Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-04-10
2002-01-01
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S123000, C156S134000, C156S272600, C156S273300, C156S274600
Reexamination Certificate
active
06334920
ABSTRACT:
BACKGROUND INFORMATION
1. Field of the Invention
The invention relates to a process for manufacturing an unvulcanized, unfinished rubber fire for a vehicle tire, which is produced by manufacturing various tire components of an unvulcanized rubber mixtures that include partially embedded reinforcing members.
2. Discussion of Background Information
In order to manufacture an unvulcanized, unfinished rubber tire (i.e., one or more components of a tire in an unvulcanized state) that exhibits a sufficient degree of firmness, it is of great importance that the unvulcanized rubber mixtures of the individual layers of the tire components be sufficiently adhesive. Such firmness is necessary in order to transport the unvulcanized, unfinished rubber tire from a tire assembly station to a vulcanization facility. Sufficient adhesiveness of the individual unvulcanized rubber mixtures also is a requirement during vulcanization to give the finished tire the necessary firmness.
It is known that the adhesiveness of unvulcanized rubber mixtures can be increased during the manufacturing process by coating the surface of the rubber mixture with a benzene solution, to produce a partially dissolved surface layer of unvulcanized rubber material. This treatment with a benzene solution, however, is very time-consuming and it may pose a health hazard for the worker. Moreover, to be made safe, the benzene solution treatment requires elaborate suction/exhaust work place systems, so that the maximum allowable workplace concentration value (MAK-value), measured in ml/m
3
or ppm (for a gas) and based on 8 hours of workplace exposure for a 40-hour work week, is not exceeded.
Further, the treatment of an unvulcanized rubber mixture with a benzene solution (which is dark) may have other disadvantages. For example, the colored side walls of pneumatic vehicle tires which have been partially dissolved with a benzene solution may develop unsightly discolorations in an unvulcanized state.
Furthermore, sufficient adhesiveness for the manufacturing process is not achievable in every case by coating the unvulcanized rubber material with a benzene solution. In particular, when two different unvulcanized rubber mixtures are to be bound to each other, for example a colored side wall and the rubber mixture surrounding a tire carcass, problems may arise with respect to sufficient adhesiveness in the unvulcanized state, such that the adhesiveness in the vulcanized state will be inadequate.
SUMMARY OF THE INVENTION
By treating at least a portion of the surface of at least one unvulcanized rubber mixture with a plasma and/or a flame, increased adhesiveness of unvulcanized rubber mixtures during the vehicle tire manufacturing process can be attained, while at the same time the use of solvents (such as a benzene solution) can be avoided, thereby enabling a more environmentally friendly process for manufacturing vehicle tires.
With a terminal plasma treatment, one should understand the effect of particles that are created by a gas discharge (e.g., a plasma composed of ion radicals, electrons and/or molecules) on an unvulcanized rubber surface, where the mean temperature of the surface is not raised above 100° C. In plasma treatment processes, one usually distinguishes between a low-pressure plasma and a normal pressure plasma. With a low-pressure plasma, a gas or gas mixture is fed into a process chamber at a relatively low pressure, for example approximately 0.5 mbar to approximately 2 mbar. The gas discharge (plasma) is ignited by using a high-frequency alternating voltage, thereby ionizing the gas medium. Air, noble gases, oxygen or nitrogen, for example, can be used as the gas medium. In accordance with the invention, the gas fragments or gas mixture fragments thus created hit the surface of the unvulcanized rubber mixture, resulting in its modification. Depending on the type of gas or gas mixture used in the process, it becomes possible, for example, to deposit polar groups on generally non-polar unvulcanized rubber.
The low-pressure plasma treatment has the advantage that the unvulcanized rubber surface being treated will generally heat up by only approximately 30° C. to approximately 60° C., such that the surface can also be treated with other materials that can not be deposited under normal pressures without causing damage. Furthermore, the low-pressure plasma process is very efficient since the life-span of the activated particles is high under reduced pressures. Specific gases or gas mixtures can be used due to the self-contained process chamber. Moreover, non-homogeneous or insufficient activation may be avoided.
Another process for treating unvulcanized rubber mixtures is with the use of normal pressure plasmas. These differ from low-pressure plasma processes in that the gas discharge does not take place in a self-contained chamber. Instead, the process operates with ambient air under ambient pressure. A corona-discharge plasma is used as a preferred process.
In principle, however, it also is possible to treat the unvulcanized rubber surface with a high-temperature plasma. However, one must pay close attention to the exposure time of the plasma to ensure that the mean surface temperature does not exceed 100° C.
A flame treatment also has proven effective for treating the surface unvulcanized rubber mixtures. By using a gas flame on the surface of the unvulcanized rubber material, the molecular chains of the rubber may be broken up due to the heat treatment and may become bonded with the oxygen-carrying components of the flame. The flame treatment may be used in combination (e.g., sequentially, one after the other) with the plasma treatment.
A discussion of the plasma treatment process and the flame treatment process is contained in the following references:
1. Jörg Friedricht: Plasmabehandlung von Polymeren, Kleben & Dichten—Adhäsion, Jahrgang 41, 1-2, 1997. S. 28-33. [Plasma Treatment of Polymers, Adhesives & Seals—Adhesion]
2. Gehard Liebel: Plasmabehandlung von Polyolefin, GAK 8/1990. S. 421ff. [Plasma Treatment of Polyolefins]
3. Fritz Bloss: Zur Koronabehandlung von Formteilen, Sonderdruck aus Oberfläche+JOT 12/88 (Vorbehandeln) [Regarding Corona-treatment of Part of a Mold]
4. Thomas H., Herrling, J., Rakowski W., Höcker, H.: Umweltfreundliche Veredlungsverfahren für Wolle durch Vorbehandlung mit elektrischen Gasentladungen (Plasmen), ITP 2/93, S. 42-49 [Environmentally Friendly improvement Process for Wool by Electrical Gas-discharge (Plasma)]
By treating unvulcanized rubber layers in accordance with the invention, it becomes possible to improve the adhesiveness of these unvulcanized rubber mixtures during the manufacturing process. The adhesiveness of an unvulcanized rubber mixture may be increased between unvulcanized, pre-vulcanized and fully vulcanized tire components. The process according to the invention, therefore, can also be used as a process for manufacturing reconditioned tires, with regard to treating and assembling the unvulcanized tire tread. Moreover, the manufacturing of vehicle tires can be performed in accordance with quality requirements and in an environmentally friendly manner, more specifically, without the use of solvents. Due to the increased adhesiveness from the treatment process, unvulcanized rubber mixtures or unvulcanized rubber mixtures that include partially embedded or fully embedded reinforcing members can be applied in specific locations, and after vulcanization of the unvulcanized, unfinished rubber tire, a vehicle tire can be produced that has improved running properties due to the precise positioning of individual layers.
It was surprising to learn that an unvulcanized rubber mixture could be treated with a plasma and/or a flame such that its adhesiveness could be increased in the unfinished (unvulcanized) state, while at the same time the process shows no sign of effecting the cross-linked (i.e., vulcanized) material. It was unexpected to find that surface adhesiveness, which in the case of non-cross-linked rubber can be trace
Glinz Michael
Homt Günter
Kunz Harry
Continental Aktiengesellschaft
Knable Geoffrey L.
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