Multilayer film laminates

Details Multilayer film laminates Multilayer film laminates

2001-05-14

2003-01-07

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C428S423500, C428S424800, C428S425500, C428S425800, C428S451000, C428S458000, C428S461000, C428S463000, C428S476300, C428S477700, C428S516000, C428S520000

Reexamination Certificate

active

06503617

ABSTRACT:

CROSS REFERENCE TO RELATED PATENT APPLICATION
The present patent application claims the right of priority under 35 U.S.C. §119(a)-(d) of German Patent Application No. 100 25 321.0, filed May 22, 2000.
FIELD OF THE INVENTION
The present invention relates to multilayer film laminates, which are particularly impermeable to gas diffusion, and to the use of these gas diffusion impermeable multilayer film laminates in the production of vacuum insulation panels.
BACKGROUND OF THE INVENTION
In some specific industrial products, such as for example in the production of vacuum insulation panels (VIP), there is a requirement for films which have extremely low gas diffusion values, in order to ensure that, once applied, the vacuum and thus the effectiveness of the VIPs are retained over a very long period of time (e.g., 10-15 years).
Conventional barrier layer films made from plastics, as described for example in EP-A 0 517 026, do not achieve the necessary gas barrier action. While composites which contain aluminum foil can provide a complete gas barrier, they are undesirable in many applications due to the thermal conductivity of the aluminum. Metallised films or films with a vapor deposited SiOx coating are furthermore known which avoid the disadvantages with regard to the thermal conductivity of pure metal foils (for example, as described in EP-A 0 878 298) and simultaneously achieve higher levels of barrier action than do pure plastics films. However, the levels of barrier action obtained with films having vapor deposited SiOx coatings are still far below the required gas barrier values.
As used herein and in the claims, the term “vacuum insulation panels (VIPs)” means sheet-like structures which include an insulating material or packing, that are vacuum packed in a high barrier film envelope. The level of the vacuum are here determined by the insulating material or packing used and the required insulation action of the VIP. Over the service life of the VIP, the high barrier film prevents the diffusion of gases which impair the vacuum and thus the insulating properties of the VIP. Metal foils are undesirable as high barrier films as they conduct heat around the edges of the sheet-form VIP, so reducing insulation performance.
SUMMARY OF THE INVENTION
The object of the present invention is accordingly to provide film laminates which achieve particularly elevated gas barrier action without using thermally conductive metal foils as a component. It is simultaneously intended to have a positive influence upon further mechanical and thermal properties of the film laminate by means of a suitable combination of materials. In particular, the intention is to provide film laminates which are suitable for the production of vacuum insulation panels (VIP).
In accordance with the present invention, there is provided a multilayer film laminate comprising at least three layers having the following sequence:
(I) at least two first plastic layers (e.g., (Ia), (Ib), (Ic), etc.), each of said first layers (I) having, on one side only, a vapor deposited coating selected independently from the group consisting of aluminum, SiOx and a metal oxide of main group 2 or 3 of the periodic table of the elements; and
(II) an exterior polyolefin heat sealing layer.
As used herein and in the claims, the term “SiOx” means silicon oxide, having x oxygen atoms, e.g., from 2 to n oxygen atoms.
As used herein and in the claims, the phrase “main group 2 or 3 of the periodic table of the elements” is meant to be inclusive of the elements Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl.
Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be under stood as modified in all instance by the term “about.”
DETAILED DESCRIPTION OF THE INVENTION
The initial expectation in this connection would be that gas barrier action is determined by the gas barrier action of the best of the individual layers or is calculated as the sum of the barrier actions of the individual layers, but, surprisingly, levels of gas barrier action are obtained which are not only distinctly higher than those of the individual layers but are in part distinctly higher than the sum of the individual layers. While not intending to be bound by any theory, this may, for example, be explained by supplementary (synergistic) coverage of defects in the individual vacuum deposit coated layers.
The vapor deposited coatings of each first film layer (I) of the multilayer film laminate of the present invention may be applied by art recognized methods.
In order to achieve still higher gas diffusion barrier values, further layers may be inserted or interposed between the layers of the multilayer film laminate of the present invention, e.g., between (Ia) and (Ib) and/or between (Ib) and (II). These additional layers may: (1) have, on one side only, a vapor deposited coating selected from aluminum, SiOx and a metal oxide of main group 2 or 3 of the periodic table of the elements; or (2) be free of a vapor deposited coating, while still having specific barrier properties, e.g., a layer of polyvinyl alcohol (PVOH) free of a vapor deposited coating.
The polymers of the layers of the multilayer film laminate of the present invention having a vapor deposited coating selected from aluminum, SiOx and a metal oxide of main group 2 or 3 may include any of the known conventional plastics, preferred examples of which include, but are not limited to polyesters, polyamides, polyolefins or the copolymers thereof. These layers having vapor deposited coatings may furthermore also be composed of coextruded plies of different polymers. The thickness of the individual layers is not essential in this connection, but will, to a small extent, influence gas barrier action and, furthermore, contribute to the mechanical and thermal properties of the multilayer film laminate of the present invention.
With the multilayer film laminates according to the invention, it is in particular possible to achieve oxygen diffusion values of less than 0.01 cm
3
/m
2
d bar (determined at a temperature of 23° C., and at 75% relative humidity) and water vapor diffusion values of less than 0.1 g/m
2
d (determined at a temperature of 38° C., and at 90% relative humidity). When the multilayer film laminates are produced with more than 3 layers, it is entirely possible also to obtain multilayer film laminates which achieve distinctly lower gas diffusion values still. By means of the combination of the various plies, it is not only possible to adjust the gas diffusion values to the values required by the application, but it is also possible to vary the mechanical and/or thermal characteristics of the resultant multilayer film laminate according to the invention by modifying the layer material which is provided with a vapor deposited coating selected from aluminium, SiOx and a metal oxide of main group 2 or 3.
If one of the first layers (I) is an external polyamide layer, e.g., an external polyamide layer (Ia), with a vapor deposited coating on one side of aluminum or SiOx or a metal oxide of main group 2 or 3, the resultant multilayer film laminate is distinguished, in addition to the good gas diffusion barrier values, by elevated mechanical stability, and in particular by elevated puncture resistance, which offers advantages in handling the multilayer film laminates according to the invention, so preventing damage to the laminates and VIPs produced therefrom. Such VIPs typically must at times withstand considerable mechanical loads both during manufacture and during installation in the final application, which may result in damage to the film and thus impaired barrier properties.
In an embodiment of the present invention, one of the first layers (I) is an external polypropylene layer, e.g., an external polypropylene layer (Ia), with a vapor deposited coating on one side of aluminum or SiOx or a metal oxide of group 2 or 3, which is distinguished by particularly good water vapor barrier action. If this external layer is then combined with a subs

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