JP2004009518A - Molding method for foamed resin molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method for a foamed resin molded body, the appearance performance of which is enhanced by preventing poor outside appearances such as silver streaks from developing through the checking of a gas blowing reaction at the injection filling of a foaming resin material in the molding method of the foamed resin molded body utilizing injection molding. <P>SOLUTION: After molds are clamped together by lowering a cavity mold 30 to its bottom dead center, the foaming resin material M is injection-filled in a product cavity C. At the injection filling, the cavity mold 30 is pushed upwards by the resin pressure of the foaming resin material M. The resin is preferably filled so as to gradually accelerate the ascending speed of the cavity mold 30 so as to perform a primary pressurizing under the condition that a proper clearance is kept. After that, the cavity mold 30 is raised forcibly so as to perform an ununiform blowing-free gas blowing reaction by ensuring a blowing space, resulting in molding the foamed resin molded body 12 with a favorable surface outside appearance and with no varied wall thickness. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a molding press molding method, a molding resin molding method utilizing an injection molding method, particularly during injection filling of a foamed resin material, without appearance defects such as silver streaks on the product surface, The present invention relates to a method for molding a foamed resin molded article having high practicality, such as being able to obtain a foamed resin molded article having excellent appearance performance and to use a molding machine having a lower mold clamping pressure.
[0002]
[Prior art]
FIG. 8 shows an automotive door trim 1 mounted on the indoor side of a door panel (not shown). Since the door trim 1 is lightweight, has excellent impact resistance and is inexpensive, it is made of PP (polypropylene). 2.) A foamed resin molded article in which a foaming agent is mixed in the resin is often used, and the door trim 1 is integrally formed with an armrest portion 1a, a door pocket opening 1b, a speaker grill 1c, etc., which bulges toward the indoor side. Have been.
[0003]
A conventional molding method for molding the seed foamed resin molded article into a required shape will be described with reference to a process explanatory diagram shown in FIG. 9 and a time chart of a mold shown in FIG.
[0004]
That is, the molding die 2 is generally constituted by the cavity die 3 and the core die 4, and the cavity die 3 is driven in a direction approaching the core die 4 to perform mold clamping. Then, in the initial mold state at the time of mold clamping, as shown in FIG. 9A, the mold position of the cavity mold 3 is a1, and the mold clearance in the product cavity is set to 2.0 mm. Have been.
[0005]
Then, in this state, a foamed resin material M is injected and filled into the product cavity C via a resin passage from an injection molding machine (not shown). FIG. 9B shows the state after the injection filling time (t1). That is, after the foamed resin material M is filled in the product cavity C, a delay time (t2) of 0 to 10 seconds elapses.
[0006]
Thereafter, the cavity mold 3 is raised. At this time, the mold position of the cavity mold 3 is a2. This a2 is set to, for example, about 3.6 mm, and after the cooling time (t3) elapses, the door trim 1 that has been subjected to the foam molding is removed from the mold. Just do it.
[0007]
The mold clamping pressure in the above molding method is 850 t, and the projection area is set to 2700 cm ² .
[0008]
[Problems to be solved by the invention]
As described above, in the conventional molding method of the foamed resin molded article, after the cavity mold 3 and the core mold 4 are clamped, the foamed resin material M is injected and filled into the product cavity C, and a predetermined time delay (primary addition) is performed. Pressure), the cavity mold 3 is raised, a foaming space is secured, and the foaming molding, that is, the molding of the foamed resin molded article is completed after a predetermined cooling time. At the time of injection filling into the product cavity C, the foaming agent foams, so that appearance defects such as silver streaks occur on the surface, which requires many man-hours for rework, which is a major factor in lowering productivity.
[0009]
In addition, a problem has been pointed out that the mold clamping pressure is as large as 850 t and it is difficult to cope with a general-purpose injection molding machine.
[0010]
The present invention has been made in view of such circumstances, and is a method for molding a foamed resin molded article by molding a foamed resin molded article by an injection molding method, comprising a step of injecting a foamed resin material into a molding die. The foaming reaction does not occur, and the appearance of defects such as silver streaks on the product surface can be reliably suppressed, the product yield can be increased, and the power source of the molding machine is also a conventional fluid pressure drive system It is an object of the present invention to provide a method of molding a foamed resin molded article that can be easily carried out by a general-purpose molding machine, for example, capable of coping.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application is directed to a method in which a foamed resin material is injected and filled into a product cavity defined between a first mold and a second mold. In the method for molding a foamed resin molded article into a required shape, the first mold is moved to a mold clamping position by a cylinder, and then the foamed resin material is injected and filled into a product cavity. When the first mold is stopped due to the injection filling step of the foamed resin material for moving the first mold in the predetermined stroke mold opening direction with the resin pressure and the balance between the resin pressure of the foamed resin material and the mold clamping pressure of the mold. A primary pressing step of pressing the foamed resin material between the molds, and after the primary pressing step, the first mold is forcibly moved in a mold opening direction by a predetermined stroke to secure a foaming space of a predetermined thickness. Foam molding of foamed resin molded body to desired thickness And foam molding step, that consists characterized.
[0012]
Here, the first mold moves a predetermined stroke between the mold clamping position and the mold opening position by driving the cylinder, and the second mold supplies the foamed resin material into the product cavity from the continuous injection molding machine. For this purpose, a resin passage such as a manifold or a gate is provided.
[0013]
For example, in a mold press molding method, the first mold is a cavity mold driven by a cylinder, and the second mold is a core mold connected to an injection molding machine.
[0014]
On the other hand, in the injection molding method, the first mold is a core mold driven by a cylinder, and the second mold is a cavity mold connected to an injection molding machine.
[0015]
Further, as the foamed resin material, a material obtained by mixing an azo foaming agent (such as azodicarbonamide) with a PP resin can be used.
[0016]
According to the first aspect of the present invention, after the mold is clamped, in the step of injecting and filling the foamed resin material into the product cavity, the resin pressure of the foamed resin material is increased. Loses, and the first mold moves in the mold opening direction. Thereafter, when the filling of the target resin amount is completed, the first mold is stopped, and primary pressurization is performed. Next, the first mold is forcibly moved in a predetermined stroke mold opening direction, a predetermined foaming space is secured, and after a predetermined cooling time has elapsed, the foam molding is completed. Can be removed.
[0017]
Therefore, when the foamed resin material is injected and filled into the product cavity, the clearance between the molds is set very small, so that the surface of the resin is solidified before the foaming agent (foaming gas) starts foaming. No appearance defects such as silver streaks occur.
[0018]
In addition, since the mold clamping pressure of the mold is set low so that the first mold moves in the mold opening direction due to the resin pressure of the foamed resin material, the class of the molding machine can be downgraded. Can respond sufficiently.
[0019]
The invention according to claim 2 of the present application is characterized in that, after the first mold and the second mold are clamped, the foamed resin material in the product cavity is injected and filled into the product cavity. When moving the first mold in the mold opening direction due to the resin pressure of the material, set the mold opening speed of the first mold to be slow at the start of injection, and to be close to the time of completion of injection, to be faster than at the start of injection. Thereby, the solidification of the surface of the foamed resin material is promoted.
[0020]
Here, the moving speed of the first mold moving in the mold opening direction by the resin pressure of the foamed resin material is determined by the mold clamping pressure of the mold and the resin pressure. For example, when the mold clamping pressure of the mold is relatively small, the moving speed of the first mold is constant. On the other hand, if the mold clamping pressure is increased, the moving speed of the first mold is slow at the start of injection and becomes high immediately before the completion of injection, and this tendency becomes greater as the mold clamping pressure is increased.
[0021]
According to the second aspect of the present invention, by adjusting the mold clamping pressure, the mold opening speed of the first mold is slowed at the start of the injection, and the mold of the first mold is nearer to the completion of the injection than at the start of the injection. Since the opening speed is set to be high, an appropriate internal pressure between the molds always acts on the foamed resin material, so that the surface of the foamed resin material is more reliably solidified. Therefore, the silver streak phenomenon can be more effectively suppressed.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a method for molding a foamed resin molded article according to the present invention will be described in detail with reference to the accompanying drawings.
[0023]
1 and 2 are a front view and a cross-sectional view of an automobile door trim partially adopting a foamed resin molded article formed by applying the method of the present invention. FIG. 3 shows a method of molding a foamed resin molded article according to the present invention. FIG. 4 is a side view showing a schematic configuration of a molding apparatus to be used, FIG. 4 is a time chart of a molding die in a molding step of the molding apparatus, and FIGS. 5 to 7 are explanatory views showing each step in a molding method of a foamed resin molded article. It is.
[0024]
The vehicle door trim 10 shown in FIGS. 1 and 2 is composed of a vertically divided door trim upper 11 and a vertically divided door trim lower 12. In the door trim upper 11, an insulated sheet 14 is attached to a part of the surface of a resin base material 13, a door pocket opening 15 is opened in the door trim lower 12, and a speaker grill 16 is integrally formed on the front side thereof. Is provided.
[0025]
The resin base material 13 of the door trim upper 11 is made of a PP resin mold-pressed or injection-molded body, and an intermediate sheet 14 such as a cloth or a nonwoven fabric is integrated when the resin base material 13 is formed.
[0026]
The door trim lower 12 is formed into a required shape by mold press molding and injection molding using a foamed resin material in which a foaming agent (azodicarbonamide or the like) is mixed into a PP resin.
[0027]
By the way, the present invention relates to a method for molding a foamed resin molded article, and is suitable for molding a foamed resin molded article such as a door trim lower 12 in a door trim 10, and improves appearance quality performance when foaming the door trim lower 12. be able to.
[0028]
The configuration of the molding apparatus 20 used for molding the door trim lower 12 will be described with reference to FIG. Although the molding apparatus 20 shown in FIG. 3 utilizes a mold press molding method, it can be applied to an injection molding method mutatis mutandis.
[0029]
The molding apparatus 20 is composed of a cavity mold 30 and a core mold 40 which can be closed and opened with each other. The cavity mold 30 can move up and down by a predetermined stroke by driving a lifting cylinder 31. As can be seen from the time chart shown in FIG. 4, (1) a state of falling to the bottom dead center, (2) a state of being pushed up by resin pressure and temporarily stopped to perform primary pressurization, (3) A series of operations (1) to (3) are performed as in a state where the foaming reaction is carried out by ascending again to secure a foaming space.
[0030]
That is, at the time of the mold clamping when the cavity mold 30 is lowered to the bottom dead center, the mold position of the cavity mold 30 is set to L0 and the clearance between the molds is set to 1.2 mm. In this state, the injection filling for the injection time T1 is performed.
[0031]
Then, at the time of injection filling, the cavity mold 30 is pushed upward by the resin pressure of the foamed resin material M, and primary pressurization is performed at the position (2), ie, the mold position L1, and the pressurization time T2 at the clearance of 2.0 mm. It is.
[0032]
The mold clamping pressure at the time of the primary pressurization is 100 to 500 t, and the number of t can be reduced as compared with the conventional mold clamping pressure of 850 t.
[0033]
Next, the cavity mold 30 is forcibly raised, and (3) foaming is performed in a state where a foaming space is secured, and a foaming reaction is performed for the foaming molding time T3. At this time, the mold position is L2. Yes, specifically, it is set to 3.6 mm. Therefore, the thickness of the door trim lower 12, which is a foamed resin molded product, is adjusted to a thickness of 3.6 mm.
[0034]
This will be described based on the time chart of FIG. 4 and the process explanatory diagrams shown in FIGS. 5 to 7. As shown in FIG. 5, when the cavity mold 30 is moved down to the bottom dead center by driving the elevating cylinder 31 ((1) in the time chart), the clearance between the cavity mold 30 and the core mold 40 in the product cavity C is obtained. (L0) is set to 1.2 mm.
[0035]
Then, from the state shown in FIG. 5, the foamed resin material M is injected and filled into the product cavity C. At this time, due to the resin pressure of the foamed resin material M, the set pressure of the cavity mold 30 is reduced by the resin pressure. 6, the cavity mold 30 is pushed upward, and as shown in FIG. 6, the cavity mold 30 is raised until the clearance (L1) of the product cavity C becomes 2.0 mm.
[0036]
At this time, the ascending mode of the cavity mold 30 may be set in a relationship in which the time and the ascending stroke of the cavity mold 30 are directly proportional (the ascending speed is constant), but in the present embodiment, the time chart of FIG. As shown in the figure, the rising speed of the cavity mold 30 is slow at the start of injection, and just before the injection is completed, the rising speed gradually changes with time so that the rising speed becomes faster than at the start of injection. Is set.
[0037]
In this way, by setting the shape in a curved shape, the solidification of the surface of the foamed resin material M can be effectively promoted, so that the silver streak phenomenon can be further suppressed. This tendency is that if the mold clamping pressure between the cavity mold 30 and the core mold 40 is set relatively large, the rising speed of the cavity mold 30 at the start of injection can be controlled to be slow, while the cavity mold 30 and the core mold 40 are not controlled. If the mold clamping pressure is set small during this period, the rising speed of the cavity mold 30 tends to be almost constant.
[0038]
After the injection filling of the foamed resin material M is completed, a delay time (T2 in FIG. 4) of 0 to 10 seconds elapses in the state shown in FIG. That is, primary pressurization is performed. Thereafter, as shown in FIG. 7, the cavity mold 30 is forcibly raised, and (3) foam molding is performed for the foam molding time indicated by T3 in FIG.
[0039]
The ascending stroke of the cavity mold 30 is such that the cavity mold 30 is forcibly raised until the clearance (L2) between the molds in the product cavity C becomes 3.6 mm, and the foaming space is effectively secured, so that the foaming unevenness is reduced. The molding of the door trim lower 12 can be performed.
[0040]
As described above, according to the method of the present invention, the cavity mold 30 is lowered to the bottom dead center to inject and fill the foamed resin material M into the product cavity C. At this time, the cavity mold 30 is pressed by the resin pressure of the foamed resin material M. Is pushed upward, and the foaming resin material M is injected and filled. Therefore, since the clearance between the molds at the start of the injection of the foaming resin material M is extremely small, the foaming agent in the foaming resin material M starts foaming. By solidifying the surface before performing, appearance defects such as silver streaks can be prevented.
[0041]
Further, the rising speed at which the cavity mold 30 is pushed up is set to be an ideal curve shown in FIG. 4 in which the rising speed is slow at the start of the injection filling of the foamed resin material M, and the rising speed increases as the resin filling amount increases. Further, the solidification of the surface of the foamed resin material M can be further promoted, and the occurrence of silver streaks and the like can be suppressed more effectively.
[0042]
In addition, since the set pressure of the pressing pressure applied to the cavity mold 30 at the time of the primary pressurization can be small, the class of the molding machine can be downgraded, which can contribute to labor saving and can be realized by a conventional molding machine (fluid pressure driving system). It is also practical.
[0043]
Further, in the foam molding process, since the cavity mold 30 is forcibly raised to effectively secure a foaming space, uneven foaming does not occur, and appearance defects such as silver streaks can be avoided. Since there is no unevenness, it is possible to mold a foamed resin molded article having excellent moldability, and there is an advantage that the product yield is greatly improved.
[0044]
【The invention's effect】
As described above, the molding method of the foamed resin molded article according to the present invention is such that after the mold is clamped, the foamed resin is injected and filled, and the first mold is moved in the mold opening direction by the resin pressure at this time, and the appropriate position is set. Perform the primary pressurization of the foamed resin, then, forcibly move the first mold in the mold opening direction to secure a foaming space, and adopt the process of performing foam molding, so before the foaming agent foams Since the surface of the resin is solidified, appearance defects such as silver streaks do not occur, and the appearance of the product can be maintained well. In addition, since the foaming space is ensured even in the foaming molding process after injection filling, foaming reaction without uneven foaming can be expected, foaming resin molding excellent in molding performance with good surface appearance and no thickness variation It has the effect that the body can be molded.
[0045]
Further, in the method for molding a foamed resin molded article according to the present invention, the mold clamping pressure at the time of the primary press can be set lower than the conventional pressure, so that the power cost can be reduced and the class of the molding machine can be reduced. At the same time, the present invention has an effect of being excellent in practicality, for example, it can sufficiently cope with a conventional fluid pressure driven molding machine.
[0046]
According to another embodiment of the method for molding a foamed resin molded article according to the present invention, in the injection filling step of the foamed resin material, the mold opening speed of the first mold moved in the mold opening direction by the resin pressure is injected. Since the mold clamping pressure is adjusted so that it is slow at the start and fast just before the injection is completed, foaming of the foaming agent during injection filling of the foamed resin material can be more effectively suppressed, and the silver streak phenomenon can be suppressed. This has the effect that the prevention can be more reliably prevented and the product appearance of the foamed resin molded article can be maintained more beautifully.
[Brief description of the drawings]
FIG. 1 is a front view showing an automobile door trim to which a foamed resin molded article molded by the method of the present invention is partially applied.
FIG. 2 is a cross-sectional view showing a configuration of the vehicle door trim shown in FIG.
FIG. 3 is an explanatory view showing a schematic configuration of a molding apparatus used for a method of molding a foamed resin molded article according to the present invention.
FIG. 4 is a time chart showing the operation of a mold in the method for molding a foamed resin molded article according to the present invention.
FIG. 5 is an explanatory view showing an initial mold state in the method for molding a foamed resin molded article according to the present invention.
FIG. 6 is an explanatory diagram showing a mold state after resin filling is completed in the method for molding a foamed resin molded article according to the present invention.
FIG. 7 is an explanatory view showing a mold state during foam molding in the method for molding a foamed resin molded article according to the present invention.
FIG. 8 is a front view showing a conventional automobile door trim.
FIG. 9 is an explanatory view showing (a) an initial mold state, (b) a mold state after resin filling is completed, and (c) a mold state at the time of foam molding in a conventional method of molding a door trim for an automobile. is there.
FIG. 10 is a time chart showing an operation of a mold in a conventional molding die.
[Explanation of symbols]
Reference Signs List 10 Door trim 11 for car 11 Door trim upper 12 Door trim lower 20 Molding device 30 Cavity mold 31 Lifting cylinder 40 Core mold T1 Injection filling time T2 Primary pressurization time T3 Foaming molding time C Product cavity M Foam resin material

Claims (2)

The foamed resin material (M) is injected and filled into the product cavity (C) defined between the first mold (30) and the second mold (40) to form the foamed resin molded body (12) into a required shape. In the method for molding a foamed resin molded article to be molded into
After the first mold (30) is moved to the mold clamping position by the cylinder (31), the foamed resin material (M) is injected and filled into the product cavity (C), and the resin of the foamed resin material (M) at this time is filled. An injection filling step of a foamed resin material for moving the first mold (30) in a predetermined stroke mold opening direction by pressure;
When the first mold (30) stops due to the balance between the resin pressure of the foamed resin material (M) and the mold clamping pressure of the molds (30, 40), the foamed resin material ( M) a primary pressurizing step of pressurizing;
After the primary pressurizing step, the first mold (30) is forcibly moved in the mold opening direction by a predetermined stroke to secure a foaming space of a predetermined thickness to foam-mold the foamed resin molded body (12) to a desired thickness. Foam molding process,
A method for molding a foamed resin molded article, comprising: After the mold clamping of the first mold (30) and the second mold (40), in the injection filling step of the foamed resin material (M), the foamed resin material (M) is injected and filled into the product cavity (C).
When the first mold (30) is moved in the mold opening direction by the resin pressure of the foamed resin material (M) in the product cavity (C), the mold opening speed of the first mold (30) is slowed down at the start of injection, and the injection is completed. 2. The foamed resin according to claim 1, wherein the solidification of the surface of the foamed resin material (M) is promoted by setting the mold opening speed of the first mold (30) to be higher immediately before the start of the injection. A method for forming a molded body.

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