JPH0771809B2 - Rubber molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding a thermosetting rubber such as a natural rubber or a synthetic rubber.

[Prior art and its problems]

Known molding machines for molding rubber include a general transfer molding machine and an injection molding machine, and a pre-plastic injection molding machine disclosed in Japanese Patent Publication No. 42-8228.

By the way, the conventional molding method using this type of molding machine is
In both cases, plasticize the thermosetting rubber raw material without vulcanization,
This plasticized rubber is filled in a mold cavity heated to a high temperature and vulcanized (cured), and there are the following problems to be solved.

First, the vulcanization time is long and the productivity is poor.

The rubber filled in the mold cavity is vulcanized by pressurization and heating, and the vulcanization time usually takes minutes although it depends on the characteristics of the raw material and the product shape (particularly the thickness). After all, even if the time for filling the mold with the rubber is short, the entire molding time becomes long.

Secondly, since burrs are generated on the molded product, a post-treatment process is required.

Burrs are caused by the flow curability of the rubber, which requires a certain amount of time for the rubber to vulcanize and cure. That is, the rubber temporarily increases in fluidity and softens when heated in the mold cavity. On the other hand, it is difficult to completely eliminate the gap of the parting line of the mold, and eventually the rubber to be pressed enters into even a slight gap to cause burrs. Therefore, in reality, in order to easily remove the burr, the burr is intentionally enlarged and removed in the post-treatment process.

An object of the present invention is to provide a rubber molding method that solves the above problems existing in the prior art.

[Means for Solving the Problems]

In the rubber molding method according to the present invention, the temperature of the mold is set to a temperature at which the rubber does not vulcanize, that is, a temperature lower than the molding temperature (temperature of the heating cylinder), and the rubber R is injection-molded in an unvulcanized state. At the same time, the unvulcanized and solidified molded product is taken out of the mold D, and then one or more unvulcanized molded products taken out of the mold D are simultaneously heated under no pressure to be vulcanized. Is characterized by. The unvulcanized molded product includes a secondary molded product obtained by inserting an unvulcanized primary molded product into another mold and then injection-molding another unvulcanized rubber R. Further, the molding method of the present invention includes a case where two or more unvulcanized molded articles taken out from the mold D are brought into contact with each other and simultaneously heated to be vulcanized to bond the two or more molded articles.

[Action]

According to the rubber molding method of the present invention, the unvulcanized rubber R plasticized in the injection device is injected and filled in the mold D. In this case, since the mold D is set to a temperature lower than the molding temperature, the rubber R in the mold D is not vulcanized, and more solidified (unplasticized state) than the softened state in the injection device. ).

On the other hand, when the filling is completed, the mold D is opened and the unvulcanized molded product is taken out. At this time, since the molded product is in a solidified state, it can be easily and surely taken out without losing its shape. The molded product taken out can be stored in a heating tank together with other unvulcanized molded products. Therefore, it is possible to simultaneously heat and vulcanize a plurality of molded products, and since the heating tank is in a non-pressurized state, the shape collapse is prevented.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, in order to help understanding of the present invention, a schematic configuration of an injection molding machine will be described with reference to the drawings.

The injection molding machine M includes an injection device J and a die D, and the injection device J further includes a front heating cylinder 2 and a rear injection cylinder 3.
It consists of a combination of. The heating cylinder 2 is provided with an injection nozzle 4 that abuts against the mold D at the tip, and water jackets 5a, 5b, 5c for temperature control and heaters 6a, 6b, 6c for heating are provided on the outer peripheral portion. Further, the heating cylinder 2 has a screw 7 incorporated therein so as to be capable of advancing and retracting and rotating, and a supply mechanism 8 for supplying a ribbon-shaped rubber raw material Ro to the rear portion of the screw 7. On the other hand, the injection cylinder 3 has an injection ram 9 for forward / backward drive.
Built in. The injection ram 9 is connected to the rear end of the screw 7,
Further, it is rotated by the rotation driving motor 10.
On the other hand, the die D includes a fixed die 11 and a movable die 12, and is opened and closed by a die clamping cylinder (not shown). Further, a cavity 13 is provided inside the die D, and a water jacket 14 for passing water is provided around the cavity 13 to cool the cavity 13 (temperature control).
I do.

Next, a rubber molding method according to the present invention using the injection molding machine M will be described.

First, water is passed through the water jacket 14 provided inside the mold D, and the temperature of the mold is lower than the molding temperature (temperature of the heating cylinder 2: usually about 60 to 100 ° C), for example, 20 ° C.
Set to a degree.

In the injection device J, the rubber raw material Ro is supplied to the inside of the heating cylinder 2, and the rotation of the screw 7 plasticizes the rubber R while kneading the rubber R in an unvulcanized state, and performs measurement. Then, after the measurement is completed, the screw 7 is moved forward, and the cavity 13 of the mold D is injected and filled with the unvulcanized rubber R.

Next, the mold D is opened and the unvulcanized molded product is taken out. In this case, since it is not vulcanized inside the mold D as in the conventional case, it can be taken out without time after injection filling.
Further, since it is cooled, it is in a more solidified state as compared with the softened state in the injection device J. Therefore, it can be easily taken out without losing its shape.

The molded product taken out is stored in a heating tank. Mold D for the heating tank
Molded products taken out from the above are sequentially stocked, and after a predetermined number (one or more) of molded products are accommodated, they are simultaneously heat treated and vulcanized. In this case, the inside of the heating tank is in a pressureless state (natural state) in which no pressure is applied. Further, as the heat medium for heating, steam, hot air, high frequency, molten metal salt, high boiling point liquid or the like can be selected and used.

The unvulcanized molded product includes a secondary molded product obtained by inserting an unvulcanized primary molded product into another mold and then injection-molding another unvulcanized rubber.

Further, in the case of a secondary molded product, it is possible to attach a heater to the mold used for the secondary molding and vulcanize it by the mold for the secondary molding. For example, when the type of rubber used for the secondary molded product has relatively low fluidity compared to the primary molded product and burrs are less likely to occur, the parting of the mold for secondary molding when the primary molded product is inserted Since there is no possibility that burrs will be generated when they do not come into contact with the line, productivity is deteriorated, but it is possible from the viewpoint of burr countermeasures. Further, after the unvulcanized molded product (primary molded product) or the secondary molded product is once taken out from the mold, it may be heated in another mold to be vulcanized. In this case, the mold is not used as the original mold, but is used as a heating tank, and no pressure is applied to the mold cavity.

Furthermore, it is also possible to bond two or more molded products by bringing two or more molded products taken out of the mold D into contact with each other, heating and vulcanizing them. This allows composite products using different rubbers, for example high hardness rubbers on the surface,
In the case of a product using a highly elastic rubber inside, the boundary portion can be chemically bonded without an adhesive, and more firmly bonded. At this time, since the shape collapses when the contact pressure is increased, each molded product is pressed down so as not to separate.

Although the embodiments have been described in detail above, the present invention is not limited to such embodiments, and the method of details, the type of the injection molding machine, etc. may be arbitrarily changed without departing from the gist of the present invention. it can.

〔The invention's effect〕

As described above, in the rubber molding method according to the present invention, the mold temperature is set to a temperature at which the rubber does not vulcanize and is lower than the molding temperature (heating cylinder temperature), and the rubber is not vulcanized. In addition to injection molding in the vulcanized state, take out the unvulcanized and solidified molded product from the mold, and then heat one or more unvulcanized molded products taken out from the mold D at the same time without pressure. ,
Since it is made to be vulcanized, the following remarkable effects are exhibited.

When performing a relatively time-consuming vulcanization process, a large number of molded products can be processed at the same time, so that the overall molding time can be significantly shortened, and cost reduction and productivity improvement can be achieved.

Since the vulcanization process does not use a mold, burrs do not occur even if it is temporarily softened during high-temperature heating, the quality of the molded product can be improved, and a post-treatment process such as deburring becomes unnecessary.

It is possible to chemically bond the boundary portion of the composite product using two or more kinds of rubber, and it is possible to bond more firmly than an adhesive or the like.

[Brief description of drawings]

Drawing: Partial longitudinal cross-sectional view of an injection molding machine that can be used in the rubber molding method according to the present invention. In the drawing, D: mold, R: rubber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Ihara, 2110 Nanjo, Sakagi-cho, Hanashina-gun, Nagano Nissei Plastic Industry Co., Ltd. Jushi Kogyo Co., Ltd. (56) Reference JP-A-54-146874 (JP, A) JP-A-51-47987 (JP, A) JP-A-52-127983 (JP, A)

Claims (3)

[Claims] 1. A mold temperature is set to a temperature at which rubber is not vulcanized and lower than a molding temperature (heating cylinder temperature), and rubber is injection-molded in an unvulcanized state. A rubber characterized by taking out an unvulcanized and solidified molded product from a mold, and thereafter, simultaneously heating one or more unvulcanized molded products taken out from the mold under no pressure to vulcanize. Molding method. 2. The two or more molded products are bonded together by bringing two or more unvulcanized and solidified molded products taken out of the mold into phase contact with each other and simultaneously heating and vulcanizing them. Item 1. A method for molding rubber according to Item 1. 3. A secondary molding obtained by inserting an unvulcanized primary molded article into another mold and then injection-molding another unvulcanized rubber into the unvulcanized and solidified molded article. The method for molding rubber according to claim 1, wherein the method comprises molding.