Plastic and nonmetallic article shaping or treating: processes – With twining – plying – braiding – or textile fabric formation
Reexamination Certificate
2000-12-29
2003-08-05
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With twining, plying, braiding, or textile fabric formation
C264S130000, C264S184000, C264S210500, C264S210800, C264S211120, C264S211140, C264S211170, C264S233000
Reexamination Certificate
active
06602453
ABSTRACT:
This application is a 371 of PCT/EP99/04180, filed Jun. 17, 1999 (PCT filing date.
The invention relates to a process for producing elastane yarn having a linear density of at least2500 dtex by the wet spinning process and the thereby producible coarse linear density elastane yarn having a wide cross section and a low residual solvent content. The process comprises the steps of spinning an at least 25% strength by weight stable-viscosity elastane solution into a coagulation bath, washing and optionally drawing, drying by contact heating, setting, spin finishing and winding the yarn, the filaments leaving the coagulation bath passing around a diverting roller disposed just above the coagulation bath liquid, the as-spun filament linear density amounting to not more than 1% of the value of the final yarn linear density, the jet stretch ratio being within the range from 0.5 to 50, the contact heating temperature being at least 220° C. and the contact time of the elastane yarn being at least 2 seconds.
BACKGROUND OF THE INVENTION
Elastane yarns are synthetic filament yarns which are produced as mono- or multifilaments—dependent on the intended use—within the linear density range from 11 to 2500 dtex (cf. F. Fourne: Chemiefasern/Textilindustrie 44/96; June 1994, page 392). Higher linear densities, which extend more or less into the typical application range of natural rubber yarns, are perfectly interesting, however, for example for use as elastic undertapes for upholstery fabrics or as leg border for underwear and swimwear articles and also for the medical and technical sector.
However, the need to evaporate the spinning solution solvent in the spinning chimney imposes technical limits on producing coarse elastane linear densities by the dry spinning process. Owing to the high linear density of 2500 dtex or more and the small yarn surface area of coarse linear densities, it is very difficult to evaporate sufficient spinning solution solvent in order that the yarn may be drawn off without sticking together. Droplets of the spinning solution solvent still present at the down-stream end of the spinning chimney lead to stuck-together filaments which, after winding onto bobbins, are no longer satisfactorily processible off the bobbins. Furthermore, without incurring reduced spinning efficiency due to a reduction in the spinning speed, it is very difficult to lower the residual solvent content in the elastane yarn to a minimum without further cost-intensive steps, such as washing or steaming of the yarn.
By using a lower spinning speed it is possible to increase the residence time in the dry spinning chimney and to reduce the residual level of, for example, dimethylacetamide (DMAC) solvent. However, this is at the expense of the spinning efficiency. Nor is it possible to raise the temperature in the spinning chimney to beyond a certain level, since this may give rise not only to discolourations but also to softening and melting of the yarn. The softening range of elastane yarn varies with the polymer composition, but is typically 180-230° C., and the melting range is about 250-270° C.
For this reason, in the field of the dry spinning of elastane yarn, yarn having a final linear density of above 2500 dtex has not been disclosed before. A fineness of up to 3240 dtex has been reported by Globe Manufacturing Comp. for elastane yarn reactively spun by the chemical spinning process, and a linear density of up to 2464 dtex has been reported by Fujibo Spandex for elastane yarn produced by wet spinning. Compare P. A. Koch: Faserstoff-Tabellen in Chemiefasern/Textilindustrie, February 1979, page 100.
In order that elastane yarn may be further processible, for example in ribbon weaving, they must have a certain minimum strength. A tenacity of at least about 0.4-0.5 cN/dtex is required in the case of coarse linear densities to meet these demands.
However, in the case of elastane yarn having a coarse linear density of greater than 2500 dtex it is very difficult to achieve adequate strength, since the higher level of residual solvents, for example dimethylacetamide, which act as plasticizer between the polymer chains, markedly reduce the yarn's strength.
It is an object of this invention to develop elastane yarn and a process for its production which meet the abovementioned requirements and more particularly to provide a high final linear density elastane yarn which has a low residual solvent content, high strength and high residual extensibility.
SUMMARY OF THE INVENTION
This object is achieved according to the invention by a process for producing wet-spun elastane yarn comprising the steps of: spinning an at least 25% strength by weight, preferably at least 30% strength by weight, stable-viscosity elastane solution into a coagulation bath to form a set of filaments, washing and optionally drawing, drying the converged set of filaments by contact heating to form elastane yarn, setting, spin finishing and winding the elastane yarn with a final linear density of at least 2500 dtex, preferably 3500 dtex to 20,000 dtex, more preferably 4000 dtex to 15,000 dtex, the filaments leaving the coagulation bath being passed around a diverting roller disposed just above the coagulation bath liquid, characterized in that
a) the as-spun filament linear density is not more than 1% of the value of the final linear density of the yarn,
b) the jet stretch ratio of the yarn is within the range from 0.3 to 50, preferably within the range from 0.5 to 50,
c) the contact heating temperature is at least 220° C., preferably at least 230° C., especially at least 250° C., more preferably at least 260° C., and
d) the contact time between the elastane yarn and the heating medium of the contact heating is at least 2 seconds, preferably at least 3 seconds, especially at least 5 seconds.
DETAILED DESCRIPTION
Preferably, the contact heating used is a heating means featuring heated rollers.
It is particularly advantageous to dry the elastane yarn in a heating means which utilizes an electrically heated roller combined with an unheated idling roller.
The temperature at the surface of the heating roller is to be particularly within the range from 250 to 280° C., particularly preferably within the range from 260 to 270° C.
Particularly good results are obtained when the contact time of the yarn on the heating roller is 10 to 30 seconds, preferably 10 to 15 seconds.
It was found that the wet spinning process of the invention makes it possible to produce elastane yarn having a final linear density of far in excess of the previously known limit of 2464 dtex whilst obtaining a tenacity of distinctly above 0.4 cN/dtex, an extensibility of above 500% and a residual solvent content below 0.5% by weight.
The invention also provides elastane yarn having a final linear density of at least 2500 dtex, especially 3500 dtex to 20,000 dtex, more preferably within the range from 4000 dtex to 15,000 dtex, and a ribbony cross section, characterized in that the ratio of width to height in the cross section through the yarn is at least 4:1, especially at least 8:1, more preferably at least 10:1.
The elastane yarn has in particular a very low residual solvent content. The residual solvent content of the yarn is less than 1.0% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight at a final linear density of up to 5000 dtex.
The residual solvent content of the yarn is less than 2.0% by weight, preferably less than 1% by weight, more preferably less than 0.6% by weight, at a final linear density of 5000 to 10,000 dtex.
The residual solvent content of the yarn is less than 3.0% by weight, preferably less than 1.5% by weight, more preferably less than 1% by weight, at a final linear density of more than 10,000 dtex.
Preferred elastane yarn has a tenacity of at least 0.4 cN/dtex, preferably at least 0.5 cN/dtex.
Preferred elastane yearn has an extensibility of at least 500%, preferably at least 550%.
Of particular interest is elastane yarn which has a ribbony cross section, the width of the yarn in cross section being grea
Anderheggen Wolfgang
Herbertz Toni
Reinehr Ulrich
Sehm Tilo
Bayer Faser GmbH
Norris & McLaughlin & Marcus
Tentoni Leo B.
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