JPH09277353A - Method for controlling die swell of viscoelastic material in screw extruder with pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently extrude a viscoelastic material under high precision die swell by setting a feedback system between the viscosity and temperature of the material detected by sensor pins attached at the end of a screw and the insertion rate of numbers of work pins. SOLUTION: Forefront pins 5a-5f closest to the end of a screw on the extrusion head 7 side are sensor pins for detecting the properties of a viscoelastic material. Hydraulic mechanisms 9-1-9-8 carry out operation to make work pins 4-1-4-8 freely movable on the inside and the outside of the radial direction of a screw 2 on the basis of the feedback command of the viscosity and temperature of the material which are detected independently by the sensor pins 5a-5f. The operation individually controls the insertion depth of the work pins 4-1-4-8 into the material by the feedback signal while the extrusion work of the material continues. The insertion depth is based on the distance between the inside wall of the cylinder and the bottom of the screw and expressed by an insertion rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw extruder with a pin for extruding a viscoelastic body such as unvulcanized compound rubber as a viscoelastic body member having a predetermined cross-sectional shape when manufacturing a rubber product such as a tire. The present invention relates to a die swell control method for a viscoelastic body.

[0002]

2. Description of the Related Art When extruding a viscoelastic body member having a predetermined cross-sectional shape by an extruder, for example, an unvulcanized rubber member, the cross-sectional shape of the viscoelastic body member after extrusion is viscoelastic just before the extrusion die of the extruder. It is a well-known fact that the body's die swell characteristics are significantly affected. However, there is no means to control this die swell characteristic.

Therefore, in the past, a viscoelastic material was extruded through the die by an extrusion experiment by providing a special viscoelastic material flow path in the extrusion head of the extruder or by appropriately selecting the hole shape in the extrusion die. Means for measuring the die swell of the body and determining the shape of the flow path in the upper extrusion head and the hole shape of the extrusion die by trial and error are used. Needless to say, it takes a lot of man-hours to reach this decision, and if the type of viscoelastic body changes, the die swell characteristics change accordingly, so the productivity of viscoelastic body members is significantly impaired under the present circumstances. is there.

Further, even if the same kind of viscoelastic body is used, the die swell characteristics thereof are not always constant and have variations. Therefore, the cross-sectional shape of the extruded member naturally has a variation which cannot be neglected. Since the shape of the flow path and the hole of the die set change with the progress of wear over the time of use, the cross-sectional shape of the extruded member has disadvantages such as increasing the distance from the desired shape, and it is unavoidable to take measures each time. I'm standing.

[0005]

Therefore, the object of the present invention is not to rely on preliminary experiments with an extruder or the like, and to achieve highly efficient and highly accurate cross-sections without extra adjustment during use. It is an object of the present invention to provide a die swell control method for a viscoelastic body in a screw extruder with a pin capable of extruding a viscoelastic body member having a shape, in particular, an unvulcanized compounded rubber member.

[0006]

In order to achieve the above object, a die swell control method for a viscoelastic body in a screw extruder with a pin according to the present invention comprises a plurality of screw radial direction pins along the screw axis direction of the extruder. When a viscoelastic body is extruded by a screw extruder composed of multiple rows, the most advanced pin of the many pins that is closest to the screw tip of the extruder is used as the sensor pin for detecting the viscoelastic property, and the remaining pins. Is a work pin that assists plasticization of the viscoelastic body, and the sensor pin detects the viscosity of the viscoelastic body from the conveyance resistance that acts on the sensor pin of the viscoelastic body conveyed by screw rotation, and at the same time the temperature provided at the tip of the sensor pin. The temperature of the viscoelastic body is detected by the sensor,
The work pins are movable in the screw radial direction by a moving mechanism connected to each pin, and the viscosity and temperature of the viscoelastic body detected by the sensor pin are fed back to the moving mechanism of each work pin to the viscoelastic body of the work pin. It is characterized by controlling the insertion depth.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The main part of an embodiment according to the present invention will be described below in detail with reference to FIGS. FIG. 1 shows a screw 2 of a screw extruder 1.
FIG. 2 is a side view of the main part of the cylinder 3 and the cylinder 3 as seen through.
FIG. 2 is a sectional view of an essential part taken along the line II-II in FIG. 1. In FIG. 1, a screw extruder 1 (hereinafter abbreviated as extruder 1) is provided with an annular groove in a feed screw portion of a screw 2, and a large number (9 in the illustrated example) along the axial direction of the screw 2 in the annular groove portion.
The screw radial direction pins 4-1 to 4-8 and 5 are arranged in a plurality of rows (in the illustrated example, six rows are arranged at equal intervals around the cylinder 3, see FIG. 2). In FIGS. 1 and 2, these pins are shown by adding subscripts a to f in order from the top of the drawing to distinguish the pin rows.

The viscoelastic body loaded from the hopper 6 is conveyed by the rotation of the screw 2 toward the extrusion head 7 located at the front end on the right side of the figure while increasing the degree of plasticization, and an extrusion die (die, not shown in detail). 8 is extruded.

Among the many pins 4-1 to 4-8, the most advanced pins 5a to 5f (hereinafter represented by reference numeral 5) closest to the screw tip on the extrusion head 7 side of the extruder 1 are the pins. The remaining pins 4-1a to 4-1f excluding the sensor pin 5 to the pins 4-8a to 4-8f are used as sensor pins for detecting the characteristics of the viscoelastic body (hereinafter, reference numerals 4-1 to 4-4).
-8) represents a work pin used for the work of assisting the plasticization of the viscoelastic body.

The sensor pin 5 has a viscoelasticity in which a strain gauge 10 is adhered to the inside of the hollow pin and is conveyed toward the extrusion head 7 by the rotation of the screw 2 as shown in the cross-sectional view of the main portion of FIG. The transport resistance acting on the sensor pin 5 when the body passes through the sensor pin 5 is measured by the strain gauge 10, and the measured resistance value is the viscosity η.
Convert to (Poise, gf / cm · s). Also sensor pin 5
Is equipped with a temperature detector 11 at its tip, and simultaneously detects the temperature of the viscoelastic body at the position indicating the viscosity η. In order to detect the maximum temperature of the viscoelastic body conveyed at that time, the pin portion length of the sensor pin 5 and the pin tip position are defined so as to detect the temperature at the intermediate position between the screw bottom of the screw 2 and the inner wall of the cylinder 3. To do. In addition to the hollow pin, a Bourdon tube (not shown) in which mercury is sealed can be applied to the sensor pin 5, and in the case of the fixed type, the Bourdon tube is better suited.

On the other hand, the work pins 4-1 to 4-8 are used to connect the respective pins to a moving mechanism, for example, a hydraulic mechanism such as a double-acting hydraulic cylinder among hydraulic actuators or a screw feed mechanism. Cylinder 9-1a ~
9-1f to 9-8a to 9-8f. These hydraulic mechanisms are also shown in FIGS. 1 and 2 by adding subscripts a to f corresponding to the work pins, but hereinafter, they are abbreviated as 9-1 to 9-8.

These hydraulic mechanisms 9-1 to 9-8 are independent of each other, based on the feedback signal command of the viscosity η of the viscoelastic body detected by the sensor pin 5 and the temperature feedback signal command.
The operation of making 1 to 4-8 movable inward and outward in the radial direction of the screw 2 is performed. In this operation, the insertion depth of the work pins 4-1 to 4-8 into the viscoelastic body is individually controlled by the feedback signal while the viscoelastic body pushing operation continues. Here, the insertion depth is based on the distance between the cylinder inner wall position and the screw bottom position of the screw, and the insertion rate is 0% (cylinder inner wall position) to 100% (screw bottom position).
It is convenient to represent it.

The above feedback system uses a control device (not shown), inputs the signal values of the viscosity and temperature of the viscoelastic body detected by the sensor pin 5 to the control device, and inputs the input signal value and the control device in advance. The difference between the viscosity and the set value of the temperature is calculated, and if there is a difference between the two, a signal corresponding to the value of the difference is output to the hydraulic mechanisms 9-1 to 9-8, and the hydraulic pressure that receives this output is output. The mechanisms 9-1 to 9-8 adjust the insertion rate of the work pins 4-1 to 4-8, and the sensor pin 5 detects the viscosity and temperature at the tip of the viscoelastic body conveyed in the extruder in this state. A system is preferred in which a feedback loop is formed and the difference signal always holds a zero value. At that time, work pins 4-1 to 4-
The insertion rate of 8 does not have to be uniform, and it is desirable to employ a system that controls for each axially arranged position of the screw 2.

4 and 5 show the results of experiments using a 4.5-inch screw extruder according to FIGS. 1 to 3 with the viscoelastic body as unvulcanized compounded rubber. Figure 4 shows the viscosity η (gf / cm
・ S) and the die swell ratio D ₁ (%) in the height direction are shown with the rotation speed (rpm) of the screw 2 as a parameter, and the rubber temperature (° C) at each measurement point (mark). ) Is also shown in FIG. 5, and in FIG. 5, the viscosity η = 80 gf / cm · s
FIG. 6 is a diagram showing the relationship between the die swell ratio D ₁ (%) and the temperature t (° C.) at the time. As is clear from FIGS.
It was found that the die swell characteristics of an extrudate made of a viscoelastic body are determined by the viscosity and temperature of the viscoelastic body immediately before extrusion. Die swell ratio D (%) is the extrusion die (base)
Let L _{0 be the} height or width of the opening and L be the height or width of the extruded article, and let the height and the width be values determined by the following formulas. The height die swell ratio is D
₁ (%), that of the width is distinguished by D ₂ (%).

[Equation 1]

Further, the experiment was conducted under the same conditions as above, and the relationship between the row numbers (1 to 8) of the work pins 4-1 to 4-8 and the viscosity in each row number was calculated by using the insertion rates A to D of the pins. The results of the investigation as parameters are shown in a diagram in FIG. 6, and the relationship between the work pin row numbers 1 to 8 and the temperature of the viscoelastic body in each row number was examined using the insertion rates A to D of the pins as parameters. The results are shown in FIG. 7 as a similar diagram. On the horizontal axis of each figure, the position immediately after the viscoelastic body is put in from the hopper 6 is i / p, and thereafter, the positions counted from the i / p side in each row of the work pins are column numbers 1 to 8. Are also shown.

In FIGS. 6 and 7, the insertion rate A is 100% for all the work pins up to the column numbers 1 to 8, and the insertion rate B is the column numbers 1 to 8.
50% for all work pins up to 8, insertion rate C is column number 1
All work pins up to 8 are set to 10%, and insertion rate D is set to 0% for work pins in row numbers 1 to 4, row number 5
Work pins up to 8 are set to 50%. The facts and effects described below can be understood from these FIGS.

Viscosity η, which is one factor that determines the die swell characteristic of the viscoelastic body, can be controlled by changing the value of the insertion rate (%) of the work pins 4-1 to 4-8.
The temperature t of the viscoelastic body, which is the other factor, can also be controlled by changing the value of the insertion rate (%) of the work pins 4-1 to 4-8. Further, it is not necessary to uniformly set the insertion rate of the work pins 4-1 to 4-8 from the result of the insertion rate D, particularly the viscosity η, and by changing the insertion rate for each work pin, the viscosity characteristics can be obtained with higher accuracy. It is also possible to control. Of course, the number of pins arranged and the number of pins arranged along the axial direction of the screw 2 contribute to the above two factors, but they can be regarded as secondary effects.

Therefore, the viscosity and temperature of the viscoelastic body detected by the sensor pin 5 arranged near the die 8 on the tip side of the screw 2 are fed back to the hydraulic mechanisms 9-1 to 9-8, respectively, and the work pins 4 are fed. By controlling the insertion rate of -1 to 4-8, it has a desired viscosity characteristic value and temperature,
Therefore, it becomes possible to extrude a viscoelastic body controlled to a predetermined die swell ratio D (%) as a member having a highly accurate cross-sectional shape, which can save the conventional complicated work and can reduce the viscoelastic body to be extruded. There is no need to be bothered by intra-lot and inter-lot variations.

Further, it is practical and advantageous to use the above-mentioned feedback system for controlling the insertion rate of each work pin 4-1 to 4-8, and the set values of the viscosity and the temperature which are input to the control device in advance are set. Although it is not shown in the figure, the control device and each moving mechanism (hydraulic mechanism) can be connected individually and the insertion rate of each work pin can be set independently so that the highest efficiency can be obtained. Can be controlled with.

[0020]

[Example] Using the screw extruder 1 and the unvulcanized compounded rubber described above, Example 1 has a viscosity η in the sensor pin 5.
= 70 poise, the work pins of row numbers 1 to 5 are controlled with an insertion rate of 50 to 100%, and the row numbers 6 to 8 are controlled.
The work pin was controlled at an insertion rate of 0 to 50% to extrude the unvulcanized rubber member.

Example 2 gives priority to control so as to maintain the viscosity η = 70 poise under the same work pin insertion rate as in Example 1, and the work pin insertion rates of the row numbers 6 to 8 are changed. The unvulcanized rubber member was extruded with the temperature detected by the sensor pin 5 set to 100 ° C. by further moving within ± 5% of the absolute value. In order to verify the effects of these embodiments, the sensor pin 5 is used as a conventional example in which trial and error is repeated.
The unvulcanized rubber member was extruded by a screw extruder having no work pins and having only work pins 4-1 to 4-8. The target values for the die swell ratio D are D ₁ = 20% in the height direction and D ₂ = 10% in the width direction, and the unvulcanized rubbers used have the same composition.

The values of viscosity, temperature and die swell ratio of the unvulcanized compounded rubbers of Examples 1 and 2 and the conventional example immediately after leaving the die 8 were obtained by intermittently measuring 10 times during rubber extrusion. The average value x _m and “variation” (standard deviation σ) were calculated for each value. Table 1 shows the calculation results. Table 1
The die swell ratio D is calculated according to the above-mentioned mathematical formula, and the height direction is expressed as the ratio D ₁ (%), and the width direction is expressed as the ratio D ₂ (%), and the viscosity (P) is the poise (gr / cm · s). Represents

[0023]

[Table 1]

From the results shown in Table 1, even in Example 1 in which only the viscosity was controlled to 70P, the deviation of the average values of the viscosity and the temperature from the target values was smaller than in the conventional example, and the "variation" was greatly improved. As a result, it was found that the average value of the die swell ratio of the rubber extruded member was close to the target value, and the "variation" was also significantly reduced. In Example 2 in which temperature control was added to Example 1, It can be seen that the average values agree with each other, the "variation" is suppressed to a significantly small level, and the die swell characteristics are controlled to a level close to perfection.

[0025]

According to the present invention, a feedback system is provided between the viscosity and temperature of a viscoelastic body detected by a sensor pin provided at the tip of a screw and the insertion rate of a large number of work pins. Preliminary experiments with the screw extruder, as well as extra adjustments during the operation of the extruder are unnecessary, and there is no need for die replacement due to wear, high efficiency, and highly accurate cross-sectional shape. It is possible to provide a method for controlling a die swell of a viscoelastic body in a screw extruder with a pin capable of extruding a viscoelastic body member having the above, and particularly, an unvulcanized compounded rubber member.

[Brief description of drawings]

FIG. 1 is a side view of an essential part of a screw and a cylinder of a screw extruder according to an embodiment used in a die swell control method according to the present invention.

2 is a sectional view taken along line II-II of the screw extruder shown in FIG.

FIG. 3 is a partial cross-sectional view of a sensor pin of one embodiment applied to the screw extruder shown in FIG.

FIG. 4 is a diagram showing a relationship between die swell and viscosity with a screw rotation speed as a parameter.

FIG. 5 is a diagram showing the relationship between the temperature of a viscoelastic body and the die swell with viscosity as a parameter.

FIG. 6 is a diagram showing the relationship between work pin row numbers and viscosities with the work pin insertion rate as a parameter.

FIG. 7 is a diagram showing the relationship between the work pin row number and the temperature, with the work pin insertion rate as a parameter.

[Explanation of symbols]

 1 Screw Extruder 2 Screw 3 Cylinder 4 (4-1 to 4-8) Work Pin 5 Sensor Pin 6 Hopper 7 Extrusion Head 8 Die 9 (9-1 to 9-8) Hydraulic Mechanism 10 Strain Gauge 11 Temperature Detector

Claims (2)

[Claims] 1. When a viscoelastic body is extruded by a screw extruder formed by arranging a large number of screw radial direction pins in a plurality of rows along the screw axial direction of the extruder, the screw of the extruder is used among the large number of pins. The most advanced pin closest to the tip is the sensor pin for detecting the viscoelastic body characteristics, the remaining pin is the work pin that assists the plasticization of the viscoelastic body, and the sensor pin is the sensor pin of the viscoelastic body conveyed by the screw rotation. The temperature of the viscoelastic body is detected by the temperature sensor provided at the tip of the sensor pin at the same time as the viscosity of the viscoelastic body is detected from the acting transport resistance, and the work pins are moved in the radial direction of the screw by the moving mechanism connected to each pin. The viscoelastic body's viscosity and temperature detected by the sensor pin are fed back to the movement mechanism of each work pin. And controlling the insertion depth for the viscoelastic body,
Die swell control method for viscoelastic body in screw extruder with pin. 2. A signal value of viscosity and temperature of a viscoelastic body detected by a sensor pin is input, a difference between the input signal value and a previously input set value of viscosity and temperature is calculated, and the difference is calculated according to the calculated difference. The viscous component according to claim 1, wherein the movement mechanism controls the insertion depth of each work pin for each screw axial direction arrangement position until the difference signal becomes zero, via a control device that controls the screw radial direction movement of each work pin. Control method for die swell of elastic body.