In-line heat treatment of homofilament crimp fibers

Details In-line heat treatment of homofilament crimp fibers In-line heat treatment of homofilament crimp fibers

2001-12-07

2003-10-14

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

With twining, plying, braiding, or textile fabric formation

C264S168000, C264S211170

Reexamination Certificate

active

06632386

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to lofty nonwoven fiber webs. The present invention relates specifically to lofty nonwoven fiber webs of homofilament crimped fibers and means for utilizing the web in its lofty and uncompressed state to retain the advantages of web structure.
BACKGROUND OF THE INVENTION
Webs of homofilament crimped thermoplastic fibers are useful for various fluid handling or retaining materials and the like because of their open structure, resiliency, and economy of manufacture. Particularly, the use of a single thermoplastic polymer in the making of the crimped fibers is good for economical and consistent manufacture. However, one may lose the benefit of the lofty crimped fiber web structure if the homofilament crimped web is processed by known means. Because a homofilament crimped web is usually loosely bonded, such means will include compaction of the web or exposure to high heat, in order to increase the integrity of the web for later processing. Compaction, as in Jacobs et al., U.S. Pat. No. 5,810,954, will decrease bulk or loft of the web through mechanical action as the web is drawn between compaction rollers. Also, this type of processing may result in mechanical failure of the rollers as the filaments become entangled in the mechanical works of the rollers.
In another known means of increasing web integrity, exposure to high heat in an effort to provide thermal bonding between filaments of the web, as in the hot air knife (HAK) teaching of U.S. Pat. No. 5,707,468 to Arnold et al., will result in relaxation of the fiber crimp with resultant loss of bulk for the web.
Conversely, it has been found that the crimps of a homofilament crimped thermoplastic fiber web may be crystallized, or set, to retain their loft through low applications of heat as in U.S. Pat. No. 6,123,886 to Slack. However this treatment does little to increase the integrity of the web for modem, high-speed, line-transfer manufacturing, and as taught in Slack, is a slow, off-line process unsuitable for economical manufacture rates.
Therefore, there is a need in the art for methods and materials utilizing the lofty crimped homofilament nonwoven web with high loft intact and with sufficient integrity to the lofty crimped web to enable high speed manufacturing processes to achieve economy.
Definitions
Within the context of this specification, each term or phrase below will include the following meaning or meanings.
“Article” refers to a garment or other end-use article of manufacture, including but not limited to, diapers, training pants, swim wear, catamenial products, medical garments or wraps, and the like.
“Bonded” or “bonding” refers to the joining, adhering, connecting, attaching, or the like, of two elements. Two elements will be considered to be bonded together when they are bonded directly to one another or indirectly to one another, such as when each is directly bonded to intermediate elements.
“Connected” refers to the joining, adhering, bonding, attaching, or the like, of two elements. Two elements will be considered to be connected together when they are connected directly to one another or indirectly to one another, such as when each is directly connected to intermediate elements.
“Cross direction assembly” refers to a process in which disposable absorbent products are manufactured in an orientation in which the products are connected side-to-side, in the transverse direction shown by arrow
49
in
FIG. 3
, a process utilizing a cross direction assembly entails products traveling through a converting machine parallel to the direction of arrow
49
, as opposed to “machine direction assembly” in which the products are connected end-to-end or waist-to-waist.
“Disposable” refers to articles which are designed to be discarded after a limited use rather than being laundered or otherwise restored for reuse.
“Disposed,” “disposed on,” and variations thereof are intended to mean that one element can be integral with another element, or that one element can be a separate structure bonded to or placed with or placed near another element.
“Fabrics” is used to refer to all of the woven, knitted and nonwoven fibrous webs.
“Film” refers to a thermoplastic film made using a film extrusion and/or foaming process, such as a cast film or blown film extrusion process. The term includes apertured films, slit films, and other porous films which constitute liquid transfer films, as well as films which do not transfer liquid.
“Flexible” refers to materials which are compliant and which will readily conform to the general shape and contours of the wearer's body.
“Homofilament” refers to a fiber formed from only one predominate polymer and made from a single stream of that polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for coloration, anti-static properties, lubrication, hydrophilicity, etc.
“Integral” or “integrally” is used to refer to various portions of a single unitary element rather than separate structures bonded to or placed with or placed near one another.
“Layer” when used in the singular can have the dual meaning of a single element or a plurality of elements.
“Liquid impermeable,” when used in describing a layer or multi-layer laminate, means that a liquid, such as urine, will not pass through the layer or laminate, under ordinary use conditions, in a direction generally perpendicular to the plane of the layer or laminate at the point of liquid contact. Liquid, or urine, may spread or be transported parallel to the plane of the liquid impermeable layer or laminate, but this is not considered to be within the meaning of “liquid impermeable” when used herein.
“Liquid permeable material” or “liquid water-permeable material” refers to a material present in one or more layers, such as a film, nonwoven fabric, or open-celled foam, which is porous, and which is water permeable due to the flow of water and other aqueous liquids through the pores. The pores in the film or foam, or spaces between fibers or filaments in a nonwoven web, are large enough and frequent enough to permit leakage and flow of liquid water through the material.
“Longitudinal” and “transverse” have their customary meaning, as indicated by the longitudinal and transverse axes depicted in FIG.
3
. The longitudinal, or long, axis lies in the plane of the article and is generally parallel to a vertical plane that bisects a standing wearer into left and right body halves, when the article is worn. The transverse axis lies in the plane of the article generally perpendicular to the longitudinal axis. The article, although illustrated as longer in the longitudinal direction than in the transverse direction, need not be so.
“Machine direction” refers to the length of a fabric in the direction in which it is produced, as opposed to “cross direction” which refers to the width of a fabric in a direction generally perpendicular to the machine direction.
“Machine direction assembly” refers to a process in which disposable absorbent products are manufactured in an orientation in which the products are connected end-to-end or waist-to-waist, in the longitudinal direction shown by arrow
48
in
FIG. 3
, a process utilizing a machine direction assembly entails products traveling through a converting machine parallel to the direction of arrow
48
, as opposed to “cross direction assembly” in which the products are connected side-to-side.
“Meltblown fiber” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity heated gas (e.g., air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed for example, in U.S. Pat. No. 3,849,241 to

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