JP2000289089A - Rubber extrusion equipment - Google Patents

Abstract

(57) [Problem] To shorten the vulcanization time and to perform precision molding when vulcanization is carried out continuously to extrusion of a vulcanizable rubber composition. SOLUTION: A gear pump 16 and a heating block 20 are connected between a rubber extruder 10 and a die head 25, and a high pressure is applied to the vulcanizable rubber composition G by the gear pump 16 to continuously connect the vulcanizable rubber composition G to the heating block 20 and the die head 25. Then, the vulcanizable rubber composition G passing through the pipe 21 of the heating block 20 is subjected to a shearing action at the narrowed portion 22 formed in the pipe 21 to generate heat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for extruding rubber, which is used for extruding a vulcanizable rubber composition into a predetermined precise sectional shape at a high temperature, and then vulcanizing the composition after extrusion. To shorten the vulcanization time.

[0002]

2. Description of the Related Art As a method of manufacturing a rubber extruded product such as a weather strip, a door seal, and a hose of an automobile,
Additives such as a reinforcing agent, a filler, a plasticizer, a vulcanizing agent and a vulcanization accelerator are added to the raw rubber, and the resulting vulcanizable rubber composition obtained by kneading is supplied to an extruder. There is known a method of extruding into a desired shape through a die head, subsequently leading to a vulcanizing device, vulcanizing, and then cutting to a desired length to produce a product.

[0003] Various extruders are used for the above-mentioned extrusion. However, it is necessary to set the extrusion pressure high for precision molding, and the pressure loss when passing through the extrusion head and the die becomes large. The backflow phenomenon occurs at the tip of the extruder, and the temperature rise further increases. If the temperature rise increases, vulcanization proceeds partially in the extruder, causing burnt rubber to enter the molded product and deteriorating the quality. was there.

A method is known in which a gear pump is interposed between an extruder and a die head to increase the extrusion pressure while preventing the temperature of the vulcanizable rubber composition from rising, thereby enabling high-speed extrusion and precision molding. However, in this case, as in the case of the tire manufacturing process, when the molding of the tire components such as the tread and the molding and vulcanization of the tire including the assembly of these components are performed separately, the extrusion is continuously performed. In the case of vulcanization, there is a problem that heat loss increases.

[0005]

SUMMARY OF THE INVENTION According to the present invention, it is possible to precisely extrude a vulcanizable rubber composition at a high temperature and at a high pressure and at a high speed. The vulcanization time can be shortened.

[0006]

The rubber extrusion molding apparatus according to the present invention comprises a rubber feed gear pump and a heating block connected in series between a rubber extruder and a rubber molding die head. The heating block has a pipe connecting the outlet of the gear pump and the inlet of the die head, and forms a throttle in the pipe to cause the vulcanizable rubber composition passing through the pipe to generate heat by shearing action. The above-mentioned gear pump applies high pressure to the vulcanizable rubber composition from the outlet side of the gear pump to the narrowed portion of the heating block, and the vulcanizable rubber composition is passed through the narrowed portion through the narrowed portion. Is continuously pressed into the die head.

The throttle formed in the pipe of the heating block narrows the vulcanizable rubber composition flowing from the gear pump toward the die head through the pipe to reduce the thickness or width of the composition. Any shape may be used as long as heat is generated by the shearing force applied to the vulcanizable rubber composition.The cross-sectional shape of the drawn portion is not limited to a simple flat shape such as an ellipse, an oval shape, a rectangle, and a long hole, but also bends a long hole. An arbitrary shape such as a corrugated shape or other bent shape or a large number of separated small holes can be selected.

It is preferable that the cross-sectional shape of the pipeline is gently changed so that vortices and stagnation do not occur before and after the constricted portion. Further, the temperature of the vulcanizable rubber composition generated by the above-described drawing is preferably from 90 to 200 ° C., particularly preferably 190 ° C. or less. If it is lower than 90 ° C., there is no effect of increasing the temperature.
If the temperature exceeds 00 ° C., vulcanization proceeds excessively, and molding with a die head becomes extremely difficult. In particular, in the case of foamed rubber, if the vulcanization rate is too high, control of foaming becomes difficult.

In the above apparatus, when the vulcanizable rubber composition is supplied to the extruder, the space from the screw tip of the extruder to the gear meshing portion of the gear pump is filled with the vulcanizable rubber composition. In this case, since the extrusion pressure of the extruder only needs to be large enough to fill the space with the vulcanizable rubber composition, the pressure is significantly smaller than when directly connecting the die head. There is no backflow and the temperature rise is small.

[0010] The vulcanizable rubber composition on the inlet side of the gear pump is sent to the outlet side of the gear pump by the rotation of the key pump, and fills the outlet side passage and the inlet side pipe line of the heating block in order, and the pressure becomes constant. When it reaches the size, it is press-fitted into the constricted portion of the pipeline, then passes through the constricted portion, gradually fills the outlet-side pipeline of the heating block, finally reaches the inlet of the die head, and the pressure increased by the rotation of the gear pump. , And is formed into a predetermined sectional shape precisely and at a high speed. During this time, the vulcanizable rubber composition generates heat due to an increase in pressure generated when the pipe is filled with the gear pump and a shearing action when passing through the constricted portion, and the temperature increases. Therefore, the vulcanization time can be shortened when vulcanizing after molding.

The heating block may be provided with a heating means such as electric heat or steam for heating the heating block from the outside, and the heating by the heating means is used in combination with the shearing heat of the throttle. Thereby, the vulcanizable rubber composition can be heated by both internal friction and external heating, whereby the temperature distribution inside the vulcanizable rubber composition becomes uniform, and the vulcanization time can be further reduced. Will be possible. However, when the shearing heat generated by the drawing is abolished and only external heating is used, only the vulcanizable rubber composition in contact with the pipe wall surface is heated, so that the vulcanization rate varies. In particular, in the case of foamed rubber, the variation in shape is large.

The rubber extrusion molding apparatus detects the pressure of the vulcanizable rubber composition at the inlet side of the gear pump,
By controlling the screw rotation speed of the extruder based on this pressure, the pressure of the vulcanizable rubber composition at the inlet side of the gear pump can be controlled to a predetermined value. In addition, multiple sets of extruders, gear pumps, and heating blocks are arranged in parallel, and the outlets of the heating blocks are integrated into one and connected to a die head, so that multilayer precise extrusion molding (including lamination molding of solid rubber and foamed rubber) Becomes possible.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 10 is a known screw type extruder, 11 is its extrusion screw, 12 is a barrel, 13 is a hopper for feeding a ribbon made of a vulcanizable rubber composition, 14 is a support frame, Reference numeral 15 denotes a driving motor. A metering gear pump 16 for rubber is connected to a tip of a barrel 12 of the screw type extruder 10. The gear pump 16 includes a body 17 and a pair of upper and lower gears 1.
8a and 18b, and one side of the gears 18a and 18b (the rubber composition supply side) is provided with an inlet side space 17a, and the other side (the rubber composition discharge side) is provided with an outlet side space 17b. I have. Reference numeral 19 denotes a driving motor for the gear pump 16.

A heating block 20 is connected to the outlet of the gear pump 16. The heating block 20 is connected to the pipeline 2 communicating with the outlet side space 17 b of the gear pump 16.
1, a narrowed portion 22 is formed in the pipeline 21, and the pipeline 21 before and after the narrowed portion is smoothly narrowed.
Note that the cross-sectional shape of the narrowed portion 22 is a zigzag shape in FIG. 2A, a plurality of parallel line shapes in FIG.
It is formed in a porous shape of (c), a leaf shape of one thin tree in FIG.

At the outlet side of the heating block 20 (FIG. 1)
A known die head 25 is connected, and a conveyor 26 is provided at the outlet side of the die head 25, and passes through a hot-air vulcanization tank 27. A pressure sensor 28 for detecting the pressure of the vulcanizable rubber composition G is installed in the space 17 a on the inlet side of the gear pump 16, and the detected value is sent to the control device 30.
, And the pressure on the inlet side of the gear pump 16 is kept constant.

In the above apparatus, when the vulcanizable rubber composition is continuously supplied to the extruder 10 from the charging hopper 13 in the form of a ribbon or a sheet, the vulcanizable rubber composition G passes through the barrel 12 through the screw 11 The rotation of the gear pump 16 is sent to the gear pump 16, and then the rotation of the gears 18a and 18b is sent to the conduit 21 of the heating block 20, filling the conduit 21 and pressurized to form a high-pressure vulcanizable rubber composition G, Subsequently, the vulcanizable rubber composition G is passed through the squeezing portion 22 and generates heat from the inside of the layer of the vulcanizable rubber composition G due to internal friction due to shearing force.
It is arbitrarily controlled in the range of 90 ° C. and passed through the die head 25 to be formed into a desired shape.

The obtained molded product Ga is discharged onto a conveyor 26, carried into a hot-air vulcanizing tank 27, and vulcanized into a product. The molded product Ga discharged onto the conveyor 26 is produced.
Maintains a high temperature (80 to 190 ° C.), vulcanization may be performed only by the hot air vulcanizing tank 27, and there is no need to use microwaves together. And the gear pump 16
Is controlled to a desired value by the control device 30 and the outlet pressure is set to a large value of about 500 kgf / cm ^{2 at the} maximum, so that the molded article Ga (see FIG. 3) is placed on the outer surface of the circular tube by the ribbon. Even a thin member such as a door seal material formed by joining the same can be formed in a precise shape.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A gear pump 16 and a heating block 20 are interposed between an extruder 10 (see FIG. 1) and a die head 25 which have been installed in an existing weather strip extrusion process. The supply pressure is ²⁰⁰ to ² from the conventional 80 to 120 kgf / cm ²
50 kgf / cm ^2, and the precision of the molded product Ga is 5-10
%Improved. The temperature of the molded product Ga is 7 °
The temperature increased from 0 to 90 ° C to 120 to 130 ° C, and the vulcanization time was reduced by about 30%. In addition, the exit temperature of the extruder 10 was almost the same as the conventional 60 to 80 ° C., but the exit pressure was
Conventional 80-120 kgf / cm ² is 40-50 kgf / cm ²
Has dropped.

[0019]

As described above, according to the present invention, the vulcanizable rubber composition can be extruded at a high temperature and at a high pressure and at a high speed. In this case, the vulcanization time can be greatly reduced, and the profile of the product can be precisely formed. In particular, according to the second aspect of the present invention, since the temperature distribution inside the vulcanizable rubber composition during molding becomes uniform, the vulcanization time can be further reduced.

[Brief description of the drawings]

FIG. 1 is a side view in which a part of an embodiment is crushed.

FIG. 2 is a cross-sectional view of a narrowed portion of a heating block.

FIG. 3 is a cross-sectional view showing an example of a molded product.

[Explanation of symbols]

 10: Extruder 15, 19: Driving motor 16: Gear pump 20: Heating block 21: Pipe line 22: Restrictor 25: Die head 26: Conveyor 27: Hot air type vulcanization tank 28: Pressure sensor 30: Control device G: Vulcanization Vulcanizable rubber composition Ga: molded product

Claims (2)

[Claims] 1. A rubber feeding gear pump and a heating block are connected in series between a rubber extruder and a rubber molding die head, and this heating block connects an outlet of the gear pump and an inlet of the die head. A throttle portion for causing the vulcanizable rubber composition passing through the pipeline to generate heat by shearing action, wherein the gear pump is connected to the gear pump from the outlet side of the gear pump. A high pressure is applied to the vulcanizable rubber composition straddling the narrowed portion of the heating block, and the vulcanizable rubber composition is continuously pressed into the die head through the narrowed portion. Extrusion equipment. 2. The rubber extruder according to claim 1, wherein the heating block has a heating means for heating the heating block from outside.