JP7095252B2 - Resin molded product - Google Patents

Description

The present invention relates to a resin molded product .

Since the resin structure is lighter than metal, it is widely used as structural parts for vehicles, vehicle-mounted products, housings for electronic devices, and the like. Among the resin structures, resin molded products are particularly lightweight, and are expected to improve fuel efficiency when used for vehicle parts such as automobiles.

As an injection foam molding method for a resin molded product used as an interior base material of an automobile, for example, the method described in Patent Document 1 is known. In this publication, molten resin is injected into cavities formed in a pair of molding dies, and foaming is performed.

Japanese Unexamined Patent Publication No. 2005-238726

When the molten resin is injected into the cavity, the portion in contact with the molding die is cooled and solidified to form a film-like skin layer. In this state, when the movable mold is cored back with respect to the fixed mold to expand the volume in the cavity, the molten resin covered with the skin layer foams to form a foamed layer, and a resin molded product is manufactured.

Here, for example, when molding a resin molded product in which a through hole is formed in an overhanging portion protruding from the peripheral edge portion of the main body portion having a design surface to the side opposite to the design surface, the terminal of the cavity (the tip of the overhanging portion) is formed. When the joints of the movable type and the fixed type are matched with each other, the slide for forming through holes provided in the movable type is provided when the movable type is core-backed with respect to the fixed type forming the design surface side. The mold also moves with the movable mold. At this time, a skin layer is formed at the opening edge on the fixed mold side of the through hole by contact with the fixed mold, and the position of the hole formed in the skin layer and the position of the slide mold by the movable core back. Misalignment occurs, and the accuracy of the through holes after molding is reduced.

On the other hand, when the joint between the movable type and the fixed type is set on the upstream side of the end of the cavity (corresponding to the middle part in the overhanging direction of the overhanging part), the outer surface and the inner surface of the overhanging part are formed by the movable type. Therefore, a decrease in the accuracy of the through hole after molding is suppressed. However, if a movable type and a fixed type joint is set on the upstream side of the terminal of the cavity, a whitening phenomenon may occur due to the stretching of the resin by the core back in the vicinity of the joint.

In consideration of the above facts, the present invention has a configuration having a main body portion having a design surface and an overhanging portion protruding from the peripheral edge portion of the main body portion to the side opposite to the design surface, and the dimensional accuracy on the tip side of the overhanging portion is improved. It is an object of the present invention to provide a resin molded product that suppresses whitening of an overhanging portion while ensuring it.

The present invention has been made in view of the above problems, and includes the following embodiments.
<1> A main body portion having a surface opposite to the design surface and having a first foam layer formed therein, and a peripheral portion of the main body portion provided on the opposite side to the design surface in the thickness direction of the main body portion. It is formed in an overhanging portion where a second foam layer is formed in the overhanging portion and an intermediate portion in the overhanging direction of the overhanging portion, and protrudes outward from the peripheral portion of the main body portion, and the second foam portion is formed inside. 3 A resin molded product having a convex portion on which a foam layer is formed.

<2> The resin molded product according to <1>, wherein the end of the top of the convex portion on the overhanging direction side is located on the parting line.

<3> The resin molded product according to <1> or <2>, wherein the first foam layer and the second foam layer are connected, and the second foam layer and the third foam layer are connected.

According to the present invention, in a configuration having a main body portion having a design surface and an overhanging portion extending from the peripheral edge portion of the main body portion to the side opposite to the design surface, the extension portion is stretched while ensuring the dimensional accuracy on the tip end side of the overhanging portion. It is possible to provide a resin molded product in which whitening of the protruding portion is suppressed.

It is a back view of the resin molded product of this embodiment. It is a vertical sectional view (2-2 line sectional view in FIG. 1) of the resin molded article of FIG. It is an enlarged view of the part pointed out by the arrow 3 of FIG. It is a schematic sectional view of a mold. It is an enlarged view of the part pointed out by the arrow 5 of FIG. It is an enlarged view of the part pointed out by the arrow 5 of FIG. 4 after the core back. It is an enlarged view of the part pointed out by the arrow 5 of FIG. 4, which shows the state just before removing a resin molded product from a mold.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.

In the present specification, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other processes. Is done.

In the numerical range indicated by using "-" in the present specification, the numerical values before and after "-" are included as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present specification, the content or content of each component in the composition is the same as that in the case where a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. It means the total content or content of substances.

In the present specification, the term "layer" refers to the case where the layer is formed in the entire region when the region is observed, and the case where the layer is formed only in a part of the region. Is also included.
In the present specification, the "layer thickness" is an arithmetic mean value obtained by measuring the thickness of nine points using a microscope in a cross-sectional cut shape.

First, the resin molded product of this embodiment will be described. Next, a manufacturing apparatus and a manufacturing method for manufacturing the resin molded product of the present embodiment will be described.

<Resin molded product>
The resin molded product of the present embodiment has a surface opposite to the design surface, and is provided on the main body portion in which the first foam layer is formed and the peripheral edge portion of the main body portion, and is provided in the peripheral portion of the main body portion in the thickness direction of the main body portion. It is formed in an overhanging portion that projects to the opposite side of the design surface and has a second foam layer formed inside, and an intermediate portion in the overhanging direction of the overhanging portion, and faces outward from the peripheral edge portion of the main body portion. It has a convex portion that protrudes and has a third foam layer formed therein. Specific examples of the resin molded product will be described with reference to the drawings, but the present invention is not limited thereto. Further, the size of each part in each figure is conceptual, and the relative relationship between the sizes of each part is not limited to this.
The resin molded product of the present embodiment can be used, for example, as an automobile part. However, the use of the resin molded product is not limited to automobile parts.

The resin molded product 10 of the present embodiment is an automobile part and is attached to a vehicle body 30 (see FIG. 2). Examples of automobile parts include bumpers, side mudguards, and fenders.

As shown in FIG. 2, the resin molded product 10 is made of a resin material and is provided on a main body portion 11 having a surface 11B opposite to the design surface 11A and a peripheral portion 11C (see FIG. 3) of the main body portion 11. It is formed in the middle portion between the overhanging portion 12 that overhangs the design surface 11A in the thickness direction of the main body portion 11 (the direction indicated by the arrow T in FIG. 2) and the overhanging portion 12 in the overhanging direction. It has a convex portion 40 that protrudes outward from the peripheral edge portion 11C of the portion 11.

The main body portion 11 has a plate shape, and a plurality of vehicle body mounting portions 11D (see FIG. 1) are formed on the opposite surface 11B. The vehicle body mounting portion 11D is a portion for mounting the main body portion 11 (resin molded product 10) to the vehicle body 30 using a mounting member (not shown). As shown in FIG. 3, the first foam layer 13A is formed inside the main body 11. Specifically, the main body portion 11 is formed between a pair of first skin layers 14A forming a front surface (design surface 11A) and a back surface (opposite surface 11B) and a pair of first skin layers 14A. It has a foam layer 13A.

As shown in FIGS. 1 and 2, the overhanging portion 12 has a plate shape and is provided on the entire peripheral edge portion 11C of the main body portion 11. That is, the overhanging portion 12 of the present embodiment is provided for one round along the peripheral edge portion 11C of the main body portion 11. The present invention is not limited to the above configuration, and the overhanging portion 12 may be provided intermittently along the peripheral edge portion 11C of the main body portion 11.

As shown in FIG. 2, the overhanging direction of the overhanging portion 12 (the direction indicated by the arrow E in FIG. 3) is inclined outward from the peripheral edge portion 11C of the main body portion 11 with respect to the thickness direction of the main body portion 11. is doing.

Further, a through hole 12B is formed on the tip 12A side of the overhanging portion 12 with respect to the convex portion 40 in the overhanging direction. The through hole 12B is used for attaching the resin molded product 10 to the vehicle body 30 or the like.

A second foam layer 13B is formed inside the overhanging portion 12. Specifically, the overhanging portion 12 has a pair of second skin layers 14B forming the front surface and the back surface, and a second foam layer 13B formed between the pair of second skin layers 14B. .. In the resin molded product 10 of the present embodiment, the foam layer is not formed between the tip 12A of the overhanging portion 12 and the through hole 12B, but it may be formed. Details will be described later. Further, as shown in FIG. 3, the first foam layer 13A and the second foam layer 13B may be connected to each other.

As shown in FIG. 3, the convex portion 40 protrudes outward from the peripheral portion 11C of the main body portion 11 from the intermediate portion of the overhanging portion 12 in the overhanging direction. The convex portion 40 is formed around the outer surface of the overhanging portion 12 in the circumferential direction. When the overhanging portion 12 is provided intermittently along the peripheral edge portion 11C of the main body portion 11, the convex portion 40 corresponding to the arrangement of the overhanging portion 12 is also formed intermittently. The convex portion 40 has a flat surface at the top 40A. Further, the end (edge of the flat surface) 40E on the projecting direction side of the top portion 40A of the convex portion 40 is located on the parting line. In other words, the end 40E of the top 40A is located at the seam 20 of the mold 15 at the time of molding (that is, it coincides with the seam 20 of the fixed mold 17 and the movable mold 19).

A third foam layer 13C is formed inside the convex portion 40. Specifically, the convex portion 40 has a third skin layer 14C forming a surface and a third foam layer 13C formed inside the third skin layer 14C. As shown in FIG. 3, the second foam layer 13B and the third foam layer 13C may be connected to each other.

In the following, the first foam layers 13A to 13C will be collectively referred to as “foam layer 13”, and the first skin layers 14A to 14C will be collectively referred to as “skin layer 14” as appropriate. In the present embodiment, the skin layer 14 forms the front surface and the back surface of the resin molded product 10, and the foam layer 13 forms the inside. The skin layer 14 refers to a portion of the resin molded product 10 having a lower foaming rate than the foamed layer 13.

The resin material forming the resin molded product 10 of the present embodiment will be described later.

<Mold>
The mold for molding the resin molded product of the present embodiment is a movable mold that is movable in the opening / closing direction with respect to the fixed mold and the fixed mold and forms a cavity that is a gap between the fixed mold. , And a wide space is formed in the cavity, and the joint between the fixed mold and the movable mold is located in the wide portion. Specific examples of the mold will be described with reference to the drawings, but the present invention is not limited thereto. Further, the size of the members in each figure is conceptual, and the relative relationship between the sizes of the members is not limited to this. The mold can be used for injection molding, can be suitably used for foam molding applications, and can be more preferably used for injection foam forming applications. However, it is not limited to these uses. Hereinafter, injection foam molding will be described as an example.

As shown in FIG. 4, the molding apparatus 16 is movable in the opening / closing direction with respect to the fixed mold 17 and the fixed mold 17, and forms a cavity 18 which is a gap between the fixed mold 17 and the movable mold 19. And have. Hereinafter, the fixed mold 17 and the movable mold 19 may be collectively referred to as "mold 15".

A portion having a wider interval S than the other portions is formed in the cavity 18. This wide portion is appropriately referred to as a cavity intermediate portion 18A. A seam 20 between the fixed mold 17 and the movable mold 19 is located in the cavity intermediate portion 18A. The seam 20 is located in the cavity intermediate portion 18A at a portion where the convex portion 40 of the resin molded product 10 is molded.

Further, the cavity 18 corresponds to the shape of the resin molded product 10, and the cavity intermediate portion 18A corresponds to the convex portion 40 of the resin molded product 10 and the portion of the overhanging portion 12 on which the convex portion 40 is formed. ing.

Further, in the present embodiment, the cavity surface 17A formed in the fixed mold 17 allows the surface (design surface 11A) of the main body portion 11 of the resin molded product 10 and the overhanging portion 40A and the overhanging portion 12 of the convex portion 40. A surface 40B opposite to the direction is formed. Further, due to the cavity surface 19A formed in the movable mold 19, the back surface (opposite surface 11B) of the main body portion 11 of the resin molded product 10, the front surface of the overhanging portion 12, the back surface of the overhanging portion 12, and the overhanging portion 12 The tip 12A of is formed. The cavity 18 is a gap between the cavity surface 17A and the cavity surface 19A in a state where the fixed mold 17 and the movable mold 19 are closed.

Further, the movable type 19 is a plurality of slide types 19B in which a portion constituting a mating surface with the fixed type 17 can slide in a direction orthogonal to the moving direction of the movable type 19. In this slide type 19B, the inner surface is a part of the cavity surface 19A, and the surface (outer surface) of the overhanging portion 12 is formed. Further, when the resin molded product 10 is taken out from the movable mold 19, the slide mold 19B moves to the outer peripheral side of the movable mold 19 as shown in FIG. 7. Therefore, it is easy to take out (demold) the resin molded product 10 from the movable mold 19.

Further, the movable type 19 is a plurality of slide types 19C in which a part of a portion constituting the facing surface of the slide type 19B can slide in a direction orthogonal to the moving direction of the movable type 19. This slide type 19C is columnar and has an outer peripheral surface as a part of the cavity surface 19A, and forms a through hole 12B of the overhanging portion 12. Further, when the resin molded product 10 is taken out from the movable mold 19, the slide mold 19C moves inside the movable mold 19 as shown in FIG. 7. Therefore, it is easy to take out (demold) the resin molded product 10 from the movable mold 19.

Further, the molding apparatus 16 includes a gate 21 that penetrates the fixed mold 17 to the cavity 18, and an injection machine 22 that injects and fills the cavity 18 with the resin material R in a molten state through the gate 21. The injection machine 22 includes a hopper (supply unit) (not shown) and a cylinder (not shown). In this injection machine 22, a mixture containing a resin, a foaming agent, an additive, etc. is supplied from a hopper (supply unit) to a cylinder, stirred in the cylinder with a screw or the like, prepared as a resin material R, and has a predetermined pressure. The resin material R is injection-filled into the cavity 18 through the gate 21. The injection machine 22 is not limited to the above configuration as long as the cavity 18 can be injected and filled with the resin material R in a molten state through the gate 21.

<Manufacturing method of resin molded products>
The method for manufacturing a resin molded product for manufacturing the resin molded product of the present embodiment includes a step of injecting a resin material containing a foaming agent into the cavity of the mold, and after filling the cavity with the resin material. A step of moving the movable mold from the fixed mold constituting the mold in the opening direction to expand the volume in the cavity is provided.

As shown in FIG. 4, the resin material R containing a foaming agent is injection-filled in the cavity 18 from the injection machine 22 through the gate 21. When the resin material R is composed of a thermoplastic resin, the resin material R is heated and fluidized and supplied into the cavity 18.

Here, it is preferable to set the cylinder temperature in the region from the hopper outlet of the injection machine 22 of the resin material R to 1/3 to 1/2 of the total length of the cylinder to 250 ° C. or lower, and it is more preferable to set it to 180 ° C. or lower. It is more preferable to set it to 150 ° C. to 180 ° C., and it is particularly preferable to set it to 150 ° C. to 170 ° C. However, the region is the temperature excluding the hopper outlet. By setting the cylinder temperature in the region to 250 ° C. or lower, it is possible to suppress the escape of foaming gas from the hopper outlet side, and it is easy to obtain effects such as improvement and stabilization of foaming property during molding.

The resin material used in this embodiment is not particularly limited. For example, the resin material used for injection foam molding generally contains a resin and a foaming agent. The resin used for this resin material R includes polyethylene resin, polypropylene resin (PP), composite polypropylene resin (PPC), polystyrene resin, polyethylene terephthalate resin, polyvinyl alcohol resin, vinyl chloride resin, and ionomer resin. At least one selected from the group consisting of a resin, a polyamide resin, an acrylonitrile / butadiene / styrene copolymer resin (ABS) and a polycarbonate resin can be mentioned. Among these, at least one selected from the group consisting of polypropylene-based resin (PP), composite polypropylene-based resin (PPC), and acrylonitrile-butadiene-styrene copolymer resin (ABS) is preferable.

Examples of the foaming agent include organic foaming agents such as azodicarbonamide and inorganic foaming agents such as sodium hydrogencarbonate (also known as sodium bicarbonate and baking soda). Currently, inorganic sodium hydrogencarbonate is mainly used as a foaming agent in foam molding of interior parts for automobiles, but an organic foaming agent is preferable from the viewpoint of improving coating film performance (heat resistance, etc.). ..

Examples of the organic foaming agent include azodicarbonamide (ADCA), N, N-dinitrosopentamethylenetetramine (DPT), 4,4-oxybisbenzenesulfonyl hydrazide (OBSH), hydrazodicarbonamide (HDCA) and the like. , Azodicarbonamide (ADCA) is preferred.

Further, the temperature of the mold 15 is usually lower than that of the supplied resin material R. Therefore, when the resin material R is filled in the cavity 18, solidification of the resin material R (formation of the skin layer 14) starts from the portion in contact with the mold.

Before injecting the resin material R into the cavity 18, it is preferable to fill the cavity 18 with nitrogen gas in advance, particularly by heating it. By heating the nitrogen gas to be filled, a rapid temperature drop in the cavity 18 (mold) can be suppressed, and the foamability of the resin material R can be stabilized. Further, by heating the nitrogen gas to be filled, the dependence of the foaming force of the resin material R on the outside air temperature can be suppressed without being influenced by the outside air temperature, and the foamability of the resin material R can be stabilized.

The temperature of the nitrogen gas filled in the cavity 18 is not particularly limited as long as it can suppress a sudden temperature drop in the cavity 18 (mold 15), and from the viewpoint of molding stability, it is 30 ° C. to 50 ° C. The temperature is preferably ° C.

Then, as shown in FIGS. 5 and 6, the movable mold 19 is opened (core back) by a predetermined amount in the opening direction (mold opening direction) with respect to the fixed mold 17, and the non-solidified resin material R is foamed. The foam layer 13 is formed. After that, the slide mold 19B and the slide mold 19C of the movable mold 19 are slid to open the fixed mold 17 and the movable mold 19, and the resin molded product 10 is removed from the fixed mold 17 to obtain the resin molded product 10.

Next, the action and effect of this embodiment will be described.
In the resin molded product 10, the first foam layer 13A is formed inside the main body 11, the second foam layer 13B is formed inside the overhanging portion 12, and the third foam layer 13C is formed inside the convex portion 40. Has been done. In other words, each foam layer is formed on the main body portion 11, the overhanging portion 12, and the convex portion 40 of the resin molded product 10 at the time of core backing. In order to form the third foam layer 13C inside the convex portion 40, it is necessary to increase (expand) the volume of the cavity 18 at the time of core back. Therefore, the seam 20 between the fixed mold 17 and the movable mold 19 is configured to be located at the top portion 40A of the convex portion 40. Here, since the joint 20 between the fixed mold 17 and the movable mold 19 is located in a portion (top 40A of the convex portion 40) where the distance S of the cavity 18 is wide on the upstream side in the resin flow direction from the cavity terminal portion, the tension is stretched. Since the front surface (outer surface) and the back surface (inner surface) of the protruding portion 12 are molded by the movable mold 19 (including the slide molds 19B and 19C), the deterioration of the accuracy of the through hole 12B after molding is suppressed.
Further, since the joint 20 between the fixed mold 17 and the movable mold 19 is located in a portion (thick portion) where the distance S between the cavities 18 is wide, the resin foams in the wide portion of the cavity 18 during core backing. Since the resin is stretched by the foaming pressure, it is possible to prevent the whitening phenomenon from occurring in the overhanging portion 12 after molding.

In the resin molded product 10, the end 40E on the overhanging direction side of the top 40A of the convex portion 40 is located on the parting line PL formed at the time of molding. Therefore, for example, the top 40A of the convex portion 40 is overhanging. The appearance is improved as compared with the one in which the end opposite to the direction is located on the parting line PL.

Further, in the resin molded product 10, the first foam layer 13A and the second foam layer 13B are connected, and the second foam layer 13B and the third foam layer 13C are connected. In other words, since a continuous foam layer is formed on the main body portion 11, the overhanging portion 12, and the convex portion 40, it is lighter than, for example, the one on which the foam layer is not formed, and the main body portion 11 and the tension portion are stretched. Rigidity is improved by improving the wall thickness of the protruding portion 12 and the convex portion 40.

The present invention is not limited to the specific configuration of the embodiment as described above, and can be variously modified without departing from the gist of the present invention.

10 Resin molded product 11 Main body 11A Design surface 11B Opposite surface 11C Peripheral part 12 Overhanging part 13A 1st foam layer 13B 2nd foam layer 13C 3rd foam layer 40 Convex part 40A Top PL parting line

Claims (4)

A main body having a design surface and an opposite surface and having a first foam layer formed inside,
An overhanging portion provided on the peripheral edge of the main body portion, which overhangs the side opposite to the design surface in the thickness direction of the main body portion, and a second foam layer is formed inside.
A convex portion formed in the middle portion of the overhanging portion in the overhanging direction, protruding outward from the peripheral portion of the main body portion, and having a third foam layer formed inside.
Have,
A through hole for attaching the main body to the attachment target is formed on the tip side of the overhanging portion with respect to the convex portion in the overhanging direction.
A resin molded product in which a portion of the overhanging portion between the tip in the overhanging direction and the through hole is formed of a skin layer having a lower foaming rate than the second foaming layer. The resin molded product according to claim 1, wherein the end of the top of the convex portion on the overhanging direction side is located on the parting line. The resin molded product according to claim 1 or 2, wherein the first foam layer and the second foam layer are connected, and the second foam layer and the third foam layer are connected. The mounting target is the vehicle body.
The resin molded product according to any one of claims 1 to 3, wherein a plurality of vehicle body mounting portions for mounting the main body portion to the vehicle body are formed on the opposite surface of the main body portion.

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