JP2005111820A - Multi-colored molded product and its molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the shortening of a molding cycle and the cost reduction of a mold while enhancing the filling properties of a vertical wall part or the like hardly filled with a filler on and after secondary molding, in a core back type multi-color molding method, and a multi-colored molded product. <P>SOLUTION: Gas G is injected in the space between a first filled resin material 13 and the mold surface 31 of a fixed mold 3 on the laminated side of a second resin material 14 and dwelled to shrink the first resin material 13 in a wall thickness direction to form a gap S. Thereafter, the movable mold 4 is moved backward and the second resin material 14 is injected to improve the filling properties of the second resin material 14. Since a large mold opening is unnecessary when the movable mold 4 is moved backward, the molding cycle can be shortened and it is unnecessary to prepare a plurality of molds in order to mold the second resin material 14. Accordingly, the cost of the mold can be reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a multicolor molded product in which at least two kinds of resin materials are laminated and integrated by injection molding, and a multicolor molded product. Specifically, the present invention relates to a core back type multicolor molding method in which an injection space is formed by moving a movable part of a mold forward and backward, and a multicolor molded product molded by this multicolor molding method. And the present invention includes parts for automobiles such as instrument panels, door panels, back doors, center consoles, parts for housing equipment such as vanities, bath counters, bathtubs, bathroom storage panels, buckets, clothes storage cases, etc. It can be widely used in the fields of daily necessities, household appliances such as TV and personal computer cases, OA equipment, and toys.

2. Description of the Related Art Conventionally, multicolor molded products that are molded products using different color tone resins, different types of resin materials, and resin materials of different color tones and types are known. As a multicolor molding method (for example, two-color molding method) for producing a multicolor molded product, there are a core back method and a core rotation method, and a special method such as DSI (die slide injection).
In the multi-color molding method using the core back method, the mold can be composed of one cavity and one core (one cavity, one core), so that the mold cost is lower than that of other multi-color molding methods. In addition, it has the advantage that the operation of the molding machine during molding can be simplified. However, since the mold can be moved only in one axial direction during the core back, it is difficult to fill the secondary material in the standing wall part with a small angle with the core back direction or a part with a large curvature. There is a drawback of being. For this reason, there is no known multicolor molding method using a core back method for the purpose of forming a laminated structure on the standing wall.
On the other hand, as a multicolor molding method other than the core back method, a multicolor molded product in which a resin is laminated on a standing wall portion using a mold composed of two cavities and one core (two cavities, one core). There has been proposed a technique for molding (see, for example, Patent Document 1).

JP-A-8-57899

However, the multicolor molding method of Patent Document 1 has a problem in that it is difficult to shorten the molding cycle because the mold must be largely opened before the secondary molding.
Furthermore, two types of cavity plates for forming the surface side of the two-color molded product are required for primary and secondary molding. Also, angular pins, core back pieces, etc. are used, and the mold structure is complicated. For this reason, careful preparation is required before molding, and it is difficult to reduce the mold cost.

  It is an object of the present invention to shorten the molding cycle and reduce the cost of the mold in the core back type multicolor molding method, and to fill up standing walls and the like that are difficult to be filled with secondary and subsequent fillers. Is to provide a multicolor molding method and a multicolor molded product.

  The molding method of the present invention is a method for molding a multicolor molded article having at least two kinds of resin materials laminated by injection molding, and having a top surface portion and a standing wall portion rising from the top surface portion, wherein the top surface portion and the standing wall In the first injection step of injecting one of the resin materials into the injection space having a dimension in the thickness direction smaller than the space corresponding to the part, and the resin material injected in the first injection step, A pressure step of injecting a gas between the side on which the resin material of the second injection step is laminated and the mold, holding the injected gas at a predetermined pressure, and holding the pressure for a predetermined time; Subsequent to the pressing step, a core back step of core-backing the movable portion of the mold in a direction substantially orthogonal to the top surface portion, and the at least two kinds of resins in the injection space formed in the core back step Material Characterized in that a second injection step of injecting the other resin material.

Here, as the standing wall portion, such as a wall portion orthogonal to the top surface portion, a wall portion having an angle with respect to the top surface portion, or a curved wall portion having a predetermined curvature, the mold is opened at the time of core back. It means the part where the opening amount becomes smaller than the top part.
Further, the first and second injection processes do not mean only the injection process of the primary material and the secondary material in the multicolor molding, but out of the injection of the resin material executed a plurality of times in the multicolor molding. , Means any injection process performed before or after. For example, in multicolor molding having a tertiary or higher injection process, the injection of the secondary material and the tertiary material may be executed by the first and second injection processes of the present invention, and the primary material and the secondary material. And injection of secondary material and tertiary material may be performed.
Further, the movable part of the mold to be core-backed may be a part of the mold (for example, a movable block or a floating core), and when the mold is composed of a movable mold and a fixed mold, The entire mold of the fixed mold may be used.

According to this invention, the resin material (two colors) injected in the second injection process in the resin material (filled material, primary material in the case of two-color molding) injected in the first stage injection process. In the case of molding, the filled material is shrunk (sinked) in the thickness direction by injecting gas and holding pressure between the mold on the side where the secondary material) is laminated, A gap is formed between them, and then a core back process is performed to form an injection space, and the second resin material is injected into the injection space, thereby improving the filling property of the second resin material. Can do. That is, in the standing wall portion where the mold opening amount at the core back is small, a gap is formed by gas injection between the filled material and the mold, and then the core back and the second injection step are performed. The standing wall portion in which the two resin materials are surely filled and the first and second resin materials are satisfactorily laminated can be formed.
According to such a molding method, in the core back process, it is not necessary to open a large mold, and it is only necessary to open the mold by the amount of movement necessary for molding the second resin material, so that the molding cycle can be shortened. Can be planned. Further, since it is not necessary to prepare a plurality of molds for molding the second resin material, it is possible to reduce the mold cost.
At this time, it is desirable to provide a gas injection port in the mold portion corresponding to the standing wall and inject gas from this gas injection port. In this way, the filled material of the standing wall portion can be effectively contracted to form a gap, so that the filling property of the second resin material can be further improved.

In the above, it is desirable that the standing wall portion is formed thicker than the top surface portion.
According to such a configuration, the shrinkage rate in the thickness direction of the filled material in the standing wall portion due to gas injection and holding pressure increases, so that there is a gap between the filled material in the standing wall portion and the mold. A large gap can be formed, and the injection space for the second resin material can be increased. At this time, the thickness dimension of the standing wall portion is preferably set to be within twice the thickness dimension of the top surface portion, and more preferably within 1.5 times.

Furthermore, prior to the pressing step, it is preferable to include a micro core back step of core-backing the movable part of the mold by a movement amount smaller than the movement amount in the core back step.
According to such a configuration, a small gap is formed between the filled material filled in the first injection process and the mold by a small movement amount of the core back, and then gas is supplied to the minute gap. By injecting, the gap between the filled material and the mold can be surely formed.

In the present invention, all thermoplastic resins can be applied as the molding material.
Examples of thermoplastic resins include propylene-ethylene random copolymers, soft polyolefin resins, polystyrene homopolymers, polystyrene resins such as rubber-modified polystyrene and syndiotactic structure-containing polystyrene, AS resins, ABS resins, and polyvinyl chloride. Resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic ester resin, polysulfone resin, and acrylate resin.

In particular, as a material having a large shrinkage rate in which the effect of the present invention is effectively exhibited, there is a crystalline resin. Examples of the crystalline resin include polyolefin resins such as polypropylene, propylene-ethylene block copolymer, polyethylene, unsaturated carboxylic acid or derivative-modified polyolefin resin, and polyamide resins.
Of these crystalline resins, polypropylene is preferable in terms of versatility and strength. Polypropylene can be used regardless of the type such as a homopolymer, a random copolymer with other α-olefin, and a block copolymer.

  Moreover, although a thermoplastic resin may be used independently, you may combine 2 or more types. For example, as in the examples described later, a multicolor molded product can be manufactured using the same resin that differs only in color tone, or two or more types of resins can be combined. Furthermore, both the base material layer and the skin layer of the multicolor molded product may be molded from a material in which two or more kinds of resins are blended.

  The above thermoplastic resins include impact strength improvers such as elastomers, reinforcing materials such as glass fiber, talc, and calcium carbonate, fillers, antioxidants, ultraviolet absorbers, antistatic agents, and weathering materials as necessary. Additives such as light stabilizers, colorants, and crystallization nucleating agents may be added.

On the other hand, the multicolor molded product of the present invention is characterized by being molded by any of the molding methods described above.
According to the present invention, the same effect as described above can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1-4 is sectional drawing which shows the metal mold | die 2 part of the injection molding machine 1 which shape | molds the multicolor molded product which concerns on one Embodiment of this invention.
The mold 2 includes a fixed mold 3 fixed to a fixed die plate (not shown) and a movable mold 4 provided on a movable die plate (not shown) and configured to be movable forward and backward with respect to the fixed mold 3. ing. The fixed mold 3 and the movable mold 4 are clamped in a state in which a cavity 5 for injecting a resin material is formed between opposing surfaces.
Further, as shown in FIG. 3, the movable die 4 is configured to be movable (core back) in a direction away from the fixed die 3. That is, the movable part of the present invention is constituted by the movable mold 4.

As shown in FIG. 4, the multicolor molded product 10 of the present invention is a two-color molded product in which the first and second resin materials 13 and 14 are laminated and molded by a core back type multicolor molding method. . The multicolor molded product 10 is molded into a box shape (tray shape) with one open, and includes a top surface portion 11 and a standing wall portion 12 that rises from the outer periphery of the top surface portion 11.
In addition, the thickness dimension of the standing wall part 12 of the multicolor molded product 10 is set to be thicker than the thickness dimension of the top surface part 11. And the rising dimension of the standing wall part 12 of the multicolor molded product 10 is 3 times or less, preferably 1 time or less, more preferably 0.5 times or less with respect to the length of the long side of the top surface part 11. Is set. Furthermore, the crossing angle between the top surface portion 11 and the standing wall portion 12 is preferably set in the range of 10 ° to 90 °, more preferably 30 ° to 90 °, and particularly preferably 60 ° to 85 °. It is a range. Here, when the top surface portion 11 or its extension line intersects the standing wall portion 12 or its extension line, the crossing angle is 90 ° when orthogonal, but in other cases it is 90 °. Larger angles and smaller angles than 90 ° are possible. In this case, an angle smaller than 90 ° is employed as the intersection angle.

  The mold surface 31 of the fixed mold 3 forming the cavity 5 includes a first mold surface 31A for molding the top surface portion 11 of the multicolor molded product 10 and a second mold surface for molding the standing wall portion 12 of the multicolor molded product 10. 31B. The mold surface 41 of the movable mold 4 is provided opposite to the first mold surface 31A of the fixed mold 3, and is opposed to the third mold surface 41A for forming the top surface portion 11 and the second mold surface 31B of the fixed mold 3. Provided, and a fourth mold surface 41B for molding the standing wall portion 12 and a fifth mold surface 41C for molding an end surface of the standing wall portion 12.

  On the first mold surface 31A of the fixed mold 3, the gates 32A and 33A of the first and second material sprue bushes 32 and 33 connected to an injection device (not shown) for injecting a resin material into the cavity 5 are opened. Has been. These first and second material sprue bushings 32 and 33 are for injecting the first and second resin materials 13 and 14 forming the multicolor molded article 10, respectively. A gas injection port 34 </ b> A of a gas injection pipe 34 for injecting gas G into the cavity 5 is opened on the second mold surface 31 </ b> B of the fixed mold 3. The gas injection pipe 34 is connected to a gas injection device (not shown) so that gas is injected into the cavity 5 at a predetermined pressure.

Next, an operation of the injection molding machine 1 according to the present embodiment, that is, a molding procedure for molding the multicolor molded product 10 by the core back type multicolor molding method will be described.
First, as shown in FIG. 1, the fixed mold 3 and the movable mold 4 are clamped to form the mold surface 31 (31A, 31B) of the fixed mold 3 and the mold surface 41 (41A, 41B, 41C) of the movable mold 4. Thus, the first cavity 5A is formed. The distance between the fixed mold 3 and the movable mold 4 in the first cavity 5A is smaller than the thickness of the multicolor molded product 10 as a finished product. Then, the first resin material 13 is injected into the first cavity 5A via the first material sprue bush 32 and filled (first injection step).

  In a state where the filled first resin material 13 is cooled to a predetermined temperature and begins to harden after a predetermined time (for example, 1 second to 20 seconds) has elapsed from the first injection step, as shown in FIG. The gas G is injected between the first resin material 13 and the mold surface 31 (31A, 31B) of the fixed mold 3 through the injection tube. By injecting the gas G, the first resin material 13 is pressed toward the movable mold 4 and contracted (sinked) in the thickness direction, so that the first resin material 13 and the mold surface 31 of the fixed mold 3 A gap S is formed between them. Then, in a state where the first resin material 13 is pressed, the injected gas G is held at a predetermined pressure (for example, 0.5 to 8 MPa), and after a predetermined time (for example, 3 to 20 seconds) has elapsed, the gas G Depressurize. Thus, the pressing process is completed.

  Next, as shown in FIG. 3, the fixed mold 3 and the movable mold 4 are once opened, and the movable mold 4 is core-backed in a direction away from the fixed mold 3 (in the direction of the arrow in FIG. 3) by a predetermined amount (core Back process). At this time, the first mold surface 31A of the fixed mold 3 and the third mold surface 41A of the movable mold 4 are substantially orthogonal to the core back direction (left-right direction in FIG. 3) of the movable mold 4, and the first mold The opening amount of the surface 31A and the third mold surface 41A is substantially the same as the movement amount of the core back. On the other hand, since the second mold surface 31B of the fixed mold 3 and the fourth mold surface 41B of the movable mold 4 are inclined with respect to the core back direction, the opening amount of the second mold surface 31B and the fourth mold surface 41B is The amount of movement of the core back is smaller. And by making the movable mold | type 4 core back, the said clearance gap S between the 1st resin material 13 and the mold surface 31 of the fixed mold | type 3 is expanded, and the 2nd cavity 5B is formed.

Next, as shown in FIG. 4, the second resin material 14 is injected and filled into the second cavity 5B through the second material sprue bush 33 (second injection step).
After the second injection step is completed and a predetermined time has elapsed, a movable die plate (not shown) is driven to separate the movable die 4 from the fixed die 3 and take out the multicolor molded product 10 from the die 2. And the process of a gate cut etc. is performed and shaping | molding of a multicolor molded product is completed.
Prior to the pressing step, the movable die 4 is core-backed by a movement amount (for example, about 0.5 mm) smaller than the movement amount by which the movable die 4 is core-backed in the core-back step (micro-core back step). Then, it is good also as a shaping | molding procedure which performs the press process shown in FIG.
In addition, after the second injection process, by repeatedly performing the pressing process, the core back process, and the second injection process shown in FIGS. 2 to 4, a multicolor molded product made of three or more types of resin materials can be obtained. It becomes possible to mold.

According to the above embodiment, the following effects are obtained.
(1) Gas G is injected between the filled first resin material 13 and the mold surface 31 of the fixed mold 3 on the side where the second resin material 14 is laminated (pressing step). Then, the first resin material 13 is contracted (sinked) in the thickness direction to form the gap S, and then the core back process is executed to form the second cavity 5B. This second cavity 5B By injecting the second resin material 14 to the second, the filling property of the second resin material 14 can be improved.

(2) In the core back process, a large mold opening is not required, and the movable mold 4 may be core-backed by the amount of movement necessary for molding the second resin material 14, thereby shortening the molding cycle. Can do. Moreover, since it is not necessary to prepare a plurality of movable molds in order to mold the second resin material 14, it is possible to reduce the mold cost.

(3) When the gas injection port 34A is provided in the second mold surface 31B of the fixed mold 3 corresponding to the standing wall portion 12, the first resin material 13 of the standing wall portion 12 is effectively contracted to form the gap S. It can be formed, and the filling property of the second resin material 14 can be further improved.

(4) If a micro core back step is provided before the pressing step, the first resin material that has been filled in the first injection step by causing the movable die 4 to core back by a small amount of movement. 13 and a mold surface 31 of the fixed mold 3 are formed, and by injecting gas G into the minute gap, a gap S between the first resin material 13 and the mold surface 31 is formed. It can be reliably formed.

(5) Since the thickness dimension of the standing wall portion 12 of the multicolor molded article 10 is set to be thicker than the thickness dimension of the top surface portion 11, the gas G is injected and the pressure in the standing wall portion 12 is maintained. Since the shrinkage rate in the thickness direction of the first resin material 13 is increased, the gap S in the standing wall portion 12 can be formed large, and the injection space for the second resin material 14 is enlarged and filled. The property can be further improved.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, the shape of the multicolor molded product is not limited to the box shape described in the above embodiment, and may be any shape. That is, the multicolor molded product 10A provided with the top surface portion 11A and the standing wall portion 12A as shown in FIG. 5 is also included in the present invention. FIG. 5 is a cross-sectional view showing a multicolor molded product 10A according to a modification of the present invention. In FIG. 5, the multicolor molded product 10 </ b> A is formed with a plurality of top surface portions 11 </ b> A and standing wall portions 12 </ b> A. . The top surface portion and the standing wall portion are not limited to a flat shape, and the top surface portion may form a three-dimensional curved surface, or the standing wall portion and the top surface portion may be in contact with each other with a curved surface shape.

In the embodiment, the gas G is injected between the mold surface 31 of the fixed mold 3 and the filled first resin material 13, and the second resin material 14 is filled on the fixed mold 3 side. However, the present invention is not limited to this, and the gas G may be injected between the mold surface 41 of the movable mold 4 and the first resin material 13, and the second resin material 14 may be filled on the movable mold 4 side.
Further, although the gas injection port 34A is provided on the second mold surface 31B of the fixed mold 3 corresponding to the standing wall portion 12, the gas injection port 34A is provided on the first mold surface 31A of the fixed mold 3 without being limited thereto. Alternatively, when the second resin material is filled on the movable mold side, the gas injection port 34A may be provided on the movable mold surface. That is, it is only necessary that the gas inlet is provided on the side where the second resin material is laminated with respect to the first resin material.

As an example of the present invention, the following configuration was adopted.
[Molding materials and molding conditions]
As the first and second resin materials, using polypropylene (J-950HP manufactured by Idemitsu Petrochemical Co., Ltd.), coloring the first resin material uncolored and coloring the second resin material gray with a color masterbatch, Injection filling was performed at a molding temperature of 200 ° C.
As the mold, a two-layer molding test mold (globe lid shape) was used, which has a stamping structure in which the movable mold is a core and the fixed mold is a cavity. The mold temperature was 40 ° C.
As the injection molding machine, a 450 ton molding machine was used, and a gas injection means was provided.

[Evaluation methods]
Whether the second resin material is filled or not is visually confirmed, particularly on the standing wall.

[Example 1]
Injection molding was performed according to the molding procedure of the above embodiment.
Specifically, 5 seconds after the filling of the first resin material was completed, nitrogen gas was injected between the mold and the first resin material from the gas injection port, and the pressure was maintained at 1 MPa for 10 seconds.
After depressurizing the nitrogen gas, the movable mold was backed by 2 mm, and the second resin material was injected.
Then, it cooled, the metal mold | die was open | released, and the molded article was taken out.

[Comparative Example 1]
From the molding procedure of Example 1, injection molding was performed according to a molding procedure in which gas injection and holding pressure (pressing step) were omitted.

[Evaluation]
In Example 1, the second resin material was filled also in the standing wall portion, and a molded product excellent in appearance was obtained.
In Comparative Example 1, as shown in FIG. 6, an unfilled portion where the second resin material 14 was not filled in the standing wall portion 12 was observed.

  The present invention relates to automotive parts such as instrument panels, door panels, back doors, and center consoles, household equipment parts such as vanities, bath counters, bathtubs, and bathroom storage panels, and daily necessaries such as buckets and clothes storage cases. It can be widely used in fields such as home appliances such as TV and personal computer casings, OA equipment fields, and toys.

It is sectional drawing which shows the metal mold | die part of the injection molding machine which shape | molds the multicolor molded product which concerns on one Embodiment of this invention. It is sectional drawing which shows the said metal mold | die part and demonstrates the formation process different from FIG. It is sectional drawing which shows the said metal mold | die part and demonstrates the formation process different from FIG. It is sectional drawing which shows the said metal mold | die part and demonstrates the formation process different from FIGS. It is sectional drawing which shows the multicolor molded product which concerns on the modification of this invention. It is a perspective view which shows the multicolor molded product which concerns on the comparative example of this invention.

Explanation of symbols

2 Mold 3 Fixed mold 4 Movable mold (movable part)
5A First cavity (injection space)
5B Second cavity (injection space)
DESCRIPTION OF SYMBOLS 10 Multicolor molded product 11 Top surface part 12 Standing wall part 13 1st resin material (one resin material)
14 Second resin material (other resin materials)

Claims (4)

A method of forming a multicolor molded product having at least two kinds of resin materials laminated by injection molding, and having a top surface portion and a standing wall portion rising from the top surface portion,
A first injection step of injecting one of the resin materials into an injection space having a dimension in a thickness direction smaller than a space corresponding to the top surface portion and the standing wall portion;
In the resin material injected in the first injection process, a gas is injected between the side on which the resin material of the second injection process is laminated and the mold, and the injected gas is held at a predetermined pressure, A pressing step of depressurizing the gas after holding for a period of time;
Following this pressing step, a core back step of core back the movable portion of the mold in a direction substantially orthogonal to the top surface portion;
And a second injection step of injecting another resin material of the at least two kinds of resin materials into the injection space formed in the core back step. In the molding method of the multicolor molded product according to claim 1,
The method of forming a multicolor molded product, wherein the standing wall portion is formed thicker than the top surface portion. In the shaping | molding method of the multicolor molded product of Claim 1 or Claim 2,
Prior to the pressing step, the method for forming a multicolor molded product includes a micro core back step of core-backing the movable part of the mold by a movement amount smaller than the movement amount in the core back step.   A multicolor molded product formed by the molding method according to any one of claims 1 to 3.

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