Coating processes – Foraminous product produced
Reexamination Certificate
2000-01-14
2002-12-17
Ball, Michael W. (Department: 1733)
Coating processes
Foraminous product produced
C156S244110, C156S244270, C427S365000
Reexamination Certificate
active
06495206
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of textiles. In particular, it relates to textiles wherein a polymeric “plastic” layer is bonded to a fabric substrate, and the plastic layer is in the form of a foamed matrix.
BACKGROUND TO THE INVENTION
In the production of plastic coated textiles, the product has customarily been made by one of the following alternate procedures:
1) casting a molten plastic layer onto a fabric carrier;
2) bonding a pre-formed plastic layer onto a fabric carrier by calendering and/or use of adhesives; and
3) extruding a molten plastic layer onto a fabric carrier.
When it has been intended to provide a plastic layer that is “foamed” and resilient due to included gas-filled cells or voids, it has been customary to create the expanded plastic matrix in two stages. First a plastic layer containing a blowing agent in a quiescent state is cast onto a fabric carrier. Then the formed composite textile is exposed to heat which causes gas to evolve within the plastic layer—the process of “blowing”.
A disadvantage of this latter process is that the level of heat that is required to activate the blowing agent will cause carrier components in many types of fabric carriers to fuse, e.g. polyethylene will fuse at 175° F., whereas various types of chemical blowing agents require a temperature in excess of 300° F. to create foaming conditions.
Attempts have been made to incorporate a blowing agent into an extruded plastic to form a foamed plastic layer. However, with the use of conventional chemical blowing agents, this process produces often a textile wherein the foamed polymeric layer lacks resistance to crushing and results in a flattened polymeric layer that has almost no or little foam voids left in the structure after crushing. In a standard extrusion procedure, a chilled calendaring roll presses the extruded sheet of a melt into a fabric carrier and sets, and bonds, the plastic layer with the textile. Extruded textiles prepared with typical classic blowing agents have typically lacked the resilience to recover sufficiently from this compression step to provide a satisfactorily foamed textile.
A need exists for a foamed plastic composite textile that is formed on a permeable carrier, e.g. a woven, knitted or non-woven fabric, with a low fusing temperature, while exhibiting good recovery or resilience in response to applied pressure. This invention addresses this need as well as providing other advantages.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a method of producing a foamed sheet textile is provided:
1) extruding a heated, extrudable polymeric melt from a linear extrusion die in the form of a sheet with two faces, the melt containing as expanding agents:
1) a first extrusion activated gas source dispersed within said melt; and
2) thermally expandable micro-spheres having encapsulating shells each containing compressed gas and being dispersed within said melt
2) allowing the expanding agents to commence to expand, with the gas source generating gases to form a compressible foamed matrix in the melt and the micro-capsules expanding into resilient, compression resistant micro-spheres suspended within said foamed matrix, thereby providing a foaming melt;
3) depositing the foaming melt onto the surface of a permeable carrier that is in sheet form and into the surface of which the foaming melt partially penetrates; and
4) allowing the foaming melt so formed to set to provide a resilient, compression-resistant, foamed plastic/polymeric layer that is bonded to the carrier to form the resulting textile.
Preferably, the extrusion melt, upon being laid-down on the permeable carrier, is carried on the carrier through a rotating gate defined by a gap between two rollers, one of the rollers being cooled to set the melt. This establishes a constant height for the foamed layer on the textile. The roller delivering the carrier may be powered, and the second cooled roller may be traction-driven off of the powered roller by end-rims extending from the second roller.
The resulting product of the invention is a textile having a permeable carrier into the surface of which the foamed plastic layer has expanded while still molten and while the expanding agents, and particularly the encapsulated expanding agent, is still expanding. Thus, the boundary surface of the carrier is at least partially embedded within the foamed plastic/polymeric layer. Expansion of the foaming layer both above and within the carrier may continue after the formed textile exits the rotating gate, and particularly while the foaming melt is confined between the carrier and the second of the two rollers for an interval of rotation of the second roller.
By inclusion of thermally expandable micro-spheres in the melt the foamed plastic layer contains inclusions of thermally expanded hollow micro-spheres having encapsulating shells that are resiliently compressible. This enhances the crushability of the textile.
An advantage of this process is that polymers like PVC, polypropylene, polyethylene and other conventional polymers may be used to provide the foamed plastic layer.
Further, a textile may be produced with an integrally-formed skin region present at it's polymer surface, the skin region containing less voids than the intermediate region of the foamed layer lying between the skin region and the carrier. This is accomplished by cooling the extrusion die through which the melt is extruded and/or cooling the roller that contacts the foaming melt as such melt passes through and beyond the gap of the rotating gate.
An advantage of this process is that a textile can be produced at lower temperatures wherein the carrier would otherwise plastically deform at temperatures above, for example, 300 degrees Fahrenheit, or even 200 degrees Fahrenheit.
To produce the textile, the extruder is fed with a composition suitable for generating a foamed polymer comprising:
1) at least one expandable thermoplastic polymer capable of being extruded;
2) a first thermally activated gas generant dispersed within said polymer; and
3) thermally expandable resiliently compressible micro-spheres, disbursed within said polymer;
said generant and micro-spheres being capable on heating of expanding said polymer.
REFERENCES:
patent: 3032828 (1962-05-01), Bethe et al.
patent: 3616170 (1971-10-01), Closson, Jr.
patent: 3735511 (1973-05-01), Gilbert et al.
patent: 5418257 (1995-05-01), Weisman
patent: 6103152 (2000-08-01), Gehlsen et al.
patent: 1264852 (1972-02-01), None
Ball Michael W.
French David J.
Morbern, Inc.
Musser Barbara J
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