JP2000272020A - Method for molding foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of high productivity for molding a foam which is recyclable and expanded uniformly. SOLUTION: In a method for molding a foam in which an expandable base material 100 obtained by mixing a blowing agent 11 with a base resin 12 comprising a thermoplastic resin is used, the base material 100 is expanded by heating to form the foam, the base material 100 is added with a conductive material 13, which is heated by induction heating, and the base material 100 is expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for molding various foams.

[0002]

2. Description of the Related Art Foams are used in various articles, including buildings, civil engineering works, moving objects such as automobiles, and everyday miscellaneous goods. As shown in FIG. 5, a foam base material 900 obtained by mixing a foaming agent 11 with a base resin 12 is introduced into an extruder 19, and is molded to form an unfoamed sheet such as an unfoamed sheet 90, as shown in FIG. Then, the unfoamed body was foamed by heating with an electric heater 94 to produce the unfoamed body.

[0003]

However, in the conventional method, the unfoamed sheet 90, which is an unfoamed body, is heated by an electric heater 94 from the outside thereof.
0, a temperature difference occurs between the outside and the inside, and as shown in FIG.
Bubbles 901, 902, and 903 having different sizes were formed inside, and the foam 9 in which the foaming state was non-uniform was manufactured. As shown in the figure, the foam 9 is well foamed on the surface side which is sufficiently heated.
1) Insufficient foaming inside (bubbles 902, 90
3).

Conventionally, a thermosetting resin (polyurethane in this case) serving as a base resin is heated by electromagnetic induction heating (induction heating using a coil) as disclosed in JP-A-5-338050.
Then, the components contained in the resin (in this case, isocyanate and active hydrogen, actually, a polyester or polyether having a hydroxyl group) are reacted by heat to generate a reaction gas (in this case, carbon dioxide gas), 2. Description of the Related Art There is known a technique for producing a foam by leaving a shape in a base resin. In this prior art, since a thermosetting resin is used as a base resin, there is a problem that a foamed molded product cannot be recycled (reused).

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a method of molding a highly recyclable and uniformly foamed foam with high productivity.

[0006]

According to the first aspect of the present invention, a foamed base material obtained by mixing a foaming agent with a base resin made of a thermoplastic resin is heated and foamed by heating the foamed base material. In the method of forming a body, a conductor is added to the foamed base material, and the heating is performed by induction heating to heat the conductor and foam the foamed base material. In the molding method.

The most remarkable feature of the present invention is that a conductor is added to a foamed base material containing a thermoplastic resin and a foaming agent,
Heating and foaming the foaming agent in the foamed base material through the conductor heated by induction heating. Next, the operation of the present invention will be described. In the present invention, since the conductor added to the foamed base material is heated by induction heating, the foamed base material can be heated from the inside. Therefore, the foamed base material can be uniformly heated, and a foam in which the foaming agent is foamed uniformly can be obtained.

Further, according to the present invention, since the induction heating is performed, there is no problem of the surface of the foam being scorched as in the case of the electric heater. Therefore, the surface of the foam is beautiful. Further, since the foaming agent in the foamed base material is gasified and expanded by induction heating to form a foam, the foaming speed is high and the foam can be molded with high productivity.

Further, since the present invention utilizes a thermoplastic resin as the base resin, it can be restored to the original state by heating, and a recyclable molded article can be obtained. In the prior art described above, since the thermosetting resin is foamed, it does not return even when heated, and cannot be recycled. As described above, according to the present invention, it is possible to provide a highly productive molding method for a recyclable and uniformly foamed foam.

In addition, by applying the present invention to a method for forming a composite molded article comprising a plurality of layers, a plurality of layers can be selectively foamed. As such a composite molded product,
An example is a skin integral molded product as shown in Embodiment 2 (see FIG. 4E).

The above-mentioned induction heating is a phenomenon in which when a high-frequency current flows near a conductor and an induction magnetic field is generated therein, the conductor is heated by Joule heat due to hysteresis loss and eddy current. As the induction heating device that can be used in the present invention, for example, a high-frequency induction heating device can be used.

The frequency of induction heating is 300 to 5
It is preferably set to 00 KHz. Thereby, the foaming base material and the foaming agent can be uniformly heated. If the frequency is less than 300 KHz, the foaming base material and the foaming agent may not be foamed uniformly, and the foaming agent may remain unfoamed. On the other hand, when the frequency is higher than 500 KHz, the heat generation temperature increases, and the foamed base material may be easily scorched.

It is preferable that the application time of the high frequency is 10 to 70 seconds. Thereby, the foaming time is short, and the productivity can be improved. If the application time is less than 10 seconds, the foaming may be insufficient. On the other hand, if it is longer than 70 seconds, the foaming temperature becomes high, and the foamed base material may be scorched.

As the conductor, a conductor made of a metal such as iron, copper, and steel can be used. Further, as the conductor, those having various shapes such as powder, scale, strip, plate, strip, column, and needle made of the above-mentioned materials can be used.

It is preferable that the amount of the conductor is, for example, 10 to 50% by weight based on the foamed base material.
If more than the above range is added, there is a possibility that unevenness of foaming and surface roughness due to foam breaking may occur. On the other hand, if it is less than the above range, foaming may be insufficient. Preferably, the conductor is uniformly dispersed in the foamed base material. Thereby, the effect according to the present invention can be reliably obtained.

Further, as the base resin for the foamed base material according to the present invention, ethylene vinyl acetate resin, olefin resin, vinyl chloride, thermoplastic elastomer and the like can be used. As the foaming agent, an inorganic foaming agent represented by sodium bicarbonate and an organic foaming agent represented by azodicarboxylic amide, dinitropentamethyltetra, benzenesulfonylhydrazide can be used.

Next, as in the second aspect of the present invention, it is preferable to heat the foamed base material after forming it into a predetermined shape. As a result, it is possible to obtain a molded article having uniform foaming and a molded article having no scorching to surrounding substances. Also,
In the case of a composite, it can be selectively foamed (such as a skin-integrated molded product described later). In addition, various molding methods such as extrusion molding, injection molding, blow molding, stamping molding and the like can be used for molding into the predetermined shape.

Next, a third aspect of the present invention relates to a foamed base material for producing a foam by foaming by heating, wherein the foamed base material comprises a base resin, a foaming agent and a conductor. Characteristic foam base material. In such a foamed base material, since the conductor generates heat by performing the induction heating as described above, it can be heated from the inside of the foamed base material. Therefore, the foamed base material can be uniformly heated from the inside, and the entire foam is foamed uniformly.
As described above, a uniformly foamed foam can be obtained. Further, the foam can be used for various articles ranging from buildings, civil engineering works, automobiles, and other moving objects to everyday miscellaneous goods.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIGS. 1 and 2 show a foam according to an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIG. 1, this embodiment uses a foamed base material 100 obtained by mixing a foaming agent 11 with a base resin 12 made of a thermoplastic resin, and heats the foamed base material 100 to cause foaming. Is formed. The conductor 13 is added to the foamed base material 100, and the heating is performed by induction heating to heat the conductor 13 and foam the foamed base material 100. Further, the foamed base material 100 is preliminarily formed into a predetermined shape and then heated.

The details will be described below. As shown in FIG. 1, a foam base material 100 including a foaming agent 11, a base resin 12, and a conductor 13 is prepared. Azodicarboxylic amide is used as the foaming agent 11, ethylene vinyl acetate resin is used as the base resin 12, and the conductor 13 has a particle size of 0.1.
鉄 2 mm iron powder is used. The amount of the conductor 13 added to the foamed base material 10 is 10 to 50% by weight. The dried pellets of the foaming agent 11, base resin 12, and conductor 13 constituting the foamed base material 100 are put into an extruder 19 and melt-kneaded. Next, the above-mentioned kneaded material is extruded into a sheet shape from a molding nozzle 190 provided at a lower portion of the extruder 19 and is continuously rolled out by a draw-out roller 18 to obtain a non-foamed sheet 10.

The unfoamed sheet 10 is heated by a high-frequency induction heating device 14. The heating is performed at a frequency of 4
It is performed at 00 KHz and an application time of 60 seconds. As a result, the unfoamed sheet 10 foams, and as shown in FIG. 2, the foamed sheet 1 has air bubbles of a uniform size. Note that the conductor 13 remains in the completed foam sheet 1.

According to the molding method of the present embodiment, the high-frequency induction heating device 14 heats the unfoamed sheet 10,
The conductor 13 in the unfoamed sheet 10 is heated. Since the unfoamed sheet 10 is evenly and uniformly heated from the inside by the conductor 13, the foamed sheet 1 which is a foam foamed uniformly can be obtained. In addition, there is no problem of scorching as in the case of using an electric heater as described above. In addition, because of induction heating, the foaming speed is high and the productivity is high.
In addition, since the base resin is a thermoplastic resin, it can be restored to the original state by heating, and a recyclable foamed product can be obtained.

Embodiment 2 Next, a method for integrally forming a skin using the present invention will be described with reference to FIGS. The skin integral molding method of this embodiment includes a sheet manufacturing process, an insert process, a molding process, and a foaming process. Hereinafter, this will be described in detail.

(A) Sheet manufacturing process First, as shown in FIG.
A foamed base material 100 including the conductor 13 and the conductor 13 is prepared. Azodicarboxylic amide is used as the foaming agent 11, and ethylene vinyl acetate resin is used as the base resin 12. The conductor 13 is iron powder having a radius of 0.1 to 2 mm, and the amount added to the foamed base material 10 is 10 to 50% by weight. As in the first embodiment, the extruder 1
9 and melt-kneaded. Next, the kneaded material is extruded into a sheet shape from a molding nozzle 190 provided at a lower portion of the extruder 19, and is continuously drawn by a drawing roller 18 to perform a roll forming method to obtain an unfoamed sheet 10.

Next, the unfoamed sheet 10 and the skin 3 are superimposed on each other, and the two are pressed by a rolling roller 17 to obtain an unfoamed sheet 4 with a skin as an integral product. As the skin 3, a fabric skin is used. Next, the unfoamed sheet 4 with the skin is cut into a desired shape by the cutter 16.

(B) Inserting Step Next, as shown in FIG. 4B, a mold 5 for insert molding is prepared. The mold 5 includes a convex mold 52 and a concave mold 53.
A cavity 51 formed between the convex mold 52 and the concave mold 53; an injection device 58 for injecting the base resin 6 into the cavity 51; and a gate 54. The size of the unfoamed sheet 4 with the skin is set to cover the entire cavity surface 50 of the concave mold 53. Next, the unfoamed sheet 4 with skin
Is arranged in the cavity 51 of the mold 5. At this time, the unfoamed sheet 4 with the skin makes the skin 3 face the cavity surface 50.

(C) Molding Step Next, as shown in FIG. 4C, after the mold 5 is clamped, the base resin 6 is injected from the injection device 58 into the cavity 51 of the mold 5 through the gate 54. Then, the insert molded product 7 is molded. Polypropylene is used as the base resin 6.

(D) Foaming Step Next, as shown in FIG.
From the cavity 51 of the mold 5. The insert molding 7 is heated by the high-frequency induction heating device 14 to heat the conductor 13 in the unfoamed sheet 10. The unfoamed sheet 10 is foamed by the heat generated in the conductor 13 to form the foamed sheet 1.

(E) Completion As shown in FIG. 4 (e), a skin integral molded product 8 in which the base resin 6 is integrally molded with the skin 3 and the foam sheet 1 is obtained. The obtained integrally molded skin 8 is used for, for example, interior door trim of automobiles, pillar garnish, and the like.

As described above, in the method for integrally molding the skin of the present embodiment, the unfoamed sheet 10 is unfoamed and thin and hard at the time of molding. Melting out of 10 is small. Therefore, as shown in FIG. 4 (e), the insert molded product 7 is heated to foam the unfoamed sheet 10, and the skin-integrated molded product lined with the foamed sheet 1 having a uniform thickness and having an excellent cushioning feeling. 8 can be molded.

As shown in FIG. 4 (d), when the insert molded article 7 is heated using the high-frequency induction heating device 14 and the conductor 13, the unfoamed sheet 10 foams. No other treatment such as corona treatment is required. Further, since a material such as ethylene vinyl acetate resin, which does not require crosslinking, is used as the base resin, irradiation with electron beams for crosslinking is not required. Therefore, the heating process is simplified, and the cost of manufacturing equipment can be reduced. Also,
Since the portion where the conductor 13 does not exist is not heated, the unfoamed sheet 10 can be selectively heated, which is efficient. Others have the same operation and effects as the first embodiment.

[0032]

As described above, according to the present invention, it is possible to provide a molding method capable of producing a recyclable and uniformly foamed foam with high productivity.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for molding a foam in a first embodiment.

FIG. 2 is an explanatory cross-sectional view of a main part of a foam according to the first embodiment.

FIG. 3 is an explanatory view showing a sheet manufacturing process in a second embodiment.

FIG. 4 is an explanatory view showing a method for integrally forming a skin in Embodiment 2;

FIG. 5 is an explanatory view showing a method of molding a foam in a conventional technique.

FIG. 6 is an explanatory sectional view of a main part of a foam according to a conventional technique.

[Explanation of symbols]

 1. . . Foam sheet, 100. . . 10. foam base material, . . Blowing agent, 12. . . 12. base resin; . . conductor,

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/26 C08K 3/26 5/23 5/23 C08L 101/16 C08L 101/00 // B29K 101: 12 505: 00 (72) Inventor Takahashi Hashimoto 100 Kanayama, Ichiriyama-cho, Kariya City, Aichi Prefecture F-term (reference) 4F074 AA00 AA16 AA17 AA35 AC05 AC06 AC10 BA03 BA13 BA16 BA18 CA21 CC04Y CC54 DA03 4F203 AA10 AD03 AH26 AH48 AH81 AK11 DA12 DB02 DC15 DH16 4F212 AA10 AD03 AH26 AH48 AH81 AK11 UA17 UB02 UF21 UG01 UH18 UN08 4J002 AA011 BB001 BB061 BD031 DA067 DA077 DA087 DC007 DE256FD00 00 006 EV006 326

Claims (3)

[Claims] 1. A method for molding a foam by using a foamed base material obtained by mixing a foaming agent with a base resin made of a thermoplastic resin and heating the foamed base material to form a foam. A method for forming a foam, comprising adding a conductor to a material and heating the conductor by performing induction heating to foam the foam base material. 2. The method for forming a foam according to claim 1, wherein the foamed base material is formed into a predetermined shape and then heated. 3. A foam base material for producing a foam by foaming by heating, wherein the foam base material comprises a base resin, a foaming agent and a conductor.