Method for manufacturing injection molding dies and two-layer molded articles

Abstract

To provide an injection molding die and a method for manufacturing a two-layer molded product that can expand the possibilities of product shape by reliably securing the resin flow path during two-layer molding. [Solution] The core-side mold 30 is provided with a closing member 33 that can extend and retract in the portion corresponding to the peripheral edge of the primary molded product 40A in the first cavity 21A when the mold is closed. The closing member 33 is provided to be movable between a protruding position in which it protrudes in the portion corresponding to the mold shape of the primary molded product 40A in the first cavity 21A when the primary molded product 40A is injected, and a retracted position in which it retracts to the molding surface of the core-side mold 30 when the secondary molded product 40B is injected to push the core-side mold back.

Description

Technical Field

[0001] The present invention relates to an injection mold having a resin surface layer portion formed of a metallic resin material, which is a resin material in which a brightening material, which is fine particles such as metal powder, is dispersed and mixed on the surface of a resin base portion, or a resin surface layer portion formed of a resin material in which a coloring agent is intermittently mixed, and a method for manufacturing a two-layer structured molded product.

Background Art

[0002] Currently, painting, plating, etc. are the mainstream for metallic decoration of two-layer structured molded products such as automotive parts. However, painting requires processes with high environmental loads such as treatment of painting dust. Plating (electroless plating on two-layer structured molded products) requires special equipment and is said to have a high environmental load in terms of waste liquid treatment. Due to these reasons, there is a movement to adopt other methods in view of the environmental load. As a method of realizing metallic decoration other than painting and plating, metallic original adhesion can be cited.

[0003] For metallic decoration by metallic original adhesion, a pellet-shaped masterbatch in which a brightening material, which is fine particles such as metal powder, is dispersed and mixed in a resin material of a base color is put in, heated and melted, and mixed with the resin material of the base color (hereinafter, also referred to as the original adhesion resin material), and then injection molded to realize metallic decoration. Metallic decoration by metallic original adhesion does not require processes with high environmental loads such as treatment of painting dust and treatment of plating solution.

[0004] Many of the brightening materials in the original adhesion resin material of metallic original adhesion are non-spherical and non-cubic shapes such as flakes and elongated flakes, and the appearance of metallic decoration can be changed by orientation. However, in metallic original adhesion, color unevenness occurs when regions with different orientations of the brightening material in the original adhesion resin material are adjacent to each other. Therefore, it is very difficult to mold metallic original adhesion without color unevenness.

[0005] For example, the technology described in Patent Document 1 involves injection molding two types of resin materials containing different luminescent materials from different injection barrels. One resin material is injected into the molded product, and the other resin material is injected from another injection barrel onto the surface of the molded product, thereby obtaining a two-layer molded product. However, it is extremely difficult to design a mold while considering the orientation of the luminescent material in the resin materials injected into the mold from each injection barrel and flowing within the mold.

[0006] Furthermore, there is a proposed molding method (second conventional molding method) in which, after a first layer molding step in which a base molded product is formed by injecting resin material into a mold in a clamped state, a second layer molding step is performed in which a first mold member, which is one side of a half-split mold, is slightly moved relative to a second mold member, which is the other side of the mold, in the mold opening direction, and a second layer is formed on the surface of the base molded product by injection molding of resin material into the gap secured between the base molded product and the first mold member. In the second conventional molding method, there is also a proposal to perform the first layer molding step and the second layer molding step by injection molding of the same resin material containing a glossy material from the same injection barrel (see, for example, Patent Document 2). However, in the second conventional molding method, if a gap is formed between the first mold member, which has been slightly moved relative to the second mold member in the mold opening direction in order to perform the second layer molding step, and the second mold member at a level that causes resin leakage, resin molding becomes impossible. Furthermore, when the mold is slightly moved relative to the second mold member in the mold opening direction in order to perform the second layer molding process, the mold is in an open state, and the first mold member is not fixed to the second mold member. As a result, a gap of a size that allows gas to pass freely is easily formed between the first and second mold members without causing resin leakage. When a gap of a size that allows gas to pass freely is formed between the first and second mold members, it becomes difficult to maintain pressure inside the mold during molding, making it difficult for the resin to adhere to the inner surface of the mold, and thus difficult to mold the resin by the inner surface of the mold. Furthermore, the slight relative movement of the first mold component relative to the second mold component in the mold opening direction for the second layer molding process is performed by the injection molding machine's functions and may not be achievable depending on the performance of the injection molding machine.

[0007] If the entire resin molded product is formed in a single molding process using the same dope-dyed resin material as that used for metallic dope-dyeing, the presence of protrusions such as ribs on the back side of the plate-like portion of the molded product, or partial differences in the thickness of the plate-like portion itself, can easily cause irregularities in the density and orientation of the glossy material, leading to uneven coloring. The presence of protrusions such as ribs on the back side of the plate-like portion of a molded product, or partial differences in the thickness of the plate-like portion itself, can cause variations in the density of fine particles mixed into the resin material used to mold resin products. This is not limited to cases where solution-dyed resin materials are used, but occurs in all cases of molding resin products using resin materials in which fine particles are dispersed and mixed. For example, in the molding of resin products using resin materials in which colorants are scattered to achieve a marble-like finish, the presence of protrusions such as ribs on the back side of the plate-like portion of the molded product causes variations in the density of the colorant in the resin material, affecting the design of the surface.

[0008] Therefore, a manufacturing method for a two-layer molded product that can easily suppress or eliminate color unevenness in the appearance of the resin surface layer and ensure stable aesthetics, which is the problem in Patent Documents 1 and 2, is known, which includes a primary molding step in which a mold having a first mold and a second mold that opens and closes relative to the first mold is used, and a metallic resin material, which is a resin material in which granular luminous material is dispersed and mixed in a cavity secured inside the first and second molds of the mold when they are closed together, is used to form the base portion of the molded product by injection molding; a movable part retraction step in which, after the primary molding step, a partially movable part which is a part of the first mold is retracted from the cavity while the first and second molds of the mold are kept closed together; and a secondary molding step in which, after the movable part retraction step, a resin surface layer is formed on the surface of the molded product base portion by injection molding of the same material as in the primary molding step to form a two-layer molded product, wherein the primary molding step, the movable part retraction step, and the secondary molding step are performed using the same injection molding machine which has only one barrel for injecting the resin material. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2015-131390 [Patent Document 2] Japanese Patent Publication No. 2001-225354 [Overview of the project] [Problems that the invention aims to solve]

[0010] In the conventional method for manufacturing two-layer molded products, which can easily suppress or eliminate color unevenness in the surface appearance of the resin layer as described above and ensure stable aesthetics, there is a need to reliably secure the resin flow path during two-layer molding in order to further expand the possibilities of product shapes, and there was room for improvement in that respect.

[0011] Therefore, the present invention has been made in view of the above circumstances, and in order to broaden the possibilities of product shapes, it provides an injection molding die that can reliably secure a resin flow path during two-layer molding and a method for manufacturing a two-layer molded product. [Means for solving the problem]

[0012] To achieve the above objective, the present invention employs the following means. (1) Embodiment 1 of the injection molding die according to the present invention is an injection molding die for molding a two-layer structure molded product having a primary molded product and a secondary molded product injected after core back based on the mold shape of the primary molded product arranged in a stacked manner, comprising a cavity side mold and a second cavity formed between the primary molded product and the cavity side mold by core back from a first position in which resin material is injected into a first cavity formed by closing the cavity side mold to mold the primary molded product to a second position in which resin material is injected into a second cavity formed between the primary molded product and the cavity side mold. The present invention comprises a core-side mold for stacking and molding the secondary molded product on the primary molded product, wherein the core-side mold includes a closing member that can extend and retract in the portion of the first cavity corresponding to the peripheral edge of the primary molded product at the first position, and the closing member is movably provided between a protruding position that protrudes into the portion of the first cavity corresponding to the mold shape of the primary molded product when the primary molded product is injected, and a retracted position that retracts to the molding surface of the core-side mold when the secondary molded product is injected to core back the core-side mold.

[0013] In the injection molding die according to the present invention, when molding the first primary molded product, the closing member can be made to protrude from a portion of the first cavity corresponding to the peripheral edge of the primary molded product, thereby closing that portion. Therefore, when molding the primary molded product, the resin material flows from the side of the closing member in the first cavity and fills the entire first cavity. Subsequently, after molding the first primary molded product, the closing portion is retracted to the molding surface of the core-side mold along with the core back of the core-side mold, thereby forming a cavity in the closing portion that was protruding into the first cavity. When molding the second secondary molded product, the cavity becomes a flow path for the resin material, and the injected resin material flows and fills the entire second cavity. By using the closing member when injecting the resin material into the first cavity in this way, the possibilities of the product shape can be expanded, the resin flow path in the second cavity can be reliably secured, and resin leakage caused by the injected resin material flowing between the primary molded product and the core-side mold during the molding of the second secondary molded product can be suppressed.

[0014] (2) A second aspect of the present invention is an injection molding die according to the first aspect, wherein the closure member is positioned with a gap between it and a part of the core-side mold corresponding to the peripheral edge of the primary molded product at the protruding position when the primary molded product is being molded, and it is preferable that at least a part of the cavity-side mold overlaps the wall formed by filling the gap with resin material when the closure member is in the retracted position.

[0015] In this injection molding die configuration, during the molding of the first primary product, a portion of the core-side die corresponding to the periphery of the primary product is closed off with a closing member, while a wall is formed between the closing member and the core-side die. Then, during the molding of the second secondary product, a flow path for the resin material is secured by the cavity formed after the closing member retracts, and the wall exposed in the cavity overlaps with a portion of the core-side die corresponding to the periphery of the primary product. Therefore, when the resin material flows through the cavity, it is possible to reliably prevent the injected resin material from flowing back between the primary product and the core-side die and causing resin leakage.

[0016] (3) Embodiment 3 of the method for manufacturing a two-layer molded product according to the present invention is a method for manufacturing a two-layer molded product in which a secondary molded product is laminated and arranged after a core back of a primary molded product based on the mold shape of a primary molded product, comprising: a primary molding step of injecting a resin material into a first cavity formed by closing a cavity-side mold and a core-side mold to mold a primary molded product; a core back step of core backing the core-side mold from a first position in which the primary molded product was molded to a second position in which the secondary molded product is molded; and a secondary molding step of injecting a resin material into a second cavity formed between the primary molded product and the cavity-side mold to laminate and mold the secondary molded product onto the primary molded product, wherein in the primary molding step, at the first position, the resin material is injected with a closing member protruding from the portion corresponding to the peripheral edge of the primary molded product in the first cavity to mold the primary molded product, and in the secondary molding step, at the second position, the closing member is retracted to the molding surface of the core-side mold.

[0017] In the manufacturing method for a two-layer molded product configured as described above, during the molding of the first layer (primary molded product), the closure member is made to protrude from a portion of the first cavity corresponding to the peripheral edge of the primary molded product, thereby closing that portion. As a result, during the molding of the primary molded product, resin material flows from the side of the closure member in the first cavity and fills the entire first cavity. Subsequently, after the molding of the first layer (primary molded product), the closure portion is retracted to the molding surface of the core-side mold along with the core back of the core-side mold, thereby forming a cavity in the closure portion that was protruding into the first cavity. During the molding of the second layer (secondary molded product), the cavity becomes a flow path for the resin material, and the injected resin material flows and fills the entire second cavity. By using the closure member when injecting resin material into the first cavity in this way, the resin flow path in the second cavity can be reliably secured, and resin leakage caused by injected resin material flowing between the primary molded product and the core-side mold during the molding of the second layer (secondary molded product) can be suppressed.

[0018] (4)Aspect 4 of the present invention is a method for manufacturing a two-layer structured molded product according to Aspect 3. In the primary molding step, a gap is provided between a part of the core-side mold corresponding to the peripheral portion of the primary molded product, and the closing member is arranged. In the secondary molding step, it is preferable to set the closing member to the retracted position and arrange at least a part of the cavity-side mold side to overlap with the wall portion formed by filling the resin material into the gap.

[0019] In the manufacturing method of the two-layer structured molded product configured as described above, when forming the first-layer primary molded product, while closing a part of the core-side mold corresponding to the peripheral portion of the primary molded product with the closing member, a wall portion can be formed between the closing member and the core-side mold. And when forming the second-layer secondary molded product, a flow path for the resin material is secured by the cavity portion formed after the closing member is retracted, and the wall portion exposed in the cavity portion is provided to overlap with a part of the core-side mold corresponding to the peripheral portion of the primary molded product. Therefore, it is possible to reliably suppress the resin material injected when the resin material flows through the cavity portion from flowing around between the primary molded product and the core-side mold and causing resin leakage.

Advantages of the Invention

[0020] By the injection mold and the manufacturing method of the two-layer structured molded product according to the present invention, by reliably securing the resin flow path during two-layer molding, the possibility of the product shape can be expanded.

Brief Description of the Drawings

[0021] [Figure 1] It is a diagram for explaining an outline of a method for manufacturing a two-layer structured molded product according to an embodiment of the present invention, and is a cross-sectional view showing a mold of an injection molding machine. [Figure 2] It is a side view of a two-layer structured molded product formed and manufactured using the mold shown in FIG. 1. [Figure 3] It is a perspective view of a main part of a two-layer structured molded product, (a) is a diagram showing a primary molded product formed by primary molding, and (b) is a diagram showing a secondary molded product formed by secondary molding. [Figure 4]This is a cross-sectional view of the mold used during secondary molding. [Figure 5] This is a perspective view of the main part of a two-layer molded product during manufacturing, where (a) is a diagram showing the flow of resin material during molding of the primary molded product, and (b) is a diagram showing the flow of resin material in the secondary molded product. [Figure 6] Figures 6(a) to 6(c) are cross-sectional views showing the work procedure for manufacturing a two-layer molded product according to the first embodiment. [Figure 7] This is a perspective view showing the configuration of the closure member according to the second embodiment. [Figure 8] (a) to (c) are cross-sectional views showing the work procedure for the manufacturing method of a two-layer molded product according to the second embodiment. [Modes for carrying out the invention]

[0022] The following describes an injection molding die and a method for manufacturing a two-layer molded product according to one embodiment of the present invention, with reference to Figures 1 to 8. In the drawings, the same or equivalent parts are denoted by the same reference numeral, and redundant explanations are omitted. Note that the dimensional ratios in each drawing are exaggerated for illustrative purposes and do not necessarily correspond to the actual dimensional ratios. Furthermore, the present invention is not limited to the following embodiments and can be implemented with various modifications within the scope of its essence.

[0023] (First Embodiment) Figure 1 is a diagram illustrating the outline of the manufacturing method for the two-layer molded product 40 of the first embodiment, and is a cross-sectional view showing the injection molding die 1. As shown in Figure 1, the injection mold 1 is used in an injection molding machine to injection mold a two-layer structure molded product 40, which is formed by core-backing a primary molded product 40A based on its mold shape, followed by injection molding of a secondary molded product 40B in a stacked arrangement. The injection mold 1 is shaped to ensure a flow path for the resin during molding.

[0024] In the following explanation, the direction of movement of the core-side mold 30, described later, in the injection molding die 1 will be defined as the vertical direction X. The axial direction (vertical direction X) is used in common for both the injection molding die 1 and the two-layer molded product 40.

[0025] First, the shape of the two-layer molded product 40 formed by the injection molding die 1 will be described. Figure 2 is a side view of the two-layer molded product 40. Figure 3 is a partial perspective view of the molded state of the two-layer molded product 40, where (a) shows the molded state of the first layer after primary molding, and (b) shows the molded state of the second layer after secondary molding. Figure 4 is a cross-sectional view of the two-layer molded product 40, shown along line AA in Figure 2.

[0026] As shown in Figures 2, 3(a), (b), and 4, the two-layer molded product 40 is formed by a primary molded product 40A made of resin and a secondary molded product 40B laminated and integrated onto the upper surface of the primary molded product 40A. In other words, the two-layer molded product 40 is a two-layer molded product in which the primary molded product 40A and the secondary molded product 40B are laminated, and both are formed from the same resin material.

[0027] The two-layer molded product 40 is formed in a shape having a recess 41c on its lower side. The two-layer molded product 40 is a long member and is curved so as to be convex to the upper side X1 when viewed in cross-section from the long axis direction. The two-layer molded product 40 has a long plate-shaped body 41, a vertical connecting piece 42 extending downward from a part of the lower edge that extends in the circumferential direction of the plate-shaped body 41, and a plate-shaped fan gate molded projection 43 that protrudes outward from the lower end portion 42b of the vertical connecting piece 42 in a substantially horizontal direction substantially perpendicular to the vertical direction X.

[0028] The plate-shaped body 41 has a top wall portion 41a extending along the long axis and a side wall portion 41b extending diagonally outward and downward from the top wall portion 41a. A recessed area 41c (see Figure 1) that is recessed downward is formed on the lower surface of the plate-shaped body 41. The plate-shaped body 41 is substantially cylindrical with a top. The side wall portion 41b has a shape that circumfers around the vertical direction X.

[0029] The vertical connecting piece 42 rises vertically upward from the base end 43a of the fangate forming projection 43 at the connection point with the fangate forming projection 43. The vertical connecting piece 42 connects the fangate forming projection 43 to the plate-shaped body 41.

[0030] The fangate molded projection 43 is formed as a plate that protrudes from a vertical connecting piece 42, which is connected to a part of the circumferential direction of the side wall portion 41b of the circumferentially shaped plate-like body 41, to the outer surface side opposite to the inner surface side of the two-layer molded product 40. The fangate molded projection 43 is formed as a substantially triangular plate shape with a protruding tip portion 43b as it gradually tapers towards the tip side from the vertical connecting piece 42. The fangate molded projection 43 is formed extending outwards from the outer circumference of the plate-like body 41 to the outside of the two-layer molded product 40 in an orientation perpendicular to the depth direction (vertical direction X) of the recess 41c of the two-layer molded product 40. The fangate molded projection 43 has a substantially uniform thickness throughout.

[0031] The two-layer molded product 40 shown in Figures 2 and 3(a) and 3(b) is just one example, and the two-layer molded product 40 is not limited to the example configuration and can take on various shapes.

[0032] As shown in Figure 1, the injection molding die 1 has a cavity-side mold 20 and a core-side mold 30 that open and close relative to each other. In the embodiment described here, the cavity-side mold 20 is a fixed mold that is fixed and supported in a stationary state by a support member (not shown). The core-side mold 30 is a movable mold that moves forward and backward relative to the cavity-side mold 20 by a movable part movement mechanism 32 (described later) to open and close the space between it and the cavity-side mold 20.

[0033] Inside the cavity-side mold 20 and the core-side mold 30, which are closed to each other, a cavity 21 is secured, which is a space in which heated and melted resin material (molten resin material) from an injection molding device (not shown) is injected, filled, and molded.

[0034] The cavity-side mold 20 has a spool (not shown), a runner (not shown), and an intermediate gate (not shown) formed therein to guide the resin material supplied from the injection cylinder of the injection molding machine to the cavity 21. The resin material supplied from the injection cylinder of the injection molding machine is guided to the cavity 21 by passing through the spool, runner, and intermediate gate in that order.

[0035] The cavity-side mold 20 has a molding recess 20a into which the entire portion of the core-side mold 30 that protrudes from the first mold body 31 toward the cavity 21 is inserted when the core-side mold 30 is closed. The molding recess 20a is a recess formed in the cavity-side mold 20, recessed from the parting surface 20b of the cavity-side mold 20 that is closed with the core-side mold 30. The inner bottom of the molding recess 20a forms the design surface of the plate-shaped body 41 of the two-layer molded product 40.

[0036] The core-side mold 30 is housed in a movable part housing hole 31b formed through the first mold body 31, which has a parting surface 31a formed thereon that closes to the parting surface 20b of the cavity-side mold 20. The core-side mold 30 is housed in the movable part housing hole 31b of the first mold body 31 so as to be movable forward and backward relative to the cavity 21. The direction of forward and backward movement of the core-side mold 30 at this time (i.e., the axial direction of the movable part housing hole 31b) is defined as the vertical direction X. The core-side mold 30 can be moved relative to the first mold body 31 in the axial direction of the movable part housing hole 31b (vertical direction X) by a movable part moving mechanism 32 provided on the back side of the first mold body 31 opposite to the cavity 21 side. One end of the movable part housing hole 31b in the axial direction opens to the parting surface 31a of the core-side mold 30.

[0037] As shown in Figure 1, the core-side mold 30 is supported by a movable part movement mechanism 32 such that the core tip 30a protrudes toward the cavity 21 side relative to the first mold body 31. By inserting the core tip 30a into the molding recess 20a of the cavity-side mold 20, a cavity 21, which is a space for molding a two-layer molded product 40, can be secured between the core tip 30a and the inner surface of the molding recess 20a.

[0038] The portion of the core-side mold 30 closer to the first mold body 31 than the core tip portion 30a (base end portion) abuts against the inner circumferential surface of the opening of the molding recess 20a that opens into the parting surface 20b of the cavity-side mold 20 when the first mold body 31 is closed against the cavity-side mold 20. As a result, the entire core tip portion 30a of the core-side mold 30 is positioned relative to the cavity-side mold 20, and a cavity 21 of the desired size is secured between the core tip portion 30a and the molding recess 20a. The base end portion of the core-side mold 30 abuts against the inner circumferential surface of the opening of the molding recess 20a without any gaps, preventing leakage of resin material from the cavity 21.

[0039] The core mold 30 can be switched between two mold closing positions P1 and P2, which have different protrusion dimensions from the first mold body 31 to the cavity 21 side, by the movable part movement mechanism 32.

[0040] The first mold closing position P1 (first position) is the position of the core-side mold 30 where primary molding is performed in the cavity 21. The second mold closing position P2 (second position) is the position of the core-side mold 30 where secondary molding is performed in the cavity 21. The second mold closing position P2 is a position where the protrusion dimension toward the cavity 21 is smaller than that of the first mold closing position P1, and the core is separated from the cavity-side mold 20 (core-back position). Here, when the core-side mold 30 is in the first mold closing position P1, the space formed between it and the cavity-side mold 20 is called the first cavity 21A. Also, when the core-side mold 30 is in the second mold closing position P2, the space formed between it and the primary molded product 40A molded in the first cavity 21 is called the second cavity 21B.

[0041] The movable part movement mechanism 32 is capable of moving the core-side mold 30 from the first mold closing position P1 backward in the vertical direction X to the opposite side (hereinafter referred to as the lower side X2) from the cavity 21 side (hereinafter referred to as the upper side X1) to position it at the second mold closing position P2, and moving the core-side mold 30 from the second mold closing position P2 forward in the upper side X1 to position it at the first mold closing position P1. Furthermore, the movable part movement mechanism 32 can switch between fixing and releasing the core-side mold 30 from the first mold closing position P1 and the second mold closing position P2, respectively. Hereinafter, the operation of moving the core-side mold 30 backward from the first mold closing position P1 to the second mold closing position P2 will be referred to as core back.

[0042] The core-side mold 30 is slidably mounted in the axial direction (vertical direction X) within the movable part housing hole 31b of the first mold body 31. The movable part housing hole 31b of the first mold body 31 is formed to penetrate the first mold body 31 with a constant cross-sectional dimension in the axial direction. The core-side mold 30 is formed with a cross-sectional shape that matches the cross-section of the movable part housing hole 31b of the first mold body 31 with high precision.

[0043] As shown in Figure 1, the core-side mold 30 is held in the first mold body 31 in a state where it is inserted and fitted into the movable part housing hole 31b. The core tip portion 30a of the core-side mold 30 protrudes upward X1 from the first mold body 31 and is formed in the same shape as the molding recess 20a of the cavity-side mold 20, and is the portion that faces this molding recess 20a. The core tip portion 30a has a molding projection 30c and a fan gate molding surface (not shown) formed thereon for molding the two-layer molded product 40 shown in Figures 2 and 3.

[0044] When the core-side mold 30 is closed into the cavity-side mold 20 and the entire core tip portion 30a of the core-side mold 30 is inserted into the molding recess 20a of the cavity-side mold 20, the core tip portion 30a is positioned facing the bottom surface of the molding recess 20a, and the fan gate molding surface of the core tip portion 30a is positioned facing the fan gate molding surface of the cavity-side mold 20.

[0045] Furthermore, as shown in Figure 1, the core-side mold 30 has a plate-shaped closing member 33 (closing member) that slides so as to protrude from a portion of the cavity 21 where the vertical connecting piece 42 is formed. The closing member 33 is provided to move back and forth in the axial direction (vertical direction X) by a moving device (not shown). The thickness of the closing member 33 is the same as the thickness of the vertical connecting piece 42 that is molded.

[0046] The core-side mold 30 has a slit portion 30b that extends in a direction perpendicular to the width direction when viewed from the vertical direction X in a plan view. The closing member 33 is provided so as to be slidable in the vertical direction X within the slit portion 30b.

[0047] Figure 5 is a perspective view of the main part of a two-layer molded product during manufacturing, where (a) shows the flow of resin material M1 during molding of the primary molded product 40A, and (b) shows the flow of resin material M2 of the secondary molded product 40B. As shown in Figures 5(a) and (b), the tip 33a of the closing member 33 can extend and retract in the portion of the first cavity 21A corresponding to the peripheral edge (vertical connecting piece 42 in this embodiment) of the primary molded product 40A at the first mold closing position P1. The closing member 33 is slidably provided between a protruding position, as shown in Figure 5(a), where it protrudes into the portion of the first cavity 21A corresponding to the mold shape of the primary molded product 40A when the primary molded product 40A is injected, and a retracted position, as shown in Figure 5(b), where it is retracted to the molding surface of the core-side mold 30 when the secondary molded product 40B is injected. The tip 33a of the closing member 33 is positioned in a portion of the second cavity 21B at the protruding position and in a position retracted from the second cavity 21B at the retracted position.

[0048] Next, a specific example of a manufacturing method for forming a two-layer molded product 40, in which a secondary molded product 40B is stacked on top of a primary molded product 40A by core-backing the core-side mold 30 and then injection molding. Figures 6(a) to 6(c) are cross-sectional views showing the work procedure of the manufacturing method for the two-layer molded product 40 according to the first embodiment. As shown in Figures 6(a) to (c), the manufacturing method for the two-layer molded product 40 includes a primary molding step in which a resin material is injected into a first cavity 21A formed by closing the cavity-side mold 20 and the core-side mold 30 to form a primary molded product 40A, and a secondary molding step in which a resin material is injected into a second cavity 21B formed between the primary molded product 40A and the cavity-side mold 20 to laminate-molde a secondary molded product 40B onto the primary molded product 40A.

[0049] In the primary molding process, as shown in Figure 6(a), at the first mold closing position P1, resin material is injected with the closing member 33 protruding from the portion corresponding to the peripheral edge of the primary molded product 40A in the first cavity 21A to form the primary molded product 40A. At this time, in the primary molding process, as shown in Figure 5(a), the resin material M1 injected from the first flow channel section 21a of the first cavity 21A where the fan gate molding protrusion 43 is formed flows through the second flow channel sections 21b on both sides of the closing member 33 in the portion where the vertical connecting piece 42 is formed, into the third flow channel section 21c where the plate-shaped body 41 is formed, and fills the entire first cavity 21A. That is, the resin material M1 fills the region (second flow channel section 21b) of the portion where the vertical connecting piece 42 is formed, excluding the closing member 33. This forms the primary molded product 40A.

[0050] In the secondary molding process, as shown in Figure 6(b), at the second mold closing position P2, the closing member 33 is retracted to the molding surface of the core-side mold 30, and as shown in Figure 6(c), resin material is injected into the second cavity 21B to form the secondary molded product 40B. That is, after the first cavity 21A is filled with resin material and hardened to form the primary molded product 40A, the core-side mold 30 is core-backed together with the primary molded product 40A. Simultaneously with the core-back of the core-side mold 30, the closing member 33 is also retracted downward within the slit portion 30b (see Figure 5(b)). The closing member 33 is retracted to a position where its tip portion 33a does not protrude above the upper surface of the primary molded product 40A.

[0051] At this time, as shown in Figure 5(b), the resin material M2 injected from the fourth flow channel section 21d of the second cavity 21B, where the fan gate molding protrusion 43 is formed, flows through the fifth flow channel section 21f formed between the molded portions 42a of the vertical connecting piece 42, which is formed after the closure member 33 is retracted, into the sixth flow channel section 21g where the plate-shaped body 41 is formed, and fills the entire second cavity 21B. As a result, the secondary molded product 40B is formed, and a two-layer molded product 40 is formed in which the secondary molded product 40B is stacked on top of the primary molded product 40A.

[0052] After the secondary molding process is completed, the injection molding die 1 is opened and the two-layer molded product 40, which has been molded, is removed from the injection molding die 1.

[0053] Thus, the injection mold 1 according to this embodiment molds a two-layer molded product 40, which is formed by stacking a primary molded product 40A and a secondary molded product 40B that is injected after core-backing based on the mold shape of the primary molded product 40A. The injection mold 1 comprises a cavity-side mold 20 and a core-side mold 30 that, by core-backing from a first mold-closing position P1 where resin material is injected into a first cavity 21A formed by closing the cavity-side mold 20 to mold the primary molded product 40A, to a second mold-closing position P2 where the secondary molded product 40B is molded, injects resin material into a second cavity 21B formed between the primary molded product 40A and the cavity-side mold 20, thereby stacking and molding the secondary molded product 40B on top of the primary molded product 40A. The core-side mold 30 is equipped with a closing member 33 that can extend and retract in the portion corresponding to the peripheral edge of the primary molded product 40A in the first cavity 21A at the first mold-closing position P1. The closing member 33 is provided to be movable between a protruding position that protrudes to the portion of the first cavity 21A corresponding to the mold shape of the primary molded product 40A when the primary molded product 40A is injected, and a retracted position that retracts to the molding surface of the core-side mold 30 when the secondary molded product 40B is injected to retract the core-side mold.

[0054] In the injection molding die 1 configured in this way, when molding the first primary molded product 40A, the closure member 33 can be made to protrude from a portion of the first cavity 21A that corresponds to the peripheral edge of the primary molded product 40A, thereby closing that portion. Therefore, when molding the primary molded product 40A, the resin material flows from the side of the closure member 33 inside the first cavity 21A and fills the entire first cavity 21A. Subsequently, after molding the first primary molded product 40A, the closure member 33 is retracted to the molding surface of the core-side mold 30 along with the core back of the core-side mold 30, thereby forming a cavity (fifth flow path portion 21f) in the closure member 33 that was protruding into the first cavity 21A. When molding the second secondary molded product 40B, the fifth flow path portion 21f becomes a flow path for the resin material, and the injected resin material flows and fills the entire second cavity 21B. By using the occluding member 33 when injecting the resin material 21A into the first cavity in this manner, the resin flow path in the second cavity 21B can be reliably secured, and resin leakage caused by the injected resin material flowing between the primary molded product 40A and the core-side mold 30 during the molding of the second layer secondary molded product 40B can be suppressed.

[0055] (Second embodiment) Figure 7 is a perspective view showing the configuration of the closure member 34 according to the second embodiment. Figures 8(a) to 8(c) are cross-sectional views showing the work procedure for the manufacturing method of the two-layer molded product 40 according to the second embodiment. As shown in Figures 7 and 8(a) to 8(c), in the injection molding die 1A according to the second embodiment, the closing member 34 is positioned with a gap S between it and a part of the core-side mold 30 that corresponds to the peripheral edge of the primary molded product 40A at the protruding position when molding the primary molded product 40A.

[0056] When the closure member 34 is in the retracted position, at least a portion of the cavity-side mold 20 side overlaps the wall portion 44 formed by filling the gap S with resin material. The upper end of the closure member 34 has an inclined surface 34a that gradually becomes upper X1 as it moves from the fan gate molding projection 43 toward the plate-shaped body 41. The formation of such an inclined surface 34a makes it easier for resin to flow from the fourth flow channel 21d toward the fifth flow channel 21f and the sixth flow channel 21g when the closure member 34 is retracted to the molding surface of the core-side mold 30.

[0057] In the primary molding process, as shown in Figure 8(a), at the first mold closing position P1, resin material is injected with the closing member 34 protruding from the portion corresponding to the peripheral edge of the primary molded product 40A in the first cavity 21A to form the primary molded product 40A. At this time, in the primary molding process, the resin material injected from the first flow channel section 21a of the first cavity 21A, where the fan gate molding protrusion 43 is formed, flows through the second flow channel sections 21b on both sides of the closing member 34 where the vertical connecting piece 42 is formed, and the gap S between the closing member 34 and the core-side mold 30, into the third flow channel section 21c where the plate-shaped body 41 is formed, filling the entire first cavity 21A. That is, the resin material fills the area of ​​the portion where the vertical connecting piece 42 is formed, excluding the closing member 34 (the second flow channel section 21b and the gap S). This forms the primary molded product 40A.

[0058] In the secondary molding process, as shown in Figure 8(b), at the second mold closing position P2, the closing member 34 is retracted to the molding surface of the core-side mold 30, and as shown in Figure 8(c), resin material is injected into the second cavity 21B to mold the secondary molded product 40B. That is, after the first cavity 21A is filled with resin material and hardened to form the primary molded product 40A, the core-side mold 30 is core-backed together with the primary molded product 40A. Simultaneously with the core-backing of the core-side mold 30, the closing member 34 is also retracted downward within the slit portion 30b. The closing member 34 is retracted to a position where its tip does not protrude above the upper surface of the primary molded product 40A.

[0059] At this time, the resin material injected from the fourth flow channel section 21d of the second cavity 21B, where the fan gate molding protrusion 43 is formed, flows through the fifth flow channel section 21f formed between the molded parts of the vertical connecting piece 42 that is formed after the closing member 34 is retracted, into the sixth flow channel section 21g where the plate-shaped body 41 is formed, and fills the entire second cavity 21B. As a result, the secondary molded product 40B is formed, and a two-layer molded product 40 is formed in which the secondary molded product 40B is stacked on top of the primary molded product 40A.

[0060] After the secondary molding process is completed, the injection molding die 1 is opened and the two-layer molded product 40, which has been molded, is removed from the injection molding die 1.

[0061] In the injection molding die 1A according to this second embodiment, when molding the first primary molded product 40A, a portion of the core-side mold 30 corresponding to the periphery of the primary molded product 40A is closed off by the closing member 34, and a wall portion 44 is formed between the closing member 34 and the core-side mold 30. Then, when molding the second secondary molded product 40B, a flow path for the resin material is secured by the fifth flow path portion 21f that is formed after the closing member 34 has retracted, and the wall portion 44 exposed in the fifth flow path portion 21f is provided overlapping a portion of the core-side mold 30 corresponding to the periphery of the primary molded product 40A. Therefore, when the resin material flows through the fifth flow path portion 21f, it is possible to reliably suppress the leakage of the injected resin material that would otherwise flow between the primary molded product 40A and the core-side mold 30.

[0062] Furthermore, the technical scope of the present invention is not limited to the embodiments, and various modifications can be made without departing from the spirit of the invention.

[0063] For example, in the embodiment shown above, the portion of the primary molded product 40A in the first cavity 21A through which the closing members 33 and 34 extend and retract is the vertical connecting piece 42 of the primary molded product 40A. However, it is not limited to the vertical connecting piece 42, and other parts may be used. Furthermore, the shape, dimensions, and other configurations of the closing members 33 and 34 can be changed as appropriate.

[0064] Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of Symbols]

[0065] 1. 1A Injection Molding Die 20 Cavity side mold 20a Recess for molding 21 Cavity 21A First Cavity 21B Second Cavity 21f Fifth channel section (cavity section) 30 Core side mold 30a Core tip 30b Slit section 33, 34 Closure member 33a Tip 40 Double-layer structure molded product 40A primary molded product 40B Secondary molded product 41 Plate-shaped body 42 Vertical connection piece 43 Fangate forming protrusions 44 Wall P1 First type closing position (first position) P2 Second type tightening position (second position) S Gap X vertical direction

Claims

1. An injection molding die for molding a two-layer structure molded product, wherein a primary molded product and a secondary molded product injected after core back based on the mold shape of the primary molded product are arranged in a stacked configuration, Cavity side mold and The system comprises a core-side mold that, by closing the cavity-side mold, injects resin material into a first cavity formed to form the primary molded product, and then core-backs from a first position to a second position to form the secondary molded product, thereby injecting resin material into a second cavity formed between the primary molded product and the cavity-side mold, and forming the secondary molded product by stacking it on top of the primary molded product. The core-side mold is provided with a closing member that can extend and retract in the portion of the first cavity corresponding to the peripheral edge of the primary molded product, at the first position. An injection molding die in which the closing member is provided so as to be movable between a protruding position that protrudes to a portion of the first cavity corresponding to the mold shape of the primary molded product when the primary molded product is injected, and a retracted position that retracts to the molding surface of the core-side mold when the secondary molded product is injected to retract the core-side mold.

2. The closing member is positioned at the protruding position when forming the primary molded product, with a gap between it and a portion of the core-side mold corresponding to the peripheral edge of the primary molded product. The injection molding die according to claim 1, wherein when the closing member is in the retracted position, at least a portion of the cavity-side mold overlaps the wall portion formed by filling the gap with resin material.

3. A method for manufacturing a two-layer molded product, wherein a secondary molded product is formed by core backing based on the mold shape of a primary molded product and then injection molding to create a two-layer molded product in which the secondary molded product is stacked and arranged, A primary molding process in which a resin material is injected into a first cavity formed by closing the cavity-side mold and the core-side mold to form the primary molded product, A core-back step is performed to move the core-side mold from the first position where the primary molded product was formed to the second position where the secondary molded product is formed. The process includes a secondary molding step in which a resin material is injected into a second cavity formed between the primary molded product and the cavity-side mold to laminate and form the secondary molded product onto the primary molded product. In the primary molding process, at the first position, the resin material is injected with a closing member protruding from the portion corresponding to the peripheral edge of the primary molded product in the first cavity to form the primary molded product. A method for manufacturing a two-layer molded product, wherein in the secondary molding step, the closing member is retracted to the molding surface of the core-side mold at the second position.

4. In the primary molding process, the closing member is positioned with a gap between it and a portion of the core-side mold that corresponds to the peripheral edge of the primary molded product. The method for manufacturing a two-layer molded product according to claim 3, wherein in the secondary molding step, the closing member is placed in a retracted position and positioned such that at least a portion of the cavity-side mold overlaps the wall portion formed by filling the gap with resin material.

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