Plastic and nonmetallic article shaping or treating: processes – Recycling of reclaimed or purified process material – Of excess fiber or filament
Reexamination Certificate
2001-08-20
2004-12-14
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Recycling of reclaimed or purified process material
Of excess fiber or filament
C264S102000, C264S140000, C264S169000, C264S184000, C264S205000, C264S211000, C366S098000, C366S336000, C425S19200R, C425S198000, C425S464000
Reexamination Certificate
active
06830715
ABSTRACT:
This invention relates to a process and a device for producing elastane fibres from spinning solutions by a dry or wet spinning process using elastane recycling material, which optionally can be supplemented by admixing fresh solutions of elastane material in any proportions.
BACKGROUND OF THE INVENTION
Elastane fibres are curtly produced mainly by two fundamentally different processes, the dry spinning process and the wet spinning process. In the dry spinning press, the spinning solvent of a polyurethane solution, typically in dimethylacetamide, is removed from the fibres spun in the spinning cabinet; the removal is effected by hot gas in the spinning cabinet and heating the spinning cabinet. In the wet spinning process for producing elastane fibres, the elastane solution to be spun is usually degassed, then prefiltered and transferred to a spinning tank. The polymer solution is subsequently filtered and, after optional further introduction of additives, the spinning solution is delivered to the spinnerets by means of metering pumps. This procedure is described, for example, by F. Founnée in Chemiefasern/Textilindustrie 44/96th Year, June 1994, page 365, or in U.S. Pat. No. 3,526,689.
By elastane solutions are meant solutions of polyurethanes or polyurethane ureas, which are conventionally made up of rigid and flexible segments, in suitable solvents such as dimethylacetamide or dimethylformamide. Usually polyester diols or polyether diols, depending on the intended use, are incorporated as flexible segments into the polyurethanes (polyurethane ureas).
Fresh spinning solutions, which are prepared by various solution processes, are generally used for producing elastane fibres. A practicable solution process is described, for example, in the document U.S. Pat. No. 3,428,711. Better solution processes have been disclosed by Offenlegungsschriflen DE 43 27 805 and DE 42 22 772 A1. Whereas, in the case of DE 43 27 805, one starts from a flow of liquid reaction materials, which are heated in a microwave cavity resonator in order to prepare an elastane solution, DE 42 22 772 describes a process for preparing elastane spinning solutions which have a stable viscosity and are low in gel by using a special multistep nozzle reactor. A diagram of the complicated preparation processes is reproduced in Chemiefasern/Textilindustrie 44/96th Year, June 1994, page 393, in FIG. 3.
Solution processes for elastane material in which the use of pure recycled material, i.e. for example, of already spun fibrous elastane material, are hitherto known only for a quite specific polymer composition.
According to the Canadian Patent CA 771086, spandex yams, which are produced if from metaxylylenediamine, a polyglycol and a diisocyanate, can be dissolved with a solvent, filtered and reprocessed to form elastane fibres by dry spinning through nozzles. For solution to be possible, the yams must have a linear polymer structure. In general, however, conventional elastane yams have cross-linked structures with a network in the form of biuret and allophanate bonding and consequently cannot easily be brought into solution
In another known process, according to the Japanese Offenlegungsschrift JP 56122836, solid pieces of elastane are dissolved in isopropyl alcohol together with chloroacetaldehyde and a strong acid such as, for example, sulfuric acid and the solutions formed are further used for the production of synthetic leather. A use for elastane fibres is not described. The document DD 143916 describes the preparation of polyurethane-polyurea solutions by addition of recycled polyurethane solution during the chain extending reaction. Solutions of that kind, however, are suitable only for synthetic leather production and not for producing elastane fibres. Besides these methods of utilising materials, so-called material recycling, methods of reusing raw materials, so-called chemical recycling, are also known (cf. E. Weigand; Plastverarbeiter 1995 46 (2) pages 88-92). In chemical recycling, the polyurethane material is converted back into diamine and polyether polyol, for example, by hydrolysis with superheated steam under pressure. Other possible ways of converting polyurethanes are provided by hydrogenation, pyrolysis or high-temperature gasification.
The reason why hitherto no recycling process for normal elastane waste for example, from yarn production, has been found lies in the fact that in all solution processes it is necessary to apply high solution temperatures, usually above 100° C., in order to bring the elastane waste into solution. At these temperatures, however, the viscosity of the solution increases so much that no further processing can be carried out.
As in any elastane production process, waste arises in the form of residual fibres, for example, during disturbances in the course of production, during the spinning into other types and titres or as a result of defective batches, and as the raw materials price of the polymer material is high, as a rule more than 5.00 DM/kg polymer, the reuse of elastane waste is of great interest from the economic angle. The removal of fibrous waste (whether by dumping or by combustion) is likewise very cost-intensive, so that the provision of a process which renders possible the reprocessing of elastane waste is also very relevant from the environmental aspect.
SUMMARY OF THE INVENTION
The object is achieved by a process and a device for producing elastane fibres from spinning solutions by a dry or wet spinning process using elastane recycling material, which optionally can be carried out by admixing fresh elastane spinning solutions in any weight ratio, by adding secondary aliphatic amine, preferably diethyl amine, to the solutions.
DETAILED DESCRIPTION
The invention provides a process for producing elastane fibres by the dry spinning process or the wet spinning process using spinning solutions of elastane recycling material, optionally with the addition of fresh elastane solution, characterised in that
a) the waste obtained from elastane material, in particular from elastane fibres, is cut up, in particular to a cut length of at least 0.1 mm, preferably to a cut length of at least 1 mm, particularly preferably to a cut length of 2 to 10 mm, most preferably to a cut length of 3 to 5 mm,
b) the cut elastane material and 0.1 to 2 wt. %, based on the content of solid elastane, of a secondary aliphatic amine are introduced into the spinning solvent,
c) the mixture of cut elastane material, spinning solvent and secondary aliphatic amine is heated at a temperature of 60° C. to 150° C., with homogenisation,
d) the resulting homogeneous elastane spinning solution is prefiltered,
e) optionally with the addition of fresh elastane solution, the elastane spinning solution is mixed at 70° C. to 140° C. with a fresh elastane solution, preferably having the same solids concentration, in any mixing ratio and heating is continued,
f) the resulting spinning solution is cooled to a temperature of at not more than 70° C., preferably from 50° C. to 70° C., and filtered once more,
g) the finished spinning solution is optionally remixed, for example, by stirring, degassed and subsequently spun into elastane fibres by the dry spinning process or the wet spinning process.
Preferably the elastane waste consists of both elastanes based on polyether and elastanes based on polyester, or of wastes of mixed polyether- and polyester-containing elastanes in any mixing ratio.
The secondary aliphatic amine used is in particular diethylamine (DEA), in a quantity preferably of 0.3 to 1 wt. %, in particular preferably of 0.5 to 0.8 wt. %, based on solid elastane.
The concentration of the finished spinning solution in step g) is from 22 to 45 wt. %, preferably from 30 to 40 wt. %.
Dimethylacetamide is preferably used as the spinning solvent.
In the case of a mixed spinning solution, the elastane spinning solution is mixed with a fresh elastane solution in step e) for a period of 5 to 60 minutes.
The total mixing time in steps b) and c) together is advantageously at least 10 minutes, preferably from 60
Anderheggen Wolfgang
Herbertz Toni
Judat Helmut
Reinehr Ulrich
Sehm Tilo
Bayer Faser GmbH
Norris & McLaughlin & Marcus
Tentoni Leo B.
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