JP2006130756A - Manufacturing method of raw material pellet for material recycling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of raw material pellets for material recycling using a waste plastic as a recycling raw material which enables the stable manufacture of pellets for utilizing the waste plastic as the recycling raw material to enable the production of a plastic recycled product having good surface properties. <P>SOLUTION: In the manufacturing method of the raw material pellets for material recycling from the waste plastic characterized in that a dechlorinated waste plastic of which the chlorine content is reduced to 0.4 mass% or below is obtained from the waste plastic and melted to manufacture the pellets, it is desirable that the dechlorinated waste plastic with a chlorine content of 0.4 mass% is obtained by separating and removing a chlorine-containing plastic from the waste plastic and granulated to be melted to manufacture the pellets. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pretreatment technique for recycling and recycling waste plastic, and in particular, a method for producing material recycling raw material pellets suitable for recycling general waste plastics subject to the Containers and Packaging Recycling Law. About.

  Chemicals that use the chemical properties of plastics, such as recycling waste plastics (used plastics) for effective use of resources, heat recovery, thermal recycling using plastics as fuel for power recovery, and reducing agent for blast furnaces Recycling, material recycling (material recycling), etc. that are used as plastic materials and recycled as plastic products are performed.

General waste plastics discharged from general households are contaminated with foreign substances such as food, etc. in addition to plastics, such as foods, metals, dust, and paper. It is desirable to do. When thermal recycling or chemical recycling is performed, recycled products are used after being burned or pyrolyzed, so it is not always necessary to remove the odors that cause odors. When waste plastic is regenerated as pellets for wide use as a material recycling raw material, it is desirable to recycle as pellets that do not contain contamination or moisture. In order to remove waste plastic contamination and reuse it, a technique (for example, refer to Patent Document 1) for cleaning the waste plastic with water or a water-added surfactant or the like, or spraying water vapor is used. A technique (for example, refer to Patent Document 2) for cleaning by this is known. The waste plastic that has been subjected to foreign matter removal and cleaned is heated and melted to be pelletized and used as a material recycling raw material.
JP 2001-252924 A JP 2003-251627 A

  However, even when the waste plastics from which contamination and moisture have been removed after performing the cleaning process as described in Patent Document 1 and Patent Document 2 and drying as necessary, bubbles are generated during pellet production. As a result, it may be difficult to produce pellets. In addition, even when pellets can be manufactured, when manufacturing plastic products (material recycled products) using the manufactured pellets, irregularities are generated on the surface of the product due to the generation of bubbles, resulting in good surface properties. There is a problem that it is difficult to manufacture plastic products.

  Therefore, the object of the present invention is to solve such problems of the prior art and to stably produce pellets for using waste plastic as a recycling raw material, thereby producing a plastic recycled product having a good surface property. Another object of the present invention is to provide a method for producing material pellets for material recycling using waste plastic as a raw material.

The features of the present invention for solving such problems are as follows.
(1) A method of manufacturing material recycling raw material pellets from waste plastic, wherein the waste plastic is melted as a dechlorination waste plastic whose chlorine content is 0.4 mass% or less in advance. A method for producing a raw material pellet for material recycling, which comprises producing a pellet.
(2) The method for producing raw material pellets for material recycling according to (1), wherein the chlorine-containing plastic is separated and removed from the waste plastic to make the chlorine-free waste plastic with a chlorine content of 0.4 mass% or less. .
(3) The method for producing raw material pellets for material recycling according to (1) or (2), wherein the dechlorinated waste plastic is granulated and then melted to produce pellets.

  ADVANTAGE OF THE INVENTION According to this invention, the raw material pellet for material recycling of the stable quality can be manufactured, without producing a bubble when manufacturing the pellet which uses waste plastic as a raw material. Moreover, if the raw material pellet for material recycling of the present invention is used, a plastic recycled product having a good surface property can be produced. This promotes the recycling of waste plastic.

  When the present inventors manufacture plastic products using pellets manufactured using waste plastic as a raw material, the manufactured pellets may contain bubbles, and using such pellets, for example, plastic boards As a result, it was found that a product with an uneven surface was produced. Then, considering the cause of bubbles in the pellets is the chlorine contained in the waste plastic, the chlorine content of the waste plastics is investigated, and the generation of bubbles in the pellets is suppressed by keeping the chlorine content below a predetermined value. Thus, the present invention was completed by finding that a plastic recycled product having a good surface property can be produced. That is, a method for producing material recycling raw material pellets from waste plastics, wherein the waste plastics are previously dechlorinated waste plastics having a chlorine content of 0.4 mass% or less, and the dechlorinated waste plastics are melted and pelletized Is a method for producing raw material pellets for material recycling.

  Waste plastic is used plastic, usually a mixed state of multiple types of plastics, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC) ) And polyvinylidene chloride (PVDC). The present invention can be applied to plastic waste such as industrial waste plastic in addition to general waste plastic which is waste from general households.

  In order to remove the chlorine contained in the waste plastic in order to reduce the chlorine content of the waste plastic to 0.4 mass% or less, it is desirable to use a method of separating and removing the chlorine-containing plastic. By separating and removing chlorine-containing plastics such as PVC and PVDC from the waste plastic, the chlorine content of the waste plastic can be reduced. As a technology for separating and removing chlorine-containing plastics such as PVC and PVDC from waste plastics, the waste plastics are thrown into liquids such as water using the high specific gravity of chlorine-containing plastics, and the floatation and sedimentation is sorted by specific gravity difference. A wet specific gravity difference sorting technique is known. It is also known that low specific gravity plastic and high specific gravity plastic can be separated with high precision by centrifuging waste plastic using a centrifuge that rotates a container filled with water and waste plastic. ing. In addition, it is possible to dechlorinate the waste plastic by heating it, so that the waste plastic becomes dechlorinated waste plastic.

  In order to melt the waste plastic into pellets, it is appropriate to use a melt extrusion granulation method using a molten resin extrusion apparatus having an extrusion mechanism. Waste plastic can be melted and kneaded using an extrusion device, etc., then extruded and cooled linearly from a die hole using a pelletizer, etc., and granulated by cutting it to an appropriate length in the length direction. . If the waste plastic contains chlorine exceeding a predetermined concentration, chlorine gas is generated when the waste plastic is heated and melted in the melt-extrusion apparatus, and bubbles are generated in the pellets due to this. The predetermined concentration varies depending on the heating temperature and the production line speed during pellet production, but if the chlorine concentration of the waste plastic is 0.4 mass% or less, the amount of bubbles in the pellet will not be a problem, and it will be recycled. The surface properties are not deteriorated during the production. Although a degassing mechanism is usually installed in a molten resin extrusion device, etc., only a part of the device can be evacuated, so it is difficult to degas sufficiently, and degassing may be performed for a long time. It is not realistic in terms of production efficiency.

  In addition, when the chlorine concentration of the waste plastic is high, the moisture content also increases during pellet production. This is because the deaeration process is performed by the melt extrusion apparatus as described above, and at this time, open pores are generated near the pellet surface, and when the melt-kneaded plastic is extruded into water and cooled, the open pores are formed. This is because a certain bubble absorbs moisture. Moisture in the pellet causes bubbles when the recycled product is manufactured using the pellet. For example, if the moisture content of the raw material pellets exceeds about 0.5 mass%, it may be difficult to produce a plastic board with good surface properties. Therefore, by reducing the chlorine content of the waste plastic, the water content of the pellets produced can be reduced. Therefore, if the method of the present invention is applied when using a pellet manufacturing method that performs water cooling, material recycling Pellets that are very suitable for use as raw materials can be produced.

  Before the waste plastic from which chlorine has been removed is melted and pelletized, it is desirable to perform a granulation treatment. By granulating waste plastic, handling becomes easier and productivity is improved. As a method for granulating the waste plastic, it is desirable to use a compression molding granulation method or a semi-melt granulation method. In the compression molding granulation method, the waste plastic is granulated by compressing and extruding from a ring die hole having a plurality of die holes penetrating the entire circumference. For example, a compression molding apparatus including a ring die having a plurality of die holes penetrating the entire periphery thereof, and a rolling roller that is rotatably disposed in contact with the inner peripheral surface of the ring die inside the ring die The waste plastic thrown into the ring die is pressed into the die hole of the ring die while being compressed and crushed by the rolling roller with the inner peripheral surface of the ring die, and passes through the die hole. Then, the plastic molded product extruded to the outer surface side of the ring die is cut or scraped off from the outer surface of the ring die to obtain a granular plastic molded product. A plastic molding (granular material) is obtained mainly by at least a part of the waste plastic being semi-molten or melted by frictional heat in the die hole and then solidified. In the semi-melt granulation method, waste plastic is crushed by a rotating crushing blade and the like, and at the same time, the plastic is semi-molten or melted by frictional heat or external heating, and then cooled by spraying with water to form granular plastic. This is a granulation method. Since this granulation method is a batch process, the processing efficiency (productivity) is low, and since water is used for cooling, a post-drying process is necessary. The granularity of the granular plastic obtained by the processing conditions and plastic input varies. There are drawbacks such as

  Next, a specific embodiment of the present invention will be described.

  An example of producing pellets by removing foreign substances other than plastic from waste plastic, separating the film-like plastic and setting the chlorine content to a predetermined concentration or less is shown below. In many cases, waste plastics are usually collected by local governments and crushed and solidified into a bale product. In this case, the bale product is first crushed. Next, the foreign matter is removed from the waste plastic. Various methods are known for removing foreign substances. For example, using a rocking sorter, waste plastic can be removed from heavy (solid plastic), small-diameter (metal pieces, wood chips, etc.) and lightweight (film-based). Separation into plastics) enables separation of film plastics and tray plastics, which are mainly polyolefin plastics as lightweight materials, and removes solid plastics and metals such as pet pots as heavy and small-diameter products. It is. Subsequently, the chlorine-containing plastic is removed from the film-type plastic, which is a lightweight material, and the chlorine content is reduced to a predetermined amount or less.

  Figure 1 shows how waste plastic is separated into solid plastic and film plastic, and plastics containing chlorine are separated and removed by using the light specific gravity (floating matter) of the film-based plastic to water. It is explanatory drawing which shows the case where it pelletizes and it uses as a recycled raw material.

  Waste plastics brought in as a bale 1 from the local government are crushed by a crusher 2 and separated into a solid plastic 4 and a film plastic 5 by a plastic type sorting device 3. At the same time, metal pieces, wood chips 6 and the like are removed. This plastic kind sorter 3 is constituted by the above-mentioned swing sorter, for example. The film-based plastic 5 is further crushed by a crusher 8 after further removing irons by a magnetic separator, and is conveyed to a pulverizer 10 and pulverized by an air feeding step 9.

  The pulverized film plastic is put into a specific gravity separator (centrifugal separator) 14. The specific gravity separation device (centrifugation device) 14 is a step of separating waste plastics by a specific gravity difference using a liquid as a medium, and foreign matters and chlorine-containing plastics are removed as sediments. The floated material of the specific gravity separator (centrifugal separator) 14 is mainly waste plastic that does not contain chlorine. This is granulated by a granulator 17 (an apparatus using a compression molding granulation method) and stored in a storage tank 18. To make a pellet raw material.

  The dechlorinated waste plastic granulated as described above is pelletized by using the same equipment as that for producing pellets by melt-extruding ordinary resins. FIG. 2 shows an embodiment of the pellet manufacturing facility. In FIG. 2, the pellet manufacturing facility includes a motor 21 that rotates a screw (extrusion mechanism) of the extrusion device, a speed reducer 22, an extrusion device cylinder 23 that melts waste plastic (granulated material), and a vacuum that exhausts the inside of the extrusion device. The exhaust pump 24, a screen changer 25 for removing foreign matter, a gear pump 26 for adjusting the inlet pressure of the pelletizer, a joint 27 for connecting each device, and a pelletizer 28 for producing pellets by extrusion. The extruder cylinder 23 has a screw and has a shape suitable for feeding, crushing, kneading, degassing, and pressurizing plastic. The waste plastic thrown into the extruder cylinder 23 is fed into the inside by a screw, finely crushed and melted by frictional heat generated in the kneading process, and a part of the gas generated at the time of melting is exhausted by a vacuum exhaust pump 24. Then, it is pressurized and discharged toward the pelletizer 28. In the pelletizer 28, a die having a predetermined diameter is used to extrude molten plastic into water and cut into a predetermined length to produce pellets.

  When the chlorine-containing plastic is appropriately removed by the specific gravity separator 14 and the chlorine content of the waste plastic is set to 0.4 mass% or less, a large amount of bubbles are not generated in the extruder cylinder 23 during pellet production. Good quality pellets can be produced. When a plastic product is manufactured using the pellets manufactured in this way, a product having a good surface property can be manufactured without generating irregularities on the surface of the plastic product due to bubbles.

  As waste plastics, plastic panels were manufactured using wastes that can be recycled from containers and packaging from ordinary households, which are a mixture of various types of plastics and foreign materials. The waste plastic was subjected to the same pretreatment as that shown in FIG. 1 to reduce the chlorine content. As a plastic type sorting device 3, sorting is performed by utilizing the fact that the repulsion trajectory varies depending on the weight, shape and hardness of the object when the object to be sorted is put on the inclined rebound plate attached to the crankshaft and swinging. An oscillating sorter was used. The film-type plastic crushed to a width of 60 mm or less and a maximum length of 300 mm by a crusher was further crushed to about 18 mm by a crusher. The crushed film plastic was processed by a centrifugal separator that performs specific gravity separation using water. The input to the centrifugal separator 14 had a chlorine concentration of 2.0%, whereas the levitated material 16 had a chlorine concentration of 0.3%. The floated material 16 was further dried with hot air, and then granulated into a predetermined shape (cylindrical shape having a diameter of 6 mm and a length of about 10 mm) by a granulator. The granulated product is melt-kneaded using the same pellet manufacturing equipment (having two screws) as shown in FIG. 2, extruded into water, cut, and cylindrical pellets having a diameter of 3 mm and a length of 4 mm. When a plastic panel was produced using this pellet as a raw material, a product with a high surface flatness could be produced.

  Next, when a large amount of waste plastic was put into the centrifuge at once and processed, the chlorine concentration of the manufactured granulated product increased to 0.5%. When this granulated material was melted to produce pellets, bubbles were generated, and it was difficult to sufficiently degas in the extruder cylinder, making it difficult to stabilize the production conditions. Bubbles were generated in the produced pellet, and the water content was 0.7 mass%. When trying to manufacture a plastic panel using the pellets manufactured in this way, it is difficult to stabilize the manufacturing conditions because gas is generated when the pellets are melted, and the surface of the manufactured plastic board A large number of irregularities were generated.

Explanatory drawing of the process of pelletizing waste plastic. Schematic which shows one Embodiment of pellet manufacturing equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material bale 2 Crusher 3 Plastic kind sorter 4 Solid plastic 5 Film type plastic 6 Foreign material 8 Crusher 9 Air supply pipe 10 Crusher 14 Specific gravity separator 17 Granulator 18 Reservoir 21 Motor 22 Decelerator 23 Extruder cylinder 24 Vacuum pump 25 Screen changer 26 Gear pump 27 Fitting 28 Pelletizer

Claims (3)

  A method for producing material recycling raw material pellets from waste plastics, wherein the waste plastics are previously dechlorinated waste plastics with a chlorine content of 0.4 mass% or less, and the dechlorinated waste plastics are melted to produce pellets. A method for producing raw material pellets for material recycling.   The method for producing material recycling raw material pellets according to claim 1, wherein the chlorine-containing plastic is separated and removed from the waste plastic to obtain a chlorine-free waste plastic having a chlorine content of 0.4 mass% or less.   3. The method for producing material recycling raw material pellets according to claim 1, wherein the dechlorinated plastic is granulated and then melted to produce pellets.

Images