JP6235863B2 - Rubber extrusion apparatus and method for producing rubber extrusion - Google Patents

Description

  The present invention relates to a rubber extrusion device capable of suppressing molding defects when a rubber extruded body having a flat cross section is extruded and a method for producing the rubber extruded body.

  In a pneumatic tire, the required characteristics in each part are different. For this reason, different compounded rubbers are used for rubber members such as tread rubber, sidewall rubber, bead apex rubber, clinch rubber, and cushion rubber disposed in each part.

  On the other hand, such a rubber member is formed using a flat belt-like rubber extrudate that is extruded from a rubber extruding device with a unique cross-sectional shape. However, when a rubber extrudate having a flat cross section is extruded by a rubber extruding device, as shown in FIG. 8 (A), the rubber extrudate a may have a rubber cut b at the side edge portion on the outer side in the width direction, There is a tendency that molding defects such as a crusted surface roughness c occur on the surface on the side edge side.

As a cause of such molding defects, as shown in FIG. 8B, the speed distribution in the width direction of the rubber g in the flow path d can be considered. In the flow path d, the rubber g advances while slipping from the flow path wall surface ds. For this reason, when the resistance to the flow path wall surface ds is large, the rubber surface is pulled and a crusted surface roughness c is generated. If the resistance is large, the flow velocity difference (V ₀ -V ₁ ) between the flow velocity V ₀ on the center side in the width direction and the flow velocity V ₁ on the side edge side becomes large. The side edge portion of the rubber is pulled in the pushing direction, and a piece of rubber b is generated.

Particularly in recent years, as shown in FIG. 8A, for example, a side wall rubber a1, a clinch rubber a2, and a cushion rubber a3 are often integrally extruded as a multilayer rubber extruded body a using a multilayer extrusion apparatus. . At this time, when the viscosity of the rubber on the center side in the width direction is relatively low, or when the viscosity of the rubber on the side edge side is high, the flow rate difference (V ₀ −V ₁ ) or the flow path wall surface ds As the resistance increases, the occurrence of rubber breakage b and surface roughness c becomes significant.

  Patent documents relating to the structure of the rubber extrusion device include the following.

JP 2005-349597 A

  Accordingly, the present invention provides a rubber extrusion device that can easily suppress a molding failure such as rubber breakage and surface roughness on the side edge in the width direction when extruding a rubber extrudate having a flat cross section, and manufacture of the rubber extrudate. The challenge is to provide a method.

A first invention is a rubber extrusion device that forms a flat rubber extruded body having a cross-sectional width larger than a cross-sectional thickness by rubber extruded from a rubber extruder,
An extrusion head having a head flow path attached to a front end portion of the rubber extruder and guiding the rubber from the rubber extruder to a discharge port opened on the front end side;
A pre-former having a pre-former channel attached to the extrusion head and guiding the rubber from the head channel while pre-molding to a pre-forming port opened on the front end side;
An extrusion die attached to the preformer and having a molding channel for molding the rubber extrudate by extruding a pre-formed rubber from the preformer channel from a molding port opened on the front end side; ,
It has a heating means for heating the channel wall surface forming the preformer channel.

In the rubber extruding apparatus according to the first aspect of the invention, the heating means is preferably provided in the preformer, and the heating means is provided on the outer side in the width direction of the channel wall surface forming the preformer channel. It is preferable to heat at least one channel wall surface.

In the rubber extrusion device according to the first invention, a plurality of rubber extruders are attached to the extrusion head, and the head flow path is formed as a plurality of individual flow paths through which rubber from each of the rubber extruders individually passes. As
The pre-former flow path includes a main merge flow path portion in which rubber from each individual flow path merges into one,
Moreover, it is preferable that the heating means heats at least one channel wall surface on the outer side in the width direction in the main merging channel portion.

  In the rubber extrusion device according to the first invention, the heating means preferably heats the flow passage wall surface on the side at a temperature in the range of 80 to 130 ° C.

  In the rubber extruding device according to the first invention, the preformer includes a main preform die having the main merging flow path portion and a base preformer that holds the main preform die, and the heating The means is preferably provided in the main preform die.

A second invention is a method for producing a rubber extrudate that forms a flat rubber extrudate having a cross-sectional width larger than a cross-sectional thickness by rubber extruded from a rubber extruder,
An extrusion head having a head flow path attached to a front end portion of the rubber extruder and guiding the rubber from the rubber extruder to a discharge port opened on the front end side;
A pre-former having a pre-former channel attached to the extrusion head and guiding the rubber from the head channel while pre-molding to a pre-forming port opened on the front end side;
A rubber which is attached to the preformer and has an extrusion die having a molding channel for molding the rubber extrudate by extruding a preformed rubber from the preformer channel from a molding port opened on the front end side. While using an extrusion device,
It is characterized by comprising an extruding step of extruding rubber while heating the channel wall surface forming the preformer channel.

  In the present invention, the channel wall surface of the preformer channel is heated by the heating means as described above. This heating reduces the resistance between the channel wall surface of the preformer channel and the rubber. Further, the temperature of the rubber rises, and its viscosity is relatively lowered. Therefore, the difference in flow velocity between the center in the width direction and the side edge side is reduced, and the occurrence of rubber breakage on the side edge side and the occurrence of surface roughness on the rubber surface on the side edge side can be suppressed.

It is a front view which shows one Example of the rubber extrusion apparatus of this invention. It is sectional drawing which expands and shows the principal part of an extrusion head. It is a perspective view which shows a preformer and an extrusion die. It is sectional drawing at right angles to the width direction which shows a preformer and an extrusion die. It is a perspective view which shows the preformer flow path of a preformer notionally. (A) is the top view which looked at the main preformer die from the back side (upstream side), (B) is the II sectional view taken on the line. It is sectional drawing which shows an example of a rubber extrusion body. (A) is a perspective view which shows the molding defect which arises in a rubber extrusion body, (B) is a conceptual diagram which shows the speed distribution of the width direction of the rubber | gum in a flow path.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the rubber extrusion apparatus 1 of the present invention is a rubber extruded body 3 (shown in FIG. 7) having a flat cross section whose cross section width is larger than the cross section thickness by the rubber G extruded from the rubber extruder 2. Form.

  In this example, the rubber extrusion device 1 is a multilayer rubber extrusion device, and the cross section is divided into a plurality of rubber regions R as shown in FIG. 7 by rubber G extruded from a plurality of rubber extruders 2. The case where the rubber extrudate 3 is formed is shown. The rubber extrudate 3 of this example is a side rubber for tire formation, and the cross section thereof is a side wall rubber region Ra on the width direction center side made of rubber Ga and a clinch rubber region on the side edge side in the width direction made of rubber Gb. It is divided into Rb and a cushion rubber region Rc on the other side edge in the width direction made of rubber Gc.

  As the rubber extruding machine 2, a screw shaft type well-known structure that pushes out sequentially while kneading the charged rubber is suitably employed. Each rubber extruder 2 is fixedly supported at a desired mounting angle by, for example, a base A, and the front end portion of each rubber extruder 2 (referred to as 2a to 2c when each rubber extruder 2 is distinguished) is Connected to two extrusion heads 4.

  The rubber extrusion device 1 includes the extrusion head 4 to which the front end portion of each rubber extruder 2 is attached, a preformer 5 to be attached to the extrusion head 4, and an extrusion die 6 to be attached to the preformer 5. In the present application, the downstream side in the rubber flow direction is expressed as “front”, and the upstream side is expressed as “rear”.

  As shown in FIG. 2, the extrusion head 4 includes a head flow path 7 that guides the rubber from the rubber extruder 2 to a discharge port 7 o that opens on the front end side. The extrusion head 4 of this example is configured to be divided into a V-block-shaped central head portion 4A and left and right side heads 4B and 4B arranged on both sides thereof. As a result, the inside of the head channel 7 can be opened, and the maintainability is improved.

  As shown in FIGS. 4 and 5, the preformer channel 8 for guiding the rubber Ga to Gc from the head channel 7 to the preformer 5 while preforming it to a preforming port 8 o opened on the front end side. With Further, the extrusion die 6 is provided with a molding channel 9 for molding the rubber extruded body 3 by extruding the pre-formed rubber Gabc from the preformer channel 8 from a molding port 9o opened on the front end side. . 4 conceptually shows a cross section of the preformer 5 in a direction perpendicular to the width direction, and FIG. 5 is a perspective view conceptually showing a main preform die 13 and a sub-preformer die 15 to be described later. FIG.

  In the case of this example, the head flow path 7 includes an individual flow path 10a through which the rubber Ga from the rubber extruder 2a passes individually, an individual flow path 10b through which the rubber Gb from the rubber extruder 2b passes individually, and a rubber extruder. It is formed as an individual flow path 10c through which the rubber Gc from 2c passes individually. A mounting recess 11 for detachably attaching the preformer 5 is formed at the front end of the extrusion head 4, and the discharge ports 7 o of the individual flow paths 10 a to 10 c are opened at the wall surface of the recess 11.

  The pre-former flow path 8 is configured to include a main merging flow path portion 12 where the rubbers Ga to Gc from the individual flow paths 10a to 10c merge into one. In the case of this example, the preformer 5 includes a main preform die 13 having the main merging flow path portion 12 and a base preformer 14 that holds the main preform die 13. More specifically, the preformer 5 of this example includes a main preform die 13, a base preformer 14, and a sub-preformer die 15.

  The sub-preformer die 15 has a sub-merging channel portion 15A that is connected to the individual channels 10a and 10b and joins the rubber Ga and Gb from the individual channels 10a and 10b. The base preformer 14 includes a guide channel portion 14A for guiding the merged rubber Gab from the sub-merged channel portion 15A to the main preform die 13 and the rubber Gc from the individual channel 10c as a main preform die. 13 and a guide flow path portion 14B for guiding to 13. The main pre-former die 13 joins the merged rubber Gab from the sub-merged flow path portion 15A and the rubber Gc from the individual flow path 10c to form one merged rubber Gabc. Have

  Accordingly, the preformer channel 8 of this example is formed by the sub-merged channel portion 15A, the guide channel portions 14A and 14B, and the main merging channel portion 12.

And in this invention, the heating means 20 which heats the flow-path wall surface 8S which makes the said preformer flow path 8 is provided. In this example, the heating means 20 is provided in the preformer 5 and may be referred to as at least one channel wall surface 8Se outside the width direction of the channel wall surface 8S (referred to as a “side channel wall surface 8Se for convenience”). .) Is heated.

  Particularly in this example, the heating means 20 is provided in the main preform die 13, and the flow channel wall surface 8Se on the at least one side in the main merging flow channel portion 12, particularly the flow channel on the side on the cushion rubber region Rc side. The case where the wall surface 8Se1 is heated is illustrated. The rubber Gc forming the cushion rubber region Rc is higher in viscosity than the rubber Ga forming the sidewall rubber region Ra and the rubber Gb forming the clinch rubber region Rb due to the rubber composition, and the occurrence of rubber breakage or surface roughness is remarkable. Become. Therefore, in the case of this example, the flow passage wall surface 8Se1 on the side of the cushion rubber region Rc is heated to suppress rubber breakage and surface roughness.

  Specifically, as shown in FIGS. 6A and 6B, from the viewpoint of workability, the main preform die 13 is divided into block pieces 21 and 22 on one side and the other side in the thickness direction, A cutout portion 23 for forming the main merge channel portion 12 is formed on the dividing surface. Reference numerals 25A and 25B in the figure are inlets into which the merged rubber Gab from the guide flow path portion 14A and the rubber Gc from the guide flow path portion 14B flow, respectively. The merge rubber Gab and the rubber Gc are the main merge. It merges into one in the flow path part 12 and flows out from the preforming port 8o.

  The main preform die 13 includes a mounting hole 26 extending from one side surface in the width direction toward the channel wall surface 8Se1 on the side. The heating means 20 is provided in the mounting hole 26. As the heating means 20, an electric heater 20A using a heating wire is preferably employed because it is compact and temperature control is easy. The heating means 20 heats the channel wall surface 8Se1 on the side to a temperature T8 in the range of 80 to 130 ° C. This temperature T8 means the surface temperature of the side flow path wall surface 8Se1.

By heating to a flow path wall surface 8Se1 of this side, the flow velocity V ₁ is increased by reducing the resistance between the flow path wall 8Se1 and rubber side. As a result, the flow velocity difference (V ₀ −V ₁ ) from the flow velocity V _{0 at the} center in the width direction becomes small, and rubber breakage occurs on the side edge side (cushion rubber side in this example), and surface roughness occurs. Can be suppressed. Also, due to the heating, the temperature of the rubber itself rises and its viscosity is relatively lowered. This is also considered to contribute to the reduction of the flow velocity difference (V ₀ -V ₁ ). In addition, when temperature T8 is less than 80 degreeC, the said effect will become inadequate. On the other hand, even if the temperature exceeds 130 ° C., a further increase in the above effect cannot be expected. Conversely, energy is wasted and the rubber is adversely affected such as scorch.

  The heating means 20 heats not only the channel wall surface 8Se1 on the side but also the channel wall surface 8Sh in the thickness direction in the vicinity thereof by heat transfer. However, the temperature of the channel wall surface 8Sh in the thickness direction may be not more than the range of 80 to 130 ° C. In this example, the front end of the heating means 20 is positioned inward in the width direction with respect to the flow passage wall surface 8Se1 on the side, and thus a part of the flow passage wall surface 8Sh in the thickness direction is also in the range of 80 to 130 ° C. To be heated. The width direction distance L from the channel wall surface 8Se1 on the side of the tip of the heating means 20 is 25% or less of the entire preformer channel width L8 which is the distance between the channel wall surfaces 8Se and 8Se on both sides. Preferably there is.

  In this example, the case where the heating means 20 is provided only on the cushion rubber region Rc side is shown. However, similar heating means 20 may be provided on the clinch rubber region Rb side to heat the flow path wall surface 8Se on both sides. Needless to say, the structure of the preformer 5 and the preformer flow path 8 can be appropriately changed according to the shape and structure of the rubber extruded body 3 to be extruded. Also, the rubber extrusion device 1 can be configured as a multi-layer type such as a two-layer type, a four-layer type, or a single-layer type in addition to the three-multi-layer type. The structures of the preformer 5 and the extrusion die 6 can be changed as appropriate.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the effect of the present invention, as an example, a rubber extrusion device 1 (side rubber for tire formation) having a cross-sectional structure shown in FIG. Extrusion molding was carried out at (17 mm / min). A heating means 20 is embedded in the main preform die 13 on the cushion rubber region Rc side to heat the flow channel wall surface 8Se1 on the cushion rubber region Rc side in the main merging flow channel portion. A heating wire (200 V, 180 W) was used as the heating means 20.

  Then, with the passage of time t from the start of extrusion, the change in the temperature Tc of the rubber Gc in the cushion rubber region Rc, the temperature Ta of the rubber Ga in the sidewall rubber region Ra, the temperature Tb of the rubber Gb in the clinch rubber region Rb, and the extrusion Changes in the flow rate Vc of the rubber Gc in the cushion rubber region Rc, the flow rate Va of the rubber Ga in the sidewall rubber region Ra, and the flow rate Vb of the rubber Gb in the clinch rubber region Rb with the passage of time t from the start were measured.

  In addition, the said surface temperature Ta-Tc of each rubber | gum Ga-Gc measured the surface temperature in the width direction center position in each area | region Ra-Rc immediately after extrusion using the non-contact-type thermometer (thermography). Further, the flow velocities Va to Vc of the rubbers Ga to Gc are measured immediately after the surface speeds at the center positions in the width direction in the respective regions Ra to Rc using a digital tachometer. The temperature T8 of the flow passage wall surface 8Se1 on the side is measured using a contact thermometer.

  And the presence or absence of generation | occurrence | production of the rubber | gum piece on the side edge side (cushion rubber | gum side) of extrusion rubber | gum, and a crusted surface roughness was determined by visual inspection.

  As a conventional example, the same test was performed in a state where the heating means 20 was not operated (not heated), and the results are shown in Table 2.

  Further, the surface roughness (ten-point average roughness) of the side surface of the extruded rubber at the elapsed time t = 1 minute was measured. The average surface roughness in the example (when heated) was 7.3 μm, and the average surface roughness in the conventional example (when not heated) was 34.5 μm.

As shown in Table 1, in the example, the flow rate difference Va-Vc can be greatly reduced by heating the flow passage wall surface on the side, the rubber cut on the side edge side (cushion rubber side), and the skin-like surface roughness It can be confirmed that the occurrence of the occurrence can be suppressed. On the other hand, in the conventional example, the flow velocity difference Va-Vc is large, and rubber breakage and surface roughness are generated. In the conventional example, since the heat of the cushion rubber Ga itself is transferred to the flow path wall surface, the temperature T8 of the flow path wall surface 8Se1 increases with time. Therefore, when the elapsed time exceeds 9 minutes, the flow rate difference Va-Vc is reduced to 0.45 m / min, and the occurrence of rubber breakage and surface roughness is suppressed.

  It can be seen from Tables 1 and 2 that it is difficult to reduce the flow velocity difference Va-Vc simply by raising the temperature Ta of the cushion rubber Ga, and it is necessary to raise the temperature T8 of the flow path wall surface 8Se1.

  As another example, the same test was performed by heating so that the temperature T8 of the channel wall surface 8Se1 at the start of extrusion (elapsed time t = 0) was 80 ° C. and 130 ° C. And the presence or absence of generation | occurrence | production of the rubber | gum piece and surface roughening at the time of an extrusion start was determined, and the result was described in Table 3. In both cases, it can be confirmed that the occurrence of rubber breakage and surface roughness is suppressed.

DESCRIPTION OF SYMBOLS 1 Rubber extrusion apparatus 2 Rubber extruder 3 Rubber extrusion body 4 Extrusion head 5 Preformer 6 Extrusion die 7 Head flow path 7o Discharge port 8 Preformer flow path 8o Pre-forming port 8S Flow channel wall surface 8Se side flow channel wall surface 9 Mold flow Path 9o Molding port 10 Individual flow path 12 Main merge flow path portion 13 Main preformer die 14 Base preformer 20 Heating means G Rubber

Claims (5)

A rubber extruding device that forms a rubber extrudate having a flat cross section whose cross section width is larger than the cross section thickness by rubber extruded from a plurality of rubber extruding machines,
Extrusion head having head channels formed as a plurality of individual channels that are attached to the front end portions of the plurality of rubber extruders and individually guide the rubber from each of the rubber extruders to a discharge port that opens on the front end side. When,
A pre-former having a pre-former channel attached to the extrusion head and guiding the rubber from the head channel while pre-molding to a pre-forming port opened on the front end side;
An extrusion die attached to the preformer and having a molding channel for molding the rubber extrudate by extruding a pre-formed rubber from the preformer channel from a molding port opened on the front end side; ,
A heating means for heating the flow path wall surface forming the preformer flow path;
The pre-former flow path includes a main merging flow path portion in which rubber from each of the individual flow paths merges into one,
The rubber extruding apparatus, wherein the heating means heats at least one of the channel wall surfaces on the outer side in the width direction in the main merging channel portion.   The rubber extruding apparatus according to claim 1, wherein the heating unit is provided in the preformer. The rubber extrusion device according to claim 1 or 2 , wherein the heating means heats the flow path wall surface at a temperature in the range of 80 to 130 ° C. The preformer includes a main preform die having the main merge channel portion and a base preformer that holds the main preform die, and the heating means is provided in the main preform die. The rubber extrusion apparatus according to any one of claims 1 to 3 . A rubber extruded body manufacturing method for forming a rubber extruded body having a flat cross section whose cross section width is larger than a cross section thickness by rubber extruded from a plurality of rubber extruders,
Extrusion head having head channels formed as a plurality of individual channels that are attached to the front end portions of the plurality of rubber extruders and individually guide the rubber from each of the rubber extruders to a discharge port that opens on the front end side. When,
A pre-former having a pre-former channel attached to the extrusion head and guiding the rubber from the head channel while pre-molding to a pre-forming port opened on the front end side;
A rubber which is attached to the preformer and has an extrusion die having a molding channel for molding the rubber extrudate by extruding a preformed rubber from the preformer channel from a molding port opened on the front end side. While using an extrusion device,
The rubber is pushed out while heating at least one channel wall surface on the outer side in the width direction among the channel wall surfaces forming the main merge channel part where the rubber from each individual channel of the preformer channel merges into one. A method for producing a rubber extruded body comprising an extrusion process.

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