JP2014124770A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method capable of molding a sandwich molding having a surface layer whose thickness varies partially.SOLUTION: In a provided problem-solving injection molding method, a sandwich molding portion 9h is molded by executing a substrate molding step of initially molding a substrate layer 9g comprising a first resin 9b within a mold cavity 9a and a first mold cavity expansion step of forming a mold cavity-expanded portion continuous with the substrate layer 9g and then executing, via the mold cavity-expanded portion, a first injection-filling step, a second mold cavity expansion step, and a second injection-filling step so as to laminate the sandwich molding portion 9h possessing a surface layer consisting of the first resin 9b atop the substrate layer 9g and to avail the substrate layer 9g as a portion of the surface layer of a sandwich molding 9.

Description

  The present invention relates to an injection molding method for a sandwich molded article comprising a surface layer and an inner layer.

  Conventionally, a sandwich molded article including a surface layer and an inner layer included in the surface layer is known. The sandwich molded product is one of multilayer molded products made of various combinations of different materials, the same materials, different colors, and the same colors in resin molded products. Unlike a multilayer molded product in which another layer is laminated only on one surface of one layer, such a sandwich molded product is a multilayer molded product in which the inner layer is included in the surface layer. Since it is not completely exposed on the surface layer and the appearance and design of the resin molded product itself can be secured on the surface layer, it is suitable for cost reduction and environmental response in recent years using plastic resource waste and waste plastic as raw materials. Sandwich molded products that use recycled resin as the inner layer are used as resin molded products for large parts that use large amounts of resin, such as automobile bumpers, pallets for transportation and logistics, or container boxes. Sandwich molded products are also used for members that require added value, such as weight reduction and electromagnetic wave shielding function, by ensuring foam appearance and functional resin in the inner layer while ensuring the appearance of the product by the surface layer. ing.

  As an injection molding method (co-injection method) for molding a sandwich molded product, two methods, a multistage molding method and a simultaneous molding method, are mainly known. The multi-stage molding method is a method in which the molten resin for the surface layer is injected and filled into the mold cavity, and then the molten resin for the inner layer is injected and filled into the molten resin for the surface layer, and the mold cavity is filled with these two molten resins. (Patent Document 1). In the simultaneous molding method, after injecting and filling the surface layer molten resin into the mold cavity, the surface layer molten resin and the inner layer molten resin are arranged on the outer peripheral side, and the inner layer molten resin is at the center. In this laminar flow state, the surface layer molten resin injected and filled is injected and filled, and the mold cavity is filled with these two molten resins (Patent Document 2).

Japanese Patent Laid-Open No. 08-174603 JP 2001-096566 A

  However, in general injection molding methods for molding sandwich molded products, including the injection molding methods described in Patent Document 1 and Patent Document 2, in the injection filling process of the surface layer resin and the inner layer resin, The process of filling the mold cavity will eventually proceed almost simultaneously in the mold cavity, even if there are some differences in the start and completion timing of each resin injection and filling process. Since it depends on the flow, the surface layer and the inner layer are formed at a substantially constant thickness ratio (surface layer thickness: inner layer thickness = X: Y) in a direction orthogonal to the inner surface of the mold cavity. As a result, the surface layer is formed with substantially the same thickness on substantially the entire surface of the sandwich molded product. As described above, in a general injection molding method for molding a sandwich molded product, it has been difficult to mold the sandwich molded product so that the thickness of the surface layer is partially different.

  Further, in order to prevent the occurrence of resin reversal failure due to the free flow of the surface layer resin and the inner layer resin proceeding substantially simultaneously as described above, the filling ratio of the inner layer resin to the volume of the sandwich molded product must be kept low. The filling ratio of the inner layer resin cannot be increased. This low filling ratio of the resin for the inner layer in the sandwich molded product is an obstructive factor when it is desired to form the surface layer thinly, and depending on the part of the sandwich molded product, it is a factor that only the surface layer is formed without the inner layer. Become. In particular, the latter is not a result that is intentionally controlled but a result that depends on the free flow of each resin, and the reproducibility for each molding cycle is low. Therefore, the sandwich molded product in which such a part is formed is processed as a molding defect product, and the production efficiency of the sandwich molded product is lowered. Here, the resin reversal failure means that the inner layer resin is injected and filled out of the surface layer resin instead of in the surface layer resin, or after the inner layer resin is injected and filled into the surface layer resin. Furthermore, it is a defect that flows from the inside of the surface layer resin to the outside.

  On the other hand, in recent years, the surface layer of a sandwich molded product is partially molded, for example, on the front surface side and the back surface side (designed surface and non-designed surface) so that the respective thicknesses are different, that is, the thickness of the sandwich molded product. In the direction (generally, the longitudinal direction of the injection molding machine), there is a demand for molding in a state where the inner layer is eccentric to either the front surface side or the back surface side of the sandwich molded product. Specifically, the surface layer on the surface side (design surface side) is molded with a thin wall to make use of the tactile sensation of the resin for the surface layer (the direct tactile sensation felt by direct contact), and the back surface side (the non-design surface side) The surface layer of () is a case where it is required to form the sandwich molded product thicker than the surface side in order to ensure the rigidity of the entire sandwich molded product and to secure the rigidity of attachment to other parts.

  Moreover, the function of the resin for inner layers can be utilized on the surface layer side by forming the surface layer on the surface side with a thin wall. For example, when a soft resin material is used for the inner layer, or when a soft feeling is imparted by further expanding the foam, even when a hard resin material having a scratch resistance function is used for the surface layer, The soft feeling of the inner layer can be obtained through the surface layer formed with a thin wall.

  On the other hand, when a resin having functionality such as electromagnetic wave shielding properties, vibration damping properties, sound absorption properties, flame retardancy, etc. is adopted and these functionalities are imparted to a resin molded product, these functional resins are relatively expensive. In addition, there is a possibility that the appearance of the product is impaired due to thermal degradation during molding. Therefore, there is a demand to adopt these functional resins in the inner layer to minimize the amount of resin used, and to form sandwich molded products by using inexpensive resin materials on the surface layer as the product design surface. . Even in this case, in order to fully demonstrate the functionality of the resin used for the inner layer, it is desirable to make the surface layer on the front side thin, and in order to ensure product rigidity, it is desirable to make the surface layer on the back side thick. The arrangement is such that the inner layer is eccentric on the surface side.

  Such a resin molded product having a plurality of functions can be obtained not by a sandwich molded product but also by a laminated molded product. For example, a laminate formed by laminating a layer formed by foaming and expanding a soft resin on the front side and a layer formed by thickly molding a hard resin imparted with a reinforcing additive or the like on the back side. By adopting a product, it is possible to impart different functionality between soft (soft feeling / designability) and hard (product rigidity) to a resin molded product. However, it is difficult to impart scratch resistance to such a laminated molded article unless the post-molding is a post-treatment (post-process) because the surface side layer is a soft resin. And in laminated molded products that use functional resin for the front side layer and inexpensive resin for the back side layer, depending on the type of resin, it is sufficient for the back side layer as well as the front side layer. It may be difficult to impart a good design property. For this reason, it is difficult to ensure the quality of the design surface, or in the case of a member that covers the non-design surface side, such as a cover part, or a member in which the front and back surfaces of the product are almost the design surface, There is a problem that quality degradation due to differences in touch and touch is large.

  The present invention has been made in view of the above-described demands and problems, and specifically, provides an injection molding method capable of molding a sandwich molded product such that the thickness of the surface layer is partially different. The purpose is to do.

  In order to achieve the above object, a first injection molding method according to the present invention uses a first mold and a second mold capable of forming a mold cavity to form a sandwich molded product having a surface layer and an inner layer. An injection molding method for molding, wherein the first mold and the second mold are clamped, a non-foaming first resin is injected and filled into the mold cavity, and a base layer is molded. After completion of the material molding process, the mold cavity first expansion process for expanding the mold cavity by a predetermined amount after completion of the base material molding process, and after the mold cavity first expansion process starts, In one expansion step, the first resin is injected and filled into a mold cavity expansion portion formed between the base material layer and one of the first mold and the second mold. And a first filling of the mold cavity extension with the first resin. After the completion of the first filling and filling step, a mold cavity second expansion step for further expanding the mold cavity expansion portion by a predetermined amount, and after the start of the mold cavity second expansion step, And a second injection filling step of injecting and filling the second resin into the first resin in the mold cavity extension portion.

  In order to achieve the above object, a second injection molding method according to the present invention uses a first mold and a second mold capable of forming a mold cavity to form a sandwich molded product comprising a surface layer and an inner layer. An injection molding method for molding, wherein the first mold and the second mold are clamped, a foamable first resin is injected and filled into the mold cavity, and a base layer is molded After completion of the molding step, the mold cavity first expansion step for expanding the mold cavity by a predetermined amount after completion of the base material molding step, and after the start of the mold cavity first expansion step, the mold cavity first In the expansion step, the first resin is injected and filled into a mold cavity expansion portion formed between the base material layer and one of the first mold and the second mold, A first shot filling the mold cavity extension with the first resin. A mold cavity second expansion step of expanding the mold cavity extension portion by a predetermined amount after the start of the first injection filling step and foaming the first resin in the mold cavity extension portion; After the completion of the first injection filling step and after the start of the mold cavity second expansion step, the second injection filling is performed by injection filling the second resin into the first resin in the mold cavity expansion portion. And a process.

  In the injection molding method according to the present invention, the second resin is a foamable resin, and after the start of the second injection filling process, the mold cavity expansion portion is further expanded by a predetermined amount, and the mold cavity is expanded. A mold cavity third expansion step for foaming the second resin injected and filled in the first resin in the expansion portion may be provided.

  In the injection molding method according to the present invention, the expansion of the mold cavity may be performed by at least one of a mold opening / closing operation by a mold opening / closing mechanism of the injection molding machine and a moving operation of the movable part in the mold.

  ADVANTAGE OF THE INVENTION According to this invention, the injection molding method which can shape | mold so that the thickness of a surface layer may differ partially in a sandwich molded product can be provided.

FIG. 3 is a schematic cross-sectional view of a mold showing the first half of the molding process of the injection molding method according to Example 1. FIG. 3 is a schematic cross-sectional view of a mold showing the latter half of the molding process of the injection molding method according to Example 1. 1 is a schematic cross-sectional view showing a sandwich molded product during each molding step of an injection molding method according to Example 1. FIG. It is a schematic sectional drawing of the metal mold | die which shows the mold cavity 2nd expansion process and 2nd injection filling process of the injection molding method which concerns on Example 2. FIG. It is a schematic sectional drawing which shows the sandwich molded product in each molding process other than the mold cavity 2nd expansion process of the injection molding method which concerns on Example 2, a 2nd injection filling process. It is a schematic sectional drawing of the metal mold | die which shows the mold cavity 2nd expansion process of the injection molding method which concerns on Example 3, a 2nd injection filling process, and a mold cavity 3rd expansion process. It is a schematic sectional drawing which shows the sandwich molded product in each molding process of the mold cavity 2nd expansion process of the injection molding method which concerns on Example 3, a 2nd injection filling process, and a mold cavity 3rd expansion process. It is a schematic sectional drawing of the metal mold | die which shows the mold cavity 2nd expansion process of the injection molding method which concerns on Example 4, a 2nd injection filling process, and a mold cavity 3rd expansion process. It is a schematic sectional drawing which shows the sandwich molded product in each molding process of the mold cavity 2nd expansion process of the injection molding method which concerns on Example 4, a 2nd injection filling process, and a mold cavity 3rd expansion process. It is a schematic sectional drawing of the metal mold | die which shows another form of the base material layer of the injection molding method which concerns on Example 1. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  The injection molding method according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1A to FIG. 1C are schematic cross-sectional views of a mold showing the first half of the molding process of the injection molding method according to the first embodiment. 1A shows a base material forming step, FIG. 1B shows a mold cavity first expansion step, and FIG. 1C shows a first injection filling step. 2A to 2C are schematic cross-sectional views of the mold showing the latter half of the molding process of the injection molding method according to the first embodiment. FIG. 2A shows the start of the mold cavity second expansion process and the second injection filling process, and FIG. 2B shows the completion of the mold cavity second expansion process and the second injection filling process. ) Shows the product extraction process. FIG. 3A to FIG. 3C are schematic cross-sectional views illustrating a sandwich molded product during each molding step of the injection molding method according to the first embodiment. 3A is a sandwich molded product after the completion of the first injection filling process, FIG. 3B is a sandwich molded product at the start of the mold cavity second expansion process and the second injection filling process, FIG. 3C. Shows the sandwich molded product after the product cooling process is completed. FIG. 10 is a schematic cross-sectional view of a mold showing another form of the base material layer of the injection molding method according to Example 1.

  As shown in FIG. 1 (a), the injection molding machine used in the injection molding method according to the first embodiment has a fixed mold 2 (first mold) and a movable mold 4 (first mold) capable of forming a mold cavity 9a. 2 molds), a first injection unit 17 that forms a surface layer of the sandwich molded product 9 and is capable of plasticizing (melting) the non-foamable first resin 9b and injection filling the mold cavity 9a. A non-foamable second resin 10b that forms an inner layer is plasticized, and a second injection unit 18 that can be injected and filled into a mold cavity extension 90a described later is provided. Here, in FIG. 1 and others, the second injection unit 18 is disposed above the fixed mold 2, but each of the first injection unit 17 and the second injection unit 18 is injected into the fixed mold 2. If it arrange | positions so that filling is possible, well-known arrangement | positioning, such as parallel type | mold arrangement | positioning, V-shaped arrangement | positioning, diagonal arrangement | positioning, and L-shaped arrangement | positioning, is possible, and there is no restriction | limiting which concerns on this invention about arrangement | positioning of two injection units. As long as a necessary injection filling amount can be secured by a commercially available post-injection injection unit, the post-injection injection unit may be added to a general-purpose injection molding machine.

  The fixed mold 2 is attached to a fixed platen (not shown) standing on a base (not shown). The fixed mold 2 includes a first resin flow path 9c through which the first resin 9b injected from the first injection unit 17 flows into the mold cavity 9a, and a mold of the first resin flow path 9c. A gate valve (resin shut-off switching valve) 9d provided at a gate portion communicating with the cavity 9a and the second resin 10b injected from the second injection unit 18 are directed toward the mold cavity extension 90a. A second resin flow path 10c that flows and a gate valve 10d provided in a gate portion communicating with the mold cavity extension 90a of the second resin flow path 10c are provided. The movable mold 4 is attached to a movable platen (not shown) so as to face the fixed mold 2 and can be moved in the longitudinal direction of the injection molding machine (hereinafter referred to as mold opening / closing direction) by a mold opening / closing mechanism (not shown). Is arranged.

  The first resin flow path 9c is branched in the middle by the first resin flow path switching valve 91d, and the first resin branch flow path 90c in which the first resin 9b flows into the mold cavity expansion portion 90a, And a gate valve 90d provided at a gate portion of the first resin branch flow path 90c communicating with the mold cavity extension 90a. In the first embodiment, the first resin flow path 9c, the second resin flow path 10c, and the first resin branch flow path 90c are all configured by hot runners.

  The fixed mold 2 and the movable mold 4 have a shearing edge structure on their respective mold dividing surfaces (sometimes referred to as mold dividing surfaces, parting surfaces, and split surfaces). With the mold opening / closing operation of the mold opening / closing mechanism, the volume of the mold cavity can be varied. The shear edge structure is sometimes called a hollow structure or an inlay structure, etc., and is a structure generally known as a structure of a fitting portion that forms a dividing surface of a mold. A predetermined amount of molten resin injected and filled into the mold cavity is formed between the fixed mold and the movable mold by forming a fitting portion that extends and can be inserted and removed while sliding on each other. Even if the mold is opened, it is possible to prevent leakage from the mold.

  In the first embodiment, the mold is opened with respect to the mold cavity 9a formed between the fixed mold 2 and the movable mold 4 by mold clamping, and is molded in the mold cavity 9a. The newly formed space between the base material layer 9g and the movable mold 4 is referred to as a mold cavity extending portion 90a regardless of the mold opening amount. In addition, a molded body to be molded in the mold cavity expansion portion 90a is referred to as a sandwich molding portion 9h regardless of the resin to be injected and filled.

  In the injection molding method according to the first embodiment, as shown in FIG. 1A, a mold for clamping a surface layer in a mold cavity 9a formed between a fixed mold 2 and a movable mold 4 by clamping. A molding cycle is started by a base material molding step in which the first resin 9b is injected and filled to mold the base material layer 9g. Specifically, the mold clamping force is applied after the movable mold 4 is closed to the fixed mold 2 by a mold opening / closing mechanism (not shown). Next, in a state where the mold clamping force is applied, the first resin flow path switching valve 91d is switched to the first resin flow path 9c side, the gate valve 9d of the first resin flow path 9c is opened, and the first injection is performed. A non-foaming first resin 9b is injected and filled into the mold cavity 9a from the unit 17 through the first resin flow path 9c. In this state, the first resin 9b in the mold cavity 9a is cooled and solidified, and the base material layer 9g is molded in the mold cavity 9a.

  Since the molding of the base material layer 9g by the base material molding process is based on a general injection molding method, a detailed description is omitted, but the inside of the mold cavity 9a is filled with the first resin 9b to be substantially 100%, so-called full Performed in a packed state. In the base material molding step, if necessary, an injection compression method, an injection press molding method, or the first resin 9b is made of a foamable resin, and the movable mold 4 is opened by a minute mold so that the inside of the mold cavity 9a. An expanded foam molding method may be performed in which the first resin 9b injected and filled is foamed. As will be described later, a sandwich molded part 9 h is laminated on the base material layer 9 g made of the first resin 9 b that is molded first, and becomes a surface layer of the sandwich molded product 9. The base material layer 9g may be either the front surface or the back surface (design surface and non-design surface) of the sandwich molded product 9. Thus, by using 9 g of this base material layer as the surface layer of either the front surface or the back surface of the sandwich molded product 9, the thickness of the surface layer of the sandwich molded product 9 is partially different, that is, the surface and the back surface are different. Can be molded as follows.

  In Example 1, for simplicity of explanation and illustration, the base material layer 9g is formed in a flat plate shape, and a sandwich molding portion 9h described later is laminated on the entire surface perpendicular to the mold opening / closing direction. However, as a matter of course, in actual molding, the base material layer 9g may have a predetermined shape having irregularities on at least one side of the fixed mold 2 and the movable mold 4. Furthermore, as shown in FIG. 10, the base material layer 9 g has a shape that becomes a partially thick surface layer on one of the front side surface and the back surface side of the sandwich molded product, for example, an attachment site or the like. There may be. Thus, there is no particular restriction on the arrangement and shape of the base material layer 9g with respect to the sandwich molding part 9h, and not only the front and back sides of the sandwich molded product but also the base material layer 9g is one of the surface layers of the sandwich molded product. By setting it as a part, it can be optionally shaped so that the thickness of the surface layer is partially different.

  Returning to the description of the first embodiment. After the base material forming step, as shown in FIG. 1B, the movable mold 4 is opened by a distance α (alpha) from the fixed mold 2 by a mold opening / closing mechanism (not shown) and held on the fixed mold 2 side. A mold cavity extension 90 a is formed between the base material layer 9 g and the movable mold 4. In this mold cavity first expansion step, the gate valve 90d of the first resin branch flow path 90c and the gate valve 10d of the second resin flow path 10c are openable into the mold cavity expansion portion 90a. (Mold cavity first expansion step).

  In the first embodiment, after the base material forming step, the mold cavity first expansion step is performed in a state where the base material layer 9g is held by the fixed mold 2, but the base material layer 9g is moved to the movable mold. The mold cavity first expansion step may be performed in a state of being held at 4. In this case, the mold cavity extension 90a is formed between the base material layer 9g held on the movable mold 4 side and the fixed mold 2, and the gate valve 90d of the first resin branch flow path 90c and the second The gate valve 10d of the resin flow path 10c is disposed in the mold cavity extension portion 90a so as to be openable. And when these gate valves are arranged at the overlapping position of the mold cavity 9a and the mold cavity extension 90a, at the time of injection filling of the first resin 9b into the mold cavity 9a in the base material molding step, These gate valves are closed to prevent the back flow of the first resin 9b to the respective resin flow paths.

  Returning to the description of the first embodiment. After the mold cavity first expansion step, as shown in FIG. 1C, the first resin flow path switching valve 91d of the first resin flow path 9c is switched to the first resin branch flow path 90c side, and the first resin The gate valve 90d of the branch channel 90c is opened, and the first resin 9b is again sent from the first injection unit 17 through the first resin channel 9c and the first resin branch channel 90c to the mold cavity extension 90a. The inside is injected and filled (first injection filling step). This first injection filling step is a step of injection filling the first resin 9b that becomes the surface layer of the above-described sandwich molding portion 9h. The gate valve 10d of the second resin flow path 10c is closed, and the first resin 9b injected and filled in the mold cavity expansion portion 90a does not flow back into the second resin flow path 10c. The first injection filling process may be performed in conjunction with the volume expansion of the mold cavity expansion portion 90a in the mold cavity first expansion process, not after the mold cavity first expansion process. Further, during and after the first expansion process of the mold cavity, during the first injection filling process, the movable mold 4 is maintained with a mold clamping force that opposes the injection pressure in the first injection filling process.

  Here, the distance α, which is the mold opening amount in the mold cavity first expansion process, is determined so that the mold cavity expansion portion 90a formed in the mold opening operation of the distance α in the mold cavity first expansion process is the first injection. By the filling step, a value that is approximately 100% filled with the first resin 9b injected and filled into the mold cavity extension 90a is set. That is, the first injection filling process is also performed in a full pack state in which the mold cavity expansion portion 90a is substantially 100% filled with the first resin 9b. As a result, the first resin 9b (sandwich molding portion 9h) injected and filled into the mold cavity expanding portion 90a has the design (mold inner surface) of the mold cavity expanding portion 90a as shown in FIG. The skin layer 9e formed on the contact surface (outer peripheral surface) and the contact surface with the base material layer 9g, and the inside of the skin layer 9f are still in a state of being constituted by the molten layer 9f.

  Further, in the first injection filling step that is continuous with the base material forming step, the same first resin 9b as the base material layer 9g is applied to the mold cavity extending portion 90a that is continuous with the base material layer 9g, and the surface layer resin of the sandwich molding portion 9h. Therefore, there is no problem in the fusion (adhesion) property between the base material layer 9g and the sandwich molding part 9h. Further, in view of the cooling and solidification shrinkage of the sandwich molding part 9h after the first injection filling process, in the first injection filling process, the first resin 9b is injected at least by the cooling solidification shrinkage from the volume of the mold cavity expansion part 90a. It is preferable to fill the base layer 9g and the fusion (fixation) strength between the skin layer 9e of the sandwich molding part 9h and the high transferability of the sandwich molding part 9h to the skin layer 9e.

  Next, after the completion of the first injection filling process, as shown in FIG. 2A, the volume of the mold cavity expanding portion 90a is expanded to the product volume together with the volume of the mold cavity 9a (metal mold). Mold cavity second expansion step). Specifically, from the state shown in FIG. 1C (die opening amount: distance α), the movable die 4 is further opened from the fixed die 2 to a distance β (beta) by a die opening / closing mechanism (not shown). . Then, after this mold cavity second expansion step is started, the gate valve 10d of the second resin flow path 10c is opened, and the non-foam forming the inner layer from the second injection unit 18 through the second resin flow path 10c. The second resin 10b is injected and filled into the sandwich molding part 9h (second injection filling step). FIG. 3B shows a flow state of the second resin 10b for the inner layer at the start of the second injection filling process.

  In the second injection filling step, the mold cavity second expansion step and the second injection filling step are linked to the mold cavity second expansion step, that is, in conjunction with the volume expansion rate of the mold cavity expansion portion 90a. The injection filling amount of the second resin 10b for the inner layer to be injected and filled may be controlled. Conversely, in conjunction with the second injection filling step, that is, in conjunction with the injection filling amount of the second resin 10b for the inner layer, the volume expansion of the mold cavity expansion portion 90a in the mold cavity second expansion step. The rate may be controlled, or both may be controlled so that the second resin 10b is injected and filled in the full pack state by the second injection and filling step. Further, during and after the second expansion process of the mold cavity, during the second injection filling process, the movable mold 4 is maintained with a mold clamping force that opposes the injection pressure in the second injection filling process. .

  Thus, the gate cavity 10d of the second resin flow path 10c and the design (mold inner surface) of the mold cavity expansion portion 90a are controlled by interlocking the mold cavity second expansion process and the second injection filling process. In addition, it is possible to maintain a state in which the skin layer 9e of the sandwich-molded portion 9h formed on the contact surface with the base material layer 9g is in close contact. This prevents the occurrence of resin reversal failure in the gate valve 10d portion and the skin layer 9e of the sandwich molding portion 9h, while the skin layer 9e of the first resin 9b for the surface layer is applied by the injection pressure of the second resin 10b for the inner layer. The resin can be injected and filled into the first resin 9b by penetrating the resin. Furthermore, by expanding the volume of the mold cavity expanding portion 90a, the injection filling resistance of the second resin 10b into the first resin 9b can be reduced to the same extent as the free flow of the molten resin in the mold cavity, The filling ratio of the second resin 10b for the inner layer with respect to the volume of the sandwich molding part 9h can be improved.

  Further, the skin layer 9e formed on the outer peripheral surface of the sandwich molding part 9h includes the design of the mold cavity expanding part 90a (mold inner surface) and the surface of the cooled and solidified base material layer 9g on the movable mold 4 side. It is a thin layer that is instantly cooled and solidified by contact. Although this skin layer 9e has a strength capable of preventing the resin reversal failure of the second resin 10b to be injected and filled into the sandwich molding portion 9h, it is not a completely solidified layer, and its temperature is the resin softening point temperature, or It is a layer like a thin film that exhibits a rubber-like elastic behavior in the layer direction at a temperature equal to or higher than the glass solidification temperature and cooling solidification is in progress. Therefore, it is possible to follow the volume expansion of the mold cavity expansion portion 90a (volume expansion of the sandwich molding portion 9h) in the mold cavity second expansion step. On the other hand, the first resin 9b portion including the melted portion continuous with the skin layer 9e of the sandwich molding portion 9h finally becomes a surface layer of the sandwich molding portion 9h by cooling and solidification proceeding from the skin layer 9e.

  Here, similarly to the first injection filling step, in view of the cooling solidification shrinkage of the sandwich molding part 9h, in the interlock control of the mold cavity second expansion step and the second injection filling step, are both steps completed substantially simultaneously? The second injection filling step is preferably completed after the mold cavity second expansion step is completed. Further, in the second injection filling process, it is more preferable to inject and fill the second resin 10b by at least the cooling solidification shrinkage than the volume of the mold cavity expansion part 90a after the mold cavity second expansion process. It is more preferable to secure the fusion (adhesion) strength between the layer 9g and the skin layer 9e of the sandwich molding part 9h and the high transferability to the skin layer 9e and the base material layer 9g of the sandwich molding part 9h.

  After completion of the mold cavity second expansion process and the second injection filling process, as shown in FIG. 2B, the gate valve 10d of the second resin flow path 10c is closed, and the mold cavity 9a and the mold cavity expansion section are closed. When a predetermined mold clamping force is applied to the base material layer 9g and the sandwich molding part 9h in 90a, and these are cooled and solidified, the surface layer on the fixed mold 2 side (the base layer 9g + the surface layer of the sandwich molding part 9h) ) And the surface layer on the movable mold 4 side (surface layer of the sandwich molding part 9h) are molded (sand product cooling and solidification step). The sandwich molded product 9 after completion of the product cooling and solidifying step is shown in FIG. For the sake of illustration, the second resin 10b for the inner layer in the cooled and solidified state is indicated by the same oblique lines as in the molten state.

  After the cooling and solidification of the sandwich molded product 9 is completed, as shown in FIG. 2C, the movable mold 4 is opened from the fixed mold 2 by a mold opening / closing mechanism (not shown), and sandwich molding is performed by a product take-out means (not shown). The product 9 is carried out of the injection molding machine, and the molding cycle is completed.

  As described above, by repeating the steps from FIG. 1A to FIG. 2C, the surface layer (base layer 9g + surface layer of the sandwich molding portion 9h) on the fixed mold 2 side and the movable mold 4 Sandwich molded products 9 having different thicknesses on the side surface layer (surface layer of the sandwich molded portion 9h) can be continuously formed. Moreover, since the filling ratio of the second resin for the inner layer with respect to the volume of the sandwich molding portion can be improved, it is suitable for controlling the surface layer thinly. In Example 1, due to the structure of the sandwich molded product 9, the surface layer on the fixed mold 2 side composed of the base layer 9g + the surface layer of the sandwich molded part 9h is composed of a single surface layer of the sandwich molded part 9h. The sandwich molded product thicker than the surface layer on the movable mold 4 side, that is, the inner layer made of the second resin 10b is eccentric to the movable mold 4 side in the mold opening / closing direction.

  In addition, since the injection filling in the base material forming process, the first injection filling process and the second injection filling process is performed in a full pack state, the surface layer of this sandwich molded product 9 has both front and back surfaces (the fixed mold 2 side and the movable mold). Both the mold 4 side) ensure high design transferability of the mold cavity 9a, and can prevent the occurrence of resin reversal failure when the second resin 10b for the inner layer is injected and filled into the first resin 9b for the surface layer. . Further, the first resin 9b for the surface layer and the second resin 10b for the inner layer are injected and filled into the mold cavity 9a and the mold cavity extension 90a from independent gates (gate valves), respectively. There is no need for a laminar mixing nozzle or the like, and the skin layer 9e of the first resin 9b for the surface layer is penetrated by the injection pressure of the second resin 10b for the inner layer, so the special for the second resin 10b for the inner layer No gate structure or gate valve is required. Therefore, there are few restrictions on arrangement | positioning of the resin flow path connected to these gate parts and a gate part, and design of a metal mold | die becomes easy.

Next, an injection molding method according to Example 2 of the present invention will be described with reference to FIGS. 4A to 4C are schematic cross-sectional views of a mold illustrating a mold cavity second expansion process and a second injection filling process of the injection molding method according to the second embodiment. 4A shows a mold cavity second expansion process, FIG. 4B shows the start of the second injection filling process, and FIG. 4C shows the completion of the second injection filling process. 5 (a) to 5 (e) are schematic cross-sectional views showing a sandwich molded product during the molding cavity second expansion step, the second injection filling step, and other molding steps of the injection molding method according to the second embodiment. It is. FIG. 5A is a sandwich molded product after the completion of the first injection filling, FIG. 5B is a sandwich molded product during the mold cavity second expansion process, and FIG. 5C is a start of the second injection filling process. 5 (d) shows a sandwich molded product when the second injection filling process is completed, and FIG. 5 (e) shows a sandwich molded product after the product cooling process is completed.
Indicates.

  The difference between the injection molding method according to the second embodiment and the injection molding method according to the first embodiment is that the first resin is a foamable resin, and due to this point, the mold cavity first expansion step and The execution timing of the second injection filling process is slightly different. Except for these points, the method is basically the same as the injection molding method according to the first embodiment. Therefore, the detailed description thereof is omitted or described with reference to the first embodiment, and only the differences are described in detail. . Also, in the mold and the injection molding machine, the same one as described in Example 1 is used except that the non-foamable first resin 9b is changed to the foamable first resin 9b ′. Therefore, the description is omitted. In addition, due to the difference between the non-foamable first resin 9b and the foamable first resin 9b ′, the object to be distinguished from the description of the first embodiment is denoted by the same reference sign as in the first embodiment, “” (apostrophe ) ”.

  Here, in the present Example 2, it demonstrates on the assumption that the 1st resin 9b 'is a foaming resin containing a chemical foaming agent. The first resin 9b ′ may be a foamable resin containing a physical foaming agent. In this case, the constituent requirement for appropriately mixing the physical foaming agent into the first resin 9b ′ for the surface layer is a mold. Or, it is necessary for an injection molding machine. However, since these constituent elements are not directly related to the present invention, the description thereof is omitted.

  In the injection molding method according to the second embodiment, first, the base material forming step is performed by the same method as the injection molding method according to the first embodiment, and the base material layer 9g 'is formed in the mold cavity 9a. Similarly, in the same manner as in Example 1, the mold cavity first expansion process and the first injection filling process are performed, and between the base material layer 9g ′ and the movable mold 4 held on the fixed mold 2 side. Then, the mold cavity extending portion 90a is formed, and the foamable first resin 9b ′ is again injected and filled into the mold cavity extending portion 90a from the first injection unit 17 (first injection filling step). Although description and illustration of these steps are omitted, in the description of the injection molding method according to Example 1, and in FIGS. 1 (a) to 1 (c), and FIGS. 3 (a) and 3 (b), non-foaming is performed. It is easy to understand if the first resin 9b is replaced with the foamable first resin 9b ′.

  In a general sandwich molding product injection molding method, a foamable resin material is rarely used for the surface layer due to problems such as exposure of the foam cell to the skin layer. However, as in Example 1, the first resin 9b ′ injected and filled into the mold cavity 9a is obtained by performing injection filling of the foamable first resin 9b ′ in the base molding step in a full pack state. A mold clamping force is applied substantially uniformly to substantially the entire surface of (base material layer 9g ′) to generate foamed cells in the first resin 9b ′ and to the skin layer 9e ′ of the foamed cells when the skin layer 9e ′ is formed. Even if it is a foaming resin, it can be adopted as a resin for the surface layer, as with a non-foaming resin. Further, in the base material forming step, if it is cooled and solidified in a state where a predetermined clamping force is applied, the foaming gas is contained in a compressed state in the base material layer 9g ′, and the foaming gas and the foaming cell are formed after the molding. There is no risk of exposure from the base material layer 9g '(cooling and solidification is performed in an unfoamed state). In Example 2, the base material layer 9g ′ is a molded body (surface layer) having no foamed layer. However, as described in Example 1, in the base material layer forming step, the first resin 9b ′ is used as the base material layer 9g ′. It is also possible to carry out an expanded foam molding method for foaming so that the base material layer 9g ′ is a foam molded body (surface layer) containing the foam layer.

  On the other hand, also in the first injection filling step, the first resin 9b in the mold cavity expansion portion 90c is filled in the mold cavity expansion portion 90c with the foamable first resin 9b ′ in a full pack state. Generation | occurrence | production of the foam cell in '(sandwich molding part 9h') and the expression to the skin layer 9e 'of the foam cell at the time of skin layer 9e' formation can be suppressed. Therefore, as shown in FIG. 5 (a), after the completion of the first injection filling process, the sandwich-molded portion 9h ′ has a skin layer 9e ′ in which no foam cell is exposed, and the inside thereof is the generation of the foam cell. This is a state constituted by the suppressed first resin 9b ′ that is still molten.

  In order to more reliably suppress the generation of foam cells in the first resin 9b ′ and the expression of the foam cells to the skin layer 9e ′ in the base material molding step and the first injection filling step of the second embodiment, By injecting a pressurized gas such as air or nitrogen into the mold cavity 9a or the mold cavity extension portion 90c, the mold cavity 9a or the mold cavity extension portion 90c is preliminarily pressurized at a pressure equal to or higher than the foaming expansion pressure of the foamable first resin 9b ′. A so-called gas counter pressure method of injecting and filling the foamable first resin 9b ′ may be employed.

  Next, as shown in FIG. 4A, after the start of the first injection filling process (that is, in the middle of the first injection filling process or after the completion of the first injection filling process), The volume of 90a is expanded to a product volume together with the volume of the mold cavity 9a, and the molten foamable first resin 9b ′ (sandwich molding section 9h ′) in the mold cavity expansion section 90a is expanded. Foam (mold cavity second expansion step). Specifically, from the state (die opening amount: distance α) shown in FIG. 1C of the first embodiment, the movable die 4 is further moved from the fixed die 2 by a die opening / closing mechanism (not shown) to a distance β (beta). Let the mold open.

  By this mold cavity second expansion step, the skin layer 9e ′ of the sandwich molding portion 9h ′ is continued to the skin layer 9e ′, and the generation of foamed cells is suppressed. Cooling and solidification proceeds, the thickness thereof is slightly increased (about 0.1 to 0.5 mm), and finally the surface layer of the sandwich-molded portion 9h ′ (unfoamed state). For the sake of explanation, the surface layer of the sandwich-molded portion 9h 'will be referred to as a skin layer 9e' hereinafter. On the other hand, in the first resin 9b 'in the molten state in which the generation of foamed cells within the skin layer 9e' of the sandwich-molded portion 9h 'is suppressed, foamed cells are generated and grow in almost all of them. As a result, as shown in FIG. 5B, the sandwich-molded portion 9h ′ has a skin layer 9e formed on the design surface of the mold cavity expanding portion 90a (mold inner surface) and the contact surface with the base material layer 9g ′. It is in a state constituted by “(surface layer) and the foam layer 9 f ′ including the foam cell, which is continuous with the skin layer 9 e ′.

  Next, after the completion of the first injection filling process and after the start of the mold cavity second expansion process (that is, during the mold cavity second expansion process or after the completion of the mold cavity second expansion process) 4), as shown in FIG. 4B, the gate valve 10d of the second resin flow path 10c is opened, and an inner layer is formed from the second injection unit 18 via the second resin flow path 10c. The second resin 10b is injected and filled into the sandwich molding part 9h ′ (first resin 9b ′ for the surface layer) (second injection filling step). FIG. 5C shows the flow state of the second resin 10b for the inner layer at the start of the second injection filling process.

  Here, the foam layer 9f ′ in the sandwich molded part 9h ′ formed in the first injection filling step and the mold cavity second expansion step of the injection molding method according to the second embodiment is the injection molding according to the first embodiment. In the first injection filling step of the method, the strength and density of the non-foamable first resin 9b injected and filled into the mold cavity extension 90a in a full pack state are low. Therefore, as shown in FIG. 5 (c), the second resin 10b for the inner layer that penetrates the skin layer 9e ′ of the sandwich-molded portion 9h ′ with the injection pressure remains as it is due to the injection pressure and the resin flow. While compressing the foaming gas in the foamed cell in the foamed layer 9f ′, the first resin is filled in the foamed cell or the foamed cell 9f ′ is destroyed in order from the site where the strength and density of the foamed layer 9f ′ are low. Replacement is performed in place of 9b ′. On the other hand, as described above, the skin layer 9e 'of the sandwich molding part 9h' is slightly increased in thickness to become the surface layer (unfoamed state) of the sandwich molding part 9h '.

  The step of replacing the foam layer 9f 'with the second resin 10b for the inner layer will be described in a little more detail. When a chemical foaming agent is used, the foaming gas pressure in the foam cell in the formed foamed layer varies depending on the type of chemical foaming agent and molding conditions, but is generally 0.3 to 0.5 MPa (resin temperature). 200 ° C.). On the other hand, the injection filling resin pressure (injection pressure) is generally 30 MPa to 50 MPa or more, although it differs depending on the type of resin and molding conditions.

  In the second injection filling process described above, the second pressure difference between the foaming gas pressure in the foaming cell in the foamed layer 9f ′ and the injection filling pressure of the second resin 10b for the inner layer is the second. When the resin 10b is injected and filled into the sandwich-molded portion 9h ′, the foaming gas in the foamed cell does not increase the injection-filling resistance, and most of the foamed gas in the foamed cell has no effect on the product quality. It is easily compressed to a volume that does not affect and remains in the second resin 10b for the inner layer. Further, a very small part is remelted in the second resin 10b together with the broken foam cell remnants, and is cooled and solidified while being taken into the second resin 10b, so that it does not exist as the foaming gas.

  As a result, as shown in FIG. 5 (d), the volume of the foamed layer 9f ′ of the sandwich-molded portion 9h ′ (the melted layer where the foamed layer 9f ′ is not a foamed layer) depends on the combination of resins used, product shape and molding conditions. In this case, the density reduction due to the foam cells of the foam layer 9f ′ or the foam magnification ratio) can be almost completely replaced with the second resin 10b for the inner layer. Therefore, the volume of the unfoamed portion of the sandwich molded portion 9h ′, that is, the thickness of the surface layer of the sandwich molded portion 9h ′ is controlled with a predetermined accuracy from the volume of the foamed layer 9f ′ (the amount of decrease in density or the amount of expansion ratio). It becomes possible. On the other hand, the base material layer 9g ′ which is the surface layer of either the front surface or the back surface of the sandwich molded product 9 ′ is formed on the fixed mold 2 side in the mold opening / closing direction with an arbitrary shape and an arbitrary thickness. Therefore, in the injection molding method according to the second embodiment, in the sandwich molded product, not only can the surface layer thickness be partially different, but also the thickness of each surface layer has a predetermined accuracy. It becomes possible to control with.

  Further, it is difficult to replace the volume of the foamed layer 9f ′ of the sandwich molded part 9h ′ almost completely with the second resin 10b for the inner layer, and the surface layer of the sandwich molded part 9h ′ is not covered with the unfoamed first resin 9b. Even when “and a part of the outer peripheral surface portion of the foamed layer 9f” coexist, it is possible to estimate the thickness of the surface layer of the sandwich molded part 9h ′ with a predetermined accuracy from the volume of the foamed layer 9f ′. .

  After completion of the mold cavity second expansion step and the second injection filling step, as shown in FIG. 4C, the base layer 9g ′ and the sandwich molding portion 9h in the mold cavity 9a and the mold cavity expansion portion 90a. When these are cooled and solidified in a state where a predetermined mold clamping force is applied to ', a sandwich molded product 9' is formed (product cooling solidification step). FIG. 5 (e) shows the sandwich molded product 9 'after completion of the product cooling and solidifying step. For the sake of illustration, the second resin 10b for the inner layer in the cooled and solidified state is indicated by the same oblique lines as in the molten state.

  After the cooling and solidification of the sandwich molded product 9 ′ is completed, although not shown, the movable mold 4 is opened from the fixed mold 2 by a mold opening / closing mechanism (not shown), and the sandwich molded product is taken by a product take-out means (not shown). 9 'is carried out of the injection molding machine, and the molding cycle is completed.

  As described above, after the base material forming step, the mold cavity first expanding step, and the second injection filling step similar to those in the first embodiment, the steps from FIG. 4A to FIG. 4C are repeated. Accordingly, the sandwich molded product 9 in which the thickness of the surface layer on the fixed mold 2 side (base layer 9g ′ + the surface layer of the sandwich molded part 9h ′) and the surface layer on the movable mold 4 side (the surface layer of the sandwich molded part 9h ′) are different. 'Can be continuously formed.

  As described above, the injection molding method according to Example 2 injects and fills the second resin 10c for the inner layer into the foam layer 9f ′ of the sandwich molded portion 9h ′, which has low strength and density in the second injection filling step. As in Example 1, the injection filling resistance of the second resin 10c for the inner layer can be further reduced as compared with the case where the non-foamable first resin 9b is used for the surface layer. Thereby, while preventing the resin reversal failure due to the second resin 10c for the inner layer, the filling ratio of the second resin 10c for the inner layer with respect to the volume of the sandwich molded portion 9h ′ can be further improved. It is further suitable for thin control. Further, not only can the surface of the sandwich molded product be molded so that the thickness of each surface layer differs, but also the thickness of each surface layer can be controlled with a predetermined accuracy.

  Next, an injection molding method according to Example 3 of the present invention will be described with reference to FIGS. FIGS. 6A and 6B are schematic cross-sectional views of a mold showing a mold cavity second expansion process, a second injection filling process, and a mold cavity third expansion process of the injection molding method according to the third embodiment. FIG. FIG. 6A shows the mold cavity third expansion process when the mold cavity second expansion process and the second injection filling process are completed, and FIG. 6B shows the mold cavity third expansion process. FIG. 7A to FIG. 7C are diagrams illustrating the molding cavity second expansion process, the second injection filling process, the mold cavity third expansion process, and other molding processes of the injection molding method according to the third embodiment. It is a schematic sectional drawing which shows a sandwich molded product. FIG. 7A is a sandwich molded product when the mold cavity second expansion process and the second injection filling process are completed, FIG. 7B is a sandwich molded product during the mold cavity third expansion process, and FIG. 7C. Shows the sandwich molded product after the product cooling process is completed.

  The difference between the injection molding method according to the third embodiment and the injection molding method according to the first embodiment is that the second resin is a foamable resin and, after this, after the start of the second injection filling process. And a mold cavity third expanding step of further expanding the mold cavity expanding portion by a predetermined amount. Except for these points, the method is basically the same as the injection molding method according to the first embodiment. Therefore, the detailed description thereof is omitted or described with reference to the first embodiment, and only the differences are described in detail. . Also, in the mold and the injection molding machine, basically the same one as described in Example 1 is used except that the non-foamable second resin 10b is changed to the foamable second resin 10b ′. Therefore, the description is omitted. In addition, due to the difference between the non-foamable second resin 10b and the foamable second resin 10b ′, the object to be distinguished from the description of the first embodiment is denoted by the same reference sign as in the first embodiment, “” (apostrophe ) ”.

  Here, the third embodiment will be described on the assumption that the second resin 10b 'is a foamable resin containing a chemical foaming agent. The second resin 10b ′ may be a foamable resin containing a physical foaming agent. In this case, the constituent requirement for appropriately mixing the physical foaming agent into the second resin 10b ′ for the surface layer is a mold. Or, it is necessary for an injection molding machine. However, since these constituent elements are not directly related to the present invention, the description thereof is omitted.

  In the injection molding method according to the third embodiment, first, the base material forming step is performed by the same method as the injection molding method according to the first embodiment, and the base material layer 9g is formed in the mold cavity 9a. Similarly, in the same manner as in Example 1, the mold cavity first expansion process and the first injection filling process are performed, and between the base material layer 9g and the movable mold 4 held on the fixed mold 2 side. The mold cavity extending portion 90a is formed, and the non-foamable first resin 9b is again injected from the first injection unit 17 into the mold cavity expanding portion 90a (first injection filling step). Explanation and illustration of these steps are omitted.

  Next, the mold cavity second expansion step and the second injection filling step are performed by interlocking control by the same method as in the first embodiment. Here, in the mold cavity second expanding step of the third embodiment, the volume of the mold cavity expanding portion 90a is not expanded until it becomes the product volume together with the volume of the mold cavity 9a, but is less than the product volume. Stay on the expansion. The mold opening amount at this time is β ′ (β ′ <β). In this way, as shown in FIG. 6A, the mold cavity second expansion step and the second injection filling step are completed. FIG. 6A shows a state corresponding to FIG. 2B of the first embodiment in the third embodiment.

  As in the first embodiment, the mold cavity second expansion process and the second injection filling process are controlled in conjunction, and the injection filling of the second resin 10b ′ by the second injection filling process is performed in a full pack state. The second resin 10b ′ for the inner layer injected and filled in the sandwich molding portion 9h ′ is in an unfoamed state at this stage. FIG. 7A shows a sandwich molded product 9 ′ (base material portion 9 g + sandwich molded portion 9 h ′) when the mold cavity second expansion process and the second injection filling process are completed. FIG. 7A shows the start state of the second injection filling process in which the second resin 10b for the inner layer is injected and filled into the sandwich molded portion shown in FIG. This corresponds to a state where the same process is completed.

  Next, as shown in FIG. 6B, after the start of the second injection filling process (that is, in the middle of the second injection filling process or after the completion of the second injection filling process), The volume of 90a is expanded to the product volume together with the volume of the mold cavity 9a, and the foamable second resin 10b ′ in the sandwich molding part 9h ′ is expanded (mold cavity third expansion step). Specifically, from the state shown in FIG. 6A (die opening amount: distance β ′), the movable die 4 is opened from the fixed die 2 to a distance β (beta) by a die opening / closing mechanism (not shown). Let As a result, as shown in FIG. 7B, the sandwich molded portion 9h ′ has a skin layer 9e formed on the contact surface with the design (mold inner surface) of the mold cavity extending portion 90a and the base material layer 9g. It will be in the state comprised by the 1st resin 9b containing the molten state part which is following the skin layer 9e, and cooling solidification is progressing, and foam layer 10f 'containing a foam cell.

  After completion of the mold cavity third expansion step, a predetermined clamping force is applied to the mold cavity 9a and the base material layer 9g and the sandwich molding portion 9h ′ in the mold cavity expansion portion 90a, although not illustrated. When these are cooled and solidified in the state, a sandwich molded product 9 'is formed (product cooling and solidification step). FIG. 7C shows the sandwich molded product 9 ′ after completion of the product cooling and solidifying step. For the sake of illustration, the foamed layer 10 f ′ of the second resin 10 b ′ for the inner layer in the cooled and solidified state is indicated by the same notation as when foamed.

  After the cooling and solidification of the sandwich molded product 9 ′ is completed, although not shown, the movable mold 4 is opened from the fixed mold 2 by a mold opening / closing mechanism (not shown), and the sandwich molded product is taken by a product take-out means (not shown). 9 'is carried out of the injection molding machine, and the molding cycle is completed.

  As described above, after the base material forming step, the mold cavity first expanding step, the first injection filling step, the mold cavity second expanding step, and the second injection filling step, which are the same as those in the first embodiment, FIG. By repeating the steps up to (a) and FIG. 6 (b), the surface layer on the fixed mold 2 side (base layer 9g + the surface layer of the sandwich molding part 9h ′) and the surface layer on the movable mold 4 side (sandwich molding part) 9h ′ (surface layer) having different thicknesses and the inner layer of the foamed layer 10f ′ (second resin 10b ′) can be continuously molded.

  As described above, the injection molding method according to Example 3 employs a foamable resin as the second resin for the inner layer, and performs the mold cavity third expansion step after the start of the second injection filling step. In addition, not only can the surface layer and the back surface of the sandwich molded product have different surface layer thicknesses, the inner layer can be a foamed layer. Such a sandwich molded product is suitable when a function of the foamed layer such as weight reduction is required as compared with the sandwich molded product molded by the injection molding method according to the first and second embodiments.

  Next, an injection molding method according to Example 4 of the present invention will be described with reference to FIGS. 8A and 8B are schematic cross-sectional views of a mold showing a mold cavity second expansion process, a second injection filling process, and a mold cavity third expansion process of the injection molding method according to the fourth embodiment. FIG. FIG. 8A shows the mold cavity third expansion process when the mold cavity second expansion process and the second injection filling process are completed, and FIG. 8B shows the mold cavity third expansion process. FIGS. 9A and 9B show sandwiches during the molding steps of the mold cavity second expansion step, the second injection filling step, and the mold cavity third expansion step of the injection molding method according to the fourth embodiment. It is a schematic sectional drawing which shows a molded article. FIG. 9A shows a sandwich molded product when the mold cavity second expansion process and the second injection filling process are completed, and FIG. 9B shows a sandwich molded product during the mold cavity third expansion process.

  The difference between the injection molding method according to the fourth embodiment and the injection molding method according to the first embodiment is that both the first resin and the second resin are foamable resins, and the second injection is caused by this point. It is a point provided with the 3rd mold cavity expansion process which expands a mold cavity expansion part only by the predetermined amount after the start of a filling process. That is, the injection molding method according to the fourth embodiment employs a foamable resin as the second resin in the injection molding method according to the second embodiment, and after the second injection filling process, the mold cavity extension portion is further provided. A mold cavity third expanding step for expanding by a predetermined amount is performed.

  Therefore, since these points are basically the same as the mold cavity third expansion step of the injection molding method according to Example 2 and the injection molding method according to Example 3, detailed description thereof is omitted, or The second and third embodiments will be described with reference to the drawings, and only differences will be described in detail. Also, in the mold and the injection molding machine, basically the same one as described in Example 2 is used except that the non-foamable second resin 10b is changed to the foamable second resin 10b ′. Therefore, the description is omitted. In addition, due to the difference between the non-foamable second resin 10b and the foamable second resin 10b ′, the objects to be distinguished from the description of the second embodiment are denoted by the same reference numerals as those of the second embodiment, “” (apostrophe ) ”.

  Also in the injection molding method according to the fourth embodiment, first, the base material forming step is performed by the same method as the injection molding method according to the second embodiment to form the base material layer 9g 'in the mold cavity 9a. Similarly, in the same manner as in Example 2, the mold cavity first expansion process and the first injection filling process are performed, and between the base material layer 9g ′ and the movable mold 4 held on the fixed mold 2 side. Then, the mold cavity extending portion 90a is formed, and the foamable first resin 9b ′ is again injected and filled into the mold cavity extending portion 90a from the first injection unit 17 (first injection filling step). Explanation and illustration of these steps are omitted.

  Next, after the start of the first injection filling process (that is, in the middle of the first injection filling process or after the completion of the first injection filling process) by the same method as in the second embodiment, the mold cavity extension 90a Is expanded, and the foamable first resin 9b ′ in the mold cavity expanding portion 90a is expanded. Here, in the mold cavity second expanding step of the fourth embodiment, the volume of the mold cavity expanding portion 90a is not expanded until it becomes the product volume together with the volume of the mold cavity 9a, but is less than the product volume. Stay on the expansion. The mold opening amount at this time is β ′ (β ′ <β).

  Next, in the same manner as in Example 2, after the completion of the first injection filling process and after the start of the mold cavity second expansion process (that is, in the middle of the mold cavity second expansion process, or After completion of the mold cavity second expansion step), the foamable second resin 10b ′ forming the inner layer from the second injection unit 18 is injected and filled into the sandwich molded portion 9h ′ (first resin 9b ′ for the surface layer). (Second injection filling step). In this way, as shown in FIG. 8A, the mold cavity second expansion step and the second injection filling step are completed. FIG. 8A shows a state corresponding to FIG. 4C of the second embodiment in the third embodiment.

  In addition, since the injection filling of the second resin 10b ′ in the second injection filling step is performed in the full pack state in the same manner as in the second embodiment, the second resin 10b for the inner layer injected and filled in the sandwich molding portion 9h ′. 'Is unfoamed at this stage. FIG. 9A shows the sandwich molded product 9 (base material portion 9g ′ + sandwich molded portion 9h ′) upon completion of the mold cavity second expansion step and the second injection filling step.

  Next, as shown in FIG. 8B, after the start of the second injection filling process (that is, in the middle of the second injection filling process or after the completion of the second injection filling process), the sandwich molding part 9h ′ The foamable second resin 10b ′ is foamed (mold cavity third expansion step). Specifically, since it is basically the same as the mold cavity third expansion step in the third embodiment, detailed description thereof is omitted. As shown in FIG. 9B, the sandwich molding part 9h ′ in the mold cavity third expansion step is on the contact surface between the design of the mold cavity expansion part 90a (mold inner surface) and the base material layer 9g ′. It will be in the state comprised by the skin layer 9e 'formed and the foaming layer 10f' containing a foaming cell. As described in the second embodiment, in the mold cavity second expansion step, the skin layer 9e ′ is slightly increased in thickness to form the surface layer (unfoamed state) of the sandwich molded portion 9h ′. It is possible to follow the volume expansion of the mold cavity expansion section 90a (volume expansion of the sandwich molding section 9h ′) in the mold cavity third expansion process. After the completion of the mold cavity third expansion step, a sandwich molded product 9 ′ is formed by the same process as in the third embodiment (product cooling and solidifying step). The sandwich molded product 9 ′ after completion of the product cooling and solidifying step is the skin layer 9e ′ made of the non-foamable first resin 9b and the foamable first resin 9b ′ in FIG. Since it is the same as what has been read as (unfoamed state), illustration is omitted.

  As described above, after the base material forming step, the mold cavity first expanding step and the first injection filling step, the mold cavity second expanding step and the second injection filling step, which are the same as those in Example 2, FIG. By repeating the steps leading to a) and FIG. 8B, the surface layer on the fixed mold 2 side (base layer 9g ′ + the surface layer of the sandwich molding part 9h ′) and the surface layer on the movable mold 4 side (sandwich molding) The thickness of the surface layer of the portion 9h ′ is different, and the sandwich molded product 9 ′ whose inner layer is the foamed layer 10f ′ (second resin 10b ′) can be continuously formed.

  Thus, the injection molding method according to Example 4 employs a foamable resin as the second resin for the inner layer, and performs the mold cavity third expansion process after the start of the second injection filling process. In addition, not only can the surface layer and the back surface of the sandwich molded product be molded so that the thickness of each surface layer is different, but by adopting a foamable resin for the surface layer, the inner layer relative to the volume of the sandwich molded part 9h ′ The filling ratio of the second resin 10c ′ for use can be further improved. Therefore, as in Example 3, when a foamable resin is used for the inner layer, a function having a function of the foamed layer, such as further weight reduction, is required than a sandwich molded product molded by the injection molding method according to Example 3. It is suitable for the case.

  The present invention is not limited to the above embodiment and can be implemented in various ways. For example, in the injection molding method according to the first to fourth embodiments, in order to simplify the description and the drawings, the mold is operated by the mold opening / closing operation by the mold opening / closing mechanism of the injection molding machine on the premise of the mold having the shear edge structure. Although the volume of the cavity is expanded, the means for expanding the volume of the mold cavity is not limited to this, and counteracts the resin pressure in the mold cavity such as the movement of the movable part in the mold. The volume, expansion speed, volume expansion position holding force, etc. can be arbitrarily controlled.

  In addition, in the injection molding method according to the first to fourth embodiments, the volume of the mold cavity expansion portion combined with the mold cavity is increased by the mold cavity second expansion process or the mold cavity third expansion process. In the case where the mold cavity second expansion step is performed as in the injection molding methods according to the first and second embodiments, the mold cavity second expansion step is performed. As in the injection molding method according to Example 3 and Example 4, when the process is performed up to the mold cavity third expansion step, at least one of the two expansion steps is larger than the initially set volume. After expanding the volume of the mold cavity expansion part and injecting or foaming more resin, the volume of the mold cavity expansion part is reduced to the initially set volume. By, eventually may also be desired product is obtained (mold cavity reduction step). This further improves the transferability of the design of the mold cavity to the skin layer of the base material layer that is one surface layer of the sandwich molded product and the skin layer of the sandwich molded portion that is the other surface layer. The filling ratio of the second resin for the inner layer with respect to the volume of the inner layer can be further improved.

2 Fixed mold (first mold)
4 Movable mold (second mold)
9 Sandwich molded product 9 'Sandwich molded product 9a Mold cavity 9b First resin (for surface layer / non-foaming)
9b 'first resin (for surface layer / foamability)
9g Base material layer 9g 'Base material layer 10b Second resin (for inner layer / non-foaming)
10b 'second resin (for inner layer / foamability)
90a Mold cavity extension

Claims (4)

An injection molding method for molding a sandwich molded product composed of a surface layer and an inner layer using a first mold and a second mold capable of forming a mold cavity,
A base material molding step of clamping the first die and the second die, injecting and filling a non-foamable first resin into the die cavity, and molding a base material layer;
A mold cavity first expanding step of expanding the mold cavity by a predetermined amount after the base material forming step is completed;
After the start of the first mold cavity extension process, the mold cavity first extension process forms between the base material layer and one of the first mold and the second mold. A first injection filling step of filling and filling the mold cavity extension with the first resin, and filling the mold cavity extension with the first resin;
A mold cavity second expansion step for further expanding the mold cavity expansion portion by a predetermined amount after the completion of the first injection filling step;
An injection molding method comprising: a second injection filling step of injecting and filling a second resin into the first resin in the mold cavity extension portion after the start of the second mold cavity extension step. An injection molding method for molding a sandwich molded product composed of a surface layer and an inner layer using a first mold and a second mold capable of forming a mold cavity,
A base material molding step of clamping the first die and the second die, injecting and filling a foamable first resin into the die cavity, and molding a base material layer;
A mold cavity first expanding step of expanding the mold cavity by a predetermined amount after the base material forming step is completed;
After the start of the first mold cavity extension process, the mold cavity first extension process forms between the base material layer and one of the first mold and the second mold. A first injection filling step of filling and filling the mold cavity extension with the first resin, and filling the mold cavity extension with the first resin;
A mold cavity second expansion step of expanding the mold cavity extension portion by a predetermined amount after the start of the first injection filling step, and foaming the first resin in the mold cavity extension portion;
A second injection filling step of injecting and filling a second resin into the first resin in the mold cavity expansion portion after the completion of the first injection filling step and after the start of the mold cavity second expansion step. An injection molding method characterized by comprising: The second resin is an expandable resin, and after the start of the second injection filling process, the mold cavity extension portion is further expanded by a predetermined amount, and the second resin is expanded into the first resin in the mold cavity extension portion. The injection molding method according to any one of claims 1 and 2, further comprising: a mold cavity third expansion step for foaming the second resin that has been injection-filled. The expansion of the mold cavity is performed by at least one of a mold opening / closing operation by a mold opening / closing mechanism of an injection molding machine and a moving operation of a movable part in the mold. The injection molding method according to any one of claims.

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