JP6316672B2 - Method and apparatus for extruding tire tread - Google Patents

Description

  The present invention relates to a method and an apparatus for extruding a tire tread in which a kneaded rubber sheet is put into an extruder and shaped into a tread rubber member.

  Conventionally, tire treads have been manufactured by extrusion processing. As a method for this, hot extrusion in which a kneaded rubber sheet heated with an open roll is put into an extruder for shape processing, and the kneaded rubber sheet is directly used. Two extrusion methods of cold extrusion in which shape processing is performed by feeding into an extruder are employed.

  FIG. 4 is a diagram schematically showing the configuration of a tire tread extrusion device using a hot feed extruder in the prior art, and passing the kneaded rubber sheet through three pairs (load, surge, feed) of open rolls. After the hot-rolling process, the tread rubber member is molded by supplying a certain amount of strip to a hot feed extruder (for example, Patent Document 1).

JP 2001-150511 A

  However, with the recent increase in demand for fuel-efficient tires, the silica ratio in the reinforcing agent (wt% with respect to the total amount of carbon and silica) is 65 wt% or more, and the weight part (phr) of natural rubber is (4 / 3 × (silica ratio) −260/3) or less of the tread rubber member has become mainstream, and the conventional hot extrusion method described above has the following problems.

  That is, in the work on the road roll, the worker bites the kneaded rubber sheet into the roll, but the kneaded rubber sheet with a high silica ratio is likely to lift and peel off from the surface of the load roll. It is difficult to secure enough.

  The normal heat treatment is performed on a 200-250 kg rubber sheet with 84 inch rolls. When the rubber amount (bank amount) in the surge roll is 150 kg or more, the rubber is placed between the pair of rolls. Since it cannot be bitten, it may not be hot-pressed depending on the formulation.

  Moreover, since a long time is required to complete the heating due to insufficient heating capability of the load roll, productivity is hindered.

  On the other hand, in the conventional cold extrusion method, the capital investment is large and a large installation space is required, or the ratio of the screw length L to the screw diameter D, that is, L / D, in order to perform heating with only the extruder. There is a problem that a large number of rejects are required at the time of changeover.

  Therefore, unlike the conventional hot extrusion method, the present invention can perform the hot-rolling process with sufficiently ensuring the safety of the worker, and can extrude the tire tread with high productivity. It is an object of the present invention to provide a method and an apparatus for extruding a tire tread that do not require a large capital investment and can reduce the occurrence of rejection at the time of changeover.

The invention described in claim 1
Extruded kneaded rubber with a blending ratio of silica of 65% or more with respect to the total weight of carbon and silica and a blending amount of natural rubber of (4/3 × silica ratio−260 / 3) parts by weight (phr) or less. A method for extruding a tire tread to be processed,
A step of extruding the kneaded rubber into a bar shape using a cold feed extruder;
Supplying the extruded stick-shaped kneaded rubber directly to a feed roll, applying heat, and cutting it into a sheet; and
A method for extruding a tire tread, the method comprising: feeding the cut sheet-like kneaded rubber to a hot feed extruder and extruding the tire tread.

The invention described in claim 2
The cold feed extruder is a pin type having a diameter of φ250 mm, and an extruder having a ratio L / D of a screw length L to a screw diameter D of 10 is used.
2. The tire tread extrusion method according to claim 1, wherein an extruder having a diameter of 200 and an L / D of 6 is used as the hot feed extruder.

The invention according to claim 3
Extrusion of kneaded rubber having a blending ratio of silica of 65% or more with respect to the total weight of carbon and silica and a blending amount of natural rubber of (4/3 × silica ratio−260 / 3) parts by weight (phr) or less A tire tread extrusion device used for processing,
A cold feed extruder for extruding the kneaded rubber into a rod shape;
While heating the extruded stick-shaped kneaded rubber, a feed roll that is cut into a sheet,
An apparatus for extruding a tire tread, comprising: a hot feed extruder for extruding the cut sheet-like kneaded rubber to form a tire tread.

  According to the present invention, unlike the conventional hot extrusion method, it is possible to perform the extrusion of the tire tread with high productivity by ensuring the safety of the worker and performing the hot-in process, while the conventional Unlike the cold extrusion method described above, it is possible to provide a tire tread extrusion method and an extrusion apparatus that do not require a large capital investment and can reduce the occurrence of rejection at the time of changeover.

It is a figure which shows typically the structure of the extrusion apparatus of the tread for tires examined before reaching this invention. It is a figure showing typically composition of an extrusion device of a tread for tires concerning an embodiment of the invention. It is a roll processability map based on the relationship between the natural rubber and the silica ratio in the tire tread. It is a figure which shows typically the structure of the extrusion apparatus of the tread for tires using the hot feed extruder in a prior art.

  In the case of the conventional hot extrusion method, the present inventor firstly considered that the above-described problem occurred in the load roll and the surge roll among the three pairs of open rolls, as shown in FIG. Then, it was examined to change these three pairs of open rolls to the cold feed extruder 2.

  However, in this case, since the kneaded rubber is supplied to the hot feed extruder 4 and the tire tread G3 is extruded without being sufficiently heated in the cold feed extruder 2, the cold feed extruder is used. The volume of the sheet-like kneaded rubber supplied from 2 to the hot feed extruder 4 is not stable, and the amount of supplied rubber cannot be controlled with high accuracy. As a result, the tire tread cannot be stably extruded, resulting in a decrease in productivity.

  Therefore, the present inventor then carried out extrusion using a cold feed extruder 2 as shown in FIG. 2 instead of the load roll and the surge roll in which the problem occurred among the three pairs of open rolls. The rod-shaped kneaded rubber G1 is directly supplied to the feed roll 3 and heated in the feed roll 3 and cut into a sheet shape. Extrusion of the tread G3 for use was examined.

  As a result, according to the present embodiment, the blending ratio of silica with respect to the total weight of carbon and silica is 65% or more, and the blending amount of natural rubber is (4/3 × silica ratio−260 / 3) parts by weight or less. It was found that even the kneaded rubber compounded as described above was subjected to the necessary heat input and could stably and accurately extrude the tire tread G3.

  Specifically, as shown in FIG. 2, the cold feed extruder 2 extrudes the supplied kneaded rubber into a bar shape and supplies the bar-shaped kneaded rubber G <b> 1 to the feed roll 3. At this time, the cold feed extruder 2 is preferably a pin type having a diameter of φ250 mm and having an L / D = 10 from the viewpoint of supply capability of a necessary amount of rubber and heat entry into the rubber. The

  The feed roll 3 is composed of a pair of open rolls. The open roll is heated to a predetermined temperature, and a stick-shaped kneaded rubber G1 is inserted into the gap to heat the kneaded rubber. The sheet is processed into a sheet and cut into a fixed amount, and then supplied to the hot feed extruder 4 as a sheet-like kneaded rubber G2.

  The hot feed extruder 4 performs extrusion using the sheet-like kneaded rubber G2 supplied from the feed roll 3, and forms the tire tread G3. At this time, as the hot feed extruder 4, an extruder having a diameter of 200 mm and L / D = 6 is preferably used.

  According to the present embodiment, unlike the conventional hot extrusion, since the load roll is not used, it is not necessary for the worker to bite the kneaded rubber sheet into the roll, and the safety of the worker is sufficiently ensured. be able to.

  In addition, according to the present embodiment, using a cold feed extruder instead of a surge roll, the kneaded rubber can be reliably bitten and supplied to the feed roll, so that when a conventional surge roll is used Thus, the kneaded rubber does not get stuck, and even if it is a composition that could not be hot-worked in the past, it can be hot-worked.

Specifically, in the roll processability map shown in FIG. 3, when the silica ratio is X (%) and the blending amount of natural rubber is Y (phr),
Y = 4/3 × X-260 / 3
In the part showing the compounding for low fuel consumption tires under the straight line, there was a compounding that could not be hot-worked by conventional hot extrusion, but by applying this embodiment, all the compounding is supported Thus, it is possible to perform hot-heating, and it is possible to perform hot-heating in a wider range than before.

  Moreover, according to this Embodiment, the situation which requires a long time by the completion of heating does not generate | occur | produce by lack of the heating capability of a load roll, and productivity is not inhibited.

  Further, since the kneaded rubber is supplied from the cold feed extruder to the hot feed extruder through the feed roll, the feed roll can be used without using an extruder having a large L / D as in the conventional cold extrusion method. Necessary heating can be performed, a large capital investment and a large installation space become unnecessary, and the occurrence of rejection at the time of changeover can be suppressed.

  As described above, according to the present embodiment, unlike the conventional hot extrusion method, the safety of workers is sufficiently ensured to perform hot-heating, and the tire tread is extruded with high productivity. On the other hand, unlike a conventional cold extrusion method, it is possible to provide a tire tread extrusion method and an extrusion apparatus that do not require a large capital investment and can reduce the occurrence of rejection at the time of changeover. .

1. Experiment 1
A tread for a tire was extruded using a kneaded rubber sheet having a silica ratio of 85% and a natural rubber of 15 parts by weight (phr). At this time, as the extrusion method, the conventional hot extrusion method (Comparative Example 1), the conventional cold extrusion method (Comparative Example 2), and the extrusion method according to the present embodiment (Example 1) were employed. .

In this kneaded rubber sheet, the blending amount of natural rubber is the following formula Y (parts by weight of natural rubber) ≦ 4/3 × X (silica ratio) −260/3.
It is a tread rubber compound for fuel-efficient tires.

  For each example, (1) Ensuring safe workability (whether or not rubber is lifted or peeled off from the roll surface), (2) Heating completion time (tire after starting heating in the state of a kneaded rubber sheet) (Time until start of extrusion of tread for use), (3) The rate of reject generation at the time of tread extrusion was measured and evaluated, and the amount of capital investment was estimated and index evaluation was performed with Comparative Example 1 taken as 100. The results are shown in Table 1.

  In Table 1, to ensure safe workability, the case where there is no occurrence of rubber lifting or peeling from the roll surface (0 times) during rotation of the roll 50 is “excellent”, and 1 to 5 times. A case of “good” or 6 times or more was evaluated as “impossible”.

2. Experiment 2
Next, using the kneaded rubber sheets of Formulation A to Formulation D shown in Table 2 and four types of formulations, the tread for the tire was extruded based on Comparative Example 1 and Example 1, and heated as in the above. The completion time and rejection rate were measured and evaluated, and the degree of silica dispersion in the rubber after heating was measured and evaluated. The results are shown in Table 2.

In addition, the blending amount of natural rubber is blending A and blending B, respectively.
4/3 × X (silica ratio) −260/3
It is larger than the value obtained based on the above, and is not a tread rubber compound for a fuel-efficient tire. On the other hand, the blending amounts of natural rubber and blending D are respectively
4/3 × X (silica ratio) −260/3
This is a tread rubber blend for a fuel-efficient tire that is smaller than the value obtained based on the above.

  From Table 1, by adopting the extrusion method according to the present embodiment (Example 1), sufficient workability can be ensured and the tire tread can be extruded, and the heating time can be shortened. It can be seen that the occurrence of rejection can also be reduced. It can also be seen that the capital investment can be greatly reduced.

  And from Table 2, the conventional hot extrusion method (Comparative Example 1) could not extrude the tread rubber compound for a fuel-efficient tire, whereas the extrusion method according to the present embodiment (Example 1), Even tread rubber blends for low fuel consumption tires can be sufficiently heated to extrude tire treads, and the same silica dispersion as in tread rubber blends not for low fuel consumption tires should be obtained I understand.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

2 Cold Feed Extruder 3 Feed Roll 4 Hot Feed Extruder G1 Stick-like Kneaded Rubber G2 Sheet-like Kneaded Rubber G3 Tire Tread

Claims (3)

Extruded kneaded rubber with a blending ratio of silica of 65% or more with respect to the total weight of carbon and silica and a blending amount of natural rubber of (4/3 × silica ratio−260 / 3) parts by weight (phr) or less. A method for extruding a tire tread to be processed,
A step of extruding the kneaded rubber into a bar shape using a cold feed extruder;
Supplying the extruded stick-shaped kneaded rubber directly to a feed roll, applying heat, and cutting it into a sheet; and
A method for extruding the tire tread, comprising: supplying the cut sheet-like kneaded rubber to a hot feed extruder to extrude the tire tread. The cold feed extruder is a pin type having a diameter of φ250 mm, and an extruder having a ratio L / D of a screw length L to a screw diameter D of 10 is used.
2. The method for extruding a tire tread according to claim 1, wherein an extruder having a diameter of 200 and an L / D of 6 is used as the hot feed extruder. Extrusion of kneaded rubber having a blending ratio of silica of 65% or more with respect to the total weight of carbon and silica and a blending amount of natural rubber of (4/3 × silica ratio−260 / 3) parts by weight (phr) or less A tire tread extrusion device used for processing,
A cold feed extruder for extruding the kneaded rubber into a rod shape;
While heating the extruded stick-shaped kneaded rubber, a feed roll that is cut into a sheet,
An apparatus for extruding a tire tread, comprising: a hot-feed extruder for extruding the cut sheet-like kneaded rubber to form a tire tread.

Images