JP2013103403A - Method and apparatus for manufacturing foamed resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed resin molded body whose surface skin layer is partially broken and inside foamed layer is exposed.SOLUTION: A cavity 3 is filled with a foaming resin and then the volume of the cavity 3 is expanded by core back which causes the core 5 to retreat from a fixed mold 4. During this core back, a pin member 8 retreats farther than a core body 7, next the pin member 8 advances, the tip surface thereof pierces into the foamed layer in the cavity 3, and thereafter the mold of the obtained foamed resin molded body is released.

Description

  The present invention relates to a method and apparatus for producing a foamed resin molded body.

  Conventionally, in the field of various industrial parts such as automobile parts, foamed resin molded articles having excellent characteristics such as lightness, heat insulation and soundproofing have been widely adopted. Such a foamed resin molded body is molded by selecting a suitable resin material according to the purpose and application to be used, and by setting various conditions such as the form of bubbles inside the molded body and the expansion ratio. Yes.

  As an example of the molding method, after filling a moldable mold cavity composed of a fixed mold and a movable mold with a molten foamable resin containing a foaming agent in the resin, the movable mold is moved in the mold opening direction and the cavity is moved. A so-called core back method is known in which foaming of a foamable resin is promoted by enlarging the volume of the foamed resin. According to this core back method, the foamable resin filled in the cavity is cooled from the surface by the molding die, so that a non-foamed skin layer is formed as a skin layer on the surface of the foamed resin molded body. A foam layer obtained by promoting foaming by the core back is formed inside. That is, a molded body in which the foamed layer is integrally sandwiched between the non-foamed skin layers is obtained.

  If such a foamed resin molded article is used as it is as a heat insulating material or a soundproofing material (sound absorbing material), there is a non-foamed skin layer on the surface, so that the heat insulating effect and soundproofing effect of the internal foamed layer may not be sufficiently exhibited. There is a problem to say. That is, since the heat conductivity of the skin layer on the surface is large, heat is easily transmitted to the surroundings, or sound is easily reflected by the skin layer.

  On the other hand, it is conceivable to remove the skin layer formed on the surface and to expose the internal foam layer in order to enhance the heat insulation effect and the soundproof effect.

  Regarding removal of the skin layer of the foamed resin molded body, for example, Patent Document 1 does not aim to improve the heat insulation effect and the soundproofing effect, but a sheet-like foam body in which an adhesive sheet is laminated on one side is disclosed. It is described that the entire skin layer formed and formed on the opposite surface of the sheet-like foam is removed by a slicing blade.

  In Patent Document 2, a pin member is incorporated into a movable mold, and after filling the cavity with a molten foamable resin, the pin member is core-backed together with the movable mold, and then the pin member is advanced to move into the cavity. It is described that a concave portion is formed in a foamed resin molded body by being pushed into the resin.

JP-A-6-344459 JP 2009-226784 A

  In the method described in Patent Document 1, it is necessary to provide a skin layer removing step separately from the molding step of the foamed resin molded body, which requires more man-hours and a slice blade and a roll for receiving the slice blade. As a result, the entire apparatus becomes large. In addition, this method is to slice the entire skin layer of the foamed resin molded body, and cannot meet the demand of partially removing the skin layer at a desired position and in a desired form.

  Further, the method described in Patent Document 2 is a method in which a skin layer formed on the surface of a foamed resin molded body is deformed into a concave shape with a pin member and pushed into the foamed layer, and the expected heat insulation effect and sound absorption The improvement of the effect cannot be expected, and with respect to sound absorption, the concave portion formed on the skin layer surface by the pin member may be a source of abnormal noise (aerodynamic sound).

  Therefore, the present invention provides a method and an apparatus that can easily obtain a foamed resin molded body in which the skin layer on the surface is partially punched and the internal foam layer is exposed.

  In order to solve the above problems, the present invention provides a foamed resin molded article in which a pin member incorporated in a movable main body is retracted from the movable main body during the movable core back, and then the pin member is advanced. It was made to pierce into the foam layer.

The method for producing a foamed resin molded body having a skin layer and a foamed layer, which is presented here, fills a cavity between a fixed mold and a movable mold with a foamed resin in a molten state obtained by adding a foaming agent to a raw material resin. After that, the cavity is expanded to a volume corresponding to the foamed resin molded body to be molded by a core back that retracts the movable mold from the fixed mold,
The movable mold includes a movable mold main body and a pin member, and the pin member is provided such that a tip surface thereof forms the cavity together with the movable mold main body and faces the fixed mold,
In the movable core back, the pin member is further retracted from the movable main body, and then the pin member is advanced to push the tip surface into the foam layer in the cavity, and then The method is characterized in that the foamed resin molding is released.

  That is, when the cavity is filled with a foamable resin, a skin layer is formed in a portion of the foamable resin in contact with the movable body and the pin member. When the pin member is further retracted from the movable body during the core back, the foaming pressure of the foaming resin is applied to the pin hole generated by the retraction. For this reason, the skin layer that is in contact with the pin member is separated from the skin layer that is in contact with the movable body and follows the retreat of the pin member, and a part of the foaming resin is further in the pin hole. Come in. Next, when the pin member is advanced and its tip end surface is put into the cavity, the skin layer in contact with the pin member and the foamed resin that has entered the pin hole enter the foam layer in the cavity. Thereby, a hole is opened in the site | part corresponding to a pin member in a foaming resin molding, and it will be in the state which the foaming layer exposed to the internal peripheral surface of this hole.

  Here, the skin that is in contact with the pin member when the pin member is retracted because the tension of the skin layer is still small in the core back step and in the pre-core back step after filling the cavity with the foamable resin. The layer tends to break away from the skin layer in contact with the movable body. When the pin member retreats, a part of the resin being foamed enters the pin hole and is cooled by contact with the inner surface of the pin hole. At this stage, the temperature difference between the resin and the inner surface of the pin hole is small. For this reason, even when a new skin layer can be formed by contact between the foamable resin and the inner surface of the pin hole, it becomes a thin skin layer with low strength. Therefore, the forward movement of the pin member is not hindered, and the skin layer is pushed by the pin member and peeled off from the inner surface of the pin hole, and is further easily separated from the skin layer in contact with the movable body, so that the cavity It will be pushed into the foamed resin molding inside.

  In short, the present invention is characterized in that the skin layer in contact with the pin member is separated from the skin layer in contact with the movable body by the retraction of the pin member. Thereby, by advancement of the pin member, the skin layer can be pushed into the foam layer in a state where a part of the skin layer is cut out without distorting the surroundings. Therefore, the foamed layer can be reliably exposed on the inner surface of the hole generated by this pressing. And it becomes advantageous also in reduction of the energy which a pin member requires for advance.

A manufacturing apparatus suitable for carrying out the method for manufacturing a foamed resin molded body includes a fixed mold and a movable mold that moves forward and backward toward the fixed mold, and a molten foamable resin in which a foaming agent is included in the raw resin. Is filled into the cavity between the fixed mold and the movable mold, and then the cavity is expanded to a volume corresponding to the foamed resin molded body to be molded by a core back that retracts the movable mold from the fixed mold. Is,
The movable mold is provided such that the movable mold main body and a front end surface thereof form the cavity together with the movable mold main body and face the fixed mold. And a pin member that is further retracted and then advanced so that the tip surface enters the foamed layer in the cavity.

  In the manufacturing method and manufacturing apparatus of the foamed resin molded body, it is preferable that the tip surface of the pin member has a concave shape with the center side set back with respect to the peripheral edge.

  As a result, the skin layer that is in contact with the pin member and the skin layer that is in contact with the movable body are folded at the boundary between the two, so that when the pin member is retracted, both skin layers are at the boundary. It becomes easy to be divided at the part. Further, since the edge of the peripheral edge of the pin member is sharp, even when a skin layer is formed along the inner surface of the pin hole, the skin layer is peeled off from the inner surface of the pin hole and is in contact with the movable body It becomes easy to separate from. Further, in the obtained foamed resin molded body, the bottom surface of the hole formed by pressing the pin member has a medium-high shape corresponding to the shape of the tip surface of the pin member. Therefore, the sound incident on the hole is easily reflected by the middle and high bottom surfaces so as to go to the foam layer exposed on the inner surface of the hole, and the sound absorption is increased.

  According to the present invention, in the movable core back, the pin member is further retracted from the movable main body, and then the pin member is advanced to push the tip surface into the foam layer in the cavity. After that, since the foamed resin molded product is released, a part of the skin layer can be easily and reliably cut out and squeezed into the foamed layer without distorting the surroundings. The foam layer can be exposed on the inner surface.

It is a figure which shows the whole structure of the manufacturing apparatus of a foamed resin molding. It is sectional drawing which expands and shows a part of FIG. It is a time chart of operation | movement of a movable type main body and a pin member. It is sectional drawing which shows the state of the shaping | molding die in the middle of a core back. It is sectional drawing which shows the state of the shaping | molding die at the time of completion | finish of the core back of a movable mold main body. It is sectional drawing which shows the state which pushed the pin member into the foaming layer in a cavity. It is sectional drawing which shows a part of foaming resin molding.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use.

<Configuration of manufacturing apparatus for foamed resin molding>
In the foamed resin molded body manufacturing apparatus shown in FIG. 1, reference numeral 1 denotes a foamed resin molded body mold, and 2 denotes an injection apparatus as a filling means for filling the cavity 3 of the mold 1 with a molten foamable resin. The mold 1 includes a fixed mold 4 and a movable mold 5 provided so as to advance and retreat toward the fixed mold 4, and a cavity 3 is formed by the fixed mold 4 and the movable mold 5. A sprue 6 is provided on the fixed mold 4.

  The movable mold 5 includes a movable mold body 7 and a pin member 8. The pin member 8 is inserted into a pin hole 9 formed in the movable mold body 7 so that the pin member 8 can move forward and backward toward the fixed mold 4. That is, the pin member 8 is provided so that the tip surface thereof forms the cavity 3 together with the movable mold body 7 and faces the molding surface of the fixed mold 4. The tip end surface 8a of the pin member 8 has a concave shape with the center side set back with respect to the periphery thereof, as shown in a sectional view in FIG. In the case of this example, the front end surface 8a is a funnel-shaped recess, but it can also be a spherical recess whose center is gently depressed.

  Connected to the mold 1 are movable body drive means 11 for moving the movable body 7 forward and backward toward the fixed mold 4 and pin member drive means 12 for moving the pin member 8 forward and backward toward the fixed mold 4. . These driving means 11 and 12 are controlled by a controller 13. Although only one pin member 8 is shown in FIG. 1, a plurality of pin members 8 are provided on the movable die 5 in molding a foamed resin molded body for soundproofing or heat insulation.

  The injection device 2 includes a cylinder 16 in which a screw 15 is rotatably inserted and a heating heater is provided on an outer peripheral surface. A nozzle at the tip of the cylinder 16 is connected to the sprue 6 of the fixed mold 4. On the base end side of the cylinder 16, there are provided a hopper 18 for supplying a raw material resin 17 such as PP resin, and a screw driving means 19 for rotating and advancing and retracting the screw. A nozzle 21 for injecting a fluid in a supercritical state as a physical foaming agent is connected to an intermediate portion of the cylinder 16. An inert gas (carbon dioxide, nitrogen, etc.) sent from a cylinder 22 is supplied to the nozzle 21 in a supercritical state by a supercritical state generator 23. In this case, the raw material resin 17 is melted by heating with a heater and kneading with the screw 15, and further kneaded with the foaming agent to form a foamable resin 24 in a molten state from the sprue 6 to the cavity 3 of the mold 1. Supplied.

  When molding is performed using a foamable resin containing a chemical foaming agent, the foaming agent is put into the hopper 18 together with the raw material resin 13. When obtaining a fiber-reinforced foamed resin molded body, reinforcing fibers may be mixed in the raw material resin 17 in advance.

<Core back control>
Next, the core back control of the movable mold 4 by the controller 13 and the method for manufacturing the foamed resin molded body will be described.

  The controller 13 controls the drive means 11, 12 after the foamable resin 24 is filled in the cavity 3 between the fixed mold 4 and the movable mold 5, and moves the movable mold 5 backward from the fixed mold 4. Thus, the cavity 3 is expanded to a volume corresponding to the foamed resin molding to be molded. In this core back, the pin member 8 is controlled so that the pin member 8 is further retracted from the movable body 7 during the core back of the movable body 7 and then moved forward to enter the foam layer in the cavity 3. . This will be specifically described below.

  FIG. 3 is a time chart specifically showing the operations of the movable main body 7 and the pin member 8 in the core back control.

  That is, the molten foamable resin 24 in the mold closed state with the smallest cavity volume shown in FIG. 1 is injected into the cavity 3 and filled. In this mold closed state, the peripheral edge of the tip surface 8a of the pin member 8 is positioned at the opening edge of the pin hole 9 of the movable mold body 7 (opening edge on the cavity 3 side). The portion of the foamable resin 24 filled in the cavity 3 that contacts the fixed mold 4 and the movable mold 5 is rapidly cooled to form a skin layer.

  After the injection of the foamable resin 24, the movable main body 7 and the pin member 8 are moved backward at the same speed as shown in FIG. FIG. 4 shows a state in the middle of the core back of the movable body 7. In the middle of the core back of the movable body 7, the retraction speed of the pin member 8 is made larger than the retraction speed of the movable body 7 as shown in FIG. 3. Thereby, as shown in FIG. 5, when the core back of the movable body 7 ends, the pin member 8 is in a state of being retracted from the movable body 7. In this state, the movable main body 7 and the pin member 8 are stopped.

  As described above, when the pin member 8 is retracted from the movable body 7, the skin layer 25 a in contact with the pin member 8 is in contact with the movable body 7 by the foaming pressure of the foamable resin 24. The pin member 8 follows the retraction of the pin member 8. At the same time, a part of the foamable resin enters the pin hole 9.

  At the stage where the movable mold 5 is core-backed, the tension of the skin layer is still small. Therefore, when the pin member 8 is retracted, the skin layer 25a that is in contact with the pin member 8 and the skin layer 25b that is in contact with the movable body 7 are easily separated by the foaming pressure. In addition, in the case of this example, as shown in FIG. 2, the tip surface 8 a of the pin member 8 has a concave shape, so that the skin layer 25 a in contact with the tip surface 8 a and the movable body 7 are A fold 25c is formed at the boundary with the skin layer 25b in contact. Therefore, when the pin member 8 is retracted, the folding portion 25c is the starting point, and the skin layer 25a is easily separated from the skin layer 25b.

  Next, after the movable body 7 and the pin member 8 are stopped for a predetermined time (for example, when the tension of the skin layer exceeds the foaming pressure), as shown in FIG. Only the pin member 8 is advanced while the stop state is continued. Then, as shown in FIG. 6, the tip surface 8 a of the pin member 8 is pushed into the foamed layer 26 in the cavity 3.

  Accordingly, the skin layer 25 a in contact with the pin member 8 and a part of the foam layer that has entered the pin hole 9 enter the foam layer 26 in the cavity 3.

  When the pin member 8 is retracted, there is a possibility that the resin being foamed enters the pin hole 9 and is cooled by contact with the inner surface of the pin hole to form a new skin layer. However, since the temperature difference between the resin and the inner surface of the pin hole is small when the pin member 8 is retracted, even if a skin layer is formed by contact with the inner surface of the pin hole, it becomes a thin skin layer with low strength. Become. Therefore, the forward movement of the pin member 8 is not hindered, and the skin layer is pushed by the pin member 8 and peeled off from the inner surface of the pin hole, and further easily from the skin layer 25b in contact with the movable body 7. It is cut off and pushed into the foamed resin molded body 26 in the cavity 3.

  In particular, since the tip surface 8a of the pin member 8 has a concave shape and the edge of the tip surface 8a has a sharp edge, even when a skin layer is formed along the inner surface of the pin hole, the skin layer is It becomes easy to peel off from the inner surface of the pin hole by the sharp edge, and further, it is easily cut off from the skin layer 25b in contact with the movable body 7.

  Then, when a predetermined time elapses (when the foamed resin molded body 27 is cooled to a predetermined temperature), as shown in FIG. 3, mold opening for retracting the movable mold body 7 is performed. At this time, the pin member 8 is further advanced at the same time, thereby causing the pin member 8 to function as an ejector pin for releasing the foamed resin molded body 27.

  Therefore, as shown in FIG. 7, the obtained foamed resin molded body 27 has a hole 28 opened at a portion corresponding to the pin member 8, and the foamed layer 26 is exposed on the inner peripheral surface of the hole 28. Since the foam layer 26 exposed on the inner peripheral surface of the hole absorbs sound, the soundproofing effect is enhanced. In particular, since the bottom surface 28a of the hole 28 has a medium-high shape corresponding to the concave shape of the tip end surface 8a of the pin member 8, the foam layer 26 exposed to the inner surface of the hole by the medium-high bottom surface 28a. It becomes easy to be reflected so that it goes to, and sound-absorbing property becomes high. Further, with respect to heat insulation, since the holes 28 are formed in the skin layer 25b of the foamed resin molded body 27, the thermal conductivity of the surface transmitted through the skin layer 25b is lowered, and the heat insulation effect is enhanced.

  The core back of the movable body 7 and the pin member 8 may be started before completion of filling with the foamable resin.

  Further, the pin member 8 may be retracted at a speed higher than that of the movable body 7 simultaneously with the start of the core back of the movable body 7. Alternatively, the movable body 7 and the pin member 8 may be core-backed at the same speed, and the pin member 8 may be further retracted after the core back of the movable body 7 is completed.

  Alternatively, the pin member 8 may be retracted from the time before the core back of the movable body 7 starts. For example, in the case of a component that wants to ensure impact strength, the mold temperature is set low to form a thick skin layer, or a long time is intentionally taken between the completion of injection and the start of core back. When the pin member is retracted simultaneously with the start of the core back, the skin layer is difficult to split. Therefore, it is effective to retract the pin member 8 from the time before the core back of the movable body 7 is started.

  Moreover, the cross-sectional shape of the pin member 8 does not need to be limited to a circle, and may be an appropriate shape such as a triangle, other polygons, or a bowl. The tip surface of the pin member 8 may also be formed flat without being concave.

DESCRIPTION OF SYMBOLS 1 Mold 2 Injection apparatus 3 Cavity 4 Fixed mold 5 Movable mold 6 Sprue 7 Movable mold main body 8 Pin member 8a Tip surface 25a Skin layer 25b Skin layer 26 Foamed layer 27 Foamed resin molding

Claims (3)

After filling the cavity between the fixed mold and the movable mold with a molten foamable resin containing a foaming agent in the raw material resin, the cavity should be formed by a core back that retracts the movable mold from the fixed mold. In the method for producing a foamed resin molded body having a skin layer and a foamed layer that are expanded to a volume corresponding to the foamed resin molded body,
The movable mold includes a movable mold main body and a pin member, and the pin member is provided such that a tip surface thereof forms the cavity together with the movable mold main body and faces the fixed mold,
In the movable core back, the pin member is further retracted from the movable main body, and then the pin member is advanced to push the tip surface into the foam layer in the cavity, and then A method for producing a foamed resin molded body, comprising releasing the foamed resin molded body. In claim 1,
The method for producing a foamed resin molded body, wherein the tip surface of the pin member has a concave shape whose central side is recessed with respect to the peripheral edge thereof. After filling the cavity between the fixed mold and the movable mold with a fixed mold and a movable mold that advances and retreats toward the fixed mold, and a foamable resin in a molten state containing a foaming agent in the raw material resin In the manufacturing apparatus for a foamed resin molded body having a skin layer and a foamed layer, the core is configured to retreat the movable mold from the fixed mold, and the cavity is expanded to a volume corresponding to the foamed resin molded body to be molded.
The movable mold is provided such that the movable mold main body and a front end surface thereof form the cavity together with the movable mold main body and face the fixed mold. And a pin member that moves forward so that the front end face enters the foamed layer in the cavity.

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