JP2012126023A - Mold for foam molding and foamed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent white blush marks generated on thin edge parts of a foamed molding.SOLUTION: A mold 10 for foam molding includes: a movable mold 12 movable with respect to a fixed mold 11; a cavity 14 for foam molding surrounded by the fixed mold; and a gate 15, a runner 16 or the like sequentially continued from the cavity. Melted resin 1 is filled in the cavity 14 through the runner and the gate, and then the movable mold 12 is separated from the fixed mold 11 so as to expand the melted resin 1 and to obtain the foamed molding 4. At least one of the fixed mold 11 and the movable mold 12 forming the cavity 14 includes a narrow part in a molding part of the edge part 5 in the cavity 14 so that the edge part 5 of the foamed molding 4 is formed thinly. Recesses 23 for ribs are formed for molding ribs 6 in the edge part 5 at positions corresponding to a neighborhood of the gate 15.

Description

  The present invention relates to a foam molding die for molding a foam molded product having a thin end, and a foam molded product.

In recent years, in order to reduce carbon dioxide (CO ₂ ) emitted from vehicles such as automobiles, improvement in fuel efficiency has been demanded, and vehicle weight reduction is essential. As a part of such weight reduction of vehicles, a method for reducing the weight of interior resin parts such as automobiles by reducing the thickness has been proposed so far, but it becomes difficult to secure rigidity when the product is reduced in thickness.

  Therefore, it is known to apply injection foam molding as a method of ensuring rigidity while achieving weight reduction. In the injection foam molding, for example, a pair of molds that can be opened and closed is applied, and in a state in which both molds are assembled, a molten resin added with a foaming agent is injected into the mold, and then a mold on one side is molded. This is a method of foaming by opening a predetermined amount and separating (hereinafter referred to as “core back”).

  In this injection foam molding, the pressure is released at the moment when the resin is injected into the cavity of the mold, and the resin starts to foam. Therefore, the molten resin injected into the mold flows in the mold while foaming. At this time, silver-white streaks (swirl marks) caused by bursting of bubbles are generated on the product surface. Further, when the molten resin entrains air during the flow of the molten resin, a depression is generated on the surface of the foam molded product.

  In order to prevent such appearance defects, conventionally, a thermoplastic foamed resin is injected into a mold that has been previously pressurized with a gas such as air to a pressure equal to or higher than the foaming pressure, and the mold is filled with molten resin. When foaming the molten resin by suppressing the foaming of this foamed resin to suppress appearance defects (swirl marks and dents) and escape of foaming gas, and core back the mold after completion of injection, and increasing the cavity In addition, by sucking or reducing the pressure of the gas remaining in the mold, foaming is promoted, and further, air trapped between the resin and the mold is removed to prevent the formation of depressions in the foam molded product. Have been proposed (see, for example, Patent Document 1).

JP-A-49-25061

  By the way, as shown in FIG. 8, the foam molded product 101 molded by the foam molding die 100 has a positional relationship in which the end surface 102 coincides with the parting line 103 of the foam molding die 100. The parting line 103 includes a fixed mold 104, a movable mold 105, and a foam molded product 101, which are a fixed mold 104 constituting the foam mold 100 and a movable mold 105 movable with respect to the fixed mold 104. Is a line to separate.

  8 is an injection molding machine, and the molten resin 107 from the injection molding machine 106 is foamed through a hot runner 108, a spool 109, a runner 110, and a gate 111 formed on the fixed mold 104. It is guided to the molding cavity 112 and filled in the cavity 112. The filling of the molten resin 107 in the cavity 112 is performed under a pressurized state as described above. After the filling is completed, the cavity 112 is decompressed at the same time as the movable mold 105 cores back, and the molten resin is filled in the cavity 112. 107 foams to obtain a foam molded article 101.

  As described above, when the end face 102 of the foam molded article 101 and the parting line 103 of the foam molding die 100 coincide with each other, as shown in FIG. Insufficient cooling of the resin 107 causes a bead-shaped portion 114 at the end 113 of the foam molded article 101. Therefore, in order to prevent the occurrence of the bead-shaped portion 114, as shown in FIG. 10, the molded portion of the end portion 115 in the cavity 116 is a narrow portion so that the end portion 115 of the foam molded product 101 is thin. A foam molding die 118 formed as 117 is used.

  However, when the foam molding die 118 shown in FIG. 10 is adopted, as shown in FIG. 11A, the movable die 105 is closed from the fixed die 104 (core backed state), As shown in FIG. 11B, when the movable mold 105 is separated from the fixed mold 104 and the foam molded product 101 is taken out from the foam molding die 118, the thin end 115 of the foam molded product 101 is fixed. There is a possibility that the edge portion 115 may be whitened and damaged 119 by being plastically deformed by being pulled by the solidified resin in the gate 111 of 104.

  An object of the present invention is made in consideration of the above-described circumstances, and provides a foam molding die and a foam molded product capable of preventing whitening damage from occurring at the thinned end portion of the foam molded product. There is to do.

  The foam molding die according to the present invention is formed with a movable mold movable with respect to a fixed mold, a foam molding cavity surrounded by the fixed mold, and a gate and a runner successively connected to the cavity. After filling the cavity with the molten resin through these runners and gates, in the foam molding die to obtain the foam molded product by foaming the molten resin by separating the movable mold from the fixed mold, At least one of the fixed mold and the movable mold forming the cavity is formed with a narrowed portion at the end portion of the cavity so that the end portion of the foam molded product is thin, and the end A rib recess is formed so that the rib is formed at a position corresponding to the vicinity of the gate in the portion.

  Further, the foam molded product according to the present invention is formed with a movable mold movable with respect to the fixed mold, a foam molding cavity surrounded by the fixed mold, and a gate and a runner successively connected to the cavity. Foam obtained by foaming the molten resin by filling the cavity with the molten resin through the runner and the gate using the foam molding mold and then separating the movable mold from the fixed mold. In the molded product, the end portion is thinned by the narrow portion formed in the cavity, and the end portion is ribbed at a position corresponding to the vicinity of the gate by the rib concave portion of the foam molding die. Is characterized by being molded.

  According to the foam molding die and the foam molded product according to the present invention, the end of the foam molded product is thinned by the narrow portion of the cavity of the foam molding die, and the rib recess of the foam molding die. Thus, a rib is formed at a position corresponding to the vicinity of the gate of the foam molding die at the thinned end portion of the foam molded product. For this reason, since the rigidity is secured by the rib at the thinned end of the foam molded product, when the foam molded product is taken out by moving the movable mold of the foam molding mold away from the fixed mold, The thinned end portion can be prevented from being plastically deformed by being pulled by the solidified resin in the gate. As a result, it is possible to prevent whitening damage from occurring at the thinned end portion of the foam molded product.

The longitudinal cross-sectional view which shows one Embodiment of the metal mold | die for foam molding which concerns on this invention. Sectional drawing which shows schematically the structure of the injection molding machine of FIG. Process drawing which shows the process (A)-(E) of foam molding using the metal mold | die for foam molding of FIG. FIG. 4 is an arrow view viewed in the direction of arrow IV along the parting line P of FIG. 1. The perspective view which shows the rib periphery of the foam molded product shape | molded with the metal mold | die for foam molding of FIG. FIG. It is sectional drawing which follows the VII-VII line containing the upper surface of the foaming molding shown in FIG. 1, (A) is the state which closed the foaming mold, (B) is a foaming by opening a foaming mold. Sectional drawing which each shows the state which takes out a molded article. The longitudinal cross-sectional view which shows the metal mold | die for foam molding as a comparison form. FIG. 9 is a partial cross-sectional view illustrating a bead-shaped portion that is generated when the foam molding die of FIG. 8 is core-backed. The longitudinal cross-sectional view which shows the metal mold | die for foam molding as another comparative form. It is a fragmentary sectional view in alignment with the XI-XI line containing the upper surface of the foam-molded article shown in FIG. 10, (A) has closed the foam-molding die, (B) has opened the foam-molding die. Sectional drawing which shows the state which takes out a foaming molded product, respectively.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

  As shown in FIG. 1, a foam molding die 10 according to this embodiment includes a fixed mold 11 to which a molten resin 1 is supplied from an injection molding machine 13 and a movable mold that is movably combined with the fixed mold 11. 12.

  The fixed mold 11 is configured as a block body having a convex shape as a whole, and is formed, for example, in a shape in which the convex portion 11A projects from the center position. The movable mold 12 is configured as a block body having a concave cross section having a concave recess 12A that can be fitted into the convex 11A of the fixed mold 11. The moving amount of the movable die 12 with respect to the fixed die 11 is configured to be adjustable.

  A cavity 14 for foam molding is formed at the joining position of the fixed mold 11 and the movable mold 12, that is, between the convex portion 11A of the fixed mold 11 and the concave portion 12A of the movable mold 12. Further, the fixed die 11 is formed with a gate 15, a runner 16, a spool 17 and a hot runner 18 successively formed in the cavity 14, and an injection molding machine 13 is connected to the hot runner 18 in communication therewith. The molten resin 1 from the injection molding machine 13 sequentially flows through the hot runner 18, spool 17, runner 16, and gate 15 and is supplied (injected) into the cavity 14.

  Here, as shown in FIG. 2, the injection molding machine 13 is configured such that a screw 20 is housed in a cylinder 19 so as to be rotatable about an axis and movable in an axial direction. Further, a hopper 21 is installed in the cylinder 19, and a heating source (not shown) such as a heater is arranged outside the cylinder 19. Into the hopper 21, for example, resin pellets 2 of a hot-gas plastic resin such as polypropylene (PP) and a chemical foaming agent master batch 3 are charged.

  The resin pellets 2 and the chemical foaming agent master batch 3 charged into the hopper 21 are heated by a heating source while the screw 20 moves backward while rotating, and are melted and stored at the tip of the cylinder 19. A predetermined amount of the molten resin 1 accumulated at the tip of the cylinder 19 is injected into the foam molding die 10 as the screw 20 advances, and is introduced into the cavity 14 of the foam molding die 10 as described above. Filled. The molten resin 1 filled in the cavity 14 is foamed and cooled to become a foam molded product 4 as will be described later.

  The foam molding process by the foam molding die 10 will be described with reference to FIG. As shown in FIG. 3A, after the foam molding die 10 is clamped, air is supplied to the cavity 14 from an air supply / discharge hole (not shown), and the inside of the cavity 14 is pressurized. The pressure in the cavity 14 at this time is set to a pressure that suppresses foaming of the molten resin 1.

  In this state, as shown in FIG. 3B, the molten resin 1 is injected from the injection molding machine 13 into the cavity 14 of the foam molding die 10. By pressurizing the inside of the cavity 14 as described above, foaming of the molten resin 1 is suppressed during the filling of the molten resin 1 into the cavity 14.

  After completion of the filling of the molten resin 1 into the cavity 14, as shown in FIG. 3C, the movable mold 12 is separated from the fixed mold 11 by a predetermined amount (core back) in the direction of the arrow α (core back). Molten resin 1 is foamed. At the same time as or before the core back of the movable mold 12, the air in the cavity 14 is sucked from an air supply / discharge hole (not shown) to reduce the pressure in the cavity 14. This decompression promotes foaming of the molten resin 1.

  Thereafter, as shown in FIG. 3D, the molten resin 1 is cooled and solidified in a state where the movable mold 12 is core-backed. 3E, the movable mold 12 is further separated from the fixed mold 11, and the molten resin 1 solidified in the cavity 14, that is, the foam molded product 4 molded in the cavity 14, is obtained. Take out.

  By the way, as shown in FIG. 1, the fixed mold 11 and the movable mold 12 forming the cavity 14 have a thin-walled structure as shown in FIGS. A molding portion of the end portion 5 in the cavity 14 is formed as a narrow portion 22 (FIG. 1). By reducing the thickness of the end portion 5 of the foam molded product 4, the molten resin 1 is rapidly cooled during the core back of the movable mold 12, and the bead shape portion 114 is formed on the end portion 5 of the foam molded product 4. (FIG. 9) is prevented from occurring.

  Here, a symbol P in FIG. 1 indicates a parting line when the movable mold 12 is moved away from the fixed mold 11. The parting line P is provided on the surface where the fixed mold 11, the movable mold 12, and the foam molded product 4 are separated.

  As shown in FIGS. 4 and 5, the fixed mold 11 is formed in the fixed mold 11 such that the rib 6 is formed at a position corresponding to the vicinity of the gate 15 in the end portion 5 of the foam molded product 4. ), A rib recess 23 is formed. The rib recesses 23 are formed on both sides of the gate 15 so as to be continuous with the narrow portion 22 for molding the end portion 5 of the foam molded product 4. As a result, as shown in FIGS. 4 and 5, the rib 6 formed by the rib recess 23 is integrated with the end portion 5 of the foam molded product 4, and the position corresponding to the vicinity of the gate 15 at the end portion 5. The rigidity of the is increased.

  For example, as shown in FIG. 6, the thickness t1 of the end portion 5 formed in the foam molded product 4 is t1 = 0.5 to 1.0 mm, and the width W of the gate 15 of the fixed mold 11 is W = 5 mm. At this time, the rib 6 formed on the foam molded product 4 is formed at a position where the distance S from both ends of the gate 15 is separated by S = 1 to 2 mm, with the plate thickness t2 being t2 = 0.8 to 1 mm. Accordingly, the distance L between the ribs 6 at this time is set to L = 7 to 9 mm. In this specific example, the gate 15 formed in the fixed mold 11 is formed in an elliptical cross section having a major axis of 5 mm and a minor axis of 0.5 to 1.0 mm.

  Since it was configured as described above, according to the present embodiment, the following effects (1) and (2) are achieved.

  (1) The end portion 5 of the foam molded product 4 is thinned by the narrow portion 22 of the cavity 14 of the foam molding die 10, and the rib concave portion 23 of the foam molding die 10 is used to A rib 6 is formed on the thinned end portion 5 at a position corresponding to the vicinity of the gate 15 of the foam molding die 10. For this reason, the rigidity is ensured by the rib 6 at the thinned end portion 5 of the foam molded product 4.

  As shown in FIG. 7A, the movable mold 12 is separated from the fixed mold 11 from the state in which the movable mold 12 is closed with respect to the fixed mold 11 (core-backed state). When the foam molded product 4 is taken out from the foam molding die 10, the thin end portion 5 of the foam molded product 4 and the resin solidified in the gate 15 are pulled and cut. At this time, since the rigidity of the thinned end portion 5 of the foam molded product 4 is ensured by the ribs 6, the thin end portion 5 of the foam molded product 4 is pulled by the solidified resin in the gate 15. Can also be prevented from plastic deformation. As a result, it is possible to prevent the whitening flaw 119 (FIG. 11) from occurring at the thinned end portion 5 of the foam molded product 4.

  (2) Since the end portion 5 of the foam molded product 4 is thinned, the molten resin 1 is rapidly cooled at the time of core back of the movable mold 12, and the edge 5 of the foam molded product 4 is in contact with the edge 5. Generation of the shape portion 114 (FIG. 9) is prevented. For this reason, it is not necessary to cut this bead-shaped part 114 in the process after the molding of the foam molded product 4, and the manufacturing cost can be reduced.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this, A various deformation | transformation can be made in the range which does not deviate from the main point of this invention.

DESCRIPTION OF SYMBOLS 1 Molten resin 4 Foam molded product 5 End part 6 Rib 10 Foam molding metal mold 11 Fixed mold 12 Movable mold 14 Cavity 15 Gate 22 Narrow part 23 Rib concave part

Claims (5)

A movable mold movable with respect to the stationary mold, a cavity for foam molding surrounded by the stationary mold, and a gate and a runner successively connected to the cavity are formed, and the runner and the gate pass through the cavity. After filling the molten resin, in the foam molding mold to obtain the foam molded product by foaming the molten resin by separating the movable mold from the fixed mold,
At least one of the fixed mold and the movable mold forming the cavity is formed with a narrowed portion of the end portion of the cavity so that the end portion of the foam molded product is thin,
A foam molding die, wherein a rib recess is formed so that a rib is molded at a position corresponding to the vicinity of the gate at the end. 2. The foam molding die according to claim 1, wherein the rib concave portion is formed on both sides of the gate continuously with a narrow portion for molding an end portion of the foam molded product. 2. The foam molding die according to claim 1, wherein the rib recess is formed in a fixed mold together with the gate. Using the movable mold movable with respect to the fixed mold, the foam mold surrounded by the fixed mold, and the foam molding mold in which a gate and a runner are successively formed in the cavity, the runner is used. And after filling the cavity with the molten resin through the gate, in the foam molded product obtained by foaming the molten resin by separating the movable mold from the fixed mold,
The end portion is thinned by the narrow portion formed in the cavity,
A foam molded article, wherein a rib is formed at a position corresponding to the vicinity of the gate at the end portion by a rib concave portion of the foam molding die. 5. The foam molded product according to claim 4, wherein the rib is formed integrally with the end portion at a position corresponding to both sides of the gate of the foam molding die.

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