Procedure for Producing a Multi-Compound Tread for Road Vehicle Tires

Abstract

A process for the manufacture of a tread band, wherein the blocks thereof comprise different portions having differing hysteresis losses. The process comprises a step for the extrusion of a preliminary tread band consisting of a first rubber compound and an injection step, wherein the preliminary tread band, once extruded, is subjected to the action of at least one injector arranged such as to penetrate into the layer of the preliminary tread band and to release a second rubber compound, which is distributed within the layer consisting of said first compound, maintaining exposed a surface that is suitable for defining a portion of the ground-contacting surface of the resulting tread band.

Claims

1-5. (canceled)

6. A method for manufacture of a tread band wherein the blocks thereof comprise different portions having differing hysteresis losses, the method comprising: an extrusion step of forming a preliminary tread band consisting of a first rubber compound; an injection step, wherein the preliminary tread band, once extruded, is subjected to an action of at least one injector arranged such as to penetrate into a layer of the preliminary tread band and to release a second rubber compound, which is distributed within the layer consisting of said first rubber compound, keeping exposed a surface suitably defining a portion of a ground-contacting surface of a resulting tread band; wherein said first rubber compound and said second rubber compound have different dynamic properties in terms of dynamic modulus at 30° C., tan δ at 0° C., tan δ at 30° C., and tan δ at 60° C.; wherein said first rubber compound has a dynamic modulus at 30° C. of between 11.0 and 17.0 MPa, a tan δ at 0° C. of between 0.85 and 1.1, a tan δ at 30° C. of between 0.45 and 0.65, and a tan δ at 60° C. of between 0.19 and 0.30; wherein said second rubber compound has a dynamic modulus at 30° C. of between 5.5 and 15 MPa and at least 2 MPa less than that of said first rubber compound, a tan δ at 0° C. of between 0.40 and 0.99 and at least 0.02 less than that of said first rubber compound, a tan δ at 30° C. of between 0.21 and 0.63 and at least 0.02 less than that of said first rubber compound, a tan δ at 60° C. of between 0.10 and 0.28 and at least 0.02 less than that of said first rubber compound.

7. The method of claim 6, wherein said extrusion step is continuous and said injection step is discontinuous.

8. The method of claim 7, further comprising an interconnection step, wherein said preliminary tread band, which is produced continuously, is stopped at intervals in order to then be recovered and subjected to said injection step.

9. A plant for manufacture of a tread band wherein the blocks thereof comprise different portions having differing hysteresis losses, said plant comprising: an extrusion station comprising at least one extruder supplied with a first rubber compound, wherein the extrusion station is configured to form a preliminary tread band; an injection station configured to inject portions of a second rubber compound within said preliminary tread band; movement means for moving said preliminary tread band from said extrusion station to said injection station; said injection station comprising a dispenser of said second rubber compound and a plurality of injectors connected to said dispenser for receiving a determined quantity of said second rubber compound to be injected within said preliminary tread band.

10. The plant of claim 9, comprising an interconnection station, wherein said preliminary tread band is stopped at intervals to then be recovered and transported to said injection station.

11. The plant of claim 9, wherein: said first rubber compound has a dynamic modulus at 30° C. of between 11.0 and 17.0 MPa, a tan δ at 0° C. of between 0.85 and 1.1, a tan δ at 30° C. of between 0.45 and 0.65, and a tan δ at 60° C. of between 0.19 and 0.30; and said second rubber compound has a dynamic modulus at 30° C. of between 5.5 and 15 MPa and at least 2 MPa less than that of said first rubber compound, a tan δ at 0° C. of between 0.40 and 0.99 and at least 0.02 less than that of said first rubber compound, a tan δ at 30° C. of between 0.21 and 0.63 and at least 0.02 less than that of said first rubber compound, a tan δ at 60° C. of between 0.10 and 0.28 and at least 0.02 less than that of said first rubber compound.

Description

[0016] Below is an exemplary, non-limiting embodiment of the present invention for purposes of illustration with the aid of the attached FIGURE, which illustrates in schematic form a plant, the object of the present invention.

[0017] In the FIGURE, there is indicated, in the entirety thereof with 1, the plant, the object of the present invention.

[0018] The plant 1 comprises an extrusion station 2, an interconnection station 3, an injection station 4 and movement means 5 responsible for the advancement of a preliminary tread band from the interconnection station 3 to the injection station 4.

[0019] The extrusion station 2 comprises a hopper 6, whereinto a first rubber compound is loaded, and an extruder 7 that is capable of producing, with the first rubber compound, a preliminary tread band 8.

[0020] The interconnection station 3 comprises two rollers 9 arranged such as to rotate idling and wherebetween a loop is implemented that is variable according to the action of the movement means 5.

[0021] The injection station 4 comprises a dispenser 10, connected to a supply line 10a of a second rubber compound and a plurality of injectors 11, wherein each thereof extends from said dispenser 10, from which it receives a determined quantity of the second rubber compound. Each of the injectors 11 has a free dispensing end that is capable of penetrating into the layer of the preliminary tread band and releasing within the layer itself the quantity of the second rubber compound.

[0022] The movement means 5 comprise a plurality of rollers 12 that are moved by actuator means (known and not described in detail). In essence, the rollers 12 function as a conveyor belt.

[0023] The first and second compounds have differing dynamic properties in terms of: dynamic modulus at 30° C., tan δ at 0° C., tan δ at 30° C. and tan δ at 60° C.

[0024] In particular, the first compound has a dynamic modulus at 30° C. of between 11.0 and 17.0 MPa, a tan δ at 0° C. of between 0.85 and 1.1, a tan δ at 30° C. of between 0.45 and 0.65 and a tan δ at 60° C. of between 0.19 and 0.30; whilst the second compound has a dynamic modulus at 30° C. lower than that of the first compound with a value of between 7.5 and 10.5 MPa, a tan δ at 0° C. lower than that of the first compound with a value of between 0.70 and 0.84, a tan δ at 30° C. lower than that of the first compound with a value of between 0.21 and 0.42 a tan δ at 60° C. lower than that of the first compound with a value of between 0.10 and 0.17.

[0025] As may appear obvious from the description above, the process and plant of the present invention ensure the effective preparation and high productivity of tread bands, wherein the blocks thereof are composed of parts having differing hysteresis losses.

[0026] In this way it will be possible to produce a tread band wherein the technical characteristics thereof are such as to ensure significant improvement effects in terms of wet grip performance, maintaining, at the same time, the advantages obtained in terms of rolling resistance. In particular, the tread band manufactured with the process and plant of the present invention relates to a kind of “multi-pin tread” for winter/all seasons applications. In fact, those elements that are manufactured using the second rubber compound (a stiffer compound) are incorporated into the preliminary tread band, manufactured using the first rubber compound (a softer compound), and act as studs when on roads with ice and snow.