Method for producing resin molded product, method for producing molding die, and molding die

Abstract

To provide a method for producing a resin molded product that is capable of producing the resin molded product having an antibacterial effect without adding an antibacterial agent.SOLUTION: A method for producing a resin molded product includes: a mold closing step in which a first mold 30 having a first molding surface 32 and a second mold 40 having a second molding surface 42 arranged opposite to the first molding surface 32 are closed to form a molding space S1 between the first molding surface 32 and the second molding surface 42; and a molding step that is carried out after the mold closing step, and injects molten resin at 200°C or higher into the molding space S1 to form a resin molded product. At least a part of the first molding surface 32 of the first mold 30 is formed of a chrome plating layer 34, and a grain size D1 of crystal grains 37 constituting a surface of the chrome plating layer 34 is 0.6 μm or more and 2.3 μm or less.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The technology disclosed in this specification relates to a method for manufacturing a resin molded product, a method for manufacturing a mold, and a mold.

Background Art

[0002] Conventionally, as a resin molded product, the one described in Patent Document 1 below is known. The resin molded product described in this Patent Document 1 is composed of a thermoplastic resin and is used as an interior material of a vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, the need for antibacterial properties has been increasing, and resin molded products that are expected to be touched by passengers, such as interior materials of vehicles, are required to have antibacterial effects. As a method for imparting an antibacterial effect to a resin molded product, a method of manufacturing a resin molded product by injection molding a thermoplastic resin added with an antibacterial agent can be considered. However, in such a method, an antibacterial agent and a process and equipment for adding the antibacterial agent are required, resulting in an increase in the manufacturing cost.

[0005] The technology disclosed in this specification has been completed based on the above circumstances, and an object thereof is to provide a method for manufacturing a resin molded product, a method for manufacturing a mold, and a mold capable of manufacturing a resin molded product having an antibacterial effect without adding an antibacterial agent.

Means for Solving the Problems

[0006] As a means for solving the above problems, the method for manufacturing a resin molded article disclosed in this specification includes a mold closing step of closing a first mold having a first molding surface and a second mold having a second molding surface disposed opposite to the first molding surface to form a molding space between the first molding surface and the second molding surface, and a molding step executed after the mold closing step of injecting a molten resin at 200°C or higher into the molding space to mold a resin molded article. As the first mold, at least a part of the first molding surface is constituted by a chromium plating layer, and a mold is used in which the grain size of crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

[0007] In the above method, the surface of the chromium plating layer is constituted by crystal grains having a grain size of 0.6 μm or more and 2.3 μm or less. In other words, the first molding surface has fine irregularities constituted by a large number of crystal grains. Therefore, in the molding step, it is possible to mold a resin molded article having fine irregularities with the shape of the fine irregularities on the first molding surface inverted. By forming fine irregularities on the surface of the resin molded article, an antibacterial action can be imparted. The reason why the resin molded article having fine irregularities exhibits an antibacterial action is considered to be that the bacteria adhering to the surface of the resin molded article are caught in the recesses, resulting in the suppression of movement and thus the suppression of growth. Further, at least a part of the first molding surface is constituted by a chromium plating layer. Thereby, in the molding step, by injecting a molten resin at 200°C or higher, chromium ions can be deposited from the first molding surface and adhered to the surface of the resin molded article. The chromium ions adhered to the surface of the resin molded article can exhibit an antibacterial action by binding to bacteria. Thus, by the above method, a resin molded article having an antibacterial action can be manufactured without adding an antibacterial agent.

[0008] Also, as a means for solving the above problems, the method for manufacturing a mold disclosed in this specification includes a plating step of forming a chromium plating layer on the surface of a mold base material, and is characterized in that the grain size of crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

[0009] In the above method, fine irregularities are formed on the surface of the chromium plating layer by crystal grains. By performing injection molding using such a surface with fine irregularities as the molding surface, a resin molded product having fine irregularities with the shape of the irregularities of the mold reversed can be molded. By forming fine irregularities on the surface of the resin molded product, an antibacterial action can be imparted.

[0010] Further, it can be provided with a heat treatment step that is performed after the plating step and heats the chromium plating layer at 300°C or higher. By heating the chromium plating layer at 300°C or higher, the hardness and wear resistance can be improved. Thereby, it is possible to suppress the situation where the surface of the chromium plating layer is scratched.

[0011] Further, as a means for solving the above problems, the mold disclosed in this specification has a molding surface constituted by a chromium plating layer, and is characterized in that the grain size of the crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

[0012] In the above configuration, fine irregularities are formed on the surface of the chromium plating layer by crystal grains. By performing injection molding using such a mold, a resin molded product having fine irregularities with the shape of the fine irregularities of the mold reversed can be molded. By forming fine irregularities on the surface of the resin molded product, an antibacterial action can be imparted.

Effects of the Invention

[0013] According to the present invention, it is possible to provide a method for manufacturing a resin molded product, a method for manufacturing a mold, and a mold that can manufacture a resin molded product having an antibacterial action without adding an antibacterial agent.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0015] An embodiment of the present invention will be described with reference to FIGS. 1 to 7. In this embodiment, as a method for manufacturing a resin molded product, a method for manufacturing a door trim 10 (an interior material for a vehicle, see FIG. 6) that constitutes a door for a vehicle will be exemplified. In addition, a first molding die 30 (molding die, see FIG. 6) used for manufacturing the door trim 10 and a method for manufacturing the first molding die 30 will be described.

[0016] As shown in FIG. 5, the first molding die 30 of the present embodiment constitutes a molding apparatus 20 for manufacturing the door trim 10. The molding apparatus 20 includes a first molding die 30, a second molding die 40, and an injection device 50. The first molding die 30 is disposed below the second molding die 40 and has a recess 31 that is open upward. The inner surface of the recess 31 is a first molding surface 32 for molding the design surface (the surface on the vehicle interior side) of the door trim 10. The second molding die 40 has a convex portion 41 that protrudes downward. The outer surface of the convex portion 41 is a second molding surface 42 for molding the back surface (the surface on the vehicle exterior side) of the door trim 10.

[0017] The first mold 30 is configured to be movable in the vertical direction by a driving device (e.g., an electric motor, an air cylinder, a hydraulic cylinder, etc.) not shown in the drawings. By moving the first mold 30 away from the second mold 40, an open mold state (not shown) can be achieved. Also, by bringing the first mold 30 closer to the second mold 40, a closed mold state as shown in FIG. 5 can be achieved. In this closed mold state, a molding space S1 is provided between the first molding surface 32 and the second molding surface 42.

[0018] An injection device 50 capable of injecting the thermoplastic resin constituting the door trim 10 is attached to the second mold 40. A flow path 49 for allowing the thermoplastic resin injected from the injection device 50 to flow into the molding space S1 is formed in the second mold 40. Examples of the thermoplastic resin constituting the door trim 10 include polyolefins (such as polypropylene and polyethylene), polyester resins (such as polylactic acid and polyethylene terephthalate), polystyrene, acrylic resins (resins obtained using methacrylate and / or acrylate, etc.), polyamide resins, polycarbonate resins, polyacetal resins, and ABS resins.

[0019] As shown in FIG. 7, the first mold 30 includes a mold base material 33 that forms most of it, and a chromium plating layer 34 formed on the upper surface (the surface on the side of the second mold 40) of the mold base material 33. The mold base material 33 is mainly composed of iron and contains carbon, silicon, manganese, phosphorus, sulfur, etc. The chromium plating layer 34 is made of chromium and is formed by performing a plating process on the surface of the mold base material 33.

[0020] On the upper surface of the mold base material 33, as shown in FIG. 7, a plurality of recesses 35 for forming a matte pattern on the design surface of the door trim 10 are formed. The recesses 35 can be formed by, for example, performing an etching process on the surface of the mold base material 33. The chromium plating layer 34 is formed on the protruding end surface of the convex portion 36 provided between adjacent recesses 35. Thereby, the first molding surface 32 is constituted by the surface of the chromium plating layer 34 and the inner surface of the recess 35 in the mold base material 33. The grain size D1 of the crystal grains 37 constituting the surface of the chromium plating layer 34 is set to be 0.6 μm or more and 2.3 μm or less.

[0021] Next, a method for manufacturing the first molding die 30 will be described. The method for manufacturing the first molding die 30 includes a coating step of applying a coating material 51 having insulating properties to the surface of the mold base material 33, a plating step that is performed after the coating step and forms a chromium plating layer 34 on the surface of the mold base material 33, and a heat treatment step that is performed after the plating step and heats the chromium plating layer 34 at 300°C or higher.

[0022] In the coating step, as shown in FIG. 1, a coating material 51 having insulating properties is applied to the surface of the mold base material 33. At this time, the recess 35 is filled with the coating material 51. As the coating material 51, for example, a phenolic resin can be used, but it is not limited thereto. Then, as shown in FIG. 2, a portion of the coating material 51 applied to the protruding end surface of the convex portion 36 is removed. Thereby, the protruding end surface of the convex portion 36 is exposed.

[0023] In the plating step that is performed after the coating step, as shown in FIG. 3, the mold base material 33 coated with the coating material 51 is immersed in a plating bath 52 (chromium plating bath, sergeant bath) mainly composed of chromic acid and sulfuric acid. Then, the mold base material 33 is connected to a power supply 54 so that the mold base material 33 becomes the negative electrode and the electrode 53 becomes the positive electrode, and electroplating is performed on the mold base material 33. Thereby, chromium ions in the plating bath 52 are reduced and deposited as a chromium plating layer 34 on the protruding end surface of each convex portion 36 of the mold base material 33 as shown in FIG. 7. Here, as plating treatment conditions, for example, bath temperature 25 to 40°C, current density 20 to 80 A / dm 2By doing so, the grain size D1 of the crystal grains 37 is set to be 0.6 μm or more and 2.3 μm or less. As a result, a brush-like fine unevenness composed of a large number of crystal grains 37 is formed on the surface of the chromium plating layer 34. Thereafter, the coating material 51 is removed from the mold base material 33 on which the chromium plating layer 34 is formed.

[0024] In addition, by adjusting the distance L1 (electrode distance, see Fig. 3) between the electrode 53 and the mold base material 33, the current density of the opposing surface of the mold base material 33 to the electrode 53 can be adjusted. Thereby, the grain size D1 of the crystal grains 37 in the chromium plating layer 34 can be adjusted. In the range of a current density of 20 to 80 A / dm 2 as the current density increases, the grain size D1 becomes smaller, and as the current density decreases, the grain size D1 becomes larger.

[0025] In the heat treatment step, as shown in Fig. 4, the mold base material 33 on which the chromium plating layer 34 (not shown in Fig. 4) is formed is accommodated in a heating furnace 60, and the chromium plating layer 34 is heated at 300 °C or higher, for example, for 1 hour or more using a heater 61 provided in the heating furnace 60. Thereby, the first mold 30 is completed.

[0026] Next, a method for manufacturing the door trim 10 using the molding apparatus 20 will be described. The method for manufacturing the door trim 10 of the present embodiment includes a mold closing step of closing the first mold 30 and the second mold 40, and a molding step of molding the door trim 10.

[0027] In the mold closing step, as shown in Fig. 5, by closing the first mold 30 having the first molding surface 32 and the second mold 40 having the second molding surface 42 arranged to face the first molding surface 32, a molding space S1 is formed between the first molding surface 32 and the second molding surface 42.

[0028] In the molding process performed after the type closing process, as shown in FIG. 6, molten resin at 200° C. or higher is injected from the injection device 50 into the molding space S1. Then, the molten resin cools and solidifies, thereby molding the door trim 10. On the design surface 10A of the door trim 10, as shown in FIG. 7, the uneven shape of the concave portion 35 and the convex portion 36 is transferred, thereby forming the uneven portion 11 (embossed pattern). And on the design surface of the door trim 10, at the location facing the chromium plating layer 34 (the bottom surface of the uneven portion 11), a fine uneven shape composed of crystal grains 37 is transferred, thereby forming fine unevenness 12. That is, the protrusion diameter of the unevenness 12 is about the same as the particle diameter D1 of the crystal grains 37, and is 0.6 μm or more and 2.3 μm or less.

[0029] Next, the effects of the present embodiment will be described. In the present embodiment, the surface of the chromium plating layer 34 is composed of crystal grains 37 having a particle diameter D1 of 0.6 μm or more and 2.3 μm or less. In other words, the first molding surface 32 has fine unevenness (concave portion 35 and convex portion 36) composed of a large number of crystal grains 37. Therefore, in the molding process, it is possible to mold the door trim 10 having fine unevenness 12 with the shape of the fine unevenness of the first molding surface 32 reversed. By forming fine unevenness 12 on the surface of the door trim 10, an antibacterial action can be imparted. The reason why the door trim 10 having fine unevenness 12 exhibits an antibacterial action is considered to be that the bacteria adhering to the surface of the door trim 10 are caught in the concave portions of the unevenness 12, resulting in the suppression of movement and thus the suppression of growth.

[0030] Also, at least a part of the first molding surface 32 is composed of the chromium plating layer 34. Thereby, in the molding process, by injecting molten resin at 200° C. or higher, chromium ions can be deposited from the first molding surface 32 and adhered to the surface of the door trim 10. The chromium ions adhered to the surface of the door trim 10 can combine with bacteria to exhibit an antibacterial action. Thus, in the present embodiment, it is possible to manufacture the door trim 10 having an antibacterial action without adding an antibacterial agent.

[0031] In addition, the manufacturing method of the first mold 30 of the present embodiment is executed after the plating process and includes a heat treatment process of heating the chromium plating layer 34 at 300°C or higher. By heating the chromium plating layer 34 at 300°C or higher, the hardness and wear resistance can be improved. Thereby, it is possible to suppress the situation where the surface of the chromium plating layer 34 is scratched.

[0032] <Other Embodiments> The technology disclosed in this specification is not limited to the embodiments described above and by the drawings. For example, the following embodiments are also included in the technical scope. (1) In the above embodiment, the door trim is exemplified as the resin molded product, but it is not limited thereto. For example, the resin molded product may be an interior material for vehicles other than the door trim (instrument panel, pillar garnish, roof lining, etc.), an interior material for vehicles such as airplanes and ships, or an interior component constituting furniture such as a sofa and a chair. (2) In the above embodiment, the one using a heating furnace is exemplified as the heat treatment process, but it is not limited thereto. For example, in the heat treatment process, a laser may be irradiated onto the molding surface to heat the chromium plating layer. (3) In the above embodiment, the one in which the concave portion 35 and the convex portion 36 are formed on the surface of the mold base material 33 is exemplified, but a configuration in which the concave portion 35 and the convex portion 36 are not formed may also be used. Further, all of the first molding surfaces 32 may be constituted by the chromium plating layer.

Explanation of Reference Numerals

[0033] 10... Door trim (resin molded product), 30... First mold, 32... First molding surface, 33... Mold base material, 34... Chromium plating layer, 37... Crystal grains, 40... Second mold, 42... Second molding surface, S1... Molding space, D1... Grain size of crystal grains

Claims

1. A mold closing step of closing a first mold having a first molding surface and a second mold having a second molding surface disposed opposite to the first molding surface to form a molding space between the first molding surface and the second molding surface; A molding step of performing, after the mold closing step, injecting a molten resin of 200° C. or higher into the molding space to mold a resin molded product; and A method for manufacturing a resin molded product, wherein, as the first mold, a mold is used in which at least a part of the first molding surface is constituted by a chromium plating layer, and the grain size of crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

2. A plating step of forming a chromium plating layer on the surface of a mold base material; A method for manufacturing a mold, wherein the grain size of crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

3. The method for manufacturing a mold according to claim 2, further comprising a heat treatment step of heating the chromium plating layer at 300° C. or higher after the plating step.

4. Having a molding surface constituted by a chromium plating layer; A mold in which the grain size of crystal grains constituting the surface of the chromium plating layer is 0.6 μm or more and 2.3 μm or less.

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