JP2930519B2 - Hollow injection molding method and molding die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow injection molding method (also referred to as a gas injection molding method, a gas injection injection molding method, etc.) and a molding die, and relates to a side molding or a side molding adhered to a side portion of an automobile. It can be used for molding side protectors and the like.

[0002]

2. Description of the Related Art Conventionally, a hollow injection molding method has been known as a molding method capable of obtaining a molded product made of a synthetic resin having a light weight and a high rigidity. According to this molding method, injection molding can be performed at a relatively low pressure even for a large-sized thin-walled or long-shaped molded product, so that a product without deformation or warpage after molding can be obtained. For this reason, parts requiring relatively high dimensional accuracy,
For example, application to molding of automobile parts, such as side moldings and side protectors, which are parts adhered to side surfaces of automobiles, has been attempted.

In such a hollow injection molding method,
Injection molding is performed while injecting a pressurized gas into the cavity of the mold and forming a gas channel through which the pressurized gas passes inside the molten resin. At this time, in order to form a gas channel of a predetermined length by injecting a desired amount of pressurized gas, that is, the gas channel is placed at a predetermined position of the molded article (for example, the end position of the thick part of the molded article). In order to form the spillover, a small space called a spillover is provided outside the cavity, and an excess resin is extruded into the spillover by injection of a pressurized gas (Japanese Patent Laid-Open No. 3-13812).
No. 6, Japanese Patent Application No. 5-35476, etc.).

FIGS. 6 and 7 show a cross section and a top view of an automobile side molding 90 formed by a conventional hollow injection molding method using such a spillover. The side molding 90 is attached to the side surface portion 91 of the automobile, has a substantially C-shaped cross-sectional shape in which the back surface side (the side facing the side surface portion 91) is depressed, and has a thick portion 92 disposed on the upper side. And a thin portion 93 disposed on the lower side.

[0005] Inside the thick portion 92, a gas channel 94, which is a passage for pressurized gas, is formed in the longitudinal direction thereof. An adhesive surface 95 that is adhered to the side surface portion 91 is formed on the back surface side of the thick portion 92, and the side molding 90 is adhered to the side surface portion 91 by the adhesive surface 95 with a double-sided tape 96.

Conventionally, when such a side molding 90 is hollow-injection-molded using a mold, a spillover 97 is provided at a position outside the cavity of the mold corresponding to a two-dot chain line portion in FIG. In addition, the gate of the spillover 97 is opened at a position (a position corresponding to the point A in FIG. 6) on the cavity surface of the mold to form the upper surface portion of the side molding 90.

In addition, the resin extruded into the spillover 97 is automatically cut by its own weight when the molded product is taken out from the mold, or if the resin is not cut automatically, it is gate-cut by secondary processing to cut the product portion. Is separated from
Usually, at this time, a gate mark is formed on a product portion. In the side molding 90 shown in FIG. 6, such a gate mark is formed in a gate hole 98 for communicating the outside of the product with the gas channel 94.
Are formed on the upper surface of the side molding 90.

[0008]

However, in the above-mentioned conventional hollow injection molding method, the gate of the spillover 97 is located on the surface of the cavity of the mold and the side molding 9
Since the opening is formed at the position where the upper surface portion of the "0" is formed, there is a problem that a gate mark is formed on the upper surface portion of the side molding 90 as a product, and the appearance is deteriorated.

Further, when the gate trace becomes a gate hole 98 for communicating the outside of the product and the gas channel 94 as shown in FIG. 6, rainwater or the like enters the gas channel 94 and accumulates. There was a problem. And
In such a case, if the gate hole 98 is formed so as to be in contact with the double-sided tape 96 as shown in FIG. 6, the double-sided tape 96 is always immersed in rainwater or the like, and the adhesive strength of the double-sided tape 96 is reduced. It is also conceivable that the side molding 90 is peeled off from the side surface portion 91 of the automobile. The problems such as deterioration of appearance and infiltration of rainwater are described in FIG.
Not only the side molding 90 described above, but also a molded product that is formed by hollow injection molding using spillover.

An object of the present invention is to provide a hollow injection molding method and a molding die capable of producing a molded article having a good appearance and preventing infiltration of rainwater or the like into a gas channel formed inside the molded article. To provide.

[0011]

The object of the present invention is to achieve the above object by disposing a spillover gate at a position corresponding to the bonding surface of a molded article. Specifically, the present invention performs injection molding while filling a molten resin into a cavity of a mold and injecting a pressurized gas to form a gas channel for passing the pressurized gas inside the molten resin. by, a hollow injection molding method for molding a molded article of a long, molded articles of the long is the other in the longitudinal direction
Having a bonding surface bonded to the member , injecting the pressurized gas and extruding a part of the molten resin into a spillover provided outside the cavity, and pushing the spillover to the surface of the cavity; A part of the process is performed through a gate having an opening formed in an adhesion surface forming portion that forms an adhesion surface of the long molded product.

Further, the present invention is characterized in that a cavity is filled with a molten resin, a pressurized gas is injected, and injection molding is performed while forming a gas channel through which the pressurized gas passes inside the molten resin. A molding die used for hollow injection molding for molding a long molded product, wherein the long mold
The molded product has an adhesive surface that is bonded to other members in the longitudinal direction.
The a, outside the cavity, wherein the provided spillover part of the molten resin with the injection of the pressurized gas is forced out, the gate communicating with this spillover said cavity, the surface of the cavity It is characterized in that an opening is formed in a part of the adhesive surface forming part that forms the adhesive surface of the long molded product.

In the hollow injection molding method and the molding die described above, other members include a side portion of an automobile as a typical example, and a typical molded product is an automobile. A side molding or a side protector that decorates or protects the side surface may be used.

[0014]

According to the present invention, when molding a long molded product having an adhesive surface to be adhered to other members in the longitudinal direction , the molten resin is filled into the cavity of the mold and the pressurized gas is applied. , And injection molding is performed while forming a gas channel through which a pressurized gas is passed inside the molten resin. Also, a spillover is provided outside the cavity of the mold, and a pressurized gas is injected to extrude a part of the molten resin into the spillover, and a part of the pressurized gas is also removed from the spillover.
Enter the pillover and position the gate from the gas channel
Is formed.

At this time, the gate of the spillover is formed in an opening at an adhesion surface forming portion which is a part of the surface of the cavity and forms an adhesion surface of the molded product. Occurs on the part of the adhesive surface of For this reason,
When the molded article is adhered to another member, the gate trace is hidden by the adhered portion and becomes invisible, so that the appearance of the other member with the molded article attached is improved.

In the state where the side molding 90 is attached to the side surface 91 as shown in FIG.
The entrance of the gate hole 8 is not exposed to the outside, and the entrance of the gate hole formed in the molded article is completely closed by the adhesive portion, so that rainwater or the like enters the gas channel from the gate hole and accumulates. The inconvenience of having
There is no danger that the molded product will be peeled off due to a decrease in the adhesive strength of the double-sided tape, thereby achieving the above object.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a side molding 1 for an automobile formed using the hollow injection molding method and the molding die of the present invention.
0 shows a cross section, and FIG. 2 is a perspective view of the side molding 10 viewed from the back side. 1 and 2
In FIG. 6, the side molding 10 is a component attached to the side portion 11 of the automobile, has substantially the same configuration as the side molding 90 of FIG. 6 described above, and has a thick portion 12 and a thin portion 13.
And

A gas channel 14, which is a passage for pressurized gas, is formed in the thick portion 12 in the longitudinal direction thereof. On the back side (the side facing the side surface portion 91) of the thick portion 12, an adhesive surface 15 to be adhered to the side surface portion 11 is formed. And is glued. Further, in the above-described side molding 90 of FIG. 6, the gate hole 98 as the gate mark is formed on the upper surface of the side molding 90, but in the side molding 10, the gate hole 18 is opened so as to open to the bonding surface 15. Is formed.

FIG. 3 shows a cross section of a molding die 20 used for hollow injection molding of the side molding 10. The molding die 20 is divided into a lower male die 20A and an upper female die 20B in FIG. 3, and a cavity 21 according to the shape of the side molding 10, which is a product, is formed therebetween. . FIG. 3 is a cross section of the molding die 20 corresponding to the position of the cross section BB of the side molding 10 in FIG.
The core portion of 0A is not shown.

The cavity 21 has a thick part forming space 22 for forming the thick part 12 of the side molding 10 and a thin part forming space 23 for forming the thin part 13. The surface of the thick part forming space 22 on the male mold 20A side (the lower side in FIG. 3) is an adhesive surface forming part 25 for forming the adhesive surface 15 of the side molding 10.

In the male mold 20A, a spillover 27 is formed near the end of the thick portion forming space 22, into which the molten resin extruded with the injection of the pressurized gas flows.
The spillover 27 is a small space having a size that allows the flow of the molten resin and the flow of the pressurized gas accompanying the flow of the molten resin.

A gate 28 which communicates the spillover 27 with the cavity 21 (thick portion forming space 22).
Are formed so as to open to the bonding surface forming portion 25.
Usually, the size of the gate 28 is about 1 to 5 mm in diameter, and its shape is arbitrary. An injection hole (not shown) for pressurized gas is also formed in the bonding surface forming portion 25. In addition, the filling hole of the molten resin may be used also as the injection hole of the pressurized gas, or may be provided separately from the injection hole of the pressurized gas.

In this embodiment, the side molding 10 is molded using the molding die 20 as follows. First, the male mold 20A and the female mold 20 of the molding die 20 are formed.
B, and the filling of the molten resin into the cavity 21 is started. Next, the injection of the pressurized gas into the cavity 21 is started at an appropriate timing after the filling of the molten resin is started, and the gas channel 14 (the two-dot chain line in FIG. The molten resin is spread in the cavity 21 while forming (1).

At this time, a portion of the molten resin is extruded into the spillover 27 through the gate 28 near the end position of the thick portion forming space 22. Further, a part of the pressurized gas also enters the inside of the spillover 27 through the gate 28 with the extrusion of the molten resin, thereby forming a gate hole 18 extending from the gas channel 14 to the position of the gate 28. Then, the spread of the molten resin into the cavity 21 is completed, and the gas channel 14 is formed in the thick portion forming space 2.
2 is formed up to the vicinity of the end position of the molding die 20.
The male mold 20A and the female mold 20B are opened, and the molded side product 10 is taken out.

According to the present invention, the following effects can be obtained. That is, the gate 28 of the spillover 27
Is formed in the bonding surface forming portion 25 on the surface of the cavity 21, so that the gate hole 18 which is a mark of a gate remaining on the side molding 10 which is a molded product is bonded to the side molding 10 and the side portion 11 of the automobile. Since it is hidden behind the part and cannot be seen, the appearance of the product can be improved.

Further, since the gate 28 is formed in the bonding surface forming portion 25, the entrance of the gate hole 98 is not exposed to the outside as shown in FIG. Since the entrance 18 is completely covered with the double-sided tape 16 at the adhesive portion, it is possible to solve the problem that rainwater or the like enters the gas channel 14 through the gate hole 18 and accumulates.

Further, the side molding 90 shown in FIG.
Such a state that water accumulated inside the gas channel 94 is in contact with the double-sided tape 16 for a long time can be avoided, so that the adhesive strength of the double-sided tape 16 decreases and the side molding 10 The possibility of peeling can be eliminated.

Since the side molding 10 is formed by using the spillover 27, the gas channel 14 can be formed up to the vicinity of the longitudinal end position of the thick portion 12, that is, a desired amount of pressurized gas can be supplied. Since it can be injected, there is no deformation or warpage after molding.
0 can be obtained.

Further, the following comparative experiments were conducted to confirm the effects of the present invention. Experimental Example 1 and Comparative Examples 1,
In No. 2, polypropylene (trade name: Idemitsu Polypro J-950H, MI = 20) was used as a resin material, and an injection molding machine (trade name: Mitsubishi 850MGW, 850 tons) was used as a molding machine. [Experimental Example 1] In Experimental Example 1, the side molding 10 shown in the above embodiment was molded using the hollow injection molding method and the molding die of the present invention. The molding conditions were as follows: resin temperature 210 ° C,
The mold temperature was 30 ° C. and the gas pressure was 15 MPa. Comparative Example 1 In Comparative Example 1, a side molding having the same shape as that of Experimental Example 1 was formed without using spillover. The molding conditions were a resin temperature of 210 ° C., a mold temperature of 30 ° C., and a gas pressure of 15 MPa and 30 MPa. Comparative Example 2 In Comparative Example 2, a side molding having the same shape as that of Experimental Example 1 was formed using normal spillover (a spillover having a gate at a conventional position). The molding conditions are
Resin temperature 210 ° C, mold temperature 30 ° C, gas pressure 15MP
a was the same as in Experimental Example 1.

[Experimental Results] In Experimental Example 1, the pressurized gas was injected at 100% of the desired amount, and the gas channel was formed up to the vicinity of the end position of the thick part of the side molding. Then, no deformation or warpage of the molded article occurred. In addition, the gate hole was opened at the position of the bonding surface of the side molding, and there were no problems such as a reduction in the appearance of the product, penetration of rainwater or the like into the gas channel, and a reduction in the bonding strength of the double-sided tape. In Comparative Example 1, since no spillover was used, 100% of the pressurized gas was not injected, and it was not possible to prevent deformation and warpage of the molded article after molding. That is, gas pressure 15MP
In the case of “a”, only 50% of the gas was injected, and the molded product was deformed and warped after molding. Gas pressure 3
Even when the pressure was set to 0 MPa, only 60% of the gas was injected, and the molded product was deformed and warped after molding. Comparative Example 2
In the case of using spillover, pressurized gas is 100%
It was injected (the pressurized gas flowed up to the spillover), and the molded article after molding did not deform or warp. However, a gate hole was opened at a visible position on the product, and the appearance of the product was deteriorated. In addition, there has been a problem in that rainwater or the like permeates into the gas channel and the adhesive strength of the double-sided tape is reduced. From the results of the above comparative experiments, the effects of the present invention were remarkably shown.

It should be noted that the present invention is not limited to the above-described embodiment, but includes other configurations capable of achieving the object of the present invention. For example, the following modifications are also included in the present invention. That is, the side molding which is a molded product is
The side molding 40 is not limited to the cross-sectional shape like the side molding 10 in FIG. 1 of the embodiment, and has, for example, a cross-sectional shape in which one gas channel 41 is formed in the center as shown in FIG. As shown in FIG. 5, a side molding 50 having two gas channels 51 and 52 at both ends may have a cross-sectional shape. In short, the side molding 50 has an adhesive surface at which an entrance of a gate hole as a gate mark is to be opened. It is sufficient if it is a side mall. In the case of FIG. 4, the entrance of the gate hole 44 is opened in the bonding surface 43, and in the case of FIG.
The entrances of the gate holes 55 and 56 are opened in the bonding surfaces 53 and 54, respectively.

Further, the number of spillovers of the present invention is arbitrary. In short, when a plurality of spillovers are provided, the gate of each spillover may be arranged at a position corresponding to the bonding surface of the molded product. For example, in the case of FIG. 5, at least two or more spillovers may be provided corresponding to each of the gas channels 51 and 52.

Further, the means for attaching the side molding 10 is as follows.
The adhesive is not limited to the double-sided tape 16 but may be, for example, a filled epoxy adhesive. However, if a double-sided tape is used as in the above-described embodiment, it is not necessary to wait for the curing time of the adhesive. Can be done.

In the above embodiment, the hollow injection molding method and the molding die of the present invention are applied to the molding of the side molding 10 adhered to the side portion 11 of the automobile. However, the present invention is not limited to this. Instead, the present invention can be applied to the molding of a side protector or the like adhered to the side portion 11 of an automobile. In short, the present invention is applicable to a molded article having an adhesive surface adhered to other members. can do.

The resin material used in the present invention may be any resin material suitable for hollow injection molding, such as polypropylene and polyethylene. Further, the pressurized gas used in the present invention is arbitrary, such as an inert gas such as a nitrogen gas or an argon gas, as long as it is suitable for hollow injection molding.

[0036]

As described above, according to the present invention, the spillover gate is arranged and formed so as to open to the bonding surface forming portion which is a part of the surface of the cavity and forms the bonding surface of the molded article. As a result, the gate marks left on the molded product are hidden behind the adhesive part, making it invisible, improving the appearance of the product and eliminating the inconvenience of infiltration into the gas channel such as rainwater and the reduced adhesive strength of the double-sided tape. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a side molding showing an embodiment of the present invention.

FIG. 2 is a perspective view of the side molding of the embodiment as viewed from the back side.

FIG. 3 is a cross-sectional view of the molding die of the embodiment.

FIG. 4 is a sectional view of a side molding showing a modification of the present invention.

FIG. 5 is a sectional view of a side molding showing another modification of the present invention.

FIG. 6 is a sectional view of a side molding showing a conventional example.

FIG. 7 is a top view of a side molding showing the conventional example.

[Explanation of symbols]

 10, 40, 50 Side molding which is a molded product 11 Side surface portion of automobile which is another member 14, 41, 51, 52 Gas channel 15, 43, 53, 54 Bonding surface 18, 44, 55, 56 Gate hole (gate) Trace) 20 Mold 21 Cavity 25 Bonding surface forming part 27 Spillover 28 Gate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-251425 (JP, A) JP-A-3-261523 (JP, A) JP-A-5-310085 (JP, A) JP-A-5-251 301257 (JP, A) JP-A-7-256680 (JP, A) JP-A-4-201531 (JP, A) JP-A-5-208430 (JP, A) JP-A-4-201423 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/26-45/44

Claims (4)

(57) [Claims] The method according to claim 1] by performing injection molding with the pressurized gas injection to form a gas channel through which the pressurized gas into the molten resin to fill the molten resin into the mold cavity, the length a hollow injection-molding method for molding a scale of the molded article, the molded article of the long is, of the adhesive to the longitudinal direction of the other member
The pressurized gas is injected to extrude a part of the molten resin into a spillover provided outside the cavity, and the extrusion to the spillover is a part of the surface of the cavity. And performing the process through a gate having an opening formed in an adhesion surface forming portion for forming an adhesion surface of the long molded product. 2. The hollow injection molding method according to claim 1, wherein the other member is a side portion of a vehicle, and the molded product is a side molding or a side protector for decorating or protecting the side portion of the vehicle. A hollow injection molding method. 3. A long molding is performed by filling a cavity with a molten resin and injecting a pressurized gas to form a gas channel through which the pressurized gas is passed inside the molten resin. A molding die used for hollow injection molding for molding an article, wherein the long molded article is adhered to another member in a longitudinal direction thereof.
A spillover is provided outside the cavity, and a part of the molten resin is extruded with the injection of the pressurized gas, and a gate communicating the spillover and the cavity is provided, mold, characterized in that it is opened and formed on the adhesive surface forming part of a part of the surface of the cavity to form an adhesive surface of the formed <br/> molded article of the long. 4. The molding die according to claim 3, wherein the other member is a side portion of a vehicle, and the molded product is a side molding or a side protector for decorating or protecting the side portion of the vehicle. A molding die.