Plastic and nonmetallic article shaping or treating: processes – With twining – plying – braiding – or textile fabric formation
Patent
1992-10-21
1995-03-21
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
With twining, plying, braiding, or textile fabric formation
264168, 2642106, 2642108, 264211, 524606, 528323, 528324, 528335, 528336, D01D 512, D01F 660, D02G 100, D02J 122
Patent
active
053993063
DESCRIPTION:
BRIEF SUMMARY
This invention relates to improvements in the production of nylon yarn for carpet and textile purposes.
Typical bulked continuous filament (BCF) carpet yarns (i.e. yarn having a decitex per filament (or dpf) of 15 or more) may be produced, and in this specificiation are defined as being so produced, using spin-draw-bulk processes in which the filaments, after being melt-extruded through the spinneret, and cooled in the spinning chimney, are converged to form the yarn which is fed to a feed-roll and then to one or more draw rolls having a surface speed higher than that of the feed roll dependent on the draw ratio required. Finally, the yarn is bulked (textured) by, for example, being passed into a bulking jet or by any other conventional texturing method.
Textile yarns may be produced, and in this specification are defined as being so produced using a POY (Partially Oriented Yarn) process in which the filaments, after being extruded, cooled and converged, are wound-up so that the resulting yarn is partially drawn (oriented) in a single stage.
Regardless of the type of process, for each filament the mass wound up per unit time must on average equal the mass per unit time extruded through the corresponding spinneret hole, and hence for a given filament ##EQU1##
Thus to improve the productivity of the process, either in terms of a yarn of a given dpf at an increased wind-up speed (WUS) or a yarn of increased dpf at a given WUS, the throughput/hole needs to be increased.
However, at a given WUS increasing the throughput/hole leads (other things being equal) to slower filament cooling and hence a greater distance and time from the spinneret is necessary for the filament to reach a given temperature. This results in a less stable threadline. Moreover in polymers such as nylon 6.6, spherulitic crystallisation half-times are of a similar order or less than the times needed to cool spinning threadlines to below their glass transition temperature (Tg). This also leads to increased opportunity for crystallisation, in particular for the growth of spherulites in the hot unoriented parts of the threadline.
Spherulites are essentially spherical structures based on a crystalline framework which grow from a nucleus to give, in nylon 6.6, microscopically distinctive zones which may be several microns in diameter. They are described in more detail in e.g. Macromolecular Physics by B Wunderlich Vol 1 Academic Press 1973.
Spherulites are undesirable because they can affect the tensile properties (and hence the drawing performance) and the lustre of the filament.
A reduction in the tensile properties of a spun yarn can readily lead to breakage of filaments during drawing, which in turn may render that process unworkable or commercially uneconomic. Lustre is an important aspect of the visual aesthetics of a yarn and is a measure of the degree to which a yarn reflects and scatters light, which may vary from the smooth mirror-like to the rough or chalk-like.
Lustre may be quantified by its Half Peak Width (HPW) value, more mirror-like lustre giving lower HPW values. Reference may be made to GB Patent Specification No 2190190 for a description of Half Peak Width (HPW), its photogoniometric method of measurement and related parameters such as the peak intensity (Imax) of the photogoniometric curve.
The reflection and scattering of light by filaments is of course also strongly affected by the level of any delustrant, such as TiO.sub.2, which may be included. However, such delustrants are not optically equivalent to the rough surface resulting from the presence of spherulites. TiO.sub.2 tends to reduce the peak intensity in the photogoniometric curve but not change HPW. Spherulites tend to change both parameters with low peak intensities accompanying high HPW. Thus HPW is indicative of the effect of spherulites on lustre even in the presence of TiO.sub.2.
Of course, unlike spherulites, properly incorporated TiO.sub.2 has negligible effect on the tensile properties.
There is no hard and fast rule as to the number and size of spherulites
REFERENCES:
patent: 3707522 (1972-12-01), Simons
patent: 4457883 (1984-07-01), Howse et al.
Follows Gordon W.
Richardson John
Wilson Michael P.
E. I. Du Pont de Nemours and Company
Tentoni Leo B.
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