JPS58142828A - Manufacture of inside foamed molded product - Google Patents

Abstract

PURPOSE:To obtain an inside foamed molded product having a good appearance and a skin layer, by setting a premolded product composed of the thermoplastic resin of a prefoamed state in the cavity of a mold having the electrical insulation properties and a heat resistance and dielectric-heating it. CONSTITUTION:The premolded product 1 which is composed of the thermoplastic resin of a prefoamed state and has a shape corresponding to a cavity 3a is set in the cavity 3a of a mold 3 which has the electrical insulation properties and a heat resistance and is provided with an upper electrode 6 and a lower electrode 7 embedded and connected to the circuit of a high-frequency oscillator etc. Then, the high-frequency voltage is loaded to the upper electrode 6 and the lower electrode 7, the premolded product 1 is heated, foamed and expanded from its inside by a dielectric heat and fills the cavity 3a. By this, a heat is radiated to the mold 3 near the surface of the premolded product 1, also an expansion is suppressed at the inner face of the mold 3, then the shape of a foam becomes small and the inside foamed molded product having a good skin layer is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an internally foamed molded product that provides a desired shape, structure, and pattern with a good appearance (surface of the molded product) and a skin layer.

Hereinafter, a side molding used for automobiles and the like as an internally foamed molded product will be explained, but of course this is not limited to Q.

Recently, from the perspective of improving the fuel efficiency of automobiles, various auto parts are becoming more and more lightweight, and side moldings also need to be made lighter from this perspective. Foamed side moldings were manufactured by extrusion molding.

However, conventional foamed side moldings have problems such as difficulty in obtaining a good appearance and skin layer equivalent to those of solid materials even when various factors such as the expansion ratio are taken into consideration, or the new dimension accuracy tends to decrease.

This invention was invented in view of the above points, and by dielectrically heating and foaming an f-prepared molded product made of a pre-foamed thermoplastic resin in a mold, it is possible to reduce the weight and size. It is an object of the present invention to provide a method for manufacturing an internally foamed molded product that improves accuracy and provides a good appearance and skin layer.

The gist of this invention is to install a preformed tube made of prefoamed thermoplastic resin into a cavity of a mold having electrical insulation and heat resistance, and to attach the preformed tube to a dielectric horn. - Internally foamed molded products manufactured by heating! 11! It's in the construction method.

Hereinafter, the present invention will be described in detail based on illustrated examples.

FIG. 1 is an explanatory diagram showing a state in which a preform according to the first embodiment of the present invention is installed in a mold, FIG. 2 is an explanatory diagram showing a state in which the preform according to the first embodiment is foamed, and FIG. Figure 3 is a cross-sectional view of the foamed side molding molded according to the first embodiment, and Figures 1Ia, JA, and 6A are the preforms of the second, third, and third embodiments installed in the mold. Explanatory drawings showing the state, Figure 1Ib, Figure SB, and +'bFA are sectional views of the foamed side moldings molded according to the 2nd, 3rd, and ≠ Examples.

The mold 3 used in the first embodiment is an upper mold made of a material such as electrically insulating and heat resistant synthetic resin (e.g. epoxy resin) or ceramic.
The lower mold S is formed with four cavity parts 5a, and a cavity 3a is formed when the mold 3 is closed. are upper electrodes connected to circuits such as a high frequency oscillator, high voltage power supply, etc. corresponding to the characteristics of the preformed product (not shown), which will be described later.
-7 is buried in Lt.

The four parts for the cavity of the lower mold, the pre-formed product for mounting, are made by extruding and pre-foaming a thermoplastic resin material such as vinyl chloride resin to which a foaming agent has been added.
Cut and form a length corresponding to the shape of a. This preformed product is not strictly required to have expansion ratio, appearance, and cross-sectional dimensional accuracy, and may be slightly larger or smaller than the shape of the cavity 3a.

Then, the preformed product is mounted in the cavity recess 5a of the lower mold, the mold 3 is closed, and a high frequency voltage is applied to the upper electrodes A and F. Then, the preform 1 generates heat from the inside due to dielectric heating, and foaming starts again from the inside, expanding and filling the cavity 3a (see FIG. 2).

At this time, near the surface of the preform, the heat generated on the surface is radiated to the mold 3, and the expansion is regulated on the inner surface of the Vζ mold 3, the bubble shape becomes smaller, and the surface of the preform is solid and forms a good skin layer. The preformed product/ has the same shape as the cavity 3a, and the IMI also has an appearance with a smooth surface along the cavity Javc.

After that, when the finished product is cooled and taken out, the interior becomes spongy and the surface area becomes solid, as shown in Figure 3.
A lightly wrinkled foamed side molding 2 having a good appearance and skin layer can be obtained.

Next, a second embodiment will be explained.

The mold /3 used in the second embodiment is the same as the seventh embodiment, and is an upper mold made of a material such as a synthetic resin or ceramic having electrical insulation and heat resistance.
It consists of a lower mold 15, and an upper mold /4 (-'F type /jK has an upper electrode 16 and a lower electrode 17 buried respectively.
D-type/S has a cavity recess with decorative unevenness/
ja is formed.

The preformed product /'/ of the second embodiment is made by extruding and prefoaming a thermoplastic resin material to which a foaming agent has been added, as in the seventh embodiment, and the cross section corresponding to the cavity of mold /3 is omitted. It is made into a rectangular shape by cutting it to an appropriate length. Similarly to the first embodiment, the foaming ratio, appearance, and sectional dimensional accuracy of the preform // are not strictly required, and the preform may be slightly larger or smaller than the shape of the cavity of the mold 13.

Then, the preformed product // is made into four parts for the F-type cavity /S
a, close the mold 13, and remove the upper electrode/6 and lower electrode 1.
7 to apply a high frequency voltage. Then, the preformed product 77
Then, as in the first embodiment, foaming starts again from the inside, expands, and fills the cavity of the mold 13.

At this time, the heat generated near the surface of the preform // is dissipated to the mold 73, and the expansion is regulated by the inner surface of the mold 3, so that the bubble shape becomes smaller and becomes solid. A good skin layer is formed. and,
The preform // has the same shape as the cavity of mold /3, has a good appearance on its surface, and has irregularities formed on its lower surface.

After that, when the finished product is cooled and taken out, it becomes a sponge-like interior and a solid shape near the surface, as shown in Figure 1Ib.It has a good appearance and skin layer, and has the desired external shape and lightweight foam side molding. 12 can be obtained.

Next, a third embodiment and an eleventh embodiment will be described.

The third embodiment shows a foamed side molding 22 having a decorative member 2g on its surface, and the mold 23 and preform 21 used have the same construction as in the first embodiment. Decorative parts are made of synthetic resin (such as vinyl chloride resin) with good electrical insulation and heat resistance, and are colored to display letters and
It has figures, symbols, etc. attached to it.

Then, the decorative member 2g and the preformed product 21 are placed in the do mold 5.
The mold 23 is closed, and a high frequency voltage is applied to the upper electrode 2 of the upper mold 2 and the F electrode core of the lower mold 25 to dielectrically heat the preform. Then, the preformed product begins to foam again from the inside, expands, and fills the cavity of the mold 23.

At this time, the heat generated on the surface of the preform near the surface is radiated to the mold 23, and the expansion is regulated by the inner surface of the mold 23, and the bubble shape becomes smaller, forming a decorative member. The two edges are welded together to form a solid and good skin layer. The preform 27 is then processed by the device s
By fixing the member 21, a predetermined external appearance similar to the cavity of the mold 23 is formed.

After that, when the finished product is cooled and taken out, it becomes a lightweight foamed side molding 22 with a spongy interior and a solid shape with a decorative member 21 fixed to the surface near the surface, as shown in FIG. 5b, with a good appearance and skin layer. can be obtained.

The 1st I project example shows a foamed side molding 32 in which hard members 39, 39 are provided inside to provide rigidity, and the mold 33 used has the same structure as the 1st/incorrect example. The preformed product 3/ is made of the same material as in the first embodiment, but the hard member 3 is formed by the two plate-shaped preformed products 3/ and 3/.
9 and 39 are formed in a shape that can be inserted into the cavity of the mold 33. The hard member 39 is made of a synthetic resin (for example, hard vinyl chloride resin, ABS resin, etc.) that has good electrical insulation, heat resistance, and rigidity.

Then, hard members 3q and 3 and preformed products 31 and 3
1 to the four cavity parts 33eL of the lower mold 3j as shown in FIG. 6a, the mold 33 is closed, and the L-type 31I.
A high frequency voltage is applied to the electrodes provided in each of the lower molds 3Svc, and the preforms 3/ and 3/ are dielectrically heated. Then, each of the preforms 3/31 starts foaming again from the inside, expands, and fills the cavity of the mold 33.

At this time, the preformed product 3/.31 is the hard member 3q.3
The preformed parts 31 and 31 are fused together,
In the vicinity of each surface that abuts the inner surface of the mold 33, the heat generated on the surface is radiated and expansion is regulated, the bubble shape becomes small, and a solid and good skin layer is formed. Then, the Y-equipped molded products 31, 31 are the hard members 3
9 and 39 inside, a predetermined shape and appearance similar to the cavity of the mold 33 are formed.

After that, when the finished product is cooled and taken out, the inside S becomes spongy with hard members 39, 39, and the surface area is solid, as shown in Figure 6.The lightweight foam side has a good appearance and skin layer. A mall 32 can be obtained.

In addition, Example 1-II is a preformed product l・/l・co/・
As for 3/, we have explained that the thermoplastic resin material containing a foaming agent is extruded and foamed, and then cut into a predetermined length, but of course, any material made of a pre-foamed thermoplastic resin material can be used. Therefore, it may be formed by other molding methods instead of extrusion molding.

In addition, as Example 1-1, mold 3./3.23.3
3 shows a model with embedded electrodes, but of course it is also possible to have electrodes on the upper and lower surfaces of the mold, and it is also possible to create a mold with no electrodes and place the mold inside the applicator of the microwave dielectric heating device. The present invention has the above-described structure and operation, and dielectrically heats an f-prepared cedar product made of a pre-foamed thermoplastic resin in a mold. Since it is foamed, the interior is spongy and the surface area is solid, which, combined with molding, reduces weight and improves cross-sectional dimensional accuracy, giving it a good appearance and skin layer equivalent to that of solid materials. It is possible to obtain an internally foamed molded product having , an internally foamed molded product having a desired shape, structure, pattern, etc. can be obtained.

[Brief explanation of the drawing]

The figures provide a detailed explanation of the present invention. Fig. 1 is an explanatory diagram showing the state in which the preformed product of the first embodiment is installed in the mold, and Fig. 2 shows the preformed product of the first embodiment. An explanatory diagram showing the state of foaming, FIG. 3 is a sectional view of an internally foamed molded product molded by the 1% example, FIG. 1Ia, FIG. 5a,
Figure 6a is an explanatory diagram showing how the preforms of the second, third, and first embodiments are installed in the mold, and Figures IIb, 5b, and 6b are the second and third embodiments. Example/3rd
FIG. 2 is a cross-sectional view of an internally foamed molded product molded according to Example and Example 1I. /-//-2/・31... Preformed product, 2・/2・2
2.32... Internal foam molded product (foamed side molding),
3・13・23・33...molding mold, 3a...cavity, 4(-/41'-koto3da...upper mold, s-i!
;-23・J! P-・Lower mold, ja-15a-, 2
ja・3ja...Four parts for cavity. Patent applicant

Claims (1)

[Claims] A pre-acid-shaped product made of a pre-foamed thermoplastic resin and having a shape corresponding to the cavity is placed in the cavity of a mold having electrical insulation and heat resistance, and the pre-acid molded product is heated dielectrically. A method for manufacturing an internally foamed molded product.