Plastic and nonmetallic article shaping or treating: processes – With twining – plying – braiding – or textile fabric formation
Patent
1998-11-24
2000-03-28
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
With twining, plying, braiding, or textile fabric formation
8125, 264187, 26421114, 26421115, 264233, D01D 1006, D01F 202
Patent
active
060427671
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for manufacturing a cellulosic yarn by spinning a solution of cellulose in a tertiary amine oxide, the solution possibly containing water and/or a stabilizer, to form fibers or filaments, coagulating, washing, and drying.
2. Discussion of Related Art
W095/24524 discloses a process for improving the color characteristics of woven fabrics made from so-called Lyocell yarns. Lyocell yarns are solvent-spun cellulose yarns manufactured by spinning a solution of cellulose in an organic solvent. The solvent is essentially an aqueous tertiary amine oxide, for example N-methylmorpholine-N-oxide (NMMO). In accordance with W095/24524, woven fabrics made from the cited cellulose yarns are subjected to a mercerizing process, i.e., treated with an alkaline solution. This mercerizing corresponds in principle to that common for cotton woven fabrics, and it is preferred to employ an aqueous NaOH solution with a concentration of 10 to 30% by weight at room temperature or a somewhat higher temperature (for example, up to 35.degree. C.). Subsequently, a washing of the woven fabrics with water can be carried out. To neutralize the lye bath, the fabric is treated with a diluted aqueous acid, washed repeatedly to remove the acid, and then dried. According to the examples in W095/24524, in which aqueous NaOH solutions were employed in concentrations of 14% and 25% by weight, respectively, the treatment of woven fabrics made from Lyocell yarns was carried out at room temperature over a period of 45 seconds. The woven fabrics obtained exhibited a deeper shade after dyeing than non-mercerized fabrics. Although the appearance of the mercerized fabrics was better after 5 washings than that of non-mercerized fabrics, and the yarns of the mercerized fabrics had shorter fibrils than non-mercerized fabrics, it was shown that this mercerizing conducted on the fabrics, i.e. on yarns that had previously been dried, led among other things to a deterioration of the textile properties, especially the strength.
SUMMARY OF THE INVENTION
The invention was therefore based on the objective of providing a process for manufacturing cellulosic yarns by spinning a solution of cellulose in a tertiary amine oxide, the solution possibly containing water and/or a stabilizer, to form fibers or filaments, coagulating, washing, and drying, whereby the aforementioned disadvantages are at least reduced using this process.
This objective is met in the cited process in that the yarns are treated before drying with an aqueous alkaline solution for a period less than 20 seconds.
BRIEF DESCRIPTION OF THE DRAWINGS
The Figure illustrates a wet abrasion testing apparatus used to measure the tendency of cellulosic yarns to form fibrols.
As will be explained in more detail, the process of the invention can on the one hand be employed to reduce effectively the fibrillation of Lyocell yarns. Furthermore, the process is time-saving and cost-effective, since it can be directly integrated into the manufacturing process of the yarns, thus obviating the need for a separate treatment step for the resulting textile fabrics.
Due to the treatment of the yarn with the aqueous alkaline solution, the whiteness level of the yarn increases. This has the advantage that a subsequent bleaching of the yarns is no longer required if they are to be used to produce so-called "white goods" or are to be dyed in very light shades.
Preferably, the treatment with the aqueous alkaline solution is carried out for 1 to 15 seconds, whereby 1 to 10 seconds is especially preferred and 2 to 6 seconds is most preferred. An aqueous NaOH or KOH solution is preferably used. The concentration of alkali in the aqueous alkaline solution should be between 0.5 and 20% by weight, preferably between 10 and 14% by weight. The aqueous alkaline solution can contain additional inorganic or organic auxiliaries, such as in particular emulsifiers, salts, glycerin, or the like. Through the addition of such surface-active substances
REFERENCES:
patent: 5662858 (1997-09-01), Firgo et al.
Hashemzadeh Abdulmajid
Raidt Peter
Akzo Nobel nv
Tentoni Leo B.
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