Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1996-07-17
2001-11-06
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S147000, C428S148000, C428S149000, C428S150000, C428S166000, C428S325000, C428S327000, C428S328000, C428S330000, C428S331000
Reexamination Certificate
active
06312786
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a composite sheet.
Various methods of manufacturing composite sheets are known in the art. All have various drawbacks.
SUMMARY OF THE INVENTION
The principal object of the present invention is to provide a novel method of manufacturing a composite sheet, and a composite sheet produced by the method, which overcomes the drawbacks of the prior art.
The composite sheet according to the invention comprises a supporting sheet bonded to a “hetero sheet” consisting of (1) a heterogeneous blend of an elastic thermoplastic matrix that cures semicrystalline or amorphous subsequent to processing, and (2) particles of added material distributed therein. The particles can be mixed and extruded along with the matrix although they are heterogeneously bound therein. In the hetero sheet the particles of added material heterogeneously distributed therein are detached from the surrounding matrix at their interfaces therewith and the material of the hetero sheet stands up at the many areas of detachment to create a fleecy surface.
Such a composite sheet can be produced from many different fundamental materials. The fundamental material of the hetero sheet can be a polymer in the form of a polyolefin, a polyamide, a polycarbonate, or a polyester or a copolymer thereof. The particles must be of a material that cannot be processed adhesively with the fundamental material. Appropriate added materials are, for example, such inorganic fillers as titanium dioxide, lampblack, kaolin, ground quartz, silicic acid, chalk, and lithopone.
It is, however, also possible, and indeed recommended to pair off the polymers in the hetero sheet, with each member being an organic substance, polystyrene or polyamide particles with a matrix in the form of a polyolefin, especially polyethylene or polypropylene, or other pairs of polymers that cannot be processed mutually adhesively, for example.
The supporting sheet will preferably be of elastomer, thermoplastic rubber for example, a copolymer of styrene, butadiene, and styrene, an SBR elastomer, or EPDM (ethylene-propylene rubber).
The hetero sheet can be bonded to one or to both sides of the supporting sheet, with various types of material added. The hetero sheet can be bonded to the supporting sheet with a thermoplastic adhesive. The supporting sheet can consist of several layers.
Methods of manufacturing such composite sheets can be based on different principles.
One such method comprises the steps that will now be described. As this term is used herein, the “hetero sheet” comprises a heterogenous blend of an elastic thermoplastic matrix that cures semicrystalline or amorphous with, distributed therein, one or more particles of an added material that can be mixed and extruded with the matrix but are heterogeneously bound therein. The hetero sheet is bonded to a supporting sheet consisting of an elastomer that can be stretched to a considerable extent and can return to its original or optionally to a slightly lower order of magnitude. The composite sheet is stretched to an extent below the maximal extent that the supporting sheet can be stretched to. The hetero sheet is likewise stretched and the distributed particles of added material simultaneously detach from the thermoplastic matrix enclosing them at the interfaces therewith in such a way that, as the stretched supporting sheet is released, it either returns to its original configuration or remains extensively stretched, whereas the material of the hetero sheet stands up at the many ripped interfaces and generates a fleecy surface.
The supporting sheet can be extruded along with the hetero sheet. On the other hand, it is also possible, for example, to extrude the melt from slotted dies and produce a stack of sheets. In this event the supporting sheet will either have been coated with a thermoplastic adhesive or be coated with such an adhesive on-line.
It should be noted, in particular, that the sheet can be stretched not only longitudinally and transversely but also in superimposed directions. This will provide the fleece with a “nap” and render it particularly dense.
The composite sheet should be stretched by as much as 300% of its original area. It is also possible to use a low-elasticity supporting sheet that will remain extensively stretched. The result will be less volume and larger area.
Fleeciness and elasticity can be increased if the composite sheet is embossed before being stretched. The composite sheet can be mechanically stretched longitudinally and transversely in a tenter. The composite sheet can also be co-extruded as a tube and the tube sealed and inflated in order to attain the desired fleeciness.
It is also possible to employ a stretchable woven or knit instead of a polymeric sheet.
Another object of the present invention is to employ the aforesaid method not to produce fleeciness for the purpose of improving feel, but to increase the volume of a composite sheet, whether smooth or rough.
This object is achieved by sandwiching between two supporting sheets a hetero sheet that has been rendered fleecy.
The standing up and detachment of the heterogeneous particles is in this event exploited inside the composite sheet to increase its volume.
Particularly recommended is a volume-increased composite sheet comprising five sheets, specifically a supporting sheet against a hetero sheet against another supporting sheet against another hetero sheet against another supporting sheet.
One particular embodiment of the method comprises the steps that will now be described. A composite sheet comprising a hetero sheet between two supporting sheets is extruded. The composite sheet is mechanically stressed, by wrapping it around a short radius for example, detaching the particles of added material distributed within the hetero sheet from the surrounding thermoplastic at their interfaces therewith, such that the material of the hetero sheet stands up at the many ripped sites of detachment, increasing the volume of the composite sheet.
A composite sheet comprising five sheets, specifically a supporting sheet against a hetero sheet against another supporting sheet against another hetero sheet against another supporting sheet can be co-extruded, for example, and then volume-increased.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
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Milde Hoffberg & Macklin, LLP
Nordenia Technologies GmbH
Rickman Holly C
Thibodeau Paul
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