granulation of the plastic, the extrusion molding is performed stably, and a long residence time is required so that the mixture is sufficiently kneaded. Therefore, when the effective length of the screw is L and the diameter is D, , L / D are about 28 to 34. This is because it is important to knead the plastic well, and if the kneading is insufficient, the extrusion molding becomes unstable.
[0025]
As this type of granulator, for example, a screw extrusion type extruder as shown in FIG. 2 is used. This is a spiral single-screw extruder type granulator, which mainly contains a screw 30 that extrudes from one end to the other while heating and melting and kneading fluff or flake plastic. A case 40, a hopper 42 for introducing the plastic 2 crushed into small pieces as described above into an inlet 41 above one end of the screw case 40, and a hot hopper connected to the other end of the screw case 40. And a cutting device 70.
[0026]
The screw case 40 has a double cylindrical structure including an inner cylinder and an outer cylinder. Between the inner cylinder and the outer cylinder, a band heater 32 as a heater for heating and melting the plastic in the case 40 is provided. It is arranged over the whole area in the direction. It is preferable that a plurality of band heaters 32 are arranged in the longitudinal direction of the case 40 so that the temperature can be individually controlled. The heating zones are, for example, three parts of a supply part a, a melting part b, and a compression part c. Each is heated to about 200 to 230 ° C. by automatic temperature control.
[0027]
The screw case 40 is mounted on the gantry 44 so as to extend in the horizontal direction. A rotating shaft 31 is rotatably provided coaxially in the inner cylinder of the screw case 40, and the plastic 2 put into the case 40 is kneaded on the outer periphery of the rotating shaft 31 from one end to the other end. Is provided.
[0028]
At one end of the screw case 40, a speed reducer (not shown) connected to the rotary shaft 31 is provided, and a driven pulley 48 is provided at a rotary shaft 46 of the speed reducer. A driven belt 56 wrapped around a pulley 54 of a drive shaft 52 of a motor 50 as a drive source is wrapped around the driven pulley 48, and the rotational driving force of the motor 50 is transmitted to the rotary shaft via the drive belt 56 and a speed reducer. It is supposed to be.
[0029]
At the other end of the screw case 40, a support portion 60 is provided. This support part 60 is installed on a stand 61. A through-hole 62 into which the plastic flows from the screw case 40 is provided in the support portion 60. The diameter of the through hole 62 is formed to be smaller than the inner cylinder cross section of the screw case 40. One end of a guide tube 66 that connects the support portion 60 and the entrance to the inside of the hot cut device 70 is connected to the opening 64 at the downstream end of the through hole 62.
[0030]
The hot cut device 70 is for molding the plastic from the screw case 40 into small particles. The main body 72 of the hot-cut apparatus is formed so as to be partitioned vertically along the inside thereof into an inflow section 74 to which the guide tube 66 is connected and a forming section 76.
[0031]
The inflow portion 74 and the molding portion 76 are separated by a die plate 78, and a plurality of extrusion ports 79 having a circular cross section are provided on the die plate 78, and the plastic flowing into the inflow portion 74 continuously flows from the extrusion port 79 into the molding portion 76. It is designed to be extruded. The diameter of the extrusion port 79 is formed so that it is large on the inflow portion 74 side and small on the molding portion 76 side.
[0032]
A motor 80 is provided on an upper portion of a main body 72 of the hot cut device 70, and a rotating shaft 81 connected to a driving shaft of the motor passes through the die plate 78, and a disk-shaped rotating plate 82 is provided at a tip end thereof. Have been. One or a plurality of cutters 84 are attached to the rotating plate 82, and the rotating plate 82 is rotated at a predetermined number of rotations by driving a motor 80, and the plastic extruded from the extrusion port 79 is formed into small particles by the cutter 84. It is designed to be cut.
[0033]
A plurality of cooling water jet nozzles 86 for jetting water to solidify the plastic cut into small particles by the cutter 84 as described above are provided in the molding portion 76 of the hot cut device main body 72.
[0034]
At the lower part of the molding section 76 of the hot cut device 70, a discharge port 88 for discharging the falling small-granular plastic is provided. The bottom wall of the forming section 76 is inclined downward toward the discharge port 88.
[0035]
It is preferable that the granulator 8 forms the heat-melted plastic into small particles having a size suitable for pulverization by a powder mill 10 at the subsequent stage, for example, φ10 mm or less.
[0036]
The powder mill 10 processes the small-granular plastic formed by the granulator 8 so as to be fine, for example, having a diameter of 500 microns or less. As such a processing means, a powder mill having a structure in which pulverization is performed by a commonly used fixed blade and rotary blade, which are well known, is used.
[0037]
As shown in FIGS. 3 and 4, the powder mill 10 includes a mill body 106 and a lid 108, and the mill body 106 and the lid 108 are removably connected by bolts 110.
[0038]
A supply pipe 112 extending in the vertical direction is connected to a substantially central portion of the lid 108. A supply hopper 114 is provided at the upper end, and a predetermined amount of plastic is supplied from a vibration feeder 116 above the supply hopper 114. The hopper 118 of the vibrating feeder 116 is connected to an outlet end of a suction pipe (pumping pipe) 120 for transporting small-sized plastic from the discharge port 88 of the hot cut device 70 in FIG.
[0039]
A rotary shaft (not shown) is rotatably provided on the mill main body 106, and the rotary shaft is rotatably driven by a motor 122 as a drive source via a drive belt 124. A disc-shaped rotating plate (not shown) is fixed to the other end of the rotating shaft, and a circumferential edge of a surface opposite to the side on which the rotating shaft is supported has a circumferential direction. , For example, a ring-shaped rotary blade is detachably fixed by a bolt or the like. The rotary blade is formed so as to be gradually inclined from one end to the other end of the rotary shaft from the inner peripheral edge to the outer peripheral edge when cut along a direction substantially orthogonal to the axial direction of the rotary shaft. . The rotary blade can be rotated at a high speed (3500 to 7000 rpm) by driving the motor 122.
[0040]
At a position of the lid 108 facing the blade of the rotary plate, a fixed blade having substantially the same shape as the rotary blade is provided. That is, when the lid 108 is fixed to the mill body 106, the fixed blade is disposed on the lid 108 so that the outer peripheral edge of the rotary blade and the outer peripheral edge of the fixed blade face each other. The interval between them can be adjusted arbitrarily. Specifically, by setting the interval between the outer peripheral edge blades to 0.01 to 0.5 mm and the interval between the inner peripheral edge blades to 10 mm or less, the shear force between the rotating blade and the fixed blade causes plastic Are atomized to a diameter of 500 μm or less. This atomized plastic falls into the mill body 106 from the gap between the rotary blade and the fixed blade.
[0041]
As shown in FIG. 4, a transport pipe 126 for transporting the finely divided plastic that has dropped and accumulated is connected to a lower portion of the mill body 106, and the transport pipe 126 is connected to a cyclone 128. The cyclone 128 collects fine-grained plastic. A suction tube 132 provided with a suction blower 130 is connected to the cyclone 128, and a suction gas discharge tube 134 is connected to the suction blower 130. The gas discharged from the discharge tube 134 is subjected to dust collection processing. Release to atmosphere.
[0042]
Therefore, the fine-grained plastic dropped and accumulated on the lower portion of the mill body 106 as described above is sent to the cyclone 128 via the transfer pipe 126 by the suction blower 130.
[0043]
As described above, the plastics atomized by the powder mill 10 are collected in the cyclone 128, and foreign matters that are not completely atomized may be mixed therein. For example, a foreign substance such as an aluminum foil or a piece of paper may be atomized by the shearing force between the rotating blade and the fixed blade of the powder mill 10 in a folded state. The size is also greater than the atomized plastic. Further, due to the structure of the powder mill 10, not all of the small-granular plastic is processed into uniform fine particles.
[0044]
In order to remove such foreign matter that is not atomized (including relatively large granular plastic; the same applies hereinafter), a sorting device 24 is provided below the cyclone 128. The sorting device 24 removes foreign matters of a size (unspecified) that may cause clogging in the extruder 12 from the material collected in the cyclone 128 and supplies the extruded plastic to the extruder 12. At the same time, the removed foreign matter is returned to the powder mill 10 again to be atomized.
[0045]
In the illustrated sorting apparatus 24, a vibrating sieve 138 is provided as a means for removing extraneous foreign matter. As described above, a certain amount of fine-grained plastic mixed with foreign substances collected by the cyclone 128 is supplied to the vibrating sieve 138 via the rotary valve 136.
[0046]
The vibrating sieve 138 is, for example, a screen 140 having a mesh shape, and is used to screen an appropriate size (500 μm or less) and an oversize (not specified) size. Specifically, the inside of the sieving machine main body 142 is vertically divided into two parts, a supply part 144 and a processing part 146, by a mesh screen 140 extending in the horizontal direction. An inlet 148 for introducing plastic from the rotary valve 136 is provided at an upper portion of the sieving machine main body 142, and the plastic is supplied from the inlet 148 onto the screen 140 in the supply unit 144.
[0047]
The lower part of the sieving machine main body 142 is supported on a gantry 152 via an elastic member 150 such as a spring so as to be freely vibrated. The pedestal 152 is provided with a vibrator 154 for vibrating the sieving machine main body 142, and the sifting machine main body 142 is vibrated by the vibrating machine 154. And those that are not stipulated.
[0048]
A discharge pipe 156 that discharges extraneous foreign matters remaining on the screen 140 without passing through the screen 140 is connected to the sieving machine main body 142. The discharge pipe 156 is an inlet of a screw conveyor 158 that is a transport device. 160. A conduit 164 connected to the outlet 162 of the screw conveyor 158 is connected to the supply pipe 112 of the powder mill 10 so that extraneous foreign substances can be returned to the powder mill 10 by the screw conveyor 158 and atomized again. Has become.
[0049]
A collection pipe 166 is connected below the sieving machine body 142 to collect plastic of a suitable size that has dropped through the screen 140 to the processing unit 146 and accumulated. By connecting the distal end of the recovery pipe 166 to the hopper 170 of the extruder 12 shown in FIGS. 5 and 6, plastics of an appropriate size (including foreign matter; the same applies hereinafter) can be fed into the hopper 170. Alternatively, as shown in FIG. 4, it is also possible to connect the tip of the collection pipe 166 to the collection container 168 and collect the plastic of an appropriate size in the collection container 168.
[0050]
The extruder 12 extrudes the finely divided plastic into pellets, and may have any structure as long as it can be formed into pellets. In the illustrated example, a spiral single screw type extruder is used.
[0051]
As shown in FIGS. 5 and 6, the screw-type extruder 12 includes a screw case 172 housing a screw 184 that extrudes from one end to the other end while heating and melting the finely divided plastic while kneading it. The case 172 includes a screw conveyor 176 for supplying the above-mentioned atomized plastic to the inlet 174 above one end of the case 172, and a hot cut device 178 connected to the other end of the screw case 172.
[0052]
The screw conveyor 176 is provided at a lower portion of the hopper 170, and supplies the particulate plastic supplied to the hopper 170 to the inlet 174 of the screw case 172 by a predetermined amount.
[0053]
Similarly to the above-described granulator 8, also in the extruder 12, the effective length of the screw is set to L, so that the extrusion molding is stably performed when the plastic is pelletized and sufficiently kneaded. When the diameter is D, L / D is about 28 to 34.
[0054]
The screw case 172 has a double cylindrical structure composed of an inner cylinder and an outer cylinder. Between the inner cylinder and the outer cylinder, a band heater 200 as a heater for heating and melting the plastic in the case 172 is provided. It is arranged over the whole area in the direction. It is preferable that a plurality of band heaters 200 are arranged in the longitudinal direction of the case 172 so that the temperature can be individually controlled. The heating area is, for example, a supply part a, a melting part b, and a compression part c. Each is heated to about 200 to 230 ° C. by automatic temperature control.
[0055]
The screw case 172 is mounted on the gantry 180 so as to extend in the horizontal direction. A rotating shaft 182 is rotatably provided coaxially in the inner cylinder of the screw case 40, and the outer periphery of the rotating shaft 182 is kneaded with the plastic put in the case 172 from one end to the other end. A helical screw 184 that pushes out is provided. The screw case 172 is provided with a plurality (four in the illustrated example) of blowers 202 for cooling the operation when the operation is stopped.
[0056]
At one end of the screw case 172, there is provided a speed reducer 186 to which the rotating shaft 182 is connected, and a driven pulley 190 is provided at the rotating shaft 188 of the speed reducer 186. The driven pulley 190 has a drive belt 198 wound around a pulley 196 of a drive shaft 194 of a motor 192 serving as a drive source. However, it rotates at 80 to 120 rpm, for example.
[0057]
The other end of the screw case 172 is provided with a support portion 206 having a screen 204. The screen 204 ensures that a pellet-shaped plastic consisting entirely of uniform fine particles is obtained. That is, as described above, irregular foreign substances are also mixed in the plastic atomized by the powder mill 10, and even if the foreign substances are removed by the screen 140 of the vibrating sieve 138, the final target fine particles are, for example, “ Since it is less than the minute value of "500 microns", fine particles slightly larger than "500 microns" may pass through the screen 140 of the vibrating sieve 138. Therefore, the extruder 12 is provided with a screen 204 in order to reliably remove nonstandard products from the fine-grained plastic supplied to the extruder 12.
[0058]
The support section 206 provided with the screen 204 is installed on a stand 208. In the support portion 206, a through-hole 210 through which finely divided plastic flows from the other end of the screw case 172 is provided. The diameter of the through hole 210 is formed to be smaller than the inner cylinder cross section of the screw case 172. A cover 212 is detachably connected to a downstream end of the through hole 210 of the support portion 206 by a coupling member (not shown) such as a bolt. The cover 212 has a through hole 214 having the same diameter as the through hole 210 of the support portion 206.
[0059]
The screen 204 is disposed between the other end surface of the support portion 206 and the cover 212 so as to close the through-hole 214, and is disposed in the fine-grained plastic flowing into the through-hole 210 from the screw case 172. When foreign substances having a size (a size that causes clogging by the hot cutting device 178) are mixed, such foreign substances are removed. With the use of the extruder 12, when the fine screen 204 is clogged and the fluidity of the plastic is slightly reduced, or at regular intervals, the cover 212 is removed from the support portion 206 and a new screen 204 is formed. Can be replaced with something.
[0060]
One end of a guide tube 218 that connects the support portion 206 and an entrance into the hot cut device 178 is connected to the opening 216 on the downstream side of the cover 212.
[0061]
The hot cut device 178 is for molding fine-grained plastic supplied from the screw case 172 into pellets. The main body 220 of the hot-cut device is formed so that the inside thereof is vertically divided into an inflow portion 222 to which the guide tube 218 is connected and a forming portion 224.
[0062]
The inflow portion 222 and the molding portion 224 are separated by a die plate 226, and a plurality of extrusion ports 228 having a circular cross section are provided on the die plate 226. It is designed to be extruded. The diameter of the extrusion port 228 is formed such that it is large on the inflow part 222 side and small on the molding part 224 side.
[0063]
A motor 230 is provided at an upper portion of the hot-cut apparatus main body 220, and a rotary shaft 232 connected to a drive shaft of the motor 230 penetrates the die plate 226, and a disk-shaped rotary plate 234 is provided at a tip end thereof. ing. One or a plurality of cutters 236 are attached to the rotating plate 234, and the rotating plate 234 is rotated at a predetermined number of rotations by the driving of the motor 230, and the plastic extruded from the extrusion port 228 is pelletized by the cutter 236 (see FIG. (φ2 to 8 mm).
[0064]
A plurality of cooling water jet nozzles 238 for jetting water and solidifying the plastic cut into pellets by the cutter 236 as described above are provided in the forming part 224 of the hot cut device main body 220.
[0065]
A discharge port 240 for discharging the falling pellet-shaped plastic is provided at a lower portion of the molding section 224 of the hot cut device main body 220. The bottom wall of the forming part 224 is inclined downward toward the outlet 240.
[0066]
As shown in FIG. 6, the outlet 240 is connected to a conduit 244 that guides the pellet-shaped plastic to the dehydrator 242.
[0067]
The dehydrator 242 is for dehydrating pellet-shaped plastic, and may be of any type capable of dehydrating. For example, a centrifugal dehydrator is used.
[0068]
A vibrating sieve 246 as a sorter is connected to a discharge port for discharging pellet-shaped plastic dehydrated in the dehydrator 242.
[0069]
The vibrating sieving machine 246 is for sieving the pellets having an appropriate size (φ2 to 8 mm) and the pellets having an oversize (not specified). ８8 mm) are collected in a collection container 248, from which they are fed to a flexible container 252 (FIG. 1) via a pressure feeding duct 250, where they are bagged.
[0070]
When the collected plastic 2 is processed using the plastic recycling apparatus 1 of the present embodiment, first, unnecessary foreign substances such as plastic, aluminum foil, and paper pieces are removed from the plastic 2 by the pulverizing step 4. The plastic 2 is crushed.
[0071]
Specifically, as shown in FIG. 1, the plastic 2 is finely crushed by a crusher 14, and then a foreign material such as a plastic other than the desired plastic, aluminum foil, and a piece of paper is roughly separated by a hand sorter 16. Then, after being separated by a specific gravity by a first specific gravity separator 18 and further finely pulverized by a pulverizer 20, foreign substances such as plastics, aluminum foil, and paper pieces other than the desired plastics are separated by a second specific gravity separator 22. Separated by The separated plastic is pressed by the screw press 6, and when it contains a large amount of water, is sufficiently dehydrated before being guided to the granulator 8.
[0072]
In the granulator 8 shown in FIG. 2, the plastic 2 is put into the screw case 40 from the hopper 42. By the drive of the motor 50, the rotation shaft 31 is rotationally driven via the drive belt 56 and the speed reducer, the screw 30 is rotated, and the plastic 2 is transferred and heated and melted by the heater. It is fed in, formed into small particles as described above, and discharged.
[0073]
Specifically, in the granulator 8, the input amount: 200 to 250 kg / h, the water content: 10 to 20%, the screw rotation speed: 100 to 120 rpm, the heater setting temperature: 200 to 230 ° C, and the L / D: At about 28 to 34, the plastic 2 is granulated.
[0074]
As shown in FIG. 4, the plasticized particles (for example, having a particle size of 10 mm or less) formed as described above are sucked by a suction air stream from a discharge port 88 of the granulator 8 through a suction pipe 120 to a hopper 118. And supplied from the vibration feeder 116 to the supply hopper 114 of the powder mill 10 by a predetermined amount.
[0075]
In the powder mill 10, the rotating blade is rotated at, for example, 3500 to 7000 rpm via the drive belt 124 by the driving of the motor 122, and small-grain plastic is deposited in a clearance formed between the rotating blade and the fixed blade. It enters and is atomized into powder (500 μm or less in diameter) by the shearing force between the rotating blade and the fixed blade.
[0076]
The atomized plastic falls into the mill body 106 from the gap between the rotary blade and the fixed blade. Then, the accumulated fine-grained plastic is guided to the cyclone 128 via the transport pipe 126 and collected. A certain amount of plastic collected in the cyclone 128 is supplied to the screen 140 of the supply unit 144 of the vibrating sieve 138 by the rotary valve 136, and the main body 142 of the vibrator is vibrated by the vibrator 154, so that the proper size (500 microns or less) is obtained. ) And oversized (not specified).
[0077]
That is, the oversized (unspecified) one cannot pass through the screen 140, is guided from above the screen 140 to the screw conveyor 158 via the discharge pipe 156, is returned from the screw conveyor 158 to the powder mill 10, and is again finely divided. Be converted to
[0078]
On the other hand, the appropriate-size (fine-grained) plastic that has passed through the screen 140 and dropped and accumulated in the processing unit 146 is supplied to the hopper 170 of the extruder 12 shown in FIG. You. Then, the screw conveyor 176 supplies a predetermined amount of the finely divided plastic from the inlet 174 to the screw case 172 of the extruder 12.
[0079]
In the extruder 12, the driving of the motor 192 causes the screw 184 to rotate (for example, at 80 to 120 rpm) via the drive belt 198 and the speed reducer 186, and is heated by the band heater 200 (for example, 200 In a molten state, it flows into the through-hole 210 of the support part 206 via the supply part a, the fusion part b, and the compression part c. Then, the plastic made of only uniform fine particles that have passed through the above-described screen 204 is continuously extruded through the guide tube 218 to the inflow portion 222 of the hot cut device 178.
[0080]
The plastic that has flowed into the inflow section 222 is extruded from the extrusion port 228 to the molding section 224, and cut into pellets (φ2 to 8 mm) by a cutter 236 that is rotated by driving a motor 230. The plastic cut into pellets by the cutter 236 is solidified as pellets by the water jetted from the cooling water jet nozzle 238, and falls into the lower part of the forming part 224.
[0081]
The plastic pellets thus obtained are dewatered by a dehydrator 242 through a discharge port 240 of a hot cut device 178 via a conduit 244 shown in FIG. 6, and then over-sized and oversized by a vibrating sieve 246. (Not stipulated). Then, the pellets of the appropriate size are collected in the collection container 248, and are sent therefrom to the flexible container 252 via the feed duct 250 under pressure and packed in bags.
[0082]
As described above, according to the embodiment, even if a foreign substance such as an aluminum foil or a paper piece is mixed in the plastic 2 crushed into a small piece, the plastic 2 which is heated and melted by the granulator 8 to be formed into a small particle. At the same time, the foreign matter is also atomized by the powder mill 10 and supplied to the extruder 12, so that the extruder 12 is reliably supplied with the finely divided material. Thereby, the clogging of the screen in the extruder 12 is reduced as much as possible. In other words, in a series of steps from the granulator 8 to the extruder 12, the foreign matter is also processed into a fine powder, so that the mixture of the foreign matter does not hinder the flowability of the plastic, The frequency of clogging is greatly reduced than before. As a result, the production efficiency of plastic pellets is greatly improved.
[0083]
Further, since the pellets obtained by extrusion molding with an extruder are plastic materials having uniform fine particles, the use of molded articles made of the pellets can be expanded, and the industrial value is high.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a plastic recycling apparatus according to the present invention.
FIG. 2 is a partial sectional view showing an example of a granulator.
FIG. 3 is a front view showing an example of a powder mill.
FIG. 4 is a diagram showing a relationship between a powder mill and a vibrating sieve.
FIG. 5 is a partial cross-sectional view illustrating a configuration example of an extruder.
FIG. 6 is a configuration diagram showing an example of an extruder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plastic recycling processing apparatus, 2 ... Plastic, 4 ... Pulverizing process, 8 ... Granulator, 10 ... Powder mill, 12 ... Extruder, 24 ... Sorting apparatus.

Claims (7)

Crush the plastic into small pieces,
The obtained small crushed material is heated and melted to form small particles,
The resulting small-granular molded product is processed into fine particles,
A plastic recycling method characterized by extruding the obtained fine particles into pellets. 2. The plastic recycling method according to claim 1, wherein the plastic is a plastic waste in which various plastic materials are mixed. Crushing means for crushing the plastic into small pieces,
Forming means for heating and melting the obtained small flakes to form small particles,
A processing means for processing the obtained small-granular molded product into fine particles,
An extruder for extruding the obtained fine particles into pellets. 4. The plastic recycling apparatus according to claim 3, wherein the crushing unit crushes the plastic into fluff or flake. 5. The plastic recycling process according to claim 4, wherein the molding means is a granulator for heating and melting the fluff-processed plastic, extruding the plastic, and molding the plastic into small granules. apparatus. The plastic recycling apparatus according to claim 5, wherein the processing means is a powder mill configured to process the small-granular molded product into a fine powder. 7. The plastic recycling apparatus according to claim 6, wherein said extruding means is an extruder for extruding said fine powder-processed product into pellets.

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