JPS58982B2 - Continuous vulcanization method for rubber with core metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously vulcanizing an extrusion molded product consisting of three layers of solid rubber and sponge rubber containing a flat core metal, and aims to improve the quality of the product. This is the purpose.

Recently, the number one product for car trunk packing, etc.
As shown in the figure, the demand for so-called triple extrusion molded products consisting of solid rubber 2 and sponge rubber 3 into which a core bar 1 is inserted has rapidly increased.

Conventionally, a method as shown in FIG. 2 has been known as a vulcanization system for such extrusion molded products containing a cored metal.

That is, the core metal 1' supplied from the core metal feeding device 1a is introduced into the common head 4.

Further, extruders 2a and 3a are provided for supplying rubbers 2' and 3', which are arranged on both sides of the core metal 1' and sandwiched in a sandwich-like manner, into the common head 4.

The rubbers 2' and 3' extruded by the extruders 2a and 3a are solid rubber and sponge rubber, respectively, and are extruded as a composite body having a cross section as shown in FIG. 1A.

The extruded rubber core 5 is led to the next vulcanization tank 6 and vulcanized.

The vulcanized rubber is cooled by a cooling device 7 using water or the like, then taken out by a take-off machine 8, and then shaped by a shaping section 9 as shown in Figure 1 to complete the process.

Conventionally, a fluid or powder vulcanization device has been used as the vulcanization tank 6.

That is, as for vulcanization using a fluid, there is a method (LCM method) in which the product to be vulcanized is passed through nitrate having a good specific heat for vulcanization, but there are various problems in terms of post-treatment and pollution problems.

In addition, as for vulcanization using powder, there is a method (PCM method) in which the product to be vulcanized is passed through heated glass beads, but if the shape of the rubber to be inserted into the core is complex, it is necessary to drop the fine glass beads. Moreover, since both methods use heating methods based on heat conduction from the outside, heating efficiency is poor and energy consumption is high.

In order to solve these drawbacks, attempts have been made to vulcanize rubber in which a core metal is inserted, using a high-frequency induction heating method, which is efficient for heating metal, and a microwave heating method, which is efficient for heating rubber.

Conventionally, a method of vulcanizing rubber using microwaves has been known, but as is well known, microwaves can efficiently heat dielectrics such as rubber, but cannot heat metals because they are reflected. do not have.

When rubber with a cored metal is heated with microwaves, the metal is not heated, so the cored metal absorbs heat from the rubber that covers it, causing its temperature to rise.

As a result, in the rubber with a core inserted as shown in Figure 1,
The temperature rise of the rubber part covering the core metal is delayed by the amount of heat taken by the core metal, compared to the temperature rise of the rubber part of the protruding part.
The rubber in the covering portion becomes unvulcanized or insufficiently vulcanized.

In order to compensate for this drawback, a method is known in which the metal core is heated by high-frequency induction heating, which is efficient for metals (particularly iron), immediately before heating with microwaves.

High-frequency induction heating induces a high-frequency induced current in a heated object such as iron, and the metal itself is heated by the resistance loss, so there is no problem even if the core metal is covered with a rubber layer, such as the rubber that is inserted into the core metal. There isn't.

As mentioned above, the purpose is to compensate for the heat taken away by the core metal, so it is sufficient to use high-frequency induction heating to inject an amount of heat that raises the temperature of the core metal itself to the vulcanization temperature of the rubber.

For general rubber with a cored metal, vulcanization is completed as described above (through high-frequency induction heating and microwave induction heating, and held in a secondary hot air oven for a predetermined period of time), but the vulcanization is completed when the cored metal In the case of rubber with a core made of three layers of sponge rubber, it is not possible to obtain a high-quality product with this alone.

This is because the sponge rubber part and the solid rubber part are heated rapidly under the same conditions, so foaming in the sponge rubber part precedes vulcanization, causing a so-called degassing phenomenon and making it resistant to use with rough surfaces. All you get is sponge rubber.

The present invention solves these problems in the production of extrusion molded products consisting of three layers of core metal, sponge rubber, and solid rubber, and makes it possible to efficiently produce products with a clean texture in the sponge rubber part and a good finish. This is the purpose.

In order to achieve this objective, according to the present invention, only the surface of the rubber is heated in a surface preheating furnace before heating the rubber with microwaves, thereby forming a skin on the surface of the rubber. .

More specifically, in the production of an extrusion molded product consisting of three layers of core metal, solid rubber, and sponge rubber, the molded product continuously extruded from an extruder is heated mainly with the core metal using a high-frequency induction heating device. Then, it is introduced into a surface preheating furnace using hot air or hot wire to form a skin on the sponge rubber part and uniformly heat it. Next, it is rapidly foamed and vulcanized using a microwave heating device, and then heated with secondary hot air. It is configured to complete vulcanization in a furnace.

According to this method, before microwave heating is performed, the surface of the rubber is hardened by heating in a surface preheating furnace to form a skin, and then microwave heating is used to foam the sponge rubber part and form solid rubber. When vulcanizing the sponge rubber part, the gas in the sponge rubber part is blocked by the skin and cannot be extracted from the surface. Therefore, there is no gas outlet and roughening of the skin, and the surface is smooth. You can obtain beautiful cored rubber products.

In addition, since the core metal part is heated by high frequency induction, the temperature of the rubber part near the core metal rises, but by heating the rubber surface also during skin formation, heating from the inside of the rubber part and heating from the surface are different. This also has the effect of equalizing the temperature of the rubber part.

To explain in more detail, if there is temperature unevenness in rubber, a runaway phenomenon occurs in which only the high-temperature parts are heated at an accelerated rate and carbonized during microwave heating. This also prevents vulcanization from occurring uniformly and satisfactorily.

Next, an embodiment of the method of the present invention will be described in detail based on the drawings.

FIG. 3 is a side view showing the overall configuration of an example of an apparatus for carrying out the method of the present invention, that is, a continuous rubber vulcanization apparatus with a cored metal.

Reference numeral 5 denotes a heated body, as shown in FIG.

This object to be heated 5 is pushed out from the common head 4 explained in FIG. 2 and advances in the direction of the arrow.

Next, the extruder 40 is followed by a high-frequency induction heating device 10, a surface preheating furnace 11 consisting of a hot air stove, etc., and a microwave heating device 12.
, a secondary vulcanization furnace 13 consisting of a hot air stove, etc., and a take-off machine 14 are arranged in this order.

The object to be heated 5 is pulled in the direction of the arrow by the pulling machine 14,
It is vulcanized by passing through the high frequency induction heating device 10 → preheating sulfur 11 → microwave heating device 12 → secondary vulcanization furnace 13.

Note that 15 is a vertical roller for position adjustment, and 16 is a horizontal roller for position adjustment.

The horizontal rollers 16' are horizontal rollers for preventing sagging, and are placed at appropriate locations depending on the amount of sagging, but they should be placed outside each heating furnace as much as possible and should be kept to the minimum necessary number.

Why, in the case of rubber with a core inserted as shown in Figure 1 A,
There is a protruding lip 2L at the bottom, but when the rubber is unvulcanized, a normal flat roller will not be able to handle this lip 2L.
Since L is immediately crushed and deformed, a specially shaped roller that escapes the lip 2L is required, as shown by the chain line in FIG. 1A.

Although it is preferable not to have such rollers 16, 16', since sagging actually occurs, rollers of the size shown are necessary.

Now, the high frequency induction heating device 10 includes a heating coil 10'
and a high frequency oscillator 17.
to the heating coil 10', typically 200 to 400kHz.
high frequency is supplied.

Here, the heating coil 10' can be either a spiral coil, a circular coil, or a flat end face coil.
The latter end face coil is easier to use in terms of electrical coupling and handling.

FIG. 4 shows this end face coil 10', in which a heated body 5 moves above the coil.

The surface preheating furnace 11 has a built-in hot air generator (not shown), and heats the rubber with hot air at about 200°C to form a thin skin on the surface, as well as to remove heat generated during the extrusion process and high frequency induction heating process. It plays the role of eliminating temperature unevenness.

Since the purpose here is surface heating, methods other than hot air, such as an infrared heating method, may be used.

An oscillator 19 is connected to the microwave heating device 12 via a waveguide 18, and microwave energy supplied from the oscillator 19 is absorbed by the rubber passing through the furnace and is rapidly heated.

At this time, the sponge rubber portion rapidly foams due to the action of the foaming agent, but since a hardened skin has been formed on the surface in advance in the surface preheating furnace 11, the surface is not roughened by the generated gas and the surface is You can get clean sponge rubber.

The secondary vulcanization furnace 13 has a built-in hot air generator like the surface preheating furnace 11, and performs the final finishing using hot air at around 200°C.

The take-up machine 14 transports the object to be heated 5 by sandwiching it between upper and lower belts 20, 20'.
are connected to each other and are driven by this power.

Since the cored rubber has the cored metal 1 inserted, it does not elongate due to tension as occurs during ordinary rubber vulcanization, so there is no need to rely on belt conveyance, etc., and the apparatus is simplified.

As is clear from the above illustrated embodiments, according to the method of the present invention, the rubber surface is heated in a surface heating furnace to form a skin before the rubber is heated with microwaves, so that the roughness of the skin as in the conventional method is avoided. This also prevents the occurrence of water absorption from the outside when the metal-containing rubber product is used as a car trunk gasket.

Furthermore, when high-frequency induction heating is used to heat the core metal, surface heating also equalizes the temperature within the rubber and prevents quality deterioration due to runaway phenomenon, allowing the vulcanization quality to be maintained and achieving the above-mentioned results. Coupled with the appearance and prevention of water absorption due to skin formation, the quality of the rubber inserted into the core metal is greatly improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a rubber product containing a cored metal, Fig. 2 is a block diagram showing a conventional vulcanizing device for rubber containing a cored metal, and Fig. 3 is an example of a vulcanizing device for carrying out the method of the present invention. FIG. 4 is a perspective view of the heating coil. In the figure, 4 is an extruder, 5 is an object to be heated, 10 is a high-frequency induction heating device, 10' is a heating coil, 11 is a surface preheating furnace, 12 is a microwave heating device, 13 is a secondary vulcanization furnace, 1
4 is a collection machine.

Claims (1)

[Claims] 1. In manufacturing an extrusion molded product consisting of three layers of core metal, solid rubber, and sponge rubber, the molded product continuously extruded from an extruder is heated mainly with the core metal using a high-frequency induction heating device, and then Introduced into a preheating furnace to form a skin on the sponge rubber part and equalize the heat, then rapidly foaming and vulcanization using a microwave heating device, followed by a secondary hot air furnace to complete vulcanization. A continuous vulcanization method for an extrusion molded product consisting of three layers of core metal, solid rubber and sponge rubber.