JP2004148601A - Method for producing rubber sheet body containing short fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and efficiently form a rubber sheet body in which short fibers are oriented in the thickness direction and which is excellent in dimensional precision and surface properties. <P>SOLUTION: A cylindrical rubber substrate G1 in which the short fibers (f) are oriented in the extrusion direction is cut at short intervals (t) in the extrusion direction to form tabular pellets G2. After the pellets G2 are arranged in the cavity 3 of a pressing mold 2, the pellet laminate G3 is press-molded in the cavity 3 to form the rubber sheet body G0 in which the pellets G2 are bonded integrally, and the short fibers are oriented in the thickness direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a short-fiber-containing rubber sheet body in which short fibers are oriented in a thickness direction, particularly a short-fiber-containing rubber sheet body suitable as tread rubber of a tire.
[0002]
[Prior art]
In the case of studless tires, it is necessary to increase road digging friction and adhesive friction in order to improve the performance on ice, and various studies have been attempted to increase the coefficient of friction of tread rubber on icy road surfaces. As one of them, it has been proposed to mix short fibers in the tread rubber. In particular, by arranging the short fibers in the tread thickness direction (tire radial direction), the ability to excavate the road surface is increased, and a higher friction force is obtained. Is known to be obtained.
[0003]
Meanwhile, as shown in FIG. 5 (A), the tread rubber is usually formed by a belt-shaped rubber member g1 continuously extruded and formed by a calender roll or an extruder. Therefore, the short fibers f in the rubber are oriented along the extrusion direction (length direction) due to the rubber flow, and when the rubber member g1 is used as it is for the tread rubber Tg, the short fibers f become in the tire circumferential direction. It will be oriented along.
[0004]
Therefore, in order to orient the short fibers in the thickness direction, as shown in FIG. 5B, a thin rubber member g2 to be extruded is zigzag folded with an amplitude corresponding to the thickness t of the tread rubber Tg ( (Patent Document 1) and a method of cutting a thin rubber member g2 to a width corresponding to the thickness t of a tread rubber Tg as shown in FIG. 2) has been proposed.
[0005]
[Patent Document 1]
JP 2001-310396 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-210842
[Problems to be solved by the invention]
However, in these methods, since high accuracy is required for folding the rubber member g2 and overlapping the cut pieces g2a, a large amount of time and labor is required for the operation, and mass production has been difficult. Further, there is a problem that it is difficult to stably form a high-quality tread rubber Tg having excellent dimensional accuracy and surface properties, such as unevenness on the surface and variations in external dimensions.
[0007]
Therefore, the present invention provides a rod-shaped rubber substrate to be extruded, which is sequentially cut at small intervals in the extrusion direction to form flat pellets, and the pellets are formed into a plurality of layers in a cavity for molding a rubber sheet body of a press die. After laying, on the basis of press molding, a short-fiber-containing rubber sheet body in which short fibers are oriented in the thickness direction can be easily and efficiently formed with excellent dimensional accuracy and surface properties, It is an object of the present invention to provide a method for producing a short-fiber-containing rubber sheet that can greatly contribute to its mass production.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is a method for producing a rubber sheet body containing short fibers in which short fibers are oriented in a thickness direction of the rubber sheet body,
An extrusion step of extruding an unvulcanized rubber material containing short fibers to form a rod-shaped rubber substrate in which the short fibers are oriented substantially in the extrusion direction;
A pellet forming step of forming a plurality of flat pellets in which the short fibers are oriented in the thickness direction by sequentially cutting the rod-shaped rubber substrate at small intervals in the extrusion direction,
A lamination step of forming a pellet laminate by laying the pellets in a plurality of layers and arranging them in the cavity of a press mold having a cavity in which a rubber sheet body can be formed,
And a press step of forming a rubber sheet body in which the pellets are joined together and the short fibers are oriented in the thickness direction by press-molding the pellet laminate in the cavity.
[0009]
The invention according to claim 2 is characterized in that the pellets have a disk shape.
[0010]
According to a third aspect of the present invention, the rubber sheet is a tread rubber for manufacturing a tire.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to illustrated examples.
1 and 2 are process diagrams conceptually showing a method for producing a rubber sheet body containing short fibers according to the present invention.
[0012]
In FIGS. 1 and 2, a method for manufacturing a rubber sheet body containing short fibers is as follows.
(1) an extrusion step S1 for forming a rod-shaped rubber substrate G1 in which the short fibers f are substantially oriented in the extrusion direction;
(2) a pellet forming step S2 of sequentially cutting the rod-shaped rubber substrate G1 at small intervals t in the extrusion direction to form a flat pellet G2 in which the short fibers f are oriented in the thickness direction;
{Circle around (3)} A laminating step S3 of forming the pellet laminate G3 by laying out the pellets G2 in the cavity 3 of the press mold 2 and arranging them.
{Circle around (4)} A pressing step S4 in which the pellet laminate G3 is press-formed in the cavity 3 to form a rubber sheet G0 in which the pellets G2 are integrally joined and the short fibers f are oriented in the thickness direction. And is comprised.
In this example, the case where the rubber sheet body G0 is formed as a tread rubber Tg for manufacturing a tire is illustrated.
[0013]
Specifically, in the extrusion step S1, a short fiber f is substantially oriented in the extrusion direction by extruding an unvulcanized rubber material containing short fibers using a rubber extruder having a known structure such as a screw extruder. The rod-shaped rubber substrate G1 is continuously formed. The rod-shaped rubber substrate G1 is preferably extruded and formed as a rod-shaped body having a circular cross section from the viewpoint of the workability of spreading the pellets G2 in the laminating step S3.
[0014]
As the unvulcanized rubber material containing short fibers, for example, it is desirable to mix 0.5 to 20 parts by weight of the short fiber f with respect to 100 parts by weight of the rubber component. It is compounded and kneaded together with chemicals such as agents. As the rubber component, a diene rubber is preferable. For example, one or more of natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, and the like can be blended and used.
[0015]
Further, as the short fiber f, any of an organic substance and an inorganic substance can be adopted. However, in the case of the tread rubber Tg as in this example, there is no risk of damaging the road surface and a non-metal short fiber f such as carbon fiber or glass fiber having a relatively small difference in wear rate with the rubber is used. However, this is preferable also in ensuring excellent grounding properties on an icy road surface. Particularly, the glass fiber or the carbon fiber is preferable because it is easily broken and orientated uniformly in the rubber because the glass fiber or the carbon fiber is folded into an appropriate length and shortened in the process of kneading the rubber.
[0016]
Next, in the pellet forming step S2, the rod-shaped rubber substrate G1 is sequentially cut at small intervals t in the extrusion direction to form flat (disk-shaped in this example) pellets G2. At this time, a cutting tool having cutter teeth is attached to the front end of the rubber extruder, and the rod-shaped rubber base G1 extruded from the discharge port of the rubber extruder is sequentially cut at the position of the discharge port. It is preferable from the viewpoint of cutting efficiency and the like. Note that a pellet G2 may be formed by providing a so-called pelletizer at the front end of the rubber extruder.
[0017]
In the laminating step S3, the pellet G2 is placed in the cavity 3 on the lower mold 2L side by using the press mold 2 (shown in FIG. 3) in which the cavity 3 for molding the rubber sheet body is recessed in the split surface s. A plurality of layers are laid and arranged to form a pellet laminate G3. The press die 2 is a vertically separated split die comprising a lower die 2L and an upper die 2U. A chamber 4 is formed. The cavity 3 can be formed only in the lower mold 2L.
[0018]
Here, in the pellet laminate G3, the pellets G2 are preferably arranged as densely as possible. Therefore, when the pellets G2 are disk-shaped as in this example, as shown in FIG. 4A, each pellet G2 is moved in the row direction (the width direction of the rubber sheet body in the figure) and the column direction (the rubber sheet in the figure). It is preferable that the pellets G2 are aligned and arranged in a row or a row by the radius of the pellets G2, as shown in FIG. 4B. In the former case, it is more preferable to insert an auxiliary rubber K for filling in the gap Y between the pellets G2. As the auxiliary rubber K, similarly to the pellet G2, one in which short fibers are oriented may be used, or one formed only of rubber containing no short fibers may be used.
[0019]
In addition, the reason why the pellet G2 is formed in a disk shape in this example is that there is no restriction on the orientation of the pellet G2, and the efficiency of laying work can be improved such that the pellet G2 can be arranged in any direction. However, as shown in FIG. 4C, the pellets G2 can be formed in a rectangular shape such as a square shape, and in such a case, the pellets G2 can be arranged more densely.
[0020]
In the pellet G2, the diameter D is set in advance in the extrusion step S1 so that an integer multiple of the diameter D (the width D in the case of a square shape) becomes a predetermined width W of the rubber sheet body G0. You. In the pellet laminate G3, the substantial volume V (not including the volume of the gap) is larger than the volume V0 of the rubber sheet G0 (corresponding to the volume of the molding chamber 4 in the press die 2). , The stack height H1 and the number of stacks are set. The small interval t of the cutting, which is the thickness t of the pellet G2, is preferably 100 to 150% of a predetermined thickness t0 (corresponding to the height of the molding chamber 4) of the rubber sheet body G0. From the viewpoint of handleability, it is also preferable that the thickness be 5 mm or more.
[0021]
Next, in the pressing step S4, the pellet laminate G3 is press-formed in the forming chamber 4. At this time, due to the pressing pressure, the respective pellets G2 are integrally joined, and a part of the rubber of the pellets G2 flows and fills the gap Y. As a result, it is possible to form the rubber sheet body G0 having no air pocket. For this purpose, a discharge hole (not shown) for discharging air and excess rubber is formed in the press die 2. In the pressing step S4, the flow of the rubber in the press molding is slight, so that the orientation of the short fibers f is not impaired. Therefore, in the rubber sheet body G0, the short fibers along the thickness direction thereof are provided. Can be maintained.
[0022]
As described above, in the method for producing a rubber sheet body of the present invention, the pellet G2 in which the short fibers f are oriented in the thickness direction is laid in a plurality of layers in the cavity 3 to form a pellet laminate G3, and then the pellet laminate G3 is formed. The body G3 is press-formed into a rubber sheet body G0 of a predetermined size.
[0023]
Therefore, the flow of rubber during press molding is suppressed, and the orientation of the short fibers in the thickness direction can be maintained. Also, since excellent dimensional accuracy and surface properties are ensured by press molding, high precision is not required for the work of laying the pellets G2, and the working efficiency is improved. And by these synergistic effects, a rubber sheet body in which short fibers are oriented in the thickness direction can be stably and efficiently produced with high quality.
[0024]
As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.
[0025]
【The invention's effect】
Since the present invention is configured as described above, a rubber sheet body in which short fibers are oriented in the thickness direction can be easily and efficiently formed with excellent dimensional accuracy and surface properties. Can greatly contribute to the development of
[Brief description of the drawings]
FIG. 1 is a process chart conceptually showing an extrusion step, a pellet forming step, and a laminating step in the method for producing a short fiber-containing rubber sheet of the present invention.
FIG. 2 is a process diagram showing a pressing process in the manufacturing method.
FIG. 3 is a perspective view schematically showing a press die used for the same.
FIGS. 4A to 4C are diagrams illustrating the arrangement of pellets in a cavity.
FIGS. 5A to 5C are diagrams illustrating a conventional technique.
[Explanation of symbols]
2 Press mold 3 Cavity f Short fiber G0 Rubber sheet G1 Bar-shaped rubber base G2 Pellet G3 Pellet laminate S1 Extrusion step S2 Pellet forming step S3 Laminating step S4 Pressing step Tg Tread rubber

Claims (3)

A method for producing a rubber sheet body containing short fibers in which short fibers are oriented in a thickness direction of the rubber sheet body,
An extrusion step of extruding an unvulcanized rubber material containing short fibers to form a rod-shaped rubber substrate in which the short fibers are oriented substantially in the extrusion direction;
A pellet forming step of forming a plurality of flat pellets in which the short fibers are oriented in the thickness direction by sequentially cutting the rod-shaped rubber substrate at small intervals in the extrusion direction,
A lamination step of forming a pellet laminate by laying the pellets in a plurality of layers and arranging them in the cavity of a press mold having a cavity in which a rubber sheet body can be formed,
Press-forming the pellet laminate in the cavity to form a rubber sheet body in which the respective pellets are joined together and the short fibers are oriented in the thickness direction. A method for producing a rubber sheet. The method according to claim 1, wherein the pellet has a disk shape. The method for producing a rubber sheet containing short fibers according to claim 1 or 2, wherein the rubber sheet body is a tread rubber for producing a tire.

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