Plastic-based material and method of manufacturing plastic-based material

Abstract

To provide a technology that can enhance the reaction in a low-temperature gasifier when old polyester fiber cloth is chemically recycled.SOLUTION: The plastic-based material 41 shown in Figure 6(e) consists of old polyester fiber fabric 13 and styrene foam 17, as shown in Figure 6(f), with the old polyester fiber fabric 13 locally joined to each other by styrene foam 17. Gas can pass between the old polyester fiber cloth and the adjacent old polyester fiber cloth. The passage of gas facilitates the reaction in the low-temperature gasifier.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a plastic material to be fed to a gasifier and a method for producing the same. [Background technology]

[0002] The reuse of waste plastics has been legalized and strongly promoted. There are three known methods for reusing waste plastics: material recycling, chemical recycling, and thermal recycling.

[0003] Material recycling is a processing method in which, for example, PET bottles are crushed into pellets and then the pellets are used as raw material to mold PET bottles. Chemical recycling is a processing method in which waste plastics are fed into a gasification furnace and subjected to thermal and chemical processing to obtain a synthesis gas containing carbon monoxide and hydrogen as main components. Thermal recycling is a processing method in which waste plastic is crushed, solidified, and turned into solid fuel, for example.

[0004] According to the Basics of Plastic Recycling (published by the Plastic Waste Management Institute in 2022), when the total processing volume of the above three recycling methods is 86%, "material recycling" accounts for 21%, "chemical recycling" for 3%, and "thermal recycling" for 62%.

[0005] Plastics are made from petroleum, which is made up of carbon and hydrogen. Chemical recycling, which produces hydrogen and carbon monoxide, can be said to be more preferable than thermal recycling and material recycling, because it can return most of the waste plastic to petroleum. For this reason, various gasification facilities for carrying out chemical recycling have been proposed (see, for example, Patent Document 1 (FIG. 1)).

[0006] Patent Document 1 will be explained with reference to the following figure. FIG. 9 is a schematic diagram of a conventional gasification facility. Waste 102 is stored on the moving bed 101 . The waste 102 includes municipal waste, solid fuel (RDF), slurry fuel, waste plastic, waste FRP (fiber reinforced plastic), biomass waste, automobile waste, low-grade coal, and the like (Patent Document 1, paragraph 0024).

[0007] The waste 102 is fed via a conveyor 103 into a raw material hopper 104, from which it is fed into a raw material lock hopper 105, from which it is fed into a raw material feeder hopper 106, and from which it is fed into a raw material feeder 107.

[0008] Waste 102 is fed from a raw material feeder 107, the flow rate of which is measured by a flowmeter 108, and fed into a raw material feeder 109, which feeds the waste into a low-temperature gasifier 110. In the low-temperature gasifier 110, the main elements are a fluidized bed 111 and the blown-in oxygen b and steam c, and the waste 102 reacts with the oxygen and steam while in contact with sand maintained at 500-850°C to become an intermediate gas d. Incombustible materials e such as metal pieces are discharged downward.

[0009] The intermediate gas d is sent to the high temperature gas reactor 113 via the connecting pipe 112 . In the high temperature gas reactor 113, the intermediate gas d reacts with oxygen b and steam c at a high temperature of 1200°C or higher to become synthesis gas g, which is then discharged. The synthesis gas g is mainly composed of hydrogen and carbon monoxide. Impurities are discharged in the form of slurry f.

[0010] Chemical recycling is carried out in this manner. However, the technology of Patent Document 1 has the following problems. Since the waste 102 is a mixture of various kinds of waste, a large amount of incombustible materials e and slurry f is generated. In addition, since the waste 102 is a mixture of various materials, the composition of the synthesis gas g varies widely, which increases the cost of refining the synthesis gas g.

[0011] On the other hand, when attention is paid to the waste plastic in the waste material 102, this waste plastic contains a certain amount of chemical fibers. The main chemical fibers are polyester, acrylic, and nylon. It is known that 89% of the world's production is polyester, 3% is acrylic, and 8% is nylon.

[0012] Clothing and bedding are shifting from natural fibers to synthetic fibers, the majority of which are made of polyester fibers. As lifestyles change, the lifespan of clothing and bedding is shortened, and the amount of waste polyester fiber is increasing year by year. Recycling of such waste polyester fiber is an urgent task. Therefore, the present inventors have focused on polyester fibers among chemical fibers.

[0013] Next, the present inventors investigated chemical recycling of discarded polyester fibers using a gasification facility equivalent to that described in Patent Document 1. The waste 102 is mainly composed of polyester fibers with only a small amount of dye, so the amounts of incombustible materials e and slurry f are negligibly small. In addition, since the waste material 102 is mainly composed of polyester fibers with only a small amount of dye, there is an advantage that the composition of the synthesis gas g is stable and the cost of refining the synthesis gas can be reduced.

[0014] However, even if the waste 102 is mainly composed of polyester fibers, it has been found that the following problems exist. The old polyester cloth is fed into the low-temperature gasifier 110 in a form in which pieces of cloth are stuck together. Since the thermal and chemical reactions of the fed material proceed from the surface, it takes time for the reactions to proceed to the center. If it takes a long time, it will affect the productivity of chemical recycling.

[0015] The waste 102 is extruded from the raw material extrusion machine 107 in the form of a long, thin rod. Since it is difficult to handle such a long, thin rod, the long, thin rod is cut into pieces several times the diameter of the rod, which are then used as raw material granules.

[0016] At the outlet of the raw material feeder 107, the temperature of the elongated rod is close to the melting point of polyester. Therefore, the elongated rod is in a so-called "soft" state, weak and difficult to cut. If it is forcibly cut, it will be in a torn shape (see FIG. 6(b)), and the shape of the raw material particles will be extremely irregular. If the shapes are irregular, it will affect the reaction in the low-temperature gasifier 110.

[0017] The present inventors believe that increasing the reaction rate in a low-temperature gasifier will directly lead to improved productivity in chemical recycling. As there is a demand for improved productivity in chemical recycling, there is a need for technology that can enhance reactions in low-temperature gasification furnaces when chemically recycling old polyester fiber fabric. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] JP 2006-322004 A Summary of the Invention [Problem to be solved by the invention]

[0019] An object of the present invention is to provide a technique capable of enhancing the reaction in a low-temperature gasification furnace when chemically recycling old polyester fiber cloth. [Means for solving the problem]

[0020] The invention according to claim 1 is a columnar object of a predetermined length, which is a plastic-based material to be supplied to a gasification furnace for chemical recycling, This plastic material is composed of old polyester fiber cloth as a main material and a bonding material that bonds the main material, The bonding material is a low-melting point plastic having a melting point lower than that of the polyester, The low melting point plastic is one or more selected from polystyrene, polyethylene, polypropylene, and ABS resin, The polyester fiber waste cloth is locally bonded to each other with the low melting point plastic.

[0021] The invention according to claim 2 is the plastic material according to claim 1, The polyester fiber waste cloth has a ratio of 70 to 90% by mass, and the low melting point plastic has a ratio of 10 to 30% by mass.

[0022] The invention according to claim 3 is the plastic material according to claim 1 or 2, The low melting point plastic is characterized by being polystyrene.

[0023] The invention according to claim 4 is the plastic material according to claim 3, The polystyrene is characterized in that it is expanded polystyrene.

[0024] The invention according to claim 5 is a method for producing a plastic material to be supplied to a gasification furnace for chemical recycling, comprising the steps of: A process for preparing old polyester fiber cloth, a low melting point plastic having a melting point lower than that of polyester, a crusher, and an extrusion molding machine equipped with a die plate and a cutter; Crushing the old polyester fiber cloth and the low melting point plastic with the crusher; controlling the temperature of the die plate to a temperature near the melting point of the low melting point plastic; A step of feeding the crushed old polyester fiber cloth and the crushed low melting point plastic into the extrusion molding machine in a ratio of 70 to 90 mass % and 10 to 30 mass %, respectively; extruding a rod-shaped body through a die hole of the die plate; and cutting the rod-shaped body to a predetermined length with the cutter to obtain a predetermined length of plastic material. Effect of the Invention

[0025] In the invention according to claim 1, the plastic material is made of old polyester fiber cloth that is locally bonded together with a low-melting point plastic that has a lower melting point than polyester. Gas can pass between adjacent pieces of used polyester fabric, which promotes the reaction in the low-temperature gasifier. As a result, the present invention provides a technology that can enhance the reaction in a low-temperature gasifier.

[0026] In addition, since the plastic material of the present invention is mainly made of polyester, the composition of the synthesis gas obtained by gasification is stable, and the gas purification cost can be reduced, which means that the production cost in chemical recycling can be reduced.

[0027] In the invention according to claim 2, the ratio of old polyester fiber cloth is 70 to 90 mass %, and the ratio of low melting point plastic is 10 to 30 mass %. This ratio provides a plastic-based material with adequate breathability.

[0028] In the invention according to claim 3, the low melting point plastic is polystyrene. Among polystyrene, polyethylene, polypropylene, and ABS resin, polystyrene has a low melting point of 100°C, which is significantly different from the melting point of polyester (over 255°C). The greater the temperature difference, the smaller the risk of the polyester waste fabric melting too much, making it easier to produce plastic-based materials.

[0029] Also, if the low melting point plastic is polypropylene, the temperature of the die plate of the extruder needs to be kept at about 160°C. In contrast, if the low melting point plastic is polystyrene, the temperature of the die plate only needs to be kept at about 95°C, and the amount of heat energy applied from the outside is about half that of polypropylene. As a result, according to claim 3, the efficiency of heat energy is extremely improved.

[0030] In the invention according to claim 4, the polystyrene is expanded polystyrene. Styrofoam, which is white and contains 95% air bubbles, is consumed in large quantities for use as food trays, fish boxes, insulation material, etc., and is also discarded in large quantities. According to the present invention, polystyrene foam, which is discarded in large quantities, can be effectively reused by chemical recycling.

[0031] In the invention according to claim 5, the temperature of the die plate is controlled to a temperature close to the melting point of the low-melting-point plastic. With this control, the old polyester fiber cloth remains unmelted, and the polystyrene melts and then solidifies, resulting in a plastic material in which the hardened polystyrene is dispersed in dots.

[0032] The dotted polystyrene creates appropriate gaps between the old polyester fiber cloth and the neighboring old polyester fiber cloth, through which the gas passes. The surface area (external surface area + internal surface area) of the material that comes into contact with the gas increases, promoting the reaction in the gasifier. As a result, the present invention provides a technology that can enhance the reaction in a low-temperature gasifier.

[0033] In addition, since the rod-shaped material extruded from the die plate has a core of old unmelted polyester fiber cloth, it is strong, can be cut neatly with a cutter, and the cut plastic material is uniform in size. Therefore, the present invention makes it possible to produce plastic materials with uniform shapes. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a basic configuration diagram of a production facility for a plastic material according to the present invention. [Diagram 2] FIG. 1 is a flow diagram illustrating a procedure for separating waste plastics. [Diagram 3] FIG. 1 is a basic configuration diagram of a single-shaft crusher. [Figure 4] FIG. 2 is a side view of an extruder. [Diagram 5] FIG. 2 is a plan view of an extrusion molding machine with a main part cut away. [Figure 6] (a) is a diagram of the operation of the die in the comparative example, (b) is a perspective view of the plastic material in the comparative example, (c) is an enlarged view (conceptual diagram) of part c in (b), (d) is a diagram of the operation of the die in the embodiment, (e) is a perspective view of the plastic material in the embodiment, and (f) is an enlarged view (conceptual diagram) of part f in (e). [Figure 7] FIG. 1 is a basic configuration diagram of a gasification facility. [Figure 8] FIG. 13 is a diagram illustrating a modified example of a production facility for plastic-based materials. [Figure 9] FIG. 1 is a schematic diagram of a conventional gasification facility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. EXAMPLES

[0036] [Plastic material manufacturing facilities] As shown in Figure 1, the plastic material manufacturing equipment 10 is a facility whose main elements are an incoming conveyor 12, a single-shaft crusher 20 arranged downstream of the incoming conveyor 12, an air sorter 30 arranged downstream of the single-shaft crusher 20, and an extrusion molding machine 40 arranged downstream of the air sorter 30.

[0037] [Receiving conveyor] The receiving conveyor 12 may have any shape and structure, but may be, for example, a horizontal conveyor, on which old polyester fiber cloth 13 and low-melting point plastic 14, which has a melting point sufficiently lower than that of polyester, are alternately placed, and these are transported and fed into the uniaxial crusher 20.

[0038] [Ratio of old cloth to low melting point plastic] The ratio of old cloth to low melting point plastic is such that, when the sum of old cloth 13 and low melting point plastic 14 is 100% by mass, low melting point plastic 14 accounts for 10 to 30% by mass, and the remaining 70 to 90% by mass is old cloth 13. As most of the fabric is old13, used polyester fibre is recycled efficiently.

[0039] [Old polyester fabric] The old polyester fabric 13 is, for example, a worn-out uniform. As the demand for recycling waste plastics increases, clothing stores (so-called mass retailers) collect a large amount of polyester fiber uniforms. The collected uniforms are bundled together and provided to a plastic material manufacturing facility 10 as used polyester fiber cloth 13. The used polyester fiber cloth 13 still has zippers 15, buttons 16, etc. attached.

[0040] The polyester fiber old cloth 13 may be a worn-out uniform, general clothing, bedding, etc., and the use is not limited. The old cloth 13 may be a blend of cotton and polyester fiber, so long as the main component is polyester fiber.

[0041] [Display of polyester] Clothing has a quality tag sewn onto it. The quality tag may say something like 100% polyester, or 75% polyester, 20% cotton, 5% nylon, etc. Based on this information, old polyester fabric 13 is separated from other waste plastics.

[0042] [Melting point of polyester fiber] The melting points of the polyester fibers are as shown in Table 1.

[0043] [Table 1]

[0044] [Low melting point plastic] The low melting point plastic 14 is preferably a "plastic container / packaging" as defined by the Container and Packaging Recycling Law, that is, a waste plastic container and waste plastic packaging as defined by the Container and Packaging Recycling Law. The "plastic container / packaging" as defined by the Container and Packaging Recycling Law is shown in Table 2.

[0045] [Table 2]

[0046] [Plastic Display] Plastic products are required to have a plastic container mark attached to them in accordance with the Container and Packaging Recycling Law. This plastic container mark consists of the two characters "PLA" and arrows surrounding the two characters (the letter "C" + arrow). In addition, abbreviations such as "PS" or "PE" are added to the right side or below the plastic container mark.

[0047] [Further sorting of low-melting-point plastics] Based on these abbreviations, "plastic containers and packaging" can be further separated into waste polystyrene (PS), waste polyethylene (PE), etc. An example of this separation process will be explained with reference to Figure 2.

[0048] [Separation work] As shown in Figure 2, waste plastic is accepted at ST (step number; same below) 01. In ST02, confirm that the received waste plastic is the plastic container / packaging shown in Table 2.

[0049] Once this has been confirmed, in ST03, PS (polystyrene) is separated from the received plastic containers and packaging.

[0050] When waste plastic is labeled with "PLA" and PS, or just PS, it should be separated based on this label. If there is no labeling, but you can recognize it as PS from appearance or experience, go to YES. For example, polystyrene foam food trays (foam trays) are light and white, so they can be separated even without labeling. If none of the above applies and separation is difficult, proceed to NO. The above-mentioned rules for sorting also apply to PE, PP, and ABS, as described below.

[0051] If the answer is YES in ST03, the PS is accumulated in ST04, and if the answer is NO, proceed to ST05. Separate PE (polyester) from plastic containers and packaging after PS has been removed (ST05).

[0052] If the answer is YES in ST05, PEs are accumulated in ST06, and if the answer is NO, proceed to ST07. The inventors of the present invention have found that PS (polystyrene) is the best material for joining old polyester fiber cloth together, followed by PE (polyethylene). Based on this knowledge, it may be a good idea to end the separation process at this stage. Therefore, in ST07, a decision is made as to whether or not to continue separating waste. Taking into account the cost-effectiveness perspective, if separating waste is not to be continued, proceed to NO.

[0053] If you continue further, separate the PP (polypropylene) in ST08 and collect it (ST09).

[0054] Among "plastic containers and packaging," ABS is used in the smallest amount. Therefore, in ST10, it is decided whether or not to continue sorting. Taking into account the cost-effectiveness perspective, if the decision is not to continue sorting, proceed to NO.

[0055] If the process continues, ABS (ABS resin) is separated in ST11 and the ABS is accumulated (ST12). Plastic containers and packaging that are judged as NO in ST11 are accumulated as other plastics (ST13). Waste plastics that are judged as NO in ST02, ST07, and ST10 are also collected as other plastics (ST13). Other plastics are sent for thermal recycling and are effectively used as RPF (solid fuel made of a mixture of paper and plastic).

[0056] From experience, the PS collected at ST04 contains a large amount of foamed PS, such as the white, lightweight food trays, fish boxes, and insulation materials. Foamed PS is also known as polystyrene foam. Therefore, in ST14, the foamed PS is separated from the PS accumulation and accumulated (ST15).

[0057] Furthermore, from experience, the PE collected at ST06 contains a large amount of plastic bags (polyethylene bags), commonly known as convenience store bags. Therefore, in ST16, plastic bags (polyethylene bags) are separated from the PE pile and piled up (ST17).

[0058] One or more of the above-described PS-based material (ST04), PE-based material (ST06), PP-based material (ST09), ABS-based material (ST12), foamed PS-based material (ST15), and plastic bag-based material (ST17) are used as the low melting point plastic 14 shown in FIG. 1.

[0059] In Fig. 1, old polyester fiber cloth 13 and low melting point plastic 14 are alternately fed from an input conveyor 12 into a single-shaft crusher 20. By alternately dropping the old polyester fiber cloth 13 and the low melting point plastic 14, the ratio of the old polyester fiber cloth to the low melting point plastic can be easily controlled. The structure and operation of the single-shaft crusher 20 will be described in detail later, but first crushed pieces 21 are discharged from the single-shaft crusher 20.

[0060] The first crushed pieces 21 are fed into a wind sorter 30. In the wind sorter 30, wind is sent from below into a zigzag passage 31. Lighter pieces rise up the zigzag passage 31. Metallic zippers 15 and buttons 16 are heavy and fall down. The first crushed pieces 21 with the zippers 15, buttons 16, etc. removed become second crushed pieces 32.

[0061] The second crushed pieces 32 are fed into an extrusion molding machine 40. The details of the extrusion molding machine 40 will be described later, but a plastic material 41 is discharged from the extrusion molding machine 40 and accumulated in a bucket 42.

[0062] [Single-shaft crusher] As shown in FIG. 3, the uniaxial crusher 20 is a device whose main components are a single-shaft rotating blade 22 extending in the front-to-back direction of the drawing, a screen 23 surrounding roughly the lower half of this rotating blade 22, a fixed blade 24 arranged opposite the rotating blade 22, and a pusher 25.

[0063] As explained in Fig. 1, old polyester fiber cloth 13 and low melting point plastic 14 are put in. The mixture 26 is pushed against the rotary blade 22 by a pusher 25 shown in Fig. 3. The mixture 26 is cut (crushed) by the rotary blade 22 and the fixed blade 24. Of the crushed material, large crushed pieces that do not pass through the screen 23 revolve between the screen 23 and the rotary blade 22, and are repeatedly cut by the rotary blade 22 and the fixed blade 24, gradually becoming smaller.

[0064] The crushed pieces that have become small enough to pass through the screen 23 fall through the screen 23. The fallen crushed pieces become the first crushed pieces 21. The first crushed pieces 21 are discharged by the conveyor 27. The size of the first crushed pieces 21 can be controlled to be in the range of 8 to 80 mm. That is, by changing the screen 23 to one with a different mesh size, the size of the first crushed pieces 21 can be controlled.

[0065] [Extrusion molding machine] As shown in FIG. 4, the extrusion molding machine 40 includes a base 43, a gear case 44 placed on the base 43, an extrusion motor 45 connected to the input shaft of the gear case 44, screws 46, 47 extending horizontally from the gear case 44 away from the extrusion motor 45, a barrel 48 surrounding the screws 46, 47, a hopper 49 attached to the base (the gear case 44 side) of the barrel 48, a die plate 51 arranged at the tip of the barrel 48, a cutter cover 52 arranged outside the die plate 51 (the side away from the gear case 44), a temperature sensor 53 for measuring the temperature of the die plate 51, a heater 54 for heating the die plate 51, a water passage 55 for cooling the die plate 51, and a temperature control unit 56.

[0066] The gear case 44 has the roles of supporting the screws 46 and 47 at one end, acting as a reducer, distributing the output of the extrusion motor 45, and determining the rotation direction of the screws 46 and 47. Note that it is possible to omit the reduction mechanism (function) from the gear case 44 by interposing a reducer between the extrusion motor 45 and the gear case 44.

[0067] The temperature control unit 56 plays a role in maintaining the temperature of the die plate 51 at a set temperature artificially set by a temperature setter 57. That is, the temperature control unit 56 compares the temperature information obtained by the temperature sensor 53 with the set temperature, and when the temperature of the die plate 51 is lower than the set temperature, it instructs the heater controller 58 to increase the heater output. The heater controller 58 increases the power supplied to the heater 54. When the temperature information obtained by the temperature sensor 53 approaches the set temperature, the temperature control unit 56 controls so as to reduce the power supplied to the heater 54. As a result, the die plate 51 is maintained at the set temperature.

[0068] When the temperature of the die plate 51 is higher than the set temperature, the temperature control unit 56 opens a control valve 62 provided in a water supply pipe 61. The die plate 51 is cooled by water flowing through a water passage 55. When the temperature information obtained by the temperature sensor 53 approaches the set temperature, the temperature control unit 56 narrows the control valve 62. As a result, the die plate 51 is maintained at the set temperature.

[0069] 5, screws 46 and 47 are rotated by a gear case 44. In principle, the screw 47 is rotated in the opposite direction to the screw 46 at the same speed, but the screw 47 may be rotated in the same direction.

[0070] The second crushed pieces (32 in Fig. 1) fed through a hopper (49 in Fig. 4) are kneaded by the screws 46 and 47. This kneading process further mixes and breaks down the old polyester fiber cloth (13 in Fig. 1) and the low melting point plastic (14 in Fig. 1). At the same time, frictional heat is generated by the kneading process, raising the temperature of the mixture.

[0071] The mixture is strongly pressed against the die plate 51 by the screws 46 and 47, and is extruded from the die hole 63 of the die plate 51. The hole diameter of the die hole 63 is, for example, 35 mm.

[0072] A pair of cutters 64 are disposed inside the cutter cover 52, and these cutters 64 are rotated by a cutter motor 65. It is preferable that the cutters 64 are so-called bamboo-tompo shaped cutter blades. The bamboo-tompo shaped cutter blades have a simple structure and are inexpensive.

[0073] It is possible to rotate a plurality of cutters 64 (two in this embodiment) with one cutter motor 65 via gears or a chain sprocket.

[0074] The rod-shaped body extruded from the die hole 63 is cut by a cutter 64. By cutting, a columnar object of a predetermined length is obtained. This columnar object becomes a plastic material (FIG. 1, reference numeral 41), falls by gravity, and is accumulated in a bucket (FIG. 1, reference numeral 42).

[0075] [Method of manufacturing plastic materials] The above-mentioned method for producing a plastic material can be summarized as follows with reference to FIG. That is, the method for producing a plastic material of the present invention includes the steps of preparing old polyester fiber cloth 13, low-melting-point plastic 14 having a melting point lower than that of polyester, a crusher 20, and an extrusion molding machine 40 equipped with a die plate 51 (see FIG. 4) and a cutter 64 (see FIG. 5); A process of crushing old polyester fiber cloth 13 and low melting point plastic 14 in a crusher 20; controlling the temperature of the die plate 51 (see FIG. 4) to a temperature close to the melting point of the low melting point plastic 14; A step of feeding crushed old polyester fiber cloth 13 and crushed low melting point plastic 14 into an extrusion molding machine 40 at a ratio of 70 to 90 mass % and 10 to 30 mass %, respectively; a step of extruding a rod-shaped body 18 (see FIG. 6(d)) from a die hole 63 (see FIG. 5) of a die plate 51; and cutting the rod-shaped body 18 (see FIG. 6(d)) to a predetermined length with a cutter 64 (see FIG. 6(d)) to obtain a plastic material 41 of a predetermined length.

[0076] [Comparative experiment] The present inventors conducted comparative experiments to confirm the benefits of the present invention.

[0077] [Comparative Example] In the comparative example, in Fig. 1, only old polyester fiber cloth 13 was placed on the receiving conveyor 12. As a result, the second crushed pieces 32 were composed of 100% polyester fiber.

[0078] 6(a), the set temperature of the die plate 51 is designated as Tset1. Tset1 was set to 250° C. in consideration of the melting point of polyester. In the present invention, the cutter 64 is disposed at a predetermined distance away from the die plate 51. By disposing the cutter 64 at a distance, the cutter 64 does not come into contact with the die plate 51. This can extend the life of the cutter 64.

[0079] A rod-shaped body 115 is extruded from the die hole 63. This rod-shaped body 115 is molten (or semi-molten) until just before, and is soft and weak because it has not been cooled sufficiently immediately after the die hole 63. Even if the cutter 64 is struck down in this state, it will not be cut cleanly. As a result, as shown in FIG. 6(b), the obtained plastic-based material 116 has both ends torn off.

[0080] A conceptual diagram of an enlarged portion of the fracture surface is shown in Fig. 6(c). As shown in Fig. 6(c), the old cloth 13 of molten polyester fiber is closely connected to the old cloth 13 of adjacent polyester fiber. Although horizontal lines (wavy lines) are drawn in Fig. 6(c) for convenience, these horizontal wavy lines have disappeared or almost disappeared.

[0081] [Example] 1, old polyester fiber cloth 13 and polystyrene foam 17, typically used for food trays, were alternately arranged on the receiving conveyor 12. The ratio of the old polyester fiber cloth 13 to the polystyrene foam 17 was 80% by mass and 20% by mass, respectively.

[0082] As shown in FIG. 6(f), which is a conceptual diagram of an enlarged portion of the cut surface, in the embodiment, melted and then solidified expanded polystyrene 17 was present in the form of dots (or islands) between the old cloths 13 of unmelted polyester fiber.

[0083] 6(d), the set temperature of the die plate 51 is set to Tset2. Tset2 is set to 95° C. in consideration of the melting point of the polystyrene foam 17. The rod-shaped body 18 extruded from the die hole 63 is hard and strong because the unmelted old polyester fiber cloth 13 acts as a core and the molten polystyrene foam 17 acts as an adhesive. When the cutter 64 is struck down, the tip of the rod 18 is bent, broken, and separated.

[0084] Incidentally, according to Table 2 mentioned above, the expanded polystyrene 17 can be changed to polypropylene. However, in the case of polypropylene, the temperature of the die plate of the extruder needs to be kept at around 160°C. In contrast, when the low-melting-point plastic is polystyrene, the temperature of the die plate only needs to be kept at around 95°C, and the amount of heat energy applied from the outside is about half that of polypropylene. That is, the polystyrene foam 17 of this embodiment has extremely good thermal energy efficiency.

[0085] 6(e), the obtained plastic material 41 has a preferable shape with a clean fracture surface and a uniform length. The size of the plastic material 41 is, for example, 35 mm in diameter and 50 to 60 mm in length.

[0086] [Plastic materials] As described above, the plastic material 41 of the present invention is composed of old polyester fiber cloth 13 as the main material and a bonding material that bonds the main material, and this bonding material is a low-melting point plastic that has a melting point lower than that of polyester, such as polystyrene foam 17, and has a structural feature in that the old polyester fiber cloths 13 are locally bonded together with the polystyrene foam 17 as a low-melting point plastic.

[0087] The low melting point plastic may be one or more types selected from polystyrene, polyethylene, polypropylene, and ABS resin shown in Table 2. When using two types, it is recommended to use a mixture of polystyrene and ABS resin, which have similar melting points, as the bonding material, or a mixture of polystyrene and polyethylene. When using the three types, it is recommended to use a mixture of polystyrene, polyethylene, and ABS resin, which have similar melting points, as the bonding material.

[0088] [Gasification facility] As shown in FIG. 7, a gasification facility 70 comprises a low-temperature gasification furnace 71, a high-temperature gasification furnace 72, and a connecting pipe 73 connecting these.

[0089] The plastic material 41 is fed into a low-temperature gasifier 71. Sand heated to 600 to 800° C. is circulated inside the low-temperature gasifier 71. In addition, oxygen and water vapor are blown into the low-temperature gasifier 71.

[0090] The plastic material 41 is heated by the sand and reacts with oxygen and water vapor to decompose. The intermediate gas after decomposition is sent to the high-temperature gasification furnace 72 through the connecting pipe 73. The high-temperature gasifier 72 is kept at 1300 to 1500°C, and the intermediate gas is heated while rotating and descending, and reacts with oxygen and steam to become synthesis gas. The main components of synthesis gas are carbon monoxide and hydrogen. Synthesis gas is a raw material for hydrogen, methanol, ammonia, acetic acid, etc.

[0091] [Gasification in Comparative Examples] The plastic-based material 116 shown in Fig. 6(b) was charged into the low-temperature gasifier 71. As shown in Fig. 6(c), the plastic-based material 116 has a dense structure. Therefore, the surrounding gas does not penetrate into the interior of the plastic-based material 116 but merely envelops the surface of the plastic-based material 116 . As a result, chemical reactions with oxygen and water vapor are delayed, extending production time.

[0092] In addition, the temperature of the plastic material 116 rises from the surface, and the temperature of the center rises last, which also extends the production time and affects productivity. Additionally, the plastic-based materials 116 are irregular in shape and size, and larger pieces of plastic-based materials 116 will take longer to react than smaller pieces of plastic-based materials 116. As described above, in the comparative example, there remains a problem with productivity associated with gasification.

[0093] [Gasification study in the examples] Next, the plastic material 41 shown in FIG. 6( e ) was charged into the low-temperature gasification furnace 71 . As shown in Fig. 6(f), the plastic material 41 has a coarse structure. Due to the dots of styrofoam 17, there is a sufficiently large gap a between the old polyester fiber cloth 13 and the adjacent old polyester fiber cloth 13. In addition, there is a sufficiently large unbonded area b between the dots of styrofoam 17 and the adjacent dots of styrofoam 17.

[0094] In the low-temperature gas furnace (Figure 7, symbol 71), the surrounding gas enters and passes through the plastic material 41, so the plastic material 41 becomes hot in a short time. In addition, the surface area (external surface area + internal surface area) of the plastic material 41 that comes into contact with the gas is particularly large, which promotes the chemical reaction of the old polyester fiber cloth 13. As a result, the productivity associated with gasification is improved in the embodiment.

[0095] Next, a modified example of the present invention will be described with reference to FIG. As shown in FIG. 8, the plastic-based material manufacturing equipment 10 has the same configuration as the plastic-based material manufacturing equipment 10 shown in FIG. 1, so the reference numerals from FIG. 1 are used and a detailed description of the equipment is omitted.

[0096] In a plastic material manufacturing facility 10 shown in Fig. 8, old polyester fiber cloth 13 is fed onto an incoming conveyor 12. Then, low melting point plastic 14 is fed directly into an extrusion molding machine 40.

[0097] If the low melting point plastic 14 is smaller than the size of the bottom opening of the hopper 49, this modification can be used. Alternatively, if the low melting point plastic 14 is styrofoam 17, it can be fed directly into the extruder 40 without pre-crushing since it is 95% void and easily crushed. Therefore, the low melting point plastic 14 is in principle placed on the receiving conveyor 12, but it is also acceptable to feed it directly into the extrusion molding machine 40.

[0098] [Study on the ratio of old polyester fabric to low melting point plastic] In FIG. 6(f), when the ratio of the polystyrene foam 17 as the low melting point plastic exceeds 30 mass %, the unbonded region b becomes small, and the passage of gas is prevented. Furthermore, if the ratio of the expanded styrene 17 is less than 10 mass %, it becomes difficult to ensure the gap a and the adhesive strength becomes insufficient. The ratio of old polyester fiber cloth to low melting point plastic is preferably 70 to 90 mass % for old polyester fiber cloth and 10 to 30 mass % for low melting point plastic.

[0099] Furthermore, it is more preferable that the ratio of old polyester fiber cloth to low melting point plastic is 75 to 85 mass % for old polyester fiber cloth and 15 to 25 mass % for low melting point plastic. Furthermore, it is even more preferable that the ratio of old polyester fiber cloth to low melting point plastic is 80 mass % for old polyester fiber cloth and 20 mass % for low melting point plastic.

[0100] The receiving conveyor 12 described in Fig. 1 may be a horizontal conveyor, an inclined conveyor or a screw conveyor. The single-shaft crusher 20 may be a biaxial crusher, but a single-shaft crusher is preferable because the size of crushed pieces can be changed by changing the screw. The wind sorter 30 may be a gravity sorter or a centrifugal sorter as long as it can separate light waste plastic pieces from heavy metals. The point is that it is sufficient to obtain the plastic material 41 of the present invention shown in Figures 6(e) and 6(f), and the configuration of the plastic material production facility 10 and the type of the constituent equipment may be changed as appropriate.

[0101] Furthermore, the plastic material of the present invention can be used not only as a feedstock for a gasification furnace, but also as a solid fuel for thermal recycling, and its uses can be expanded beyond chemical recycling. [Industrial Applicability]

[0102] The present invention is suitable for plastic-based materials that are fed to a gasification furnace for chemical recycling. [Explanation of symbols]

[0103] 10...plastic material manufacturing equipment, 13...waste polyester fiber cloth, 14...low melting point plastic, 18...rod-shaped body, 20...crusher (single-shaft crusher), 40...extrusion molding machine, 41...plastic material, 51...die plate, 63...die hole, 64...cutter, 71...gasification furnace (low-temperature gasification furnace).

Claims

1. A plastic-based material that is a columnar object of a predetermined length and is supplied to a gasification furnace for chemical recycling, This plastic material is composed of old polyester fiber cloth as a main material and a bonding material that bonds the main material, The bonding material is a low-melting point plastic having a melting point lower than that of the polyester, The low melting point plastic is one or more selected from polystyrene, polyethylene, polypropylene, and ABS resin, A plastic material characterized in that the old polyester fiber cloth is locally bonded to each other with the low melting point plastic.

2. 2. The plastic-based material according to claim 1, A plastic material characterized in that the proportion of old polyester fiber is 70 to 90 mass % and the proportion of low melting point plastic is 10 to 30 mass %.

3. The plastic material according to claim 1 or 2, A plastic material characterized in that the low melting point plastic is polystyrene.

4. The plastic material according to claim 3, The polystyrene is a plastic material characterized in that it is expanded polystyrene.

5. A method for producing plastic-based materials to be supplied to a gasification furnace for chemical recycling, comprising the steps of: A process for preparing old polyester fiber cloth, a low melting point plastic having a melting point lower than that of polyester, a crusher, and an extrusion molding machine equipped with a die plate and a cutter; Crushing the old polyester fiber cloth and the low melting point plastic with the crusher; controlling the temperature of the die plate to a temperature near the melting point of the low melting point plastic; A step of feeding the crushed old polyester fiber cloth and the crushed low melting point plastic into the extrusion molding machine in a ratio of 70 to 90 mass % and 10 to 30 mass %, respectively; extruding a rod-shaped body through a die hole of the die plate; and cutting the rod-shaped body to a predetermined length with the cutter to obtain a predetermined length of plastic material.

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