JPS5920632A - Manufacture of urethane foam molded article - Google Patents

Abstract

PURPOSE:To obtain an urethane foam molded article having dimensions as specified, by subjecting urethane to foam molding by using a molding die devised so that an elastic sealing body blocks up the trace of an air blow pin of a hollow insert when the die is closed. CONSTITUTION:A circular concavity 7 is provided in the core 2a of molding die 2 which faces the upper part of the trace 3 of an air blow pin of a hollow insert 1, and an elastic sealing body 8 made of silicon rubber, for instance, is fixed with an adhesive or screws to the inside of this circular concavity 7. Said elastic sealing body 8 has a ring-shaped sealing part 10 which is in tight and close contact with a projection 9 piercing through the trace 3 of the air blow pin of the hollow insert 1 and with the upper surface 6 of the hollow insert 1. When an urethane foam molded article is manufactured by the molding die thus prepared, the hollow insert 1 is set in a cavity 2b, and then the core 2a is moved to close the molding die 2. Next, an urethane stock solution is injected into the die and foamed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a urethane foam molded product having a synthetic resin hollow insert, such as, for example, an armrest, an assist grip, a headrest, a glove box lid, or an air spoiler of an automobile.

A conventional method for producing a urethane foam molded product having a hollow insert made of synthetic resin is as follows: Fig. 1 shows a plan view, Fig. 2 shows a cross-section along line 8-A, and Fig. 3 shows a cross-section along line B-B. The hollow insert 1, which is formed by blow molding a synthetic resin such as polypropylene, is treated with a primer to increase its adhesion to urethane. FIG. 4 shows a partially cutaway plan view, and FIG. As shown in the cross section C-C and the cross section D-D in FIG. Inje
cation molding) and then covering almost the entire circumference with urethane foam. In this case, the air blow pin marks 3 used during blow molding remain on the hollow insert. Also, 4 is a boss hole for the hole.

In such a conventional method for manufacturing urethane foam molded products, first, a urethane stock solution is injected into the mold 2 through a gate (not shown) provided on the PL surface up to the dotted line position in FIG. Ru. The foam expands in the mold, but the hollow insert 1 softens due to the heat generated by the reaction (approximately 90 to 150°C), and as shown in FIG. It deforms in a dotted line shape due to the foaming pressure, and at this point, the air inside the hollow insert 1 escapes from the air blowing pin mark 3, and then as the urethane stock solution rises due to foaming, the air blowing pin mark 3 is removed by the foamed urethane. Blocked. Then, due to the expansion of the air inside the hollow insert 1 due to the continued deformation of the long inclined portion 5 and the rise in temperature, the air pressure inside the hollow insert 1 notebook 1 becomes higher than that of the atmosphere. Therefore, not only does the appearance of the molded product deteriorate due to the deformation of the sloped portion 5, but also the hollow insert 1 is still softened when the mold is opened, so the upper surface 6 of the hollow insert 1 is in contact with atmospheric pressure and the internal air is Due to the pressure, it also deforms into a dotted line shape, which not only deteriorates the appearance of the molded product but also causes misalignment of the mounting boss hole 4, resulting in product defects.

Various proposals have been made in the past to improve these drawbacks. For example, it is conceivable to mold the hollow insert using a synthetic resin with a high heat distortion temperature, but such materials are generally expensive and have poor top blow moldability. It is possible to improve the strength of the hollow insert by putting ribs on it or increasing the wall thickness, but this would tend to cause sink marks in the thicker parts, resulting in poor appearance, and the top surface would be deformed due to internal air pressure. cannot be prevented. Furthermore, a method can be considered in which the hollow insert is molded by closing the air blowing pin marks and then inserting it into a mold, but although deformation of the long sloped portion can be prevented, deformation of the upper surface portion of the hollow insert cannot be prevented.

This invention was made in view of the above-mentioned current situation, and involves inserting a hollow insert obtained by blow molding a synthetic resin into a mold, and covering almost the entire circumference of the hollow insert with a urethane foam by RIM molding of urethane. To obtain a molded product, foam molding of urethane is performed using a mold that has an elastic seal firmly attached around the air blowing pin mark of the hollow insert when the mold is closed. This is a method for producing a urethane foam molded product.

The present invention will be explained below based on the drawings.

FIG. 8 is a perspective view of the inner surface of the core mold 2a of the mold 2 used in an embodiment of the present invention, and FIG. 9 is a perspective view of the inner surface of the core mold 2a of the mold 2 used in an embodiment of the present invention, and FIG. A sectional view of the main parts is shown.

A circular recess 7 is provided in the core mold 2a of the mold 2 facing above the air blowing pin trace 3 of the hollow insert 1, and an elastic sealing body 8 made of, for example, silicone rubber is provided within the four circular parts 7.
Fix with adhesive or screws. The elastic sealing body 8 has a protrusion 9 that passes through the air injection pin mark 3 of the hollow insert 1 and a ring-shaped sealing part 10 that tightly contacts the upper surface 6 of the hollow insert 1.

To make a urethane foam molded product using such a mold,
A polyethylene blow-molded hollow insert 1 which has been previously treated with a primer is placed in a cavity mold 2b, and then the core mold 2a is moved to close the mold 2. At this time core type 2
The protruding part 9 of the elastic sealing body 8 attached to the inner surface a passes over the air blowing pin trace 3 of the hollow insert 1, and the sealing part 1o comes into close contact with the upper surface 6 of the hollow insert 1 around the protruding part 9. - When the urethane stock solution is injected into the mold and foamed in this way, the long inclined portion 5 of the hollow insert 1 tends to deform as shown by the dotted line in FIG. 7 due to the softening caused by the reaction heat and the foaming pressure. Since the inside of the hollow insert 1 is sealed, the amount of deformation thereof is greatly suppressed compared to the conventional method.

Immediately before the mold is opened, the air pressure inside the hollow insert 1 is considerably higher than atmospheric pressure due to air expansion due to temperature changes and volume reduction due to slight deformation of the long slope, but when the mold is opened, the protrusion 9 Since it sag from the air injection pin trace 3, it is communicated with the atmosphere, and the internal air escapes from here, so that the hollow insert 1 does not deform.

FIG. 10 shows another embodiment, in which parts with the same names as those in FIG. Circular recess 7
When the mold is closed, it simply comes into contact with the upper surface of the air blowing pin trace 3 to seal the mold.

As explained above, according to the present invention, when the mold is closed, the elastic seal body closes the air blowing pin marks in the hollow inlet, so the inside of the hollow insert is sealed when the urethane is foamed, and when the mold is removed, the hollow insert is sealed when the mold is opened. The inside of the insert is connected through the air blowing pin trace, and the upper surface of the well-sloped part of the hollow insert can be prevented from being deformed, resulting in the effect that a product with specified dimensions can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the flat insert of the hollow insert. Figure 2 shows A- of Figure 1.
A sectional view, Figure 3 is a BB sectional view in Figure 1, Figure 4 is a partially cutaway plan view showing the hollow insert in the molded state, and Figure 5 is a C-C in Figure 4. Cross-sectional view, Figure 6 is '4th
7 is an explanatory diagram showing a deformed state of the hollow insert according to the conventional manufacturing method, and FIG. 8 is a perspective view of an example of an elastic seal body suitable for implementing the present invention. FIG. 9 is a cross-sectional view of the main part when the mold is closed in an example of its use, and FIG. 10 is a cross-sectional view of the main part showing another embodiment. 1...Hollow inserter 1~2...Mold 2a...
Core mold 2b...Cavity mold 3...Air blow pin mark 4...Boss hole for (=l) 5...Long inclined part 6...
...Top surface 7...Circular recess 8...Elastic seal body 9...Protrusion 10...Seal portion Patent applicant Nippon Blast Co., Ltd. Agent Patent attorney Hide Komatsu Figure 1! Figure 5 Figure 4 Figure 6 Figure 8 Figure n Figure 9 Figure 10

Claims (1)

[Claims] A hollow insert obtained by blow molding a synthetic resin was placed in a mold, and the mold was closed to obtain a molded product that covered almost the entire circumference of the hollow insert with urethane foam by RIM molding of urethane. A method for producing a urethane foam molded product, which is characterized by carrying out foam molding of urethane, sometimes using a mold in which an elastic sealing body is firmly installed around the air blowing pin trace of a hollow insert.