Process for producing a vehicular pneumatic tire

Details Process for producing a vehicular pneumatic tire Process for producing a vehicular pneumatic tire

1999-04-13

2004-03-02

Knable, Geoffrey L. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C152S152100, C152S209500, C152SDIG002, C156S117000, C156S128100, C156S130500

Reexamination Certificate

active

06699344

ABSTRACT:

INTRODUCTION AND BACKGROUND
The present invention pertains to a process for producing a vehicular pneumatic tire in which, in order to produce and apply a preferably unvulcanized tread strip to a partially completed tire which already has a cambered carcass and a ply packet radially outward therefrom, at least two strips of material, each consisting of a mixture of rubber and/or plastic, are applied to the partial tire, while at least one strip of material is wound in numerous essentially adjoining windings running in the circumferential direction of the tire.
A process for producing a vehicular pneumatic tire, in which a strip of rubber material is wound in numerous essentially adjoining windings around a partial tire, is known from the state of the art (e.g., R. A. Cronin: Elastomerics, August 1987, pages 2427). The advantages of this process lie specifically in the fact that only small extruders need to be made ready for the treadstrip mixtures.
Various demands are placed on the tread strip of a vehicular pneumatic tire. For instance, the part of the tread strip that has direct contact with the roadway must have optimal road grip. At the same time, resistance to wear, roll resistance and adequate grounding capability for electrostatic charges should be optimized. Heretofore, a single rubber mixture was used for the part of the tread strip that makes contact with the roadway. This rubber mixture must fulfill almost all demands. However, it is disadvantageous that each characteristic of the mixture coming into contact with the roadway can be varied only within certain limits so as not to negatively affect other characteristics.
In order to optimize still further the characteristics of the vehicular pneumatic tire, it is known that the tread strip can be made up of two parts of different mixture compositions running in the radial direction. Thus, part of the tread strip coming into contact with the roadway (cap) should already possess the characteristics cited above as to wear, adherence and resistance to roll. At the same time, the base rubber mixture directly beneath the cap rubber mixture should be optimized in such a way that, e.g., the resistance to roll is positively affected.
The production of such unvulcanized tire tread strips is usually accomplished with an extruder, the nozzle of which determines the pattern of the tread strip slug. However, it is not easily and uncomplicatedly possible, e.g., to provide different zones of the surface of the tread strip (e.g., shoulder area and midsection) coming into contact with the roadway with mixtures of different composition, e.g., in order to improve the traction of the tire still further. Specifically, complicated extruder nozzles would be required in order to divide the tread strip slug into appropriately different zones with different mixtures. Furthermore, in the customary process for building tires, in which the tread strip slug is designed as a complete component, there exists the problem that the two ends of the tread strip slug form an abutment point (splice) where they are joined together. This splice must be separately pretreated (coated with a naphtha solution) in order to ensure adequate adhesion of the two ends.
It is therefore a fundamental objective of the present invention is to make available a vehicular pneumatic tire, the tread strip of which has outstanding characteristics in driving operation and can, at the same time, also be produced in a simple and uncomplicated process.
SUMMARY OF THE INVENTION
The above and other objects can be achieved according to the invention, in that, in the case of two strips of material, these consist of different mixtures and, depending upon the desired characteristics of the tire, they are arranged simultaneously or sequentially on different areas in the inner or the radially outer zone of the space occupied by the finished tread strip.
In keeping with the invention, the process of the winding of a strip of material to form the tread strip can be modified in such a way that the totality of the tire characteristics can be considerably improved. For the production of such a vehicular pneumatic tire, two or more essentially flat strips of material (preferred ratio of width to thickness >7:1) of rubber and/or plastic are used. In principle, it is also possible to apply several adjoining strips of material in the longitudinal direction. The individual strips of material consist of a single mixture of rubber and/or plastic and are arranged on their respective zones in the tire. The mixture of rubber and/or plastic also contains, in addition to the respective polymers customarily used in the tire art (e.g., SBR, BR, NR), customary fillers (e.g., carbon black, silica), and additives (e.g., sulfur, accelerators, processing adjuvants).
In the winding of the material strips according to the invention, no splice results as in the case of the conventional tire building process. Since the strip of material is wound while warm and therefore has sufficient adhesiveness, the use of naphtha containing adhesion enhancers can be dispensed with.
It is especially advantageous when the radially inner part of the tread strip (base) and the part between the base and the surface (cap) coming into contact with the roadway is produced from at least two different strips of material. In this way it is possible that the strip of material forming the base layer can be first wound on completely. After the application of the base layer, there follows the winding on of the next strip of material which forms the cap. Ideally, however, the cap and the base are applied simultaneously. So it is possible that, e.g., beginning at an axial limit of the tire slug, the material strip of the base is first applied by winding and offset therefrom (offset, e.g., by one winding) e.g., a strip of material of the cap mixture is applied to the wound strip of material of the base mixture. Using such a procedure, the tire tread strip slug is completed especially in a timely fashion. In a conventional cap and base buildup, large extruder facilities with complicated nozzles were required in order to prepare such a vehicular pneumatic tire. It is also possible in keeping with the invention to undertake rapid and uncomplicated conversion to various mixtures in order to ensure optimal adaptation of the production, e.g., from summer to winter tires.
It is also advantageous when the radially inner part of the tread strip (base) and parts forming the surface of the tread strip coming into contact with the roadway are formed from a strip of material filled with a carbon black base mixture and that the remaining areas between the base and the surface coming into contact with the roadway are filled by winding on a second strip of material of a cap mixture or by inserting a single thick strip. The thickness of the zone occupied by the base mixture (in the radial direction) in certain zones of the tire and depending upon the dimension of the tire, is 2-5 mm and in other zones corresponds with the total thickness of the tread strip. The zones that do not have the full thickness of the tread strip are filled in by winding on a second strip of material or by inserting a single thick strip.
The winding on of a second strip of material, which consists of a cap mixture, can preferably be accomplished during the winding of the strip of base material, e.g., with a different rate of advance. The mixture of the second strip of material or the single strip preferably contains silica as a filler. The advantage of such a combination lies in the fact that running surface mixtures containing silica impart to the tire a slight resistance to roll and good skid characteristics on wet pavement although it does impart to the tread strip a low grounding capability due to its low electrical conductivity. With the combination mixture containing carbon black and silica according to the invention in the surface of the tread strip coming into contact with the roadway, the strip of material containing carbon black, which is itself in contact with conductive layer

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