JPH0761666B2 - Method for manufacturing hollow urethane foam molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention provides a hollow core made of synthetic resin such as an automobile armrest, an assist grip, a headrest, a glove box lid, and an air spoiler. The present invention relates to a method for producing a hollow urethane foam molded article having the same.

(Prior Art) Third example of a conventional method for producing a hollow urethane foam molded article
A description will be given with reference to FIGS.

Reference numeral 1 denotes a hollow core body formed by blow molding a synthetic resin such as polyethylene and polypropylene. The blow core 1 is blow-molded so that the hollow portion 2 of the inner space communicates with the outer space. Imprint pin mark 3 is generated. Further, on both sides of the hollow core body 1, there are formed tapered fitting holes 4 opening to the lower surface in FIGS. 4 to 8, and the upper part of the fitting holes 4 has a reduced diameter portion. 5 and opened on the upper surface.

Further, 11 is a urethane foam molding die, and this molding die 11
Is composed of an upper mold 12 and a lower mold 13 which can be freely contacted and separated, and a cavity 14 is formed inside the upper mold 12 and the lower mold 13 when the mold is closed. Bosses fitted in the fitting holes 4 of the hollow core body 1 are formed on both sides of the inner bottom surface of the lower mold 13.
15 is formed, and a reduced diameter portion 16 is formed on the upper portion of the boss 15 so as to penetrate the reduced diameter portion 5 of the fitting hole 4 and contact the upper die 12 when the die is closed.

Then, in molding, after the hollow core 1 is treated with a primer in order to enhance the adhesive strength with urethane, the hollow core 1 is placed in the molding die 11 as shown in FIGS. 5 and 6.
Put on. In this state, the fitting hole 4 of the hollow core 1 and the lower mold
The hollow core body 1 is supported in the molding die 11 by being fitted into the bosses 15 of 13 so as to float inside. Next, as shown in FIG. 7, a urethane undiluted solution is injected between the inner surface of the molding die 11 and the hollow core body 1 to mold the urethane foam 21 covering substantially the entire circumference of the hollow core body 1. To do.

At that time, the urethane undiluted solution injected into the molding die 11 expands and expands, but the heat generated by the reaction (about 80 ° C. to 150 ° C.) softens the hollow core body 1 and, as shown in FIG. , Each surface of the hollow core 1 is dented by the foaming pressure of the urethane stock solution. At this time, the air inside the hollow core body 1 flows out from the air blow-in pin mark 3 to the outside, and then the pin mark 3 is closed by the urethane foam 21 due to the rise of foaming of the urethane undiluted solution. The urethane foam 21 is hardened with the respective surfaces of the core 1 left depressed. Further, after releasing the mold, as shown in FIG. 8, as the urethane foam 21 is cooled, the air inside the hollow core 1 is also cooled and contracts. The hollow urethane foam molded article 22 including the body 21 has a recessed central portion on each surface, resulting in a defect as a product.

Therefore, various proposals have been conventionally made in order to improve such defects. FIG. 9 to FIG. 11 show an example thereof, but in this method, as shown in FIG. 9, solid particles 31 from the air blown pin traces 3 are previously provided inside the hollow core body 1. Is completely filled, the pin mark 3 is closed by the seal body 32, and urethane foam molding is performed. However, since the air blowing pin mark 3 is blocked,
As the air remaining between the solid particles 31 filled in the hollow core body 1 expands due to the reaction heat of the urethane stock solution,
As shown in FIG. 10, the hollow core 1 swells and hardens as it is. Therefore, after releasing the mold, as shown in FIG. 11, as the urethane foam 21 is cooled, the air inside the hollow core 1 is cooled and contracted, and the hollow core 1 is removed. Returning to the shape, the central portion of each surface of the molded product 22 is dented, which also causes a defect as a product.

In the method shown in FIGS. 9 to 11, after molding,
Through holes are formed in the urethane foam 21 and the hollow core body 1, and the solid particles 31 in the hollow core body 1 are removed.

(Problems to be Solved by the Invention) As described above, in the conventional method for producing a hollow urethane foam molded article, since the urethane foam is molded in a state where the inside of the hollow core body is hollow, the urethane undiluted solution is used. There is a problem that each surface of the finished molded product is dented due to the shrinkage due to the foaming pressure and the subsequent shrinkage due to cooling. Also, in the method of molding the urethane foam by filling the solid particles in the hollow core, since the air remaining between the solid particles expands and contracts,
There has been a problem that it is not possible to sufficiently prevent the depressions formed on each surface of the molded product.

The present invention is intended to solve the problems as described above, and an object thereof is to prevent deformation of the hollow core in the production of a hollow urethane foam molded article and to obtain a molded article of a predetermined shape. It is what

[Structure of Invention]

(Means for Solving Problems) A method for producing a hollow urethane foam molded article of the present invention is to fill a hollow core body hollow-molded with a synthetic resin with solid particles, and to prepare a hollow core body filled with the solid particles. Install it in the molding die,
By urethane reaction injection molding, a hollow urethane foam molded article obtained by covering substantially the entire circumference of the hollow core with a urethane foam is obtained, in which case the internal space of the hollow core and the external space of the molding die are separated from each other. Urethane is foamed and cured in a state of being communicated.

(Function) In the method for producing a hollow urethane foam molded article of the present invention, the solid particles filled inside the hollow core body prevent the shrinkage and deformation of the hollow core body against the foaming pressure of the urethane stock solution. Also,
The air remaining in the solid particles and expanded by the reaction heat of the undiluted urethane solution is allowed to flow out of the molding die to prevent the hollow core body from expanding and deforming. Further, even when the hollow core and the urethane foam are cooled and cured, the shrinkage and deformation of the hollow core is prevented by the inflow of air into the solid particles and the hollow core.

(Example) An example of a method for producing a hollow urethane foam molded article of the present invention will be described below with reference to FIGS. 1 and 2. Since the configuration is basically the same as that of the conventional example described above, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, the upper die 12 of the molding die 11 is formed with, for example, a pair of screw holes 41 opened on the upper surface in the drawing, and the upper die 12 is continuously formed below the screw holes 41. An injection needle fitting hole 42 is formed on the lower surface of 12, ie, on the cavity surface, and the diameter of the lower portion is reduced. Then, these fitting holes 42
A cylindrical injection needle 43 as a hollow pin having a base portion (upper part in the drawing) having an enlarged diameter and a sharply pointed tip is fitted to the cylindrical hollow screw screwed into the screw hole 41. It is fixed by 44. The injection needle 43 has a tip end on the lower surface of the upper mold 12 so that when the lower mold 13 and the upper mold 12 are closed, the injection needle 43 penetrates into the hollow core body 1 mounted in the cavity 14 of the molding mold 11. It has a more suitable length.

Then, in molding, first, in the hollow core body 1 which has been blow-molded with polyethylene or polypropylene and which has been pre-treated with primer, the tip portion of the injection needle 43 from the air blow pin mark 3 at the time of blow molding. After completely filling the solid particles 31 such as sand particles, glass beads, wood powder or plastic molding pellets having a particle size larger than the pore diameter of the above, the air blown pin mark 3 is closed by the seal body 32.

Next, after mounting the hollow core body 1 in the lower mold 13, the upper mold 12 is moved to close the molding mold 11 as shown in FIG.
At this time, the injection needle 43 provided on the upper mold 12 is inserted into the hollow core body 1. In this state, the hollow portion 2 which is the internal space of the hollow core 1 and the external space of the molding die 11 are communicated with each other through the injection needle 43, the hollow screw 44 and the screw hole 41.

Next, the urethane stock solution is injected between the inner surface of the molding die 11 and the hollow core body 1 to foam it. Due to the heat of reaction of the urethane stock solution in such reaction injection molding, the hollow core 1 is
Although it tries to expand due to the expansion of the air remaining between the solid particles 31 filled in the inside, the expanded air is injected into the injection needle 43.
Since it is discharged into the outer space of the molding die 11 through the inside, expansion deformation of the hollow core body 1 is completely prevented. Moreover, since the solid particles 31 are filled in the hollow core body 1, as described above, even if the air in the hollow core body 1 is released to the outside of the molding die 11, it is hollowed by the foaming pressure of the urethane stock solution. The core body 1 does not contract and deform, that is, each surface of the hollow core body 1 is not recessed inward.

After that, when the urethane foam 21 has cooled and hardened to some extent, the molding die 11 is opened to form an integrated hollow core body 1.
The urethane foam 21 is released from the mold.

In the process of cooling and curing the urethane foam 21, the air between the solid particles 31 of the hollow core 1 is also cooled and contracts, but the solid particles 31 prevent the hollow core 1 from contracting and deforming. As the air between the solid particles 31 cools, air flows from the outside into the hollow core body 1 through the injection needle 43 or through the through hole 51 formed after the injection needle 43 is removed. Further, as described above, since the expansion and deformation of the hollow core body 1 due to the reaction heat of the undiluted urethane solution is prevented, when the urethane foam 21 is cooled and cured, the hollow core body 1 contracts and deforms due to its restoring force. Nothing. Therefore, no dent is formed on each outer surface of the urethane foam 21.

Further, after cooling and curing are completed, as shown in FIG. 2, the urethane foam 21 and the hollow core body 1 are provided with discharge holes on the side of the mounted body (top surface shown in the figure) on which there is no hindrance to the appearance, for example, the mounting surface to the vehicle. By forming openings 52 and discharging the solid particles 31 from the inside of the hollow core body 1, a hollow urethane foam molded article 22 is obtained in which the urethane foam body 21 covers almost the entire circumference of the hollow core body 1. In this way, the solid particles 31 in the hollow core body 1 are finally removed, so that a lightweight hollow urethane foam molded article 22 is obtained. The solid particles 31 taken out are then reused.

Thus, according to the above method, it is possible to reliably obtain the hollow urethane foam molded article 22 having a predetermined shape in which each outer surface is flat.

Instead of implanting the injection needle 43, a breathable net is used as the seal body 32, the outer circumference of the net is surrounded by a seal material, and the mold cavity surface facing the air blowing pin mark 3 is made of sintered metal. By doing so, the inner space of the hollow core body 1 and the outer space of the mold may communicate with each other.

〔The invention's effect〕

According to the present invention, since urethane is foam-cured in a state where the inner space of the hollow core filled with solid particles and the outer space of the molding die are in communication with each other, the hollow core is contracted and deformed by the foaming pressure of the urethane undiluted solution. Not only can this be prevented, but the air remaining in the solid particles and expanded by the reaction heat of the undiluted urethane solution can also flow out of the molding die to prevent expansion and deformation of the hollow core, and also during cooling and curing. The hollow core body can also be prevented from contracting and deforming, and thus a hollow urethane foam molded article having a predetermined shape can be obtained.

[Brief description of drawings]

1 and 2 show an embodiment of a method for producing a hollow urethane foam molded article of the present invention. FIG. 1 is a cross-sectional view of a urethane foam when molded, and FIG. It is a sectional view of a urethane foam molded article. Further, FIGS. 3 to 8 show an example of a conventional method for producing a hollow urethane foam molded article. FIG. 3 is a plan view of the hollow core body, and FIG. 4 is a sectional view taken along line IV-IV of FIG. 5 and FIG. 5 are plan views in which a hollow core is mounted in a molding die and a part of which is cut away. FIG.
FIG. 7 is a cross-sectional view taken along line VI-VI of FIG. 7, FIG. 7 is a cross-sectional view of a urethane foam during molding, and FIG. 8 is a cross-sectional view of a manufactured hollow urethane foam molded article. Furthermore, FIGS. 9 to 11 show another example of the conventional method for producing a hollow urethane foam molded article. FIG. 9 is a sectional view of the hollow core body, and FIG. FIG. 11 is a sectional view of the hollow urethane foam-molded product produced. 1 ... Hollow core, 11 ... Mold, 14 ... Cavity,
21 …… Urethane foam, 22 …… Hollow urethane foam molded product, 31 …… Solid particles, 43 …… Injection needle as hollow pin.

Claims (2)

[Claims] 1. A hollow core body hollow-molded with a synthetic resin and filled with solid particles inside is mounted in a molding die, and urethane reaction injection molding covers substantially the entire circumference of the hollow core body with a urethane foam. In order to obtain a hollow urethane foam molded article, the method for producing a hollow urethane foam molded article, wherein urethane is foam-cured in a state where the inner space of the hollow core body and the outer space of the molding die are in communication with each other. . 2. A hollow pin provided in the molding die for communicating between a cavity in the molding die and an external space of the molding die is inserted into the hollow core body when the die is closed so that the inside of the hollow core body is penetrated. The method for producing a hollow urethane foam molded article according to claim 1, wherein the space is communicated with the external space of the molding die.