Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2001-04-04
2003-02-25
Boykin, Terressa M. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423300, C428S423700
Reexamination Certificate
active
06524712
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to resilient thermoplastic multilayer films having at least two layers. The multilayer films of the present invention have at least one first layer (1) of thermoplastic polyurethane, and at least one second layer (2), which is formed from a thermoplastic elastomer with low water vapor permeability. The combination of at least one layer of thermoplastic urethane polymer and at least one layer of a thermoplastic elastomer results in a flexible multilayer film having a good mechanical property profile and a very good water vapor barrier effect.
BACKGROUND OF THE INVENTION
Flexible films with good mechanical properties are required for the production of flexible filled articles filled with gaseous or liquid media, such as water beds, for example. It is known that such applications may be served by films of plasticised PVC. Given the specific properties of PVC, a relatively large amount of material has to be typically used.
It is additionally known that thermoplastic polyurethanes are used for producing flexible containers for gaseous or liquid media. Of advantage here is the high mechanical property level, whereby relatively small wall thicknesses may be achieved. A problem is the high diffusion coefficient for polar media such as water vapor, for example.
Single-layer films of thermoplastic polyurethanes (TPE-U), processes for the production thereof and the use thereof are known according to the prior art for example from EP-A-0 308 683, EP-A-0 526 858, EP-A-0 571 868 or EP-A-0 603 680. The structures described in these specifications may be incorporated into laminating films as a higher melting-point layer or layers for multilayer films or are already incorporated into the laminating films known in the art. The production of TPE-U films using substantially incompatible polymers as flatting agents in TPE-U is also described, e.g., in DE-A 41 26 499.
Multilayer, coextruded films of TPE-U and other raw materials assigned to the thermoplastics group have also been described. In addition to coextrusion with polyolefinic thermoplastics, in which the polyolefinic layer does not as a rule undergo any interlayer adhesion with regard to the TPE-U layer and merely exhibits the function of a supporting or separating layer, multilayer structures with good interlayer adhesion are also known. EP-A-0 842 768 describes, for example, a multilayer structure of TPE-U and a polyolefinic coupling agent. In the case of such structures, cracking occurs in the thermoplastic layer as a result of the low elasticity of the thermoplastics in the event of relatively frequent cyclic loads with high strain values, thereby resulting in functional impairment.
In addition to thermoplastic polyurethanes, there exist further flexible materials which are generally covered collectively by the generic term thermoplastic elastomers (TPE). Of primary importance among the groups suitable for film processing are block copolymers. These include, in addition to TPE-U, styrene-based systems (TPE-S), polyether ester types (TPE-E) and polyether block amides (TPE-A). Films based on TPE-E are described for example in U.S. Pat. No. 5,859,083, wherein particular emphasis is placed therein on high water vapor permeability. The same applies to the films of TPE-A described in EP-A-0 761 715. TPE-S suitable for films and the use thereof are described in DE-A-1 9628 834, for example. An overview of the thermoplastic elastomer group is given for example in: Thermoplastic elastomers: a comprehensive review, ed. N. R. Legge, G. Holden and H. E. Schroeder, Carl Hanser Verlag, Munich 1987 and Thermoplastische Elastomere—Herausforderung an die Elastomerverarbeiter, ed.: VDI-Gesellschaft Kunststofftechnik, VDI Verlag, Düsseldorf, 1997.
SUMMARY OF THE INVENTION
The object was thus to provide a flexible film with a mechanical property profile superior to that of plasticised PVC combined with high water vapor impermeability. To minimize production costs, the combination of properties should, where possible, be obtained in a single-stage process.
In accordance with the present invention, there is provided a multilayer film comprising:
at least one first layer (1) of thermoplastic polyurethane;
at least one second layer (2) of thermoplastic elastomer; and
optionally a third layer (3) of thermoplastic polyurethane (which may be the same or different than the thermoplastic polyurethane of the first layer),
wherein the ratio of the water vapor permeability level of said first layer (1) to the water vapor permeability level of said second layer (2) is at least two, and when said optional third layer (3) is present, said first (1) and third (3) layers together enclose said second layer (2).
Other than in the operation examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified in all instances by the term “about.”
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, the water vapor permeability of the multilayer film of the present invention are very low. If the ratio of the water vapor permeabilities of the layers (1) and (2) is increased to at least six, the water vapor permeability of the multilayer films of the present invention may be further minimized. Therefore, in a preferred embodiment of the multilayer film of the present invention, the ratio of the water vapor permeability level of the first layer (1) to the water vapor permeability level of the second layer (2) is at least six.
The first layer (1) and optional third layer (3) of the multilayer film of the present invention are each independently composed of at least one thermoplastic polyurethane elastomer, preferably of a predominantly linear thermoplastic polyurethane elastomer, the relatively long chain diol component of which is a polyester diol or polyether diol and which exhibits a Shore-A hardness of 70-95, preferably 85-95, as determined in accordance with DIN 53,505.
Suitable thermoplastic polyether/ or polyester/polyurethane elastomers and/or mixtures thereof may for example be produced by art-recognized batch and/or partially and/or fully continuous processes, in particular by the reaction in a screw extruder of the following components a) through e).
a) organic, preferably aromatic or cycloaliphatic diisocyanates;
b) polymeric diols with molecular weights of preferably 500 to 8000;
c) chain-extending components with molecular weights of preferably 60 to 400;
d) optionally in the presence of catalysts; and
e) optionally in the presence of auxiliary substances and/or additives.
Components a) through e) which may be used in the production of suitable thermoplastic polyether/ or polyester/polyurethane elastomers and/or mixtures thereof are described in further detail as follows.
a) The organic diisocyanates (a) preferably comprise aromatic or cycloaliphatic diisocyanates. In detail, the following may be mentioned by way of example: aromatic diisocyanates, such as 2,4- and 2,6-tolylene diisocyanate, 4,4′-, 2,4′- and 2,2′-diphenylmethane diisocyanate or mixtures thereof, cycloaliphatic diisocyanates, such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate and 4,4′-, 2,4′- and 2,2′-dicyclohexylmethane diisocyanate or mixtures thereof.
b) Suitable higher molecular weight diol compounds (b) with preferred molecular weights of 400 to 8000 are preferably molecules of linear structure with a low glass transition temperature or softening point. These include polyetherols and polyesterols. However, hydroxyl group-containing polymers, for example polyacetals such as polyoxymethylenes and in particular water-insoluble formals and aliphatic polycarbonates, in particular those from diphenyl carbonate and 1,6-hexanediol, produced by transesterification, are also worthy of consideration. Moreover, hydroxyl group-capped diol compounds of polyolefins, in particular aliphatic hydroxyl group-capped copolymers of ethylene and butylene are also feasible. The diol compounds have t
Brandt Rainer
Cassel Antoine
Craig Aileen
Schledjewski Ralf
Akorli Godfreid R.
Boykin Terressa M.
Franks James R.
Wolff Walsrode AG
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