JP2007112028A - Method and apparatus for manufacture of recycle plastic panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture a recycle plastic panel having no camber using a relatively narrow space for processing and to manufacture a recycle plastic panel having sufficient stiffness and nailing resistance as an alternative for wood, by the use of wastes corresponding to 'other plastics' among the general wastes according to the Act of Recycle of Containers as raw material. <P>SOLUTION: The method comprises charging a material based on waste plastics into a melt kneader, feeding the molten material to a reservoir and then injecting the molten material into the mold of a press molding machine and cooling the molded panel gradually in a cooling section. The use of the reservoir improves the bending strength, bending stiffness and impact strength of the panel, and gradual cooling in the cooling section prevents cambering of the panel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a recycling that has physical properties that can be used as a substitute for wood, in particular bending rigidity and resistance to nailing, from waste corresponding to other plastics in general waste that is mainly discarded from households in the Container Recycling Law. The present invention relates to a method and apparatus suitable for manufacturing a plastic panel.

  The total amount of plastic waste is said to be 10 million tons per year, and the huge amount of emissions has caused resource and environmental problems, so polyethylene terephthalate (PET) has been collected and recycled by the Container Recycling Law. However, other plastics in general waste that are most commonly disposed of as household waste are various types such as thermoplastics such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, nylon, polycarbonate, and thermosetting resins. Applicable to applications that require high physical properties as materials for material recycling because it is made of plastic, and in addition, it is contaminated with food and contaminated with foreign materials such as paper such as labels, soil, sand and metal. could not.

  However, while there is a long-awaited development of recycling technology for general waste plastics collected in large quantities, waste plastic materials mainly composed of polyethylene and polypropylene, which have a lower specific gravity than water, are selected, washed, dried, and pelleted. It came to be obtained.

  On the other hand, the demand for wood panels with a thickness of about 10-50mm is increasing due to the increasing demand for architecture, civil engineering, furniture, transport packaging, etc. Is becoming unstable. Therefore, if a recycled plastic panel molded from waste plastic material mainly composed of polyethylene and polypropylene as a raw material can be used as a substitute material for wood panels, it can be said that it is an application development of two birds with one stone.

  However, the sorted waste plastic with a specific gravity smaller than that of water is a mixture of the main components of polyethylene and polypropylene, which are produced and consumed in the largest amount of plastics. In addition, polyethylene and polypropylene are originally different in molecular structure and crystal structure and are incompatible with each other, and the mechanical properties of the mixture are significantly lower than those of a single product. Furthermore, in order to use it as a substitute for wood, it requires appropriate rigidity and nailing resistance. Therefore, it is difficult to obtain recycled plastic that can be used for such applications from the above-mentioned waste plastic. It was done.

  Patent Document 1 listed below describes a method for producing a plate material that can be used as a concrete formwork from waste plastic. However, since this method uses thermosetting waste plastic and waste polystyrene as raw materials, it is necessary to sort thermosetting plastic and polystyrene from waste, and this sorting requires a lot of labor. It is. Furthermore, although it is described that the molding method is compression molding, injection molding, extrusion molding, etc., in the case of raw materials mainly composed of incompatible polyethylene and polypropylene, bending by simply molding by these methods is described. Physical properties such as strength and bending rigidity will be extremely poor. Further, when a panel is molded by compression molding or injection molding, there is a problem that the panel is warped due to non-uniform temperature distribution inside the panel immediately after molding.

Further, Patent Document 2 below discloses a plastic composite panel for a concrete form using a plastic mixture having a specific gravity of 1.0 or less separated from used plastic as a raw material. Since the outer layer is made of foamed plastic and the center layer is made of foamed plastic, it is inevitably lacking in rigidity to be generally used as a substitute for wood. It is described that the molding method is by extrusion molding. In general, when molding a panel-like plastic, an extrusion molding method is used. FIG. 4 is an explanatory diagram when a panel is formed by a conventional extrusion method. The raw material melted and kneaded by the extruder 20 is extruded in a band shape through a mold 21, slowly cooled between a large number of rollers 22, and cut into a panel by a cutter (not shown). In order to obtain a panel, it was necessary to gradually cool a long distance through a roller, and a very large space was required.
Japanese Patent Laid-Open No. 7-124947 JP 2002-322809 A

  The object of the present invention is firstly to enable production of a plastic panel without warping in a relatively small space, and secondly to other plastics in general waste by the Container Recycling Law. It is to be able to manufacture recycled plastics with rigidity and resistance to nailing that can be used as a substitute for wood, using waste as a raw material.

[Claim 1]
The present invention includes a step of charging a raw material mainly composed of waste plastic into a melt-kneader to melt and knead the raw material, a step of feeding the melt-kneaded raw material into a reservoir and storing the raw material in the reservoir, Injecting a raw material into a mold of a press molding machine, a step of press molding the raw material injected by the press molding machine, a step of taking out a panel after molding from the mold and sending it to a cooling unit, In the cooling unit, the method includes a step of gradually cooling the panel while sandwiching and pressing the panel between two cooling plates.

[Claim 2]
Further, the present invention provides the method according to claim 1, wherein the raw material has a specific gravity of 1.0 or less and 4 to 49% by weight (including a limit value) of waste plastic containing 70% by weight or more of polyolefin. A method for producing a recycled plastic panel, which is a mixture of inorganic fillers.

[Claim 3]
Further, the present invention provides the recycled plastic panel according to claim 2, wherein the raw material is a mixture of inorganic fillers by adding a polyolefin composite material containing inorganic fillers. It is a manufacturing method.

[Claim 4]
Further, the present invention provides the method according to claim 1, wherein the raw material has a specific gravity of 1.0 or less and 4 to 49% by weight (including a limit value) of waste plastic containing 70% by weight or more of polyolefin. A method for producing a recycled plastic panel, which is a mixture of an inorganic filler and 2 to 10% by weight (including a limit value) thermoplastic elastomer.

[Claim 5]
Further, the present invention provides the recycled plastic panel according to claim 4, wherein the raw material is a mixture of inorganic fillers by adding a polyolefin composite material containing inorganic fillers. It is a manufacturing method.

[Claim 6]
Further, the present invention is the manufacturing method according to any one of claims 1 to 5, wherein the thickness of the recycled plastic panel is 10 to 50 mm (including a limit value). .

[Claim 7]
The present invention also includes a melt-kneader, a reservoir, a press molding machine, and a cooling unit, wherein the melt-kneader melts and kneads the raw material and feeds the melt-kneaded raw material to the reservoir with a screw. The piston has a piston that moves forward and backward in the cylinder. The raw material fed from the melt kneader is stored in the cylinder by moving the piston backward, and then the piston is advanced to press the raw material into the press molding machine. The press molding machine press-molds the raw material injected into the mold into a panel, and the cooling section has two panels molded by the press molding machine. It is a recycling plastic panel manufacturing apparatus characterized by cooling gradually while pressing between the cooling plates.

  The melt kneader in the present invention may be any of a single screw extruder, a twin screw extruder, a kneader kneader, etc., and the L / D (L is the screw length, D is the screw diameter) of the screw of the kneader is at least 20. It is necessary to have the length necessary for kneading as mentioned above, and it is desirable that there is at least one vent part. Especially, the biaxial extruder and kneader kneader supply resin to prevent thermal oxidation deterioration due to air mixing. It is desirable to enclose the vent portion with nitrogen gas.

  The reservoir in the present invention has a cylinder and a piston that moves forward and backward in the cylinder by hydraulic pressure or the like. If the waste plastic used as raw material is a mixture of polyethylene, polypropylene, other plastics, etc., these different plastics are evenly distributed by transferring the raw material that has been melted and kneaded by the melt-kneader to the reservoir. The panel that has been kneaded and molded is homogeneous and has excellent physical properties.

  The press molding machine according to the present invention is, for example, as shown in Japanese Patent No. 2951944, an inclined press system that uniformly disperses and fills the material in the cavity while controlling the upper die to a predetermined inclination, It is desirable to do. It is desirable that the temperature of the mold be controlled in advance, and the number of raw material inlets should be set as appropriate at appropriate locations such as the bottom and side surfaces of the mold, and the inflow rate should be as short as possible so that cooling is not uneven. It is desirable to carry out in time, and it is desirable to keep cooling until the deformation | transformation and shrinkage | contraction of a shape panel do not occur as much as possible.

  The cooling unit in the present invention is a unit that cools gradually while sandwiching and pressing a panel molded by a press molding machine between two cooling plates. The cooling plate, for example, supplies water to a water passage provided inside. It can be set as the structure which flows. The pressing may be such that the molded panel can be held without warping. If the cooling plate has a sufficient weight, it may be pressed with that weight, and if not, with a suitable pressing means such as a press cylinder. Press.

  The size of the panel targeted by the present invention is not particularly specified, but a width of about 100 mm to 2000 mm, a length of about 500 mm to 4000 mm, and a thickness of about 10 to 50 mm are suitable.

  The raw material used in the present invention can be a waste plastic having a specific gravity of 1.0 or less and 70% by weight or more of polyolefin. Waste corresponding to other plastics in general waste by the Container Recycling Law can be easily obtained by specific gravity separation with water. Waste plastic used by the Container Recycling Law is mainly composed of inexpensive polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, and polyvinylidene chloride, which are manufactured and consumed in large quantities, and other thermoplastic resins. In addition to heat and thermosetting resin, paper, fiber, wood, sand, metals, etc. are also mixed. As a method for separating these wastes, wind separation, magnetic separation, specific gravity separation, filtration separation and the like are performed. In the present invention, specific gravity exceeds 1.0 by performing specific gravity separation with water. PET, thermosetting resin, vinyl chloride, metal and the like are removed, and a waste plastic containing 70% by weight or more of polyolefin mainly composed of polyethylene and polypropylene is obtained. A material obtained by washing and drying the waste plastic as necessary, or pelletizing the waste plastic by a melt-kneading extruder, and further blending a resin for improving processability can be used as a raw material.

  The new polyethylene and polypropylene are rarely blended due to their incompatibility, but the strength is increased when compatibilizers such as ethylene propylene rubber and ethylene propylene terpolymer with both polyethylene and polypropylene structural elements are added. It is known that physical properties such as elongation at break and impact strength can be improved. However, when a compatibilizing agent is added, the rigidity required most for the thick plate molded article is remarkably lowered, so that it cannot be used as a substitute for wood.

  In addition, a novel blend of polyethylene and polypropylene as main components can be filled with an inorganic filler in order to increase the rigidity, but this leads to a decrease in strength and impact strength, and the desired high rigidity and yet still Thus, it has not been possible to obtain a thick plate molded body having a high impact strength and a resistance to nailing which can withstand nailing required for assembling wood.

  However, waste plastic materials with a specific gravity of 1.0 or less (including 70% by weight or more of polyolefin) selected by separation of specific gravity with water from other plastics in general waste by the Container Recycling Law are used for talc and charcoal cal. Surprisingly, recycled plastics formed by a suitable means of a mixture containing an inorganic filler such as a new resin have increased rigidity as well as new polyolefin blends, and at the same time there is almost no decrease in impact strength. As a result, it was found that the addition of an inorganic filler is remarkably effective in improving the physical properties of the recycled material.

  Inorganic fillers have already been added to polyethylene and polypropylene and are widely used in the market as composite materials. The amount of filling is as large as 20 to 60% by weight and is discarded in large quantities. Separation has a higher specific gravity than water, so it is separated separately and currently looking for recycling applications, but when this is filled in the above waste plastic for the purpose of filling with inorganic filler, the rigidity increases at the same time. It was found that the nailing resistance was improved as compared with the case of directly adding an inorganic filler, contributing to the recycling of the composite material, and the low physical properties due to incompatibility could be improved at once.

  In addition, recycled plastics molded with appropriate means by adding thermoplastic elastomers such as styrene-butadiene-styrene block copolymer elastomers (SBS elastomers) and hydrogenated products (SBES elastomers) to these mixtures are rigid. In addition to maintaining the rate, the nailing resistance was significantly improved.

  Typical examples of the inorganic filler used in the present invention include oxides such as silica, titanium oxide, alumina, magnesium oxide, antimony oxide, and pumice, and hydroxides such as magnesium hydroxide, aluminum hydroxide, and basic calcium carbonate. Calcium carbonate, dolomite, etc. as carbonate, calcium sulfate, barium sulfate, etc. as sulfate, talc, clay, mica, glass, calcium silicate, montmorillonite, etc. as silicate, carbon black, graphite, carbon nanotube, etc. as carbon Iron powder, stainless steel powder, etc., and zeolite, borate, etc., with an average particle size of 100 μm or less, and the shape is mostly spherical, but there are also plates, columns, fibers, etc. From the viewpoint of improving physical properties, Wei filler is desirable.

  Examples of the fibrous filler used in the present invention include glass fiber, carbon fiber, aromatic aramid fiber, potassium titanate whisker, silicon carbide fiber, alumina fiber, ceramic fiber, and asbestos fiber.

  In addition, the inorganic filler used in the present invention is added with a titanate coupling agent and a silane or amino coupling agent to improve dispersion in the plastic before adding the inorganic filler. It may be surface-treated, or may be added with a dispersant such as calcium stearate or magnesium, and the addition method may be added when pelletizing the waste plastic and pelletized. It may be inserted at the same time as the addition.

  In addition, many of these inorganic fillers used in the present invention have already been added to polyethylene and polypropylene and used in various applications. However, such plastic and inorganic filler composites can be separated from waste. When added to waste plastic, it was found that the rigidity and anti-nailing performance were improved more than simply adding an inorganic filler.

  This is because the filler is already dispersed in the polyolefin and is familiar with the polyolefin, so it is considered that the filler filling effect and the compatibility effect are fully exhibited. First, it can contribute to the recycling of polyolefin composites. The effect of two birds with one stone can be obtained because the physical properties can be improved against each other.

  The addition of an elastomer in addition to an inorganic filler was particularly effective in improving the resistance to nailing, so the elastomer is described as polyisoprene typified by natural rubber, styrene-butadiene rubber, etc. Rubber materials are also effective, but thermoplastic elastomers are preferred for the present invention.

  Examples of the thermoplastic elastomer used in the present invention include styrene, olefin, vinyl chloride, urethane, ester, amide, isoprene, and fluorine, but styrene, olefin, and isoprene are desirable, Styrenic thermoplastic elastomers are particularly desirable.

  According to the recycled plastic panel manufacturing method and the recycled plastic panel manufacturing apparatus of the present invention, it is possible to manufacture a plastic panel without warping in a relatively small space, and it corresponds to other plastics in general waste by the Container Recycling Law. By using waste as a raw material, a recycled plastic panel having rigidity and resistance to nailing that can be used as a substitute for wood can be manufactured. Recycled plastic panels manufactured according to the present invention are suitable as substitutes for wooden boards, so they have a wide range of uses as civil engineering / building materials, furniture materials, packing materials, materials for cargo handling pallets, etc. This contributes to the promotion of plastic recycling.

  The recycled plastic panel manufacturing method of the present invention can be carried out, for example, by the recycled plastic panel manufacturing apparatus of the embodiment shown in FIGS. In FIG. 1, reference numeral 1 is a melt kneader (single screw extruder, twin screw extruder, kneader kneader, etc.), 2 is a reservoir, 3 is a press molding machine, 4 is a cooling unit, and 5 and 6 are valves. These devices are operated by a control device (not shown).

  The melt kneader 1 melts and kneads the supplied raw materials such as waste plastic and inorganic filler, and sends them to the reservoir 2 by a screw. At this time, the valve 5 is open and the valve 6 is closed, and the reservoir stores a predetermined amount of raw material melted and kneaded in the cylinder 2b as the internal piston rod 2a moves backward. Waste plastic is a mixture of polyethylene, polypropylene, and other plastics. By sending them to a reservoir and temporarily storing them, these different plastics are evenly kneaded, and the molded panel is homogeneous and has excellent physical properties. It becomes. After completion of the storage, the valve 5 is closed and the valve 6 is switched to open, the piston rod 2a moves forward, and the melted and kneaded material is injected into the mold of the press molding machine 3.

  A so-called inclined press type press molding machine 3 shown in FIG. 2 includes a mold (upper mold 8, lower mold 7), a pressure cylinder 10, a sensor 11, and the like, and includes an upper mold 8 and a lower mold 7. The space between them is a cavity 9. The upper mold 8 and the lower mold 7 are temperature-controlled by cooling water, and a raw material inlet is provided at the center of the lower mold 7. The pressurizing cylinder 10 is hydraulic and moves the upper mold 8 up and down and pressurizes the raw material in the cavity 9. Further, the height and inclination of the upper mold are detected by the sensor 11, and a control device (not shown) controls the operation of the left and right cylinders and controls the upper mold in a predetermined inclination while controlling the upper mold. The raw material is uniformly dispersed and filled. After injecting the raw material into the cavity 9, the mold is clamped and held by the pressure cylinder 10, the raw material is cured, and then the upper mold 8 is raised to take out the molded panel. The taken-out panel is sent to the cooling unit 4 by a well-known conveying means such as a roller conveyor, a crane equipped with a suction board, or a robot.

  The cooling device 4 includes two upper and lower cooling plates 12 each having a water passage 13 formed therein, and the upper cooling plate is moved up and down by a cylinder 14. The panel immediately after molding is placed on the lower cooling plate with the upper cooling plate raised, and then the upper cooling plate descends and gradually cools the panel while pressing with the weight of the upper cooling plate. To do. Water whose temperature is controlled to 15 ° C. flows through the water passage 13. It is desirable that the panel is gradually cooled until the interior reaches room temperature. If the panel is 15 mm thick, it takes about 5 minutes. The panel after the slow cooling is transferred to a stock yard (not shown).

  Wastes corresponding to other plastics in the general waste by the container recycling method were separated by specific gravity separation with water to obtain waste plastics having a specific gravity of 1.0 or less and 70% by weight or more of polyolefin. A recycled plastic panel was manufactured by the above-described manufacturing apparatus using a material obtained by adding 30% by weight of a polypropylene composite containing 40% by weight of talc and 5% by weight of a styrene-butadiene-styrene thermoplastic elastomer. The melt kneader 1 is a hydraulic plan in which the kneaded melt is kneaded at 70 mmφ, L / D 40, vent type with a temperature setting of 180 to 220 ° C. and a screw rotation speed of 280 rpm, and a diameter of 250 mm and a length of 850 mm at 220 ° C. Injection into the jar-type reservoir 2 and switching the valves 5 and 6 to a mold having a cavity of 15 mm (thickness) x 600 (width) x 2400 mm (length) with injection pressure and holding pressure of 15 MPa And pressure-holding molding. The molded panel was immediately conveyed to the cooling unit 4 by a roller conveyor and gradually cooled for 5 minutes. As a result, a smooth recycled plastic panel having no warpage was obtained.

The panel was subjected to a bending test in accordance with JIS K 7171 to determine bending strength and bending elastic modulus, and Izod impact strength was determined in accordance with JIS K 7110. In the nail driving test, a thick plate cut into 90 mm × 40 mm is left in a room with a temperature of 20 ° C., and then a roll nail machine is used in a room with a temperature of 20 ° C. Using a mold, the state of fracture of the plate was visually observed, and the number of fractures (number of fractures / number of tests) relative to the number of samples was determined as the nail damage rate. As a result, the bending stiffness is 1 GPa, the Izod impact strength is 4.2 KJ / m ² , which is a level that can be used as a substitute for wood. The hammering was 0/30 and the nailing resistance was sufficient. In addition, this panel could be easily cut with a saw.

  When the raw material is poured directly from the melt kneader into the mold without using the reservoir, the bending strength of the molded panel is reduced by about 30% on average. Further, when the panel immediately after molding was left at room temperature without using a cooling device, warpage of about 20 mm on average occurred.

It is a top view of a recycled plastic panel manufacturing apparatus. 3 is a cross-sectional view of the press molding machine 3. FIG. 3 is a cross-sectional view of a cooling unit 4. FIG. It is explanatory drawing of the panel manufacturing method by extrusion molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melt kneader 2 Reservoir 3 Press molding machine 4 Cooling part 5 Valve 6 Valve 7 Lower die 8 Upper die 9 Cavity 10 Pressure cylinder 11 Sensor 12 Cooling plate 13 Water passage 14 Cylinder 20 Extruder 21 Mold 22 roller

Claims (7)

  A step of charging a raw material mainly composed of waste plastic into a melt-kneader and melting and kneading the raw material, a step of feeding the melt-kneaded raw material into a reservoir and storing it in the reservoir, and pressing the raw material stored from the reservoir In the step of injecting into the mold of the molding machine, the step of press-molding the raw material injected by the press molding machine, the step of taking out the completed panel from the mold and sending it to the cooling unit, A method for producing a recycled plastic panel, comprising the step of gradually cooling the panel while sandwiching and pressing between the two cooling plates.   2. The manufacturing method according to claim 1, wherein said raw material has a specific gravity of 1.0 or less and waste plastic containing 70% by weight or more of polyolefin is mixed with an inorganic filler of 4% by weight to 49% by weight (including limit value). A method for producing a recycled plastic panel, characterized in that   The manufacturing method of Claim 2 WHEREIN: The said raw material mixed the inorganic filler by adding the polyolefin composite material containing an inorganic filler, The recycled plastic panel manufacturing method characterized by the above-mentioned.   2. The manufacturing method according to claim 1, wherein the raw material has a specific gravity of 1.0 or less and a waste plastic containing 70% by weight or more of polyolefin, 4% by weight to 49% by weight (including limit value) of inorganic filler, A method for producing a recycled plastic panel, comprising a mixture of 10% by weight (including a limit value) of a thermoplastic elastomer.   5. The method for producing a recycled plastic panel according to claim 4, wherein the raw material is a mixture of inorganic fillers by adding a polyolefin composite material containing inorganic fillers.   6. The method for manufacturing a recycled plastic panel according to claim 1, wherein the thickness of the recycled plastic panel is 10 to 50 mm (including a limit value).   A melt kneader, a reservoir, a press molding machine, and a cooling unit are provided. The melt kneader melts and kneads the raw material and feeds the melt-kneaded raw material to the reservoir with a screw. The reservoir advances in the cylinder and the cylinder. The piston has a retreating piston, and the raw material fed from the melt kneader is stored in the cylinder by retreating the piston, and then the piston is advanced to put the raw material in the mold of the press molding machine. The press molding machine press-molds the raw material injected into the mold into a panel, and the cooling unit sandwiches the panel molded by the press molding machine between two cooling plates. Recycled plastic panel manufacturing equipment characterized by being gradually cooled while being pressed.

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