JP2016196089A - Extrusion molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extrusion molding device without generating air pocket in a molding head in the extrusion molding device nor including air inside of a rubber member after molding.SOLUTION: An extrusion part 16 extruding in a side of a molding window 19a having smaller diameter than an outer side dimension D of the screw body part 15 and longer dimension than the outer diameter dimension D of the screw body part 15 is provided on terminal in a side of a molding head 14 in the screw body part 15 of an extrusion molding device having a cylinder 11 having an insertion part capable of inserting a rubber composition to a terminal side, a screw 12 having the screw body part 15 freely rotatably arranged inside of the cylinder 11 and transferring the same to the other terminal side of the cylinder 11 while mixing the rubber composition and the molding head 14 provided on the other terminal side of the cylinder 11 and having a contraction part S extruding the rubber composition transferred from the screw body part 15 from a molding window 19a which is smaller than a cross section of the cylinder 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an extrusion molding apparatus, and more particularly to an extrusion molding apparatus capable of suppressing air inclusion in a molded product after molding in extrusion molding of a rubber member or the like.

  2. Description of the Related Art Conventionally, an extrusion molding apparatus is provided in a cylinder and mixes a rubber composition put into the cylinder by rotating a screw having a shaft portion and a blade portion formed around the shaft portion. While gradually moving to the side of the molding head attached to the end of the cylinder and extruding the rubber composition from a die provided on the molding head, for example, a rubber member of a desired shape such as a flat tire tread Can be obtained. Also, since the inside of the molding head attached to the end of the cylinder is narrowed from a continuous circular shape corresponding to the cylinder to a desired molding shape, friction between the rubber composition and the inner wall surface of the molding head causes the rubber to It is known that the composition is not extruded uniformly toward the die. In order to solve such a problem, in the extrusion molding apparatus described in Patent Document 1, a roller is provided along the inner wall of the molding head, and the rubber composition is pressed in a direction away from the wall surface by rotation of the roller. Thus, the movement of the rubber composition toward the die of the molding head is made uniform.

JP 7-237259 A

However, in the extrusion molding apparatus disclosed in Patent Document 1, the non-uniformity of the movement of the rubber composition caused by friction with the inner wall surface of the molding head can be eliminated, but an air pocket that causes a molding defect can be eliminated. There is a problem that cannot be suppressed.
That is, as described above, the screw is composed of a shaft portion that extends coaxially with the cylinder, and a blade portion that is formed around the shaft portion, and the blade portion is against the rubber composition that exists in the cylinder. The rubber composition present in the section where the blade portion is formed is pushed along the inner wall surface of the cylinder and the inner wall surface of the molding head in order to give a pushing force in the direction of the die. Since the direct pressing force to the rubber composition is lost at the time of passing, the rubber composition whose pressing force has been lost is pushed out to the base side while surrounding the periphery of the screw shaft inside the molding head, There is a drawback that air is easily trapped in the process of surrounding the tip of the shaft. Then, the air pool stays in the molding head for a long time, and the air in the air pool is partly separated and contained in the molded product pushed out from the die, resulting in a molding defect. There was a problem.
Accordingly, in order to solve the above-described problems, the present invention provides an extrusion molding apparatus that suppresses air from being trapped in the molding head and prevents air from being encapsulated in the molded rubber member. The purpose is to do.

In order to solve the above problems, the extrusion molding apparatus according to the present invention has a configuration in which a cylinder having a charging portion into which a rubber composition can be charged on one end side and a rotatable rotation inside the cylinder are provided, and the rubber composition is kneaded. A screw having a screw main body that is transferred toward the other end of the cylinder, and a rubber composition that is provided on the other end of the cylinder and transferred by the screw main body from a molding port that is smaller than the cross-sectional area of the cylinder. An extrusion molding apparatus including a molding head having a drawn-out portion to be extruded, and having a diameter smaller than the outer diameter of the screw main body at the end on the molding head side in the screw main body and longer than the outer diameter of the screw main body Since the protrusion part which has a dimension and protrudes in the molding port side was provided, the rubber composition extruded from the screw main body part is the outer periphery of the protrusion part, and the molding head. Since the air is smoothly pushed out toward the molding port along the inner wall surface of the throttle part, there is almost no air accumulation near the shaft end of the screw, so that air is not included in the molded product after molding. Thus, the occurrence of defects in the molded product can be suppressed.
Further, as another configuration of the extrusion molding apparatus according to the present invention, since the protruding portion enters the throttle portion, in addition to the above effects, the internal volume of the extrusion head is reduced, so that the rubber extruded by the screw body portion The composition can be smoothly transferred toward the molding port.
Further, as another configuration of the extrusion molding apparatus according to the present invention, since the protruding portion is tapered toward the molding port side, in addition to the above effect, the rubber composition extruded by the screw main body portion is used as the surface of the protruding portion. Can be smoothly extruded toward the forming port.
Further, as another configuration of the extrusion molding apparatus according to the present invention, since the protruding portion has a conical shape, the tip is pointed, and the rubber composition extruded from the screw main body portion extends along the outer periphery of the protruding portion. Therefore, air accumulation at the end of the screw can be reliably prevented.
In addition, as another configuration of the extrusion molding apparatus according to the present invention, since the outer diameter of the screw main body portion is 200 mm or more, the thickness of the shaft portion of the screw main body portion is also increased, so that an air pool is generated at the screw end portion. Although it tends to occur, as described above, the shaft portion of the screw main body portion is provided with the protruding portion, so that the air can be eliminated and the rubber composition can be smoothly extruded from the molding port.
Further, as another configuration of the extrusion molding apparatus according to the present invention, since the surface of the protrusion is mirror-finished, since the resistance of the surface of the protrusion is reduced, the rubber composition is smoother on the surface of the protrusion. Therefore, it is possible to efficiently perform extrusion molding while suppressing the occurrence of defects.

It is the schematic of the extrusion molding apparatus which concerns on this invention. It is the elements on larger scale at the front end side of a screw. It is the elements on larger scale at the front end side of the screw concerning a comparative example and an embodiment. It is a figure which shows the movement inside the shaping | molding head of the rubber composition extruded by the screw which concerns on a comparative example. It is a figure which shows the movement inside the shaping | molding head of the rubber composition extruded by the screw which concerns on embodiment. It is the figure which investigated the relationship between the length of a protrusion part, and the incidence rate of a defect. It is a figure which shows the other shape of a protrusion part.

  Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

  FIG. 1 is a schematic view showing an embodiment of an extrusion molding apparatus according to the present invention. Hereinafter, the extrusion molding apparatus will be described with reference to FIG. In addition, although this embodiment demonstrates the molded object shape | molded by the extrusion molding apparatus 1 as a tread rubber, a molding object is not limited to a tread rubber.

The extrusion molding apparatus 1 includes a cylinder 11 and a screw 12 that rotates inside the cylinder 11.
The cylinder 11 is a cylindrical body having a heater (not shown) that heats the inner wall surface. The cylinder 11 is provided with an insertion port communicating with the outside at one end in the longitudinal direction, and the hopper 13 is connected to the insertion port. A molding head 14 is detachably attached to the other end side of the cylinder 11.
As shown in FIG. 2A, the molding head 14 according to this embodiment has an internal space that is tapered by a smooth curved surface from a circular shape to a substantially rectangular shape so as to be continuous with the inner wall surface 11a of the cylinder 11. It is formed as a fishtail-shaped throttle part S. A base 19 is attached to the tip of the molding head 14, and the base 19 is provided with a molding port 19a communicating with the throttle part S of the molding head 14, and the rubber composition that has passed through the throttle part S passes through the molding port 19a. Extruded outside. The cross-sectional shape of the molding port 19a of the base 19 can be arbitrarily set according to the shape of the molding object.

  The screw 12 extends along the longitudinal direction of the cylinder 11 in the cylinder 11, and on the side of the base 19 attached to the molding head 14 while kneading the rubber composition charged into the cylinder 11 via the hopper 13. Transport. The screw 12 includes a screw main body 15 and a protrusion 16 that protrudes from the screw main body 15 toward the base 19. The screw main body 15 includes a shaft portion 15A and a blade portion 15B formed around the shaft portion 15A. The shaft portion 15 </ b> A is a columnar shaft body that serves as a base of the screw 12, and is connected to the driving means 10 provided at one end of the cylinder 11. The blade portion 15B is a spiral body extending along the longitudinal direction on the outer periphery of the shaft portion 15A, and the outer peripheral surface 12a that is the maximum outer diameter of the screw 12 is separated from the inner wall surface of the cylinder 11 with a gap of a predetermined distance. It is set to be. In addition, as shown in FIG. 1, the blade | wing part 15B is comprised in the outer periphery of the axial part 15A from the two edge parts 21b; 22b, and is comprised by the 2 item | slice spiral body extended in a longitudinal direction. Thus, when increasing the number of strips of the spiral body constituting the blade portion 15B, it is preferable to gradually increase the number of strips in the direction of conveyance of the rubber composition (on the base 19 side). Thereby, a blade | wing part can be added, without affecting the transfer of a rubber composition. Also, as the number of blades 15B increases, less pressure is applied to each blade, so the thickness of the blades is reduced to widen the flow path of the rubber material so that the rubber flows more smoothly. The thickness variation of the tread rubber pushed out from the base 19 can be further suppressed.

  Next, the protrusion 16 that protrudes from the screw body 15 will be described with reference to FIGS. As shown in the figure, the protrusion 16 has an outer diameter smaller than the outer diameter D of the screw 12 (screw main body 15), and the end of the base 19 from the end of the screw main body 15 on the molding head 14 side. It protrudes in the direction with a length L longer than the outer diameter D of the screw body 15. The length L of the protrusion 16 protruding from the end of the screw main body 15 in the direction of the base 19 is the length from the end (terminal part) on the base 19 side of the blade 15B to the apex 16A formed at an acute angle. Defined by The projecting portion 16 may be formed integrally with the shaft portion 15A of the screw main body portion 15, or is formed as a separate body from the shaft portion 15A of the screw main body portion 15, and the end portion of the shaft portion 15A on the base 19 side. It may be fixed by fixing means not shown.

  The protruding portion 16 has a base portion that is formed in a cylindrical shape having the same diameter as the shaft portion 15A, and a conical portion that is formed so as to be tapered from the base portion toward the base 19 side and has an acute apex portion 16A. The top portion 16 </ b> A is set so as to be positioned on the axis of the shaft portion 15 </ b> A, and terminates in the narrowed portion S of the forming head 14. That is, the length L of the protruding portion is set to a length that allows the top portion 16 </ b> A to enter the narrowed portion S of the forming head 14. Further, the conical portion is set so that the generatrix 16z thereof is parallel to the inclined portion 14b having a large inclination angle in the diaphragm portion S.

  By setting the protruding portion 16 as described above, the rubber composition that passes through the blade portion 15B of the screw main body portion 15 and is transferred to the molding head 14 side causes the surface 17 of the protruding portion 16 and the inner wall surface of the molding head 14 to move. 14a enters the molding head 14 side in a state along 14a, and is pushed out from the molding port 19a of the base 19, so that the air inside the cylinder 11 and the molding head 14 is transferred from the molding port 19a to the outside as the rubber composition is transferred. It is discharged and it can suppress that an air pocket arises in the edge part by the side of the nozzle | cap | die 19 of the screw main-body part 15. Since the air accumulation can be suppressed, the rubber composition can be smoothly pushed out from the molding port 19a of the base 19, and air is contained in the tread rubber molded into a predetermined shape through the molding port 19a. Therefore, the occurrence of defects in the extrusion molding of tread rubber can be prevented. In addition, the surface 17 of the protrusion 16 is subjected to a surface treatment such as a mirror finish so as to reduce friction and adhesion with the rubber composition.

Hereinafter, the operation of the extrusion molding apparatus 1 having the above configuration will be described.
The rubber composition charged into the cylinder 11 via the hopper 13 is kneaded by the rotation of the screw 12 while being heated by the heater in the cylinder 11 and gradually transferred toward the molding head 14 and the base 19 side. The rubber composition that has passed through the section where the blade portion 15B is formed by the rotation of the screw 12 is transferred to the base 19 side while being squeezed between the inner wall surface 14a of the molding head 14 and the surface 17 of the protruding portion 16. The At this time, the rubber composition in contact with the surface 17 of the protrusion 16 is transferred to the top 16A side along the surface 17 while rotating so as to wrap around the surface 17 of the protrusion 16 by the rotational force of the screw 12. At the top portion 16 </ b> A, they merge together and become a lump toward the base 19, and are smoothly pushed out from the molding port 19 a of the base 19.
Therefore, since most of the air inside the extrusion molding apparatus 1 is pushed out from the molding port 19a of the base 19 by the rubber composition, it is not included in the tread rubber after molding.

  3 (a) and 3 (b) show the screw 120 according to the comparative example and the screw according to the embodiment in which the length of the protruding portion 16 is changed in the same extrusion molding apparatus in order to verify the effect of the present invention. 12 is a schematic view when 12 is provided. Both the screw 120 and the screw 12 have an outer diameter D of 254 mm (10 mm) in the blade portion 15B. As shown in FIG. 3A, in the screw 120, the length L of the projecting portion 160 from the end portion 21b located on the tip side to the top portion 160A among the end portions 21b; 22b of the blade portion 15B is 200 mm. The top portion 160 </ b> A is located on the inner side of the cylinder 11 from the end surface 11 b of the cylinder 11 in contact with the end surface of the molding head 14.

  In contrast, in the screw 12, as shown in FIG. 3B, the length L of the protruding portion 16 from the end 21b of the blade portion 15B to the tip is 330 mm, and 130 mm longer than the protruding portion 160 of the screw 120. The top portion 16 </ b> A is long and protrudes 80 mm from the end surface 11 b of the cylinder 11 in contact with the end surface of the forming head 14 and enters the narrowed portion S of the forming head 14.

  4 (a), 4 (b) and 5 (a), 5 (b) show the rubber inside the molding head 14 when it is actually extruded by the extrusion molding apparatus shown in FIGS. 3 (a), 3 (b). It is a schematic diagram which shows the mode of a composition. 4 (a) and 4 (b) show the flow of the rubber composition in the cross section of the central portion along the axis of the molding head 14 of the rubber composition extruded by the screw 120, and the rubber composition in the cross section on the inner wall surface 14a side. Shows the flow. 5A and 5B show the flow of the rubber composition in the cross section of the central portion along the axis of the molding head 14 of the rubber composition extruded by the screw 12, and the rubber in the cross section on the inner wall surface 14a side. It is a figure which shows the flow of a composition.

  As shown in FIGS. 4A and 4B, in the screw 120 according to the comparative example, the rubber composition is extruded in a clean flow toward the base 19 near the inner wall surface in the inner space of the molding head 14. However, a staying portion is generated in the vicinity of the top portion 160A of the projecting portion 160 in the central portion, and a large air pocket is generated in a portion indicated by a broken line in FIG.

On the other hand, as shown in FIGS. 5A and 5B, in the screw 12 according to the embodiment, in the inner space of the molding head 14, the inner wall surface 14 a of the molding head 14 and the surface 17 of the protruding portion 16 are also located in the center. The rubber composition is extruded along and is extruded in a laminar flow toward the molding port 19a. In addition, since the rubber composition that moves along the surface 16a of the protruding portion 16 moves so as to gather toward the top portion 16A of the protruding portion 16, no air pocket is formed. That is, it can be seen that the conventional air retention due to the retention region of the rubber composition is eliminated.
That is, like the screw 12 according to the embodiment, the protruding portion 16 has a smaller diameter than the outer diameter D of the screw main body portion 15 at the end of the screw main body portion 15 on the molding head 14 side, and the outside of the screw main body portion 15. By providing the projecting portion 16 having a dimension longer than the diameter dimension D and projecting toward the molding port 19a, the air pool in the throttle portion S of the molding head 14 is eliminated and the projecting portion 16 rotates. Since the flow of the rubber composition is generated in the entire internal space of the narrowed portion S of the molding head 14, the adhesion of the molding head 14 to the inner wall surface 14 a is suppressed, and a smooth flow can be generated toward the base 19. . As a result, the tread rubber extruded into a predetermined shape by the base 19 does not contain air, so that no molding failure occurs in the extrusion molding.

The above-mentioned bubble accumulation on the screw tip side becomes remarkable particularly when the outer diameter D of the screw 12 is increased.
FIG. 6 is a diagram showing the relationship between the length L of the protrusion 16 with respect to the outer diameter D of the screw 12 and the air reservoir. As shown in the figure, the increase in the outer diameter D of the screw 12 tends to cause retention and air retention occurs. For example, when the outer diameter dimension D is doubled, the length of the entire apparatus is also doubled. On the other hand, the volume of the narrowed portion S of the forming head 14 is 8 times the cube of 2. For this reason, when the outer diameter dimension D of the screw 12 is increased as much as possible, the influence is great, and the rubber composition pushed out by the screw 12 to the throttle portion S is retained and an air pocket is generated.
Therefore, as shown in the experimental results shown in FIG. 6, a particularly great effect can be obtained when the outer diameter D of the screw 12 is 200 mm or more. Further, since a proportional relationship is established between the outer diameter dimension D of the screw 12 and the outer diameter dimension of the shaft portion 15A, the length L of the protruding portion 16 corresponding to the change of the outer diameter dimension D of the screw 12 is established. Only need to be considered.

  The table in FIG. 6A summarizes the defect occurrence rates in the first 30 pieces from the start of operation of the extrusion molding apparatus. As shown in the figure, (the length L of the protruding portion 16) / (screw outer diameter dimension D) is 1 as a critical value, and the (length L of the protruding portion 16) / (screw outer diameter dimension D) is 1. Is smaller than the above, a defect occurs. When (the length L of the protrusion 16) / (screw outer diameter D) is 1 or more, the occurrence of a defect immediately after the start of molding may be suppressed. Recognize. That is, the length L of the protruding portion 16 protruding from the screw main body 15 is set to the outer diameter size D of the screw 12 so that the ratio of the (length L of the protruding portion 16) to the (screw outer diameter D) is 1 or more. By making the length longer than this, it becomes possible to perform molding with no defects immediately after the start of extrusion molding.

Moreover, the graph shown in FIG.6 (b) investigated the influence of the length L of the protrusion part by the difference in the screw outer-diameter dimension D. FIG. The diagram plots P1 to P3 shown in the figure indicate the length L of the protruding portion in each screw having a screw outer diameter D of 6 mm, 8 mm, and 10 mm (254 mm), respectively. In addition, the length L of each protrusion corresponds to the length L of the conventional protrusion. Next to each of the diamond plots P1 to P3, it indicates whether or not there is a defect when the extrusion is actually performed, meaning that OK does not occur immediately after the start of molding, and NG causes a defect immediately after the start of molding. Means that In addition, the diagram plot P3 has shown about the extrusion molding apparatus of the comparative example shown to Fig.3 (a). Moreover, the square plot Q1 has shown about the extrusion molding apparatus which concerns on this invention shown in above-mentioned FIG.3 (b).
As shown in FIG. 6B, the lengths L of the protruding portions of the 6 mm and 8 mm screws are about 50 mm and 100 mm, respectively. In this case, it was confirmed that the molding was formed without air accumulation immediately after the start of the extrusion molding operation. However, in the 10 mm extrusion molding apparatus, as shown in FIG. Air pockets were found inside.
From this result, it can be seen that in the extrusion molding apparatus having a screw outer diameter D of 8 mm or less, the length of the conventional protrusion may be used. On the other hand, in an extrusion molding apparatus having a screw outer diameter dimension D of 10 mm, molding failure occurs, and therefore, air accumulation has started to occur in the range of the screw outer diameter dimension D of 8 mm to 10 mm. Therefore, based on the results shown in the table of FIG. 6A, the screw outer diameter D is 8 mm or more in order to perform extrusion without causing air accumulation in the molded product immediately after the start of operation. It can be seen that in the extrusion molding apparatus having the screw, the length L of the protruding portion may be extended so as to be equal to or longer than the screw outer diameter D. That is, when the screw outer diameter D shown in the diagram plot P2 is 8 mm, the length L of the protruding portion is extended as shown by a circle plot R1 in the figure, and the screw outer diameter D shown in the diagram plot P3 is 10. In the case of scissors, the length L of the protrusion may be extended by 50 mm as indicated by a circle plot R2 in the figure. Therefore, in an extrusion molding apparatus having a screw having a screw outer diameter D of 8 mm or more, the length L of the protruding portion is longer than this straight line, with the straight line extending the line segment f connecting the round plots R1, R2 as the lower limit. By setting so as to be, it becomes possible to reliably suppress the occurrence of defects immediately after the start of operation. The screw outer diameter dimensions of 6 mm, 8 mm, and 10 mm are approximately regarded as 150 mm, 200 mm, and 250 mm in MKS units.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the said embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made to the above-described embodiments, and embodiments to which such changes or modifications are added can also be included in the technical scope of the present invention. It is clear from the description.
For example, as shown in FIG. 7 (a), the shape of the protruding portion 16 on the tip side may be a truncated cone shape whose tip side smaller than the outer diameter D of the screw body portion 15 is tapered. As shown in FIG. 7B, it may be a cylindrical shape in which the shaft portion 15 </ b> A of the screw 12 is extended as it is. It is set to be longer than the outer diameter dimension D, and preferably enters the narrowed portion S of the forming head 14. In addition, in the case as shown in FIGS. 7A and 7B, the tip of the protrusion 16 may be formed in a spherical shape.

1 Extruder, 11 Cylinder, 12 Screw, 14 Molding Head,
15 Screw body part, 16 protrusion part.

Claims (6)

A cylinder having a charging part capable of charging the rubber composition on one end side;
A screw having a screw main body portion that is rotatably provided inside the cylinder and transfers the rubber composition toward the other end of the cylinder while kneading the rubber composition;
A molding head provided on the other end side of the cylinder and having a squeezing part for extruding the rubber composition transferred by the screw main body part from a molding port smaller than a cross-sectional area of the cylinder;
An extrusion apparatus comprising:
Provided at the end of the screw main body portion on the molding head side is a protrusion having a size smaller than the outer diameter of the screw main body portion and longer than the outer diameter of the screw main body portion and protruding toward the molding port side. An extrusion apparatus characterized by the above.   The extrusion apparatus according to claim 1, wherein the protruding portion enters the narrowed portion.   The extrusion molding apparatus according to claim 1, wherein the protruding portion is tapered toward the molding port side.   The extrusion apparatus according to any one of claims 1 to 3, wherein the protrusion has a conical shape.   The extrusion molding apparatus according to any one of claims 1 to 4, wherein an outer diameter of the screw main body is 200 mm or more. The extrusion molding apparatus according to any one of claims 1 to 5, wherein a surface of the protruding portion is mirror-finished.

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