Strand materials

Details Strand materials Strand materials

1996-05-08

1998-06-16

Thomas, Alexander

Stock material or miscellaneous articles

Structurally defined web or sheet

Nonplanar uniform thickness material

156494, 156229, 2642102, B32B 326

Patent

active

057667306

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to strand material.
Strand material is usually made from synthetic materials by spinning filaments from a spinnerette and performing various operations on the filaments, the first of which usually involves drawing the filaments. Threads and yarns suitable for clothing and finer household textiles, for weaving, knitting and sewing as well as for making non-woven fabrics, are made from such filaments.
Strand material has been made principally, however, for coarser material than the filamentary materials aforementioned, by slitting and/or fibrillating tape or sheet plastics materials. Attempts to produce yarns and threads from film materials, while promising much from the point of view of costs of production and usability of less expensive polymer materials, have not in practice yielded acceptable products of the fineness required for weaving, knitting and sewing.
GB 1 091 588 describes a process for making "elongated articles", referred to as cords and said to be suitable for use in wrappers, handicrafts, and ornaments and as tire cords, by stretching a composite type of 0.5-50 mm in width consisting of a stretchable base layer and a lamina or coated layer thereon which is chemically or physically different from the base layer and then longitudinally stretching the tape so it becomes curled or convoluted along each side marginal position. The films, whether as base layer or laminated or coated layer, must be non-orientated or partially orientated thin films capable of being stretched in at least one direction.
The curled or convoluted configuration can be made to contain linear or core articles such as monofilament, multifilament, spun yarn, thread, cord and metal articles such as wire, by feeding in such articles as the tape is stretched to form the convolutions.
U.S. Pat. No. 3,967,038 discloses the production of untwisted synthetic resin string comprising two rolled portions each spiral in cross section and formed by inwardly rolling toward each other the opposite side edges of a strip of thermoplastic resin film stretched at least longitudinally thereof.
Despite the fact that these patents are already time-expired, their products have not apparently appeared as articles of commerce.
WO 93/11931 covers essentially the same ground as GB-1 091 588, though, surprisingly, written without knowledge of GB-1 091 588. In the course of experimental work aimed at producing commercial products on the basis of the disclosure of WO 93/11931, it was established that the teachings of WO 93/11931 and of GB-1 091 588 and U.S. Pat. No. 3,967,038 lack an essential element for the production of stable, permanently coiled strand material that will find utility in a wide variety of areas that can be as demanding even as sewing thread. The present invention includes the essential element aforementioned.


SUMMARY OF THE INVENTION

The invention comprises a method for making strand material comprising drawing a laminar material having a first layer of drawable material and a second layer of elastically extensible material so that the first layer extends inelastically while the second layer extends elastically so that the drawn material tends to curl into a coiled strand configuration.
The drawable material may be drawn until it is fully drawn, and may be overdrawn--by "overdrawn" is meant drawn to a higher draw ratio than the minimum normally sufficient to produce a fully drawn material.
The laminar material may have an associated drawable filament material which may be a filament yarn--which may be drawn with said first layer. Indeed, such filament material may be coated with a drawable polymer coating to form said first layer. On the other hand, the filament material may be coated with an elastomeric material to form said second layer.
At least one of said first and second layers may contain inclusions that modify its behaviour under extension. The second layer may contain compressible or fluid inclusions, such for example as gas bubbles.
The second layer may contain incompre

REFERENCES:
patent: 3416991 (1968-12-01), Yoshimura
patent: 4082598 (1978-04-01), Katagi
patent: 4167234 (1979-09-01), Gordon et al.

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