Elastane package

Details Elastane package Elastane package

2002-01-11

2004-08-10

Cole, Elizabeth M. (Department: 1771)

Fabric (woven, knitted, or nonwoven textile or cloth, etc.)

Woven fabric

C428S397000, C242S118000, C242S159000

Reexamination Certificate

active

06774064

ABSTRACT:

This invention relates to an elastane spool comprising a winding of elastane threads having a titre of greater than 160 dtex, particularly from 160 dtex to 1400 dtex, and a bobbin weight of elastane threads of at least 1.5 kg, characterised in that the elastane threads have a ribbon-shaped fiber cross-section, wherein the ratio of the width of the elastane threads to the thickness of the elastane threads in cross-section is at least three to one.
This elastane spool is used for the production of textile sheet products and for the production of disposable articles of hygiene.
Elastane threads in the sense of the present invention are mono- or multi-filamentary continuous fibres, of which at least 85% by weight consist of segmented polyurethanes or polyurethane-ureas. The fiber-forming polymers have a segmented structure, i.e. they consist of “crystalline” and “amorphous” blocks (“hard segments” and “soft segments”). On account of their crystallinity, the hard segments act as fixed points of the network and are thus definitive for the strength of mouldings or fibres produced from these polymers. In contrast, the soft segments, the glass transition temperature of which has to be below the temperature of use, are definitive for the elasticity of these elastanes.
Elastanes of this type are usually produced by the addition polymerisation of long chain dihydroxyl compounds (macrodiols) with diisocyanates and low molecular weight dihydroxyl- or diamino compounds as chain lengtheners. Polyurethane-ureas which are obtained by chain lengthening with diamines are used for high-grade elastane filaments (also known as Spandex), firstly because they exhibit a high hard segment melting point compared with diol-lengthened polyurethanes, due to their larger number of hydrogen bonds between the polymer chains, and secondly because they exhibit excellent mechanical and elastic properties. Elastane threads are usually produced by spinning solutions of these segmented polyurethane-ureas in highly polar solvents such as dimethylformamide and dimethylacetamide, by means of what is termed the dry spinning processes or the wet spinning processes, or alternatively are produced by spinning from the melt, with a spinning solvent being dispensed with. After spinning, and optionally after conditioning, elastane threads are usually wound to form bobbins.
As a rule, the bobbin weights for elastane threads range from 0.5 to 1.5 kg, depending on the titre and on the field of use. However, there are fields of use where an even greater bobbin length of elastane threads is desirable. This is always the case if the further processing procedure in which the elastane threads are used must not be interrupted too often, which would result in more frequent machine stoppages and thus in additional undesirable costs.
An example of one of the aforementioned areas of use is the production of articles of hygiene, e.g. disposable nappies, in which elastic fibres are incorporated in nappy liners which contain an absorbent material. Good adaptability of these nappies to the corresponding body shape is thereby achieved. In general, 2-3 elastic fibres are incorporated on each longitudinal side of nappy liners. Elastane threads are generally incorporated in nappy liners by adhesive bonding with hot melt adhesives termed “hotmelts”. Hot melt adhesives of this type, which are suitable for the structural adhesive bonding of PE and PP liners and of other nonwoven liners, for example, generally consist of isoprene/styrene-based synthetic rubbers, which are treated with mineral oils and additives in order to improve their flowability.
In order to achieve good adhesive bonding of elastane threads to nappy liners, the elastane threads should usually be produced as free as possible from conditioning agents or with a low content of conditioning agents.
Two processes which describe the production of elastane threads have hitherto become known in the prior art. Japanese Patent JP 2,000,038 describes elastane spools with a bobbin weight of at least 1.5 kg, wherein the conditioning agent content of the elastane threads on the bobbin is less than 2% by weight. The elastanes described there comprise a titre range from 308 to 1232 dtex, corresponding to about 280 to 1120 den.
Japanese Patent JP 10,305,060 claims elastane spools weighing more than 0.8 kg which are produced via a fiber reserve on another bobbin. For this purpose, elastane threads with the same titre range from 308 to 1232 dtex and with a conditioning agent content of 0.01-1% by weight are wound on bobbin spools.
In practice, this type of elastane spool is very difficult to process further, particularly if the bobbin weight is high, because elastane threads have a tendency to adhere to each other strongly. Due to the high bobbin weights, the outer layers of fibres of course press more intensively on the inner layers of fibres, so that after production and storage the fibres only run off the bobbins in an inferior manner. What is termed the “shoe sole effect” is observed here. This means that entire layers of fiber adhere to the bobbins and can no longer be unwound unless the elastane threads have already been conditioned to a sufficient extent during their production.
On the other hand, as mentioned above, the conditioning agent content of elastane threads on larger bobbins must not be too high, in order to achieve good adhesive bonding of the fibres to nappy liners.
Surprisingly, it has now been found that this problem can be solved by forming elastane threads from fibres which have a quite definite cross-sectional shape, so that even if the conditioning agent content of the elastane fiber on the bobbin is possibly relatively high, e.g. greater than 1% by weight , or in particular if it is even greater than 2% by weight, it is possible to achieve good adhesive bonding to nappy liners.
The present invention relates to an elastane spool comprising a winding of elastane threads having a titre of greater than 160 dtex, particularly from 160 dtex to 1400 dtex, and a bobbin weight of elastane threads of at least 1.5 kg, characterised in that the elastane threads have a ribbon-shaped fiber cross-section, wherein the ratio of the width of the elastane threads to the thickness of the elastane threads in cross-section is at least three to one, particularly at least five to one, more preferably at least seven to one, most preferably at least ten to one.
The bobbin weight of the elastane spool preferably ranges from 1.5 to 10 kg, particularly from 1.8 to 9 kg, most preferably from 3 to 8 kg.
As mentioned above, starting from elastane threads of defined cross-sectional shape, and despite a significantly higher content of conditioning agent, elastane threads can be produced on bobbins with bobbin weights from 1.5 to 5 kg or more, and can subsequently still be perfectly adhesively bonded under customary production conditions during their incorporation in nappy liners. A further advantage of the invention results from the fact that even finer elastane threads, of 150 dtex for example, can still be perfectly adhesively bonded, despite their reduced cross-sectional areas, by spraying on an adhesive. This is because they do not exist in the usual, compact, round cross-sectional shape, but exist in the form of a ribbon with a greater ribbon width.
Recycled material obtained from elastanes, which still contains considerable proportions of the original conditioning agents, is also particularly suitable for producing the elastanes of the elastane spools.
An elastane spool is preferred in which the elastane fiber has a content of conditioning agent of more than 1% by weight, particularly more than 2% by weight, most preferably more than 2.2% by weight, which is contained distributed in the fiber volume and/or on the fiber surface.
More especially, the elastane threads are multi-filamentary and in particular comprise more than 80, preferably more than 160, most preferably more than 400 elementary filaments.
An elastane spool is particularly preferred which comprises a winding of elastane threads in which t

Affiliated with

Also associated with

Rating

Elastane package does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Elastane package, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Elastane package will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3358931