Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1997-02-28
2003-01-07
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S689000, C427S419200, C427S487000
Reexamination Certificate
active
06503634
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to composites of substrate material and more particularly to composites of substrate material coated with a barrier film. The coated composite substrate material is substantially impermeable to gases and water vapor. The invention also concerns a method for producing these composites. Such composites can be used in packaging, for example, in the form of foils, panels, shapes and hollow parts. Such composites can also be used for technical applications, for example, as membranes or protective films for sensors.
2. Summary of Related Art
Presently, metals, e.g., aluminum or tinplate, glass, polymers, e.g., EVOH or PVDC, and polymers provided with vaporized thin metallic or oxidic films or combinations thereof are generally employed as barrier materials. In comparing glass and metals to polymers, polymers are characterized by their low weight and the small amounts of material needed, for which reason they are frequently used especially in the packaging field. On the other hand, due to their structure and associated permeability to gases and water vapor, polymers are unsuited for applications involving especially high requirements as to barrier properties. Gaining increasingly in significance, especially due to ecological concerns, are the renewable or recycleable polymers. However, they display a comparatively high permeability to gas and present extremely insufficient barrier properties to water vapor. Therefore, they are barred from many applications.
Because of mostly insufficient barrier effect to gases and water vapor, polymers are often used in combination with other materials. For example, the barrier properties of polymers are improved by application of thin films of aluminum, aluminum oxide or silicon oxide, but the permeation rates continue to be excessively high for many applications and can be detected using conventional measuring techniques (oxygen permeability >0.5 dm
3
/(m
2
d bar)). Moreover, coated renewable polymers have exhibited, by far, higher permeation rates than coated standard polymers such as polyethylene or polypropylene.
Vaporized films are very sensitive to mechanical stresses. Therefore, it is mostly necessary to laminate the coated substrates, for example with a foil.
For some time it has been known (e.g., DE-OS 38 28 098 Al) to produce scratchproof coating materials by hydrolytic polycondensation of an organofunctional silane, for example with an aluminum compound, and, as the case may be, with inorganic oxide components. Hybrid polymers (so called ORMOCERS) synthesized in this fashion possess both inorganic and organic network structures. The inorganic siliceous network structure is obtained by the sol-gel process (e.g., C. J. Brinker, D. W. Scherer, Sol-Gel-Science; The Physics and Chemistry of Sol-Gel Processing, Academic Press, Inc., New York, 1989) via controlled hydrolysis and condensation of alkoxy silanes. The siliceous network allows specific modification by including additionally metal alkoxides in the sol-gel process. Additionally, an organic network is produced by polymerization of organofunctional groups that are introduced in the material by the organoalkoxy silanes. Reactive methacrylate, epoxy or vinyl groups are polymerized by thermal or photochemical induction. The ORMOCERs produced in this way can be applied on the medium to be coated by means of conventional application techniques (spraying, brushing, etc.). Despite suitable wetting behavior and sound film adhesion, even a composite of an ORMOCER film and a polymer foil is unable to reduce the high permeability of many polymers, and notably renewable polymers, to a degree that would be required, e.g., in foodstuff packaging.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, the objective underlying the present invention is to coat substrate materials such that they become extensively impermeable to gases and water vapor.
This objective is satisfied according to the invention by composites with the characterizing features set forth in claim 1 and, in process-related respects, in claim 21. Favorable embodiments and improvements of the inventive composites are disclosed in the subclaims.
A composite substrate material having at least two films. At least one of the two films is a barrier film that contains inorganic-organic hybrid polymers (ORMOCER film). At least one other film is a substrate material, another barrier material in comparison to the original substrate material, or a single-coated substrate material having a far lower permeability.
The inventive composites have a high barrier effect to gases and water vapor.
Surprisingly, even the permeation rates of native polymers are reduced to such an extent that these polymers are extensively impermeable to gases and water vapor. Thus new applications for native polymers are created.
When applying an ORMOCER film 1 &mgr;m to 15 &mgr;m thick on a substrate material coated with a barrier film containing a metal, a metal oxide, a semiconductor, or a mixture thereof improves the barrier effect of the composite. Also, the mechanical stability of a coated substrate material is dramatically improved. Thus, the ORMOCER film assumes at the same time the function of a mechanical protective film that may make further process steps, such as lacquering or laminating, superfluous. For this reason it will mostly prove suitable to apply the ORMOCER film as the concluding film on the substrate material that has already been coated otherwise.
Of course, it is also possible to apply an ORMOCER film directly on the substrate material. Thereafter, further barrier films (for example a silicon oxide film) and/or a further substrate material film may be applied. For example, the silicon oxide sides of two coated substrate materials or the silicon oxide side of a coated and an uncoated substrate material can be combined on a conventional laminating system with ORMOCER as a laminating adhesive.
Surprisingly, a composite of two substrate materials with a barrier film arranged between the two substrates possess outstanding barrier properties. An example of this is polymer foils with an ORMOCER barrier film arranged between the foils. The ORMOCER film may also in this case serve as a laminating adhesive.
The barrier properties of polymers are improved by a factor of 100 by the application of a 100 nm thick silicon oxide barrier film. Surprisingly, on average, the barrier properties of this composite increase once again by a factor of 100 after the additional application and curing of an ORMOCER film. This fact shows the exact significance attached to a double-film application.
Instead of the silicon oxide film, metal films may also be used, e.g., films of aluminum or other prior art coating metals. Semiconductor films such as silicon film may also be used instead of silicon oxide film. Metal oxide films may also be used instead of silicon oxide films. Suitable metal oxide films include aluminum oxides, magnesium oxides, cerium oxides, hafnium oxides, tantalum oxides, titanium oxides (such as titanium dioxide, titanium trioxide, or titanium monoxide), yttrium oxides, or zirconium oxides, such as zirconium monoxide. Barrier films containing mixtures of the above listed substances are also suitable substitutes for silicon oxide. The metal films, metal oxide films, semiconductor films, or mixtures thereof typically have a thickness of 5 nm to 1000 nm, preferably between 20 and 150 nm.
All of the polymers (e.g., polyamide, polyethylene, polyproylene or polyester) lend themselves as substrate materials for coatings according to the invention.
Especially applicable as substrate materials are biologically decomposable polymers and particularly native polymers (cellophane, proteinaceous or starchy polymers) which have an inherently low barrier effect. Also paper, cardboard, coated paper or coated cardboard are suitable substrate materials. Particularly pronounced improvements in view of gas and water vapor permeability are achievable with the inventive coating in the case of thin substrate
Amberg-Schwab Sabine
Schottner Gerhard
Utz Helmar
Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung
Marshall & Melhorn LLC
Tarazano D. Lawrence
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