Coating processes – Immersion or partial immersion
Reexamination Certificate
1999-12-10
2001-07-10
Beck, Shrive (Department: 1762)
Coating processes
Immersion or partial immersion
C427S387000, C427S434200
Reexamination Certificate
active
06258414
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for manufacturing woven fabrics made from synthetic fibers and coated with silicone, in particular for use in airbags, by coating the fabric with an aqueous emulsion containing organosiloxanes.
BACKGROUND
The coating of woven fabrics with silicone, also termed siliconization, for use in airbags is known to offer the advantage that the hot combustion gases and particles of the propellant charge cannot penetrate the fabric as rapidly, due to the ability of the silicone to absorb heat when the airbag is triggered. Such coatings thereby contribute to protecting the vehicle occupants from possible burns.
Furthermore, a silicone coating reduces the yarn-to-yarn friction produced by vibrations to which the airbag fabric, often enclosed for years in a tight space, is subjected and which can lead to a reduction in the tear resistance.
Finally, the air permeability of the airbag fabric can also be reduced via the silicone coating.
It is evident that the adhesion between the silicone layer and the airbag fabric must be such that, even after years of storage, no peeling of the silicone layer away from the fabric takes place, which would at least severely impair the function of the layer when the airbag is triggered.
Such a coating process is described in EP-A-0,758,666, for example. This publication discloses aqueous, organosiloxane-containing emulsions that are applied to an undried textile.
In accordance with EP-A-0,758,666, the application of the coating material takes place during or directly after the washing process. Particularly suited are synthetic fabrics that must be washed and dried. Care is required that the composition required for coating is applied directly to the still-wet fabric immediately after the washing step and is vulcanized during the drying step.
The coating process according to EP-A-0,758,666 offers the advantage over such processes in the prior art that, when using the organosiloxane-containing emulsions described in this patent, the fabrics can be coated without a preceding drying step, i.e., an additional coating step is no longer necessary after drying and nevertheless the adhesion of the silicone layer to the fabric is improved. Particularly in the case of fabrics made from synthetic fibers, a washing step is regarded as essential.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide an additional coating process that offers increased economy and with which the adhesion between the fabric and the silicone layer is better than, or at least as good as, the processes known in the prior art.
The invention addresses this and other objects by providing a process for manufacturing woven fabrics made from synthetic fibers and coated with silicone, in particular for use in airbags, by coating the fabric with an aqueous emulsion containing organosiloxanes. In the process, the fabrics obtained from the weaving process are coated in the raw state with the aqueous emulsion containing organosiloxanes.
“Raw” in the context of the present invention refers to any woven fabric as obtained from the power loom and not yet washed. In this respect, the fabrics can be coated with the aqueous emulsion containing organosiloxanes without a previous washing step. The time between weaving and coating is generally not critical. Only after a very long storage time can it be advantageous for the fabric to be slightly moistened with water before the coating step.
It has been shown that, in using the process according to the invention, the adhesion between the fabric and the silicone layer is stronger than, or at least comparable to, the adhesion resulting when using the washing step described in the prior art. The washing of the fabric serves to free the fabric of adhered materials such as finishing and brightening agents, which derive from the weaving and intermediate processes and impair subsequent processing activity. These adhered materials are generally regarded as detrimental to the adhesion between the fabric and the coating, and it is therefore an objective of the prior art to remove them by performing a washing step. Surprisingly, it has been shown that, when conducting the process according to the invention, the washing step can be eliminated without having to accept the disadvantages related to adhesion.
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Bernlohr Werner
Eichert Hans Ulrich
Graefe Hans Albert
Leymann Frank
Siejak Volker
Akzo Nobel nv
Barr Michael
Beck Shrive
Oliff & Berridg,e PLC
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