JP2018039207A - Rubber extrusion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber extrusion device capable of suppressing shrinkage after extrusion.SOLUTION: A rubber extrusion device 1 includes a casing 2 and a screw shaft 3 housed inside the casing 2. The casing 2 includes: an insert port 21 for inserting unvulcanized rubber G into the casing 2; a discharge port 22 for discharging the unvulcanized rubber G; and a deairing port 23 which is located therebetween and connected to a vacuum device. The screw shaft 3 includes a helical blade 32 for mixing and extruding the unvulcanized rubber G inside the casing 2 toward the discharge port 22. The helical blade 32 includes a first blade 41 on an upstream side of the deairing port 23 and a second blade 42 on a downstream side of the deairing port 23. A lead angle α2 of the second blade 42 in a part right before the discharge port 22 is smaller than a lead angle α1 of the second blade 42 in a part right after the deairing port 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber extrusion device for extruding unvulcanized rubber.

  Conventionally, in a rubber extrusion device, a deaeration port for degassing an unvulcanized rubber is provided in a casing.

  For example, Patent Document 1 below discloses a rubber extrusion device in which the transfer speed after degassing is higher than the transfer speed before degassing. In addition, in the rubber extrusion device, the filling property of the rubber is improved by providing a connecting piece for connecting the axially opposed screw blades immediately before the deaeration port to reduce the cross section of the flow path of the unvulcanized rubber. The rubber is prevented from being discharged from the deaeration port. Furthermore, the lead angle of the screw blade after degassing is made larger than the lead angle of the screw blade before degassing so that air does not enter the degassed unvulcanized rubber. The transfer rate of unvulcanized rubber is increased (see paragraphs “0014” and “0015” of the same document).

Japanese Patent No. 4863392

  In general, it is known that unvulcanized rubber extruded from a discharge port of a rubber extrusion device shrinks over time. In the rubber extrusion device disclosed in Patent Document 1, the lead angle of the screw blade from the deaeration port to the discharge port is large, and therefore the pressure of the unvulcanized rubber at the discharge port tends to decrease. For this reason, the shrinkage | contraction after extrusion becomes large and there exists a possibility of affecting the dimensional accuracy of unvulcanized rubber.

  The present invention has been devised in view of the actual situation as described above, and has as its main object to provide a rubber extrusion device capable of suppressing shrinkage after extrusion.

  The present invention is a rubber extrusion device for extruding unvulcanized rubber, and includes a casing and a screw shaft accommodated in the casing, and the casing puts the unvulcanized rubber inside the casing. An injection port for charging, a discharge port for discharging the unvulcanized rubber, and a deaeration port located between them and connected to a vacuum device; A spiral blade that extrudes the unvulcanized rubber while kneading the unvulcanized rubber toward the discharge port, and the spiral blade is a first blade on the upstream side of the degassing port and a downstream side of the degassing port. A lead angle α2 of the second blade immediately before the discharge port is smaller than a lead angle α1 of the second blade immediately after the deaeration port. .

  In the rubber extrusion device according to the present invention, it is preferable that the lead angle α of the second blade decreases stepwise toward the discharge port.

  In the rubber extrusion device according to the present invention, it is preferable that the lead angle α of the second blade gradually decreases toward the discharge port.

  In the rubber extrusion device according to the present invention, it is preferable that the lead angle α of the second blade gradually decreases toward the discharge port over the entire range of the second blade.

  In the rubber extrusion device according to the present invention, it is desirable that the lead angle α of the second blade is uniformly reduced toward the discharge port.

  In the rubber extrusion device according to the present invention, the interval between the second blades adjacent in the screw axial direction immediately before the discharge port is the second adjacent to the screw axial direction immediately after the degassing port. It is desirable that the distance is 5% to 20% smaller than the blade interval.

  In the rubber extrusion device according to the present invention, it is preferable that the rubber extruding device further includes a compression portion for increasing the pressure of the unvulcanized rubber at a portion immediately before the deaeration port.

  In the rubber extrusion device of the present invention, the spiral blade of the screw shaft includes the first blade on the upstream side and the second blade on the downstream side of the deaeration port, and the lead angle α2 of the second blade immediately before the discharge port. Is smaller than the lead angle α1 of the second blade immediately after the deaeration port. Such a second blade increases the pressure of the unvulcanized rubber passing through the discharge port, and the shrinkage of the unvulcanized rubber after extrusion is suppressed.

It is sectional drawing which shows one Embodiment of the rubber extrusion apparatus of this invention. It is a figure which expands and shows the screw shaft of the downstream from the deaeration port of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a rubber extrusion device 1 according to this embodiment. As shown in FIG. 1, the rubber extrusion device 1 includes a casing 2 and a screw shaft 3 accommodated in the casing 2. On the downstream side of the casing 2, a pair of calender rolls 7 for rolling the unvulcanized rubber extruded by the rubber extrusion device 1 is provided.

  The casing 2 is located between the inlet 21 for feeding the unvulcanized rubber G into the casing 2, the outlet 22 for discharging the unvulcanized rubber G, and a vacuum device (not shown). And a deaeration port 23 connected to the other.

  The screw shaft 3 includes a shaft main body 31 and a spiral wing 32 protruding from the shaft main body 31 to the outside in the radial direction of the screw shaft 3. The spiral blade 32 is continuously formed in the circumferential direction while being displaced in the axial direction of the screw shaft 3. The spiral blade 32 pushes the unvulcanized rubber G in the casing 2 toward the discharge port 22 while kneading.

  The discharge port 22 is formed in a base 24 that is attached to the tip on the downstream side of the casing 2. The unvulcanized rubber G discharged from the discharge port 22 is supplied to, for example, the calendar roll 7 and rolled into a rubber sheet having a predetermined shape. A gear pump or the like may be provided between the base 24 and the calendar roll 7.

  The spiral blade 32 includes a first blade 41 on the upstream side of the deaeration port 23 and a second blade 42 on the downstream side of the deaeration port 23. The downstream end of the first blade 41 is formed continuously with the upstream end of the second blade 42. Thereby, the first blade 41 and the second blade 42 constitute one spiral blade 32 that is continuous in the axial direction of the screw shaft 3.

  The first blade 41 is formed with a lead angle β, and the second blade 42 is formed with a lead angle α.

  FIG. 2 shows the screw shaft 3 on the downstream side of the deaeration port 23 in an enlarged manner. In the present embodiment, the lead angle α of the second blade 42 is not constant, and the lead angle α2 of the second blade 42 immediately before the discharge port 22 is the lead angle of the second blade 42 immediately after the deaeration port 23. It is smaller than α1. That is, the interval (lead) L2 between the second blades 42 adjacent in the axial direction of the screw shaft 3 immediately before the discharge port 22 is the second blade adjacent in the axial direction of the screw shaft 3 immediately after the deaeration port 23. 42 is smaller than the interval L1.

  By such a second blade 42, the flow path cross section of the unvulcanized rubber G at the portion immediately before the discharge port 22 is reduced, and the pressure of the unvulcanized rubber G passing through the discharge port 22 is increased. Therefore, the time-dependent shrinkage of the unvulcanized rubber G after extrusion is suppressed, and the dimensional accuracy of the unvulcanized rubber G after extrusion can be increased.

  It is desirable that the lead angle α of the second blade 42 decreases stepwise toward the discharge port 22. Such a second blade 42 increases the pressure of the unvulcanized rubber G stepwise toward the discharge port 22. Thereby, excessive heat generation of the unvulcanized rubber G is suppressed, and vulcanization of the unvulcanized rubber G in the casing 2 is suppressed.

  It is desirable that the lead angle α of the second blade 42 gradually decreases toward the discharge port 22. By such second blades 42, the pressure of the unvulcanized rubber G is gradually increased toward the discharge port 22, and excessive heat generation of the unvulcanized rubber G is further suppressed. Vulcanization of the vulcanized rubber G is suppressed.

  Furthermore, it is desirable that the lead angle α of the second blade 42 gradually decreases toward the discharge port 22 over the entire range of the second blade 42. By such second blades 42, excessive heat generation of the unvulcanized rubber G is further suppressed, and vulcanization of the unvulcanized rubber G in the casing 2 is suppressed.

  In addition, it is desirable that the lead angle α of the second blade 42 decreases uniformly toward the discharge port 22. By such a second blade 42, the flow path cross section of the unvulcanized rubber G is monotonously reduced, the excessive heat generation of the unvulcanized rubber G is further suppressed, and the unvulcanized rubber G in the casing 2 is suppressed. Vulcanization is suppressed.

  The interval L2 between the second blades 42 immediately before the discharge port 22 is desirably 5% to 20% smaller than the interval L1 between the second blades 42 immediately after the deaeration port 23. That is, the ratio L2 / L1 between the distance L2 and the distance L1 is preferably 0.80 to 0.95. When the ratio L2 / L1 is less than 0.80, the unvulcanized rubber G excessively generates heat in the casing 2 and vulcanization may proceed. When the ratio L2 / L1 exceeds 0.95, the pressure of the unvulcanized rubber G passing through the discharge port 22 is not sufficiently increased, and the shrinkage of the unvulcanized rubber G after extrusion may not be sufficiently suppressed. .

  As shown in FIG. 1, a compression portion 43 that increases the pressure of the unvulcanized rubber G is provided immediately before the deaeration port 23. The compression part 43 is implement | achieved by reducing the flow path cross section of the unvulcanized rubber G in the part immediately before the deaeration port 23, for example. In the present embodiment, a protruding portion 44 that protrudes in a dam shape from the shaft body 31 to the radially outer side of the screw shaft 3 is provided immediately before the deaeration port 23. The protrusion 44 connects between the blade surfaces facing each other in the axial direction of the screw shaft 3 of the first blade 41. The protrusion 44 may not be connected to the opposed blade surface. Further, the lead angle β of the first blade 41 may be formed small immediately before the deaeration port 23.

An unvulcanized rubber sheet was extruded using the rubber extrusion apparatus shown in FIG. 1 and a screw shaft based on the specifications of Table 1, and the pressure, shrink resistance and vulcanization resistance in the casing were tested. The specifications and test methods of the rubber extruder are as follows.
Casing diameter: φ90mm
Screw shaft rotation speed: 30.0rpm

<Pressure in casing>
The pressure at the time of extruding unvulcanized rubber was measured by a pressure gauge provided immediately before the deaeration port and immediately before the discharge port in the casing.

<Shrink resistance>
Shrink resistance was evaluated based on the thickness and width of the unvulcanized rubber measured 20 minutes after being discharged from the discharge port. The result is expressed by a score of Example 1 being 100, and the larger the numerical value, the smaller the shrink and the better.
<Vulcanization resistance>
The Mooney viscosity and scorch time of the unvulcanized rubber discharged from the discharge port 22 were measured, and the vulcanization resistance was evaluated. The result is expressed by a score of Example 1 being 100. The larger the value, the smaller the progress of vulcanization and the better.

  As a result of the test, it was confirmed that the rubber extruder of the example had a larger pressure immediately before the discharge port than the comparative example, and the shrink resistance performance was good.

  As mentioned above, although embodiment of this invention was described in detail, this invention is changed and implemented in various aspects, without being limited to said specific embodiment.

DESCRIPTION OF SYMBOLS 1 Rubber extrusion apparatus 2 Casing 3 Screw shaft 21 Input port 22 Discharge port 23 Deaeration port 32 Spiral blade 41 First blade 42 Second blade α Lead angle G Unvulcanized rubber

Claims (7)

A rubber extrusion device for extruding unvulcanized rubber,
A casing and a screw shaft housed in the casing;
The casing includes an inlet for introducing the unvulcanized rubber into the casing, an outlet for discharging the unvulcanized rubber, and a detachment unit positioned therebetween and connected to a vacuum device. Including mouthpieces,
The screw shaft includes a spiral blade that pushes out the unvulcanized rubber in the casing while kneading the unvulcanized rubber toward the discharge port,
The spiral wing includes a first wing upstream of the deaeration port and a second wing downstream of the deaeration port,
The rubber extrusion device according to claim 1, wherein a lead angle α2 of the second blade immediately before the discharge port is smaller than a lead angle α1 of the second blade immediately after the deaeration port.   The rubber extrusion device according to claim 1, wherein the lead angle α of the second blade gradually decreases toward the discharge port.   The rubber extrusion device according to claim 2, wherein the lead angle α of the second blade gradually decreases toward the discharge port.   The rubber extrusion device according to claim 3, wherein the lead angle α of the second blade gradually decreases toward the discharge port over the entire range of the second blade.   The rubber extrusion device according to any one of claims 2 to 4, wherein the lead angle α of the second blade uniformly decreases toward the discharge port.   The interval between the second blades adjacent in the screw axis direction immediately before the discharge port is 5% to 20% higher than the interval between the second blades adjacent in the screw axis direction immediately after the deaeration port. The rubber extrusion device according to claim 1, which is smaller by%.   The rubber extrusion device according to any one of claims 1 to 6, further comprising a compression portion for increasing the pressure of the unvulcanized rubber immediately before the deaeration port.

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