Resin extrusion die

Abstract

To provide a resin extrusion die that can facilitate a lamination process of a single resin layer and mold a multi-layered tubular-shaped parison that is a resin extrusion die for forming a tubular-shaped parison having a plurality of single resin layers laminated thereon.SOLUTION: There is provided a resin extrusion die 100 for forming a tubular-shaped parison, comprising: a plurality of pouring ports 110 through which molten resin is poured; a plurality of layer forming flow paths 130 arranged in multiple stages, each of which molds a single resin layer; a lamination flow path 140 formed in a tubular shape, in which multiple single resin layers extruded from the plurality of layer forming flow paths are stacked; and a plurality of branch supply paths 120 connecting the plurality of layer forming flow paths and the plurality of pouring ports so that the single resin layers overlap each other within the lamination flow path. The layer formation flow path having a small diameter end connected to the lamination flow path, a large diameter end connected to the branch supply path, and the small diameter end that is disposed toward an outlet flow path of the tubular-shaped parison.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin extrusion die for forming a tubular parison having a plurality of single resin layers laminated thereon. [Background technology]

[0002] It is generally known that resin tubes formed from multiple single resin layers are used as packaging containers for food, cosmetics, medicines, etc. Examples of the single resin layers constituting the resin tube include ethylene-vinyl alcohol copolymer resin, so-called EVOH (registered trademark), etc. In the resin tube, the resin layer formed from the ethylene-vinyl alcohol copolymer resin functions as a gas barrier layer, reducing the permeability of gases including oxygen to protect the contents. Patent Document 1 is an example of a method for molding a resin tube formed from multiple single resin layers.

[0003] Patent Document 1 discloses a die head structure for a blow molding device, which extrudes a parison in which multiple resin layers are laminated. In this die head structure, disk-shaped dies for extruding the resin material of each layer are vertically laminated, and multiple material flow paths are formed between the dies through which the resin material extruded from the extruder flows. The material flow paths are connected to a parison flow path that vertically communicates with each die, and a parison formed by combining the materials of each layer extruded from each material flow path flows down the parison flow path. As a result, the die head structure of Patent Document 1 can mold a resin tube formed from multiple resin layers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication 2014-104692 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, the ethylene-vinyl alcohol copolymer resin used in the resin tube has the advantage of having high gas barrier properties, but has the disadvantage of being expensive and not suitable for reuse. Therefore, there has been a demand for a resin tube that can exhibit the desired gas barrier properties by using only inexpensive and reusable resin materials such as polyethylene and polypropylene. Even if only a resin material with poor gas barrier properties such as polyethylene is used, it is thought that a multi-layered resin tube can maintain the same gas barrier properties as a resin tube using an ethylene-vinyl alcohol copolymer resin. However, since the mechanism of the mold for increasing the resin layers becomes complicated, it takes a lot of time and money to create the mold.

[0006] Furthermore, since the mold for molding a multi-layered resin tube must overlap single resin layers in an orderly manner, it is necessary to devise a method for making the flow speed of the molten resin being overlapped as uniform as possible. [Means for solving the problem]

[0007] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a resin extrusion die for molding a tubular parison made of a plurality of laminated single resin layers, which can facilitate the lamination process of the single resin layers and mold a multi-layered tubular parison.

[0008] That is, the present invention is a resin extrusion die for molding a tubular parison having a plurality of laminated single resin layers, the die comprising: a plurality of injection ports into which different types of molten resin are fed from a molten resin extruder; a plurality of layer-forming flow paths arranged in multiple stages along the extrusion direction of the tubular parison, each of which molds the single resin layer; a lamination flow path formed in a cylindrical shape and continuing to an outlet flow path of the tubular parison, in which the single resin layers extruded from each of the plurality of layer-forming flow paths are laminated from the inside to the outside; and a plurality of branch supply paths connecting the plurality of layer-forming flow paths and the plurality of injection ports so that the different types of single resin layers are laminated within the lamination flow path, each of the plurality of layer-forming flow paths being formed in a shape simulating the outer peripheral surface of a truncated cone, and the small diameter end of the layer-forming flow path being connected to the lamination flow path, while the branch supply path is connected to a large diameter end of the layer-forming flow path, and the small diameter end is arranged toward the outlet flow path. Effect of the Invention

[0009] According to the resin extrusion die of the present invention, a plurality of layer forming flow paths for forming a plurality of single resin layers are arranged in multiple stages along the extrusion direction of the tubular parison. The plurality of lamination flow paths are connected to the lamination flow path, and discharge the formed plurality of single resin layers into the lamination flow path. Each single resin layer discharged into the lamination flow path is laminated in order from the inside to the outside, so that the plurality of single resin layers can be laminated in an orderly manner. Therefore, the resin extrusion die is less likely to cause molding defects, and can form a multi-layered tubular parison with excellent design. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing a resin extrusion die of the present invention. [Diagram 2] FIG. 2 is an enlarged view showing a branched supply passage and a layer forming passage of the resin extrusion die of the present invention. [Diagram 3] FIG. 2 is an enlarged view showing a layer forming flow path and a lamination flow path of the resin extrusion die of the present invention. [Figure 4] FIG. 2 is an enlarged view showing a lamination flow path of the resin extrusion die of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The resin extrusion die of the present invention will be described in detail below with reference to the accompanying drawings.

[0012] FIG. 1 is a schematic diagram showing a resin extrusion die 100. The resin extrusion die 100 is for forming a tubular parison in which a plurality of single resin layers are laminated. The tubular parison is molded into a packaging container for food, cosmetics, medicines, etc. by blow molding or the like. The resin material used for the tubular parison includes various materials such as polypropylene, polyethylene, ethylene-vinyl alcohol copolymer resin, soft polyvinyl chloride resin, thermoplastic polyurethane, polyethylene terephthalate resin, thermoplastic olefin resin, nylon 6, nylon 66, biodegradable resin (PLA), polyvinyl alcohol (PVA), etc. The resin extrusion die 100 has a plurality of injection ports 110, a plurality of branch supply paths 120, a plurality of layer formation flow paths 130, and a lamination flow path 140 communicating with each layer formation flow path 130.

[0013] The injection ports 110 are provided in two numbers on the side surface of the housing 150 that houses the resin extrusion die 100. A joint 111 is inserted into each injection port 110. An extruder (not shown) of a different type of molten resin is connected to each joint 111, and the molten resin is supplied from each extruder. As a result, different types of molten resin are fed into each injection port 110. Therefore, a first molten resin a is fed into the injection port 110a, while a second molten resin b is fed into the injection port 110b. The number of injection ports 110 can be appropriately changed according to the number of the extruders. The resin extrusion die 100 can mold a cylindrical parison from the molten resin received from the multiple injection ports 110, and discharge the cylindrical parison from the outlet flow path 101. In this embodiment, an example using two types of resin materials is described, but the number of types of resin materials used can be appropriately changed.

[0014] The branched supply path 120 is connected to the injection port 110. The branched supply path 120 is provided for each of the injection ports 110. The resin extrusion die 100 of this embodiment has a branched supply path 120a corresponding to the injection port 110a and a branched supply path 120b corresponding to the injection port 110b. The branched supply path 120 has a receiving section 121 that receives the molten resin from the injection port 110, and a plurality of supply pipes 122 that supply the molten resin from the receiving section 121 to each layer formation flow path 130 described later. That is, the plurality of injection ports 110 and the plurality of layer formation flow paths 130 are connected by the branched supply path 120. A first molten resin a is fed into the branched supply path 120a connected to the injection port 110a, while a second molten resin b is fed into the branched supply path 120b connected to the injection port 110b.

[0015] As shown in FIG. 2, each layer formation flow path 130 is formed in a shape simulating the outer peripheral surface of a truncated cone. The small diameter end of the layer formation flow path 130 is arranged in the extrusion direction α of the cylindrical parison, i.e., toward the outlet flow path 101. Therefore, the layer formation flow path 130 forms a cylindrical flow path narrowing toward the outlet flow path 101. The large diameter end of the layer formation flow path 130 is connected to the supply pipe 122 of the branch supply path 120, while the small diameter end is connected to a stacking flow path 140 described later. Therefore, the branch supply path 120 and the stacking flow path 140 are communicated through the layer formation flow path 130. The layer formation flow path 130 can mold the molten resin received from the branch supply path 120 into a cylindrical single resin layer and discharge the single resin layer to the stacking flow path 140.

[0016] The layer forming channels 130 are arranged in multiple stages along the extrusion direction α of the tubular parison. The plurality of layer forming channels 130 are arranged such that the first layer forming channel 130a and the second layer forming channel 10b are alternately arranged. While the first molten resin a is fed into the first layer forming channel 130a from the supply pipe 122a, the second molten resin b is fed into the second layer forming channel 130b from the supply pipe 122b. Thereby, the plurality of layer forming channels 130 can discharge different types of single resin layers alternately into the lamination channel 140. Thus, the branch supply path 120 connects the plurality of layer forming channels 130 and the plurality of injection ports 110 such that different types of single resin layers overlap within the lamination channel 140. When using three or more types of molten resin, the layer forming channels 130 may be provided in any order such that different single resin layers are adjacent to each other.

[0017] Figure 3 is an enlarged view of the layer forming channel 130 and the lamination channel 140. Each layer forming channel 130 has a filling channel 131 that receives molten resin from the branch supply path 120, and a discharge channel 132 provided continuously with the filling channel 131. Since the filling channel 131 and the discharge channel 132 are part of the layer forming channel 130, they are each formed in a shape simulating the outer peripheral surface of a frustum of a cone. The filling channel 131 is formed on the upstream side of the layer forming channel 130. One end of the filling channel 131 is connected to the branch supply path 120, while the other end is connected to the discharge channel 132. The flow path width of the filling channel 131 at the connection point with the branch supply path 120 is wider. The filling channel 131 is formed with a wider flow path width than the discharge channel 132, and can cause the molten resin received from the supply pipe 122 of the branch supply path 120 to flow in the circumferential direction of the layer forming channel 130. Thereby, the filling channel 131 is filled with molten resin, and the filling channel 131 can form a cylindrical single resin layer.

[0018] The discharge flow passage 132 is formed downstream of the layer formation flow passage 130. Therefore, the discharge flow passage 132 is configured as a flow passage having an inner diameter smaller than that of the filling flow passage 131. One end of the discharge flow passage 132 is connected to the filling flow passage 131, while the other end is connected to the lamination flow passage 140. The discharge flow passage 132 can discharge the single resin layer formed in the filling flow passage 131 to the lamination flow passage 140. The discharge flow passage 132 is formed with a flow passage width narrower than that of the filling flow passage 131, and is responsible for adjusting the extrusion speed of the single resin layer to the lamination flow passage 140.

[0019] In this embodiment, the discharge flow path 132a of the layer formation flow path 130a that receives the first molten resin a and the discharge flow path 130b of the layer formation flow path 130b that receives the second molten resin b are formed with the same flow path width and flow path length, but the flow path width and flow path length of the discharge flow path 132a and the flow path width and flow path length of the discharge flow path 132b may be different depending on the type of resin material. For example, when the viscosity of the first molten resin a is higher than the viscosity of the second molten resin b, the flow path width of the discharge flow path 132a of the first molten resin a can be made larger than the flow path width of the discharge flow path 132b of the second molten resin. This makes it possible to make the flow speed of the molten resin flowing in the discharge flow path 132 of each layer formation flow path 130 uniform even when resin materials with different viscosities are used.

[0020] The laminated flow path 140 is a cylindrical passage that receives a plurality of single resin layers from each of the plurality of layer forming flow paths 130. The laminated flow path 140 is provided along the extrusion direction of the tubular parison formed by laminating the plurality of single resin layers and is continuous with the outlet flow path 101 of the tubular parison. The flow path width of the laminated flow path 140 gradually expands as it approaches the outlet flow path 101. As shown in FIGS. 1 and 2, the laminated flow path 140 is formed in a tapered shape, and its inner diameter gradually expands as it approaches the outlet flow path 101. Thereby, within the laminated flow path 140, the single resin layers extruded from each of the plurality of layer forming flow paths 130 are superposed from the inside to the outside. Therefore, the layer forming flow path 130 is gradually arranged outward as the outlet of the discharge flow path 132 approaches the outlet flow path 101.

[0021] FIG. 4 is an enlarged view of the laminated flow path 140. A plurality of resin guide surfaces 310 arranged along the laminated flow path 140 are formed on the outer periphery of the laminated flow path 140. The resin guide surface 310 is formed in an annular shape, is provided from the connection portion between the layer forming flow path 130 and the laminated flow path 140 toward the extrusion direction α, and is continuous with the layer forming flow path 130. The resin guide surface 310 can guide the single resin layer discharged from the layer forming flow path 130 into the laminated flow path 140 toward the outlet flow path 101. Thereby, the single resin layer hangs down within the laminated flow path 140 along the resin guide surface 310.

[0022] The diameter of the resin guide surfaces 310 becomes larger as they approach the outlet flow path 101. As shown in FIG. 4, the diameter of the resin guide surface 310b below the resin guide surface 310a is larger than that of the uppermost resin guide surface 310a. Therefore, the resin guide surface 310b can guide the single resin layer discharged from the layer formation flow path between the resin guide surface 310a and the resin guide surface 310b to the outside of the single resin layer guided to the outlet flow path 101 along the resin guide surface 310a. As a result, these single resin layers smoothly overlap without being mixed when they join, and hang down with approximately the same vector toward the outlet flow path 101 in the stacking flow path 140. In this way, in the resin extrusion die 100, the single resin layers discharged from each layer formation flow path 130 are stacked in order from the inside to the outside to form a cylindrical parison. Among the multiple resin guide surfaces 310, the diameter of the resin guide surface 310 adjacent to the outlet flow path 101 may be larger than the diameter of the resin guide surface 310 adjacent to the upper side by an amount equal to the flow path width of the discharge flow path 132.

[0023] The resin extrusion die 100 is difficult to form by machining, but can be easily manufactured by a 3D printer using metal powder.

[0024] Next, a flow of molding a cylindrical parison from the molten resin received from the extruder will be described.

[0025] First, when molten resin is extruded from a plurality of extruders, a first molten resin a is fed to the injection port 110a, while a second molten resin b is fed to the injection port 110b. The molten resin fed to the injection port 110 flows into the receiving portion 121 of the branch supply path 120. The molten resin in the receiving portion 121 flows to each layer formation flow path 130 by the plurality of supply pipes 122 of the branch supply path 120. The branch supply path 120 supplies the molten resin to the plurality of layer formation flow paths 130 so that different types of single resin layers are overlapped in the stacking flow path 140. That is, layer formation flow paths 130 to which the branch supply path 120a supplies the first molten resin a and layer formation flow paths 130 to which the branch supply path b supplies the second molten resin are alternately present.

[0026] When the molten resin flows into the layer-forming flow paths 130, a cylindrical single resin layer is formed by the filling flow path 131 corresponding to each layer-forming flow path 130. Each single resin layer is discharged from the discharge flow path 132 into the stacking flow path 140. In the stacking flow path 140, each single resin layer is stacked in order from the inside to the outside. This allows the resin extrusion die 100 to mold a cylindrical parison. The molded cylindrical parison passes through the outlet flow path 101 and is discharged from the resin extrusion die 100. Air is blown from the compressed air outlet 320 to the inside of the cylindrical parison discharged from the resin extrusion die 100. As a result, the cylindrical parison is in a state where a constant pressure is applied from the inner peripheral surface to the outside, and the cylindrical shape is maintained.

[0027] According to the resin extrusion die 100 of the present embodiment configured as described above, the single resin layers discharged into the stacking flow path 140 are stacked in order from the inside to the outside, so that the plurality of single resin layers can be stacked in an orderly manner. As a result, the resin extrusion die 100 is less likely to cause molding defects, and can mold a multi-layered tubular parison that is excellent in design.

[0028] Moreover, the resin extrusion die 100 discharges the single resin layer molded in the filling flow path 131 from the discharge flow path 132 of the layer formation flow path 130 to the laminate flow path 140. The discharge flow path 132 is formed with a flow path width narrower than that of the filling flow path 131. This allows the resin extrusion die 100 to adjust the flow rate of the single resin layers discharged from each layer formation flow path 130 to the laminate flow path 140. Therefore, the resin extrusion die 100 can make the flow rate of the single resin layers discharged from each layer formation flow path 130 to the laminate flow path 140 as uniform as possible, which also contributes to the prevention of molding defects and aesthetic appearance of the molded product. Furthermore, the resin extrusion die 100 can change the flow path width of the discharge flow path 132 depending on the type of molten resin used, so that even when multiple molten resins with different viscosities are used, the flow rate of the single resin layers discharged from each layer formation flow path 130 can be made uniform. [Explanation of symbols]

[0029] 100... resin extrusion die, 110 injection port, 120... branched supply channel, 121... receiving section, 122... supply pipe, 130... layer formation channel, 131... filling channel, 132... discharge channel, 140... lamination channel

Claims

1. A resin extrusion die for forming a tubular parison having a plurality of single resin layers laminated thereon, A plurality of injection ports into which different types of molten resin are fed from a molten resin extruder; a plurality of layer forming flow paths arranged in multiple stages along the extrusion direction of the cylindrical parison, each of which molds the single resin layer; a lamination flow path formed in a cylindrical shape, continuous with an outlet flow path of the cylindrical parison, and in which the plurality of single resin layers extruded from each of the plurality of layer forming flow paths are laminated from the inside to the outside; a plurality of branch supply paths connecting the plurality of layer formation paths and the plurality of injection ports so that different types of single resin layers are overlapped in the stacking path; Equipped with Each of the plurality of layer forming flow paths is formed in a shape simulating the outer peripheral surface of a truncated cone. a small diameter end of the layer formation flow path being connected to the lamination flow path, a large diameter end of the layer formation flow path being connected to the branch supply path, and the small diameter end being disposed toward the outlet flow path.

2. The laminated flow path has a flow path width gradually increasing as the laminated flow path approaches the outlet flow path, 2. A resin extrusion die according to claim 1, wherein an inner diameter of said lamination flow passage gradually increases as it approaches said outlet flow passage.

3. 3. The resin extrusion die according to claim 1, wherein the layer formation flow path comprises: a filling flow path that receives the molten resin from the branch supply path and flows the molten resin in a circumferential direction to form the single resin layer; and a discharge flow path that is continuous with the filling flow path and has a flow path width narrower than that of the filling flow path, and that adjusts the flow rate of the single resin layer extruded into the lamination flow path.

4. 4. The resin extrusion die according to claim 3, wherein a flow path width of the discharge flow path in each layer formation flow path differs depending on the type of the molten resin.

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