JP6114119B2 - Rubber sheet extrusion molding method and rubber extruder - Google Patents

Description

  The present invention relates to a method for extruding a rubber sheet for use in, for example, a tread rubber, a side wall rubber, and a belt of a tire, and a rubber extruder, and in particular, the amount of rubber scrap in the rubber sheet extrusion process. It is intended to reduce.

  A rubber sheet to be used for tread rubber or the like uses a rubber extruder (hereinafter also referred to as an extruder) in which a screw is disposed in a cylinder, and raw rubber is introduced into the cylinder, and is kneaded by the screw and moved forward in the cylinder. It is transferred and extruded from the die at the tip of the extruder into a desired shape and molded.

  Conventionally, when extruding a rubber sheet, the operation of the extruder is started at the same time when the raw rubber is introduced, and the screw rotation speed is increased as it is to increase the extrusion speed of the extruder to a steady speed. It is usual to perform steady operation. This steady speed is set in advance mainly according to the composition of the raw rubber, provided that the extruder can be operated at a speed that ensures the quality and productivity of the rubber sheet.

  However, even after the screw rotation rises to the steady speed and reaches steady operation, the quality of the extruded rubber sheet is poor until the heated state of the rubber in the cylinder and the screw rotation are stabilized. A rubber molding which is stable and cannot be used as a product, that is, a so-called rubber scrap was generated.

  In Patent Document 1, the rubber scrap generated at the initial stage of extrusion is extruded by detecting the discharge speed of the rubber sheet extruded at the initial stage of extrusion and setting the speed of the drawer conveyor based on the detection result. A technique is disclosed in which a tensile force or a compressive force is applied to rubber to control the weight per unit length of the rubber sheet, thereby improving the productivity of the rubber sheet. Particularly, the speed of the drawer conveyor is set from the initial stage of extrusion where the extrusion speed changes rapidly, and the rubber scrap is reduced by keeping the weight and cross-sectional shape of the rubber sheet constant.

JP-A-7-214642

  However, by controlling the pull-out speed of the pull-out conveyor according to the discharge speed of the rubber sheet, it is possible to control defects due to the speed difference between the two, but the occurrence of rubber scrap occurring at the initial stage of extrusion is eliminated. However, it was still a challenge. Under such circumstances, there has been a demand for a method of suppressing rubber scrap in the initial stage of extrusion and improving the productivity of rubber sheets.

  Therefore, an object of the present invention is to propose a method capable of suppressing the generation of rubber scrap at the initial stage of extrusion without impairing productivity.

As described above, the acceleration of the screw rotation to the steady speed set from the viewpoint of the quality and productivity of the rubber sheet is temporarily stopped, and the operation in the low speed range, which was conventionally considered to hinder the productivity, is performed. Has been found to be effective in suppressing rubber scrap, and the present invention has been completed. That is, the gist of the present invention is as follows.
(1) A rubber sheet is extruded from a die at the tip of the extruder while supplying the raw rubber to a screw-type extruder and rotating the screw to knead the raw rubber,
When raising the extrusion speed from the extruder to one steady extrusion speed in the steady operation of the extruder, the quality of the rubber sheet to be extruded is initially maintained at an extrusion speed lower than the speed range that is the steady extrusion speed. The rubber sheet extrusion molding method characterized by accelerating the extrusion speed so as to shift to the steady operation at a stage where the determination criterion is satisfied.

  (2) When taking the rubber sheet after extrusion molding on the exit side of the die, the acceleration of the take-off speed is synchronized with the acceleration of the extrusion speed when shifting to the steady operation (1) A method for extruding a rubber sheet as described in 1.

(3) An extruder having a cylinder incorporating a screw and a die installed at the tip of the cylinder,
Determination means for determining the quality of the rubber sheet immediately after the extrusion of the die,
Control means for controlling the rotational speed of the screw based on the determination result of the determining means, when the extrusion speed from the extruder is raised to one steady extrusion speed in steady operation of the extruder. Initially, the extrusion speed is maintained at an extrusion speed lower than the speed range that is a steady extrusion speed, and the extrusion speed is accelerated so as to shift to the steady operation at the stage where the quality of the extruded rubber sheet satisfies the criterion. A rubber sheet extruder comprising: a control means for performing ;

  In the present invention, once the extruder is operated at a certain speed lower than the steady speed and then shifted to the steady operation, the generation of rubber scrap can be suppressed without impairing the productivity. .

It is a figure which shows 1st Embodiment of the rubber extruder of this invention. (A) is a graph which shows the change of the extrusion speed of an extruder in the extrusion molding method of the rubber sheet of this invention. (B) is a graph which shows the change of the extrusion speed of the extruder in the extrusion molding method of the conventional rubber sheet. In 1st Embodiment, it is a flowchart showing the process in which a control part controls a rubber extruder. It is a figure which shows 2nd Embodiment of the rubber extruder of this invention. In 2nd Embodiment, it is a flowchart showing the process in which a control part controls a rubber extruder. It is a graph which shows the change of the acceleration of an extruder, and the acceleration of a take-off apparatus when an extruder transfers from a low speed operation to a steady operation.

Hereinafter, the rubber sheet extrusion molding method of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an extruder used directly in the method of the present invention. In the extruder 1, when the raw rubber 100 is supplied into the extruder 1 from a supply port (hopper) 13 installed near the rear end of the cylinder 11, the screw 12 disposed inside the cylinder 11. , And the rubber moves toward the tip while kneading the rubber, and is extruded from the die 14 installed at the tip of the cylinder and formed into the rubber sheet 101. Here, the extruder 1 starts its operation at the same time when the raw rubber 100 is charged from the hopper 13, but the rubber supply sensor 16 makes it possible. The rubber supply sensor 16 is composed of a light emitting element 16a and a light receiving element 16b disposed to face the inner surface of the hopper 13, and when the raw rubber 100 is supplied from the hopper 13 into the extruder 1, the light emitting element 16a It is detected that the raw rubber 100 has been put into the extruder 1 by blocking the light irradiated to the light receiving element 16b by the raw rubber 100. When this detection signal is sent to the control unit 3, the control unit 3 sends a signal to the drive source 15 to start up the rotation of the screw 12.
That is, the screw 12 is rotationally driven by a drive source 15 installed at the base end of the screw 12 and under the control of the control unit 3. When the drive source 15 starts up the screw rotation, the drive source 15 once maintains the rotation at a speed lower than the steady speed.
In addition to the drive source 15, the control unit 3 is connected to a measuring instrument 4 that measures the quality of the extruded rubber sheet 101 on the exit side of the die 14. The control unit 3 determines the quality based on the information from the measuring device 4 and performs control to increase the rotation of the screw 12 to a steady speed when the determination criterion is satisfied. The extrusion speed is controlled by the above screw speed control. This extrusion speed control will be described in detail below.

  Here, referring to the graph of FIG. 2 showing the change in the extrusion speed of the extruder 1 and the control flow of the control unit 3 shown in FIG. And will be described. A graph (a) in FIG. 2 shows a change in the extrusion speed of the extruder 1 in the method of the present invention. As described above, the extrusion speed of the extruder 1 is controlled by controlling the number of rotations of the screw 12 by the control unit 3, and S1 to S5 on the graph of FIG. 2 are changed to steps S1 to S5 of FIG. It corresponds. On the other hand, the graph (b) shows the change in the extrusion speed of the extruder 1 in the conventional method.

  When the raw rubber 100 is supplied into the extruder 1, the control unit 3 that has received the detection signal from the rubber supply sensor 16 gives a command to the drive source 15 to start up the rotation of the screw 12 (step S1). . As described above, here, the extrusion speed control of the extruder 1 is performed by the rotational speed control of the screw 12 by the control unit 3. Subsequently, when increasing the extrusion speed of the extruder 1, the control unit 3 controls the drive source 15 to increase the extrusion speed to a speed lower than the steady speed (step S2).

  Here, a speed lower than the above-described steady speed is referred to as a low speed. The low speed is a speed calculated in advance according to the mixing ratio of the raw rubber 100, is a speed at which it is not difficult to extrude a rubber sheet having a desired cross-sectional shape, and production per hour. The amount is determined as appropriate for each rubber type to be extruded after satisfying conditions such as a speed that is not inferior to the conventional production amount. Hereinafter, in the present specification, the low speed of the extruder 1 is X1, and the steady speed is X2.

  In step S2 in which the extrusion speed increases to X1, the raw rubber 100 is kneaded by the screw 12 that increases the rotation speed. Then, when the extrusion speed reaches X1, the speed is maintained for a certain period (step S3). The rubber sheet 101 extruded during the period in which the extrusion speed is X1 is measured for width, weight, and temperature by a measuring device 4 having a plurality of sensors. The measured value is transmitted to the control unit 3. And it is determined by the calculator (determination means) with which this control part 3 is provided whether each numerical value satisfy | fills the criterion (process S4).

Subsequently, when it is confirmed in step S4 that the quality of the rubber sheet 101 satisfies the determination criterion, the control unit 3 controls the drive source 15 to increase the extrusion speed from X1 to X2 (step). S5). And after extrusion speed reaches X2, it shifts to steady operation P in this speed X2 like the conventional extrusion method. In Step S4, when it is determined that the quality of the rubber sheet 101 does not satisfy the determination criterion, the extrusion speed of the extruder 1 is maintained at X1 as it is.
On the other hand, the graph (b) shows the change in the extrusion speed of the extruder in the conventional method. In the conventional method, in extrusion molding under the same conditions as in (a), the extrusion speed is raised to X2 at once (step S2 ′), and therefore the point of shifting to steady operation P is different from (a). As described above, in the conventional method, there is no step of increasing the extrusion speed of the extruder 1 stepwise, and a steady operation is performed before the point t ′ at which the rubber sheet 101 that satisfies the determination standard is extruded. Yes.

Although the first embodiment of the present invention has been described above, the method of the present invention mainly brings two effects.
First, the rubber sheet 101 having a quality that satisfies the determination criteria can be produced earlier than the conventional method. This is clear from the relationship of t <t ′ shown in FIG. In this way, at the initial stage of the extrusion process, the raw rubber 100 is kneaded by operating the extruder 1 at a low speed X1 calculated in advance according to the composition of the raw rubber, which is lower than the steady speed X2. It is possible to extrude the raw rubber in a state in which the balance between the time and the time during which the raw rubber 100 stays in the cylinder 11 is excellent.

Second, the amount of rubber scrap generated at the beginning of the extrusion process can be reduced. Referring again to the graph (b) in FIG. 2, the conventional extrusion method has shifted to the steady operation P at the initial stage of the extrusion process. ′ Previously extruded rubber sheet is made into rubber scrap.
On the other hand, referring to the graph (a), in the method of the present invention, the low speed operation is performed at the low speed X1 before shifting to the steady operation P to improve the kneading state of the raw rubber 100, and the low speed operation is performed. Since the quality of the rubber sheet extruded sometimes shifts to the steady operation when the judgment criteria are satisfied (point t), the quality of the rubber sheet 101 is stabilized and rubber scrap is generated during the steady operation of pushing the rubber sheet in large quantities. I will not let you.

  As described above, in the method of the present invention, the rubber sheet 101 with stable quality can be extruded from an early stage of the extrusion process, and the amount of rubber scrap at the initial stage of the extrusion process can be reduced, thereby improving the productivity of the rubber sheet. Can be made.

  Next, FIG. 4 shows a rubber extruder and a take-up device for taking out a rubber sheet extruded from the rubber extruder according to the second embodiment of the present invention. 4, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the second embodiment of the present invention, a take-up device 2 is connected to the extruder 1 to take up and convey the rubber sheet 101, and the control unit 3 is further driven to control the operation speed of the take-up device 2. It is connected to the take-up device 2 via a source 21.

  The extrusion process of the second embodiment of the present invention is as shown in FIG. 5, and thus the effect of the present invention is further increased by including the process of drawing the rubber sheet 101 extruded from the extruder 1. (Step S6). The take-up device 2 can be, for example, a belt conveyor as shown in FIG. The belt conveyor pulls the rubber sheet 101 in the same direction as the extruder 1 pushes the raw rubber 100 from the die 14.

First, when the take-up device 2 is attached to the extruder 1, it is fundamental to synchronize the extrusion speed of the extruder 1 and the take-up speed of the take-up device 2, and when the extrusion speed is accelerated (steps S2 and S5). ), It is preferable to make both accelerations equal.
Further, in the operation of the extruder 1 described above, the extrusion speed is accelerated at a time from X1 to X2, but stepwise acceleration may be performed as shown in FIG. That is, either the extrusion speed or the drawing speed is set on condition that the acceleration of the extruder 1 and the take-up device 2 is equal to the acceleration start point S starting at the extrusion speed X1 and the acceleration end point E ending at the extrusion speed X2. , Or both may accelerate while repeating the period of acceleration and the period of maintaining a constant speed. At this time, in order to prevent the rubber from staying in the vicinity of the die 14, it is preferable to increase the drawing speed on the outlet side of the extruder 1 and to give a tensile force to the extruded rubber sheet 101 before the acceleration of the extrusion speed.

  In this way, the rubber sheet 101 extruded from the extruder 1 is taken out by synchronizing the take-up speed of the take-up device 2 with the push-out speed of the pusher machine 1, thereby preventing the acceleration of the extruder 1 and the take-up device 2. It is possible to avoid the deformation of the rubber sheet 101 caused by harmony and the retention of the raw rubber near the die 14, thereby contributing to the suppression of rubber scrap and the improvement of the productivity of the rubber sheet 101.

Examples of the present invention will be described below. Here, the time required to produce a rubber sheet by the method of the present invention and the conventional method in the second embodiment described above and to produce a rubber sheet of quality that satisfies the judgment criteria (quality stabilization time) The above two methods were evaluated according to the number of rubber scraps extruded (the number of rework). The results are shown in Table 1. In addition, the production conditions of the rubber sheet in an Example are as follows.
Screw speed (during low speed operation): 336 rpm
Screw rotation speed (during steady operation): 420 rpm
Operating speed of the take-up device (take-off speed): 25.5 m / min
Low speed ratio for low speed steady operation: 80%

(Quality stabilization time)
The quality stabilization time, which was 28 seconds in the conventional method, was reduced to 15 seconds in the method of the present invention. Approximately 46% of the time reduction is realized. From this, it became clear that the quality of the rubber sheet can be stabilized at an early stage of the process in the method of the present invention.

(Number of repeats)
In the same manner, the number of rework that occurred in the conventional method was reduced to 3 in the method of the present invention. In terms of the number of repeats, a reduction of approximately 57% was achieved.
From the above results, it became clear that the amount of rubber scrap can be reduced by about 50% by using the method of the present invention.

DESCRIPTION OF SYMBOLS 1 Rubber extruder 2 Taking-out apparatus 3 Control part 4 Measuring instrument 11 Cylinder 12 Screw 13 Supply port (hopper)
14 Die 15 Drive source 21 Drive source 100 Raw rubber 101 Rubber sheet

Claims (3)

A method of extruding a rubber sheet, supplying raw rubber to a screw-type extruder, and extruding from a die at the tip of the extruder while kneading the raw rubber by rotating the screw,
When raising the extrusion speed from the extruder to one steady extrusion speed in the steady operation of the extruder, the quality of the rubber sheet to be extruded is initially maintained at an extrusion speed lower than the speed range that is the steady extrusion speed. The rubber sheet extrusion molding method characterized by accelerating the extrusion speed so as to shift to the steady operation at a stage where the determination criterion is satisfied.   2. The acceleration of the take-off speed is synchronized with the acceleration of the extrusion speed when shifting to the steady operation when the rubber sheet after extrusion molding is taken on the exit side of the die. Rubber sheet extrusion molding method. An extruder having a cylinder containing a screw and a die installed at the tip of the cylinder,
Determination means for determining the quality of the rubber sheet immediately after the extrusion of the die,
Control means for controlling the rotational speed of the screw based on the determination result of the determining means, when the extrusion speed from the extruder is raised to one steady extrusion speed in steady operation of the extruder. Initially, the extrusion speed is maintained at an extrusion speed lower than the speed range that is a steady extrusion speed, and the extrusion speed is accelerated so as to shift to the steady operation at the stage where the quality of the extruded rubber sheet satisfies the criterion. A rubber sheet extruder comprising: a control means for performing ;

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