DYEING OF TRANSPARENT POLYAMIDE FIBRES.pdf原版资料

All-Russian Scientific-Research Institute of Synthetic Fibres, Tver'. Translated from Khimicheskie Volokna, No. 6, pp. 30-32, November-December, 1997.
The granulate dyed by this method is processed with difficulty. Undrawn monofilaments have nubs and break during drawing. This can be attributed to the effect of the residual concentration of acetic acid used for maintaining the pH of the dye bath. For a more stable spinning regime, dyed granulate is mixed with undyed granulate in the ratio of 50:50 or 30:70. The concentration (in %) of dye in the polymer increases correspondingly. Due to the complexity of the problem of purifying wastewaters and the duration and laboriousness of the process, it is expedient to add the dye in the form of powder in the spinning stage [10]. However, it is not yet possible to add small amounts of dye (0.05-0.15%) directly to the polymer melt.
The simplest method of dyeing is dusting. However, simultaneous dusting of the granulate with the modifier and dye causes them to be unevenly distributed in the melt, makes spinning unstable, and produces different shades, and consequently nonuniformity of the monofilaments with respect to the tenacity. For this reason, the possibility of simultaneous application of dye and modifier on the polymer in a centrifugal mixer was tested [I0]. The mixer's working parts rotated at the rate of 900 rpm and the duration of mixing was 6 rain. The dye and modifier are strongly and uniformly bound to the surface of the granules in high-speed mixers. Processing such mixtures into monofilaments involved no difficulties.
First washing
Second washing
[
Index
[
Concentrationof caprosols,%
pH of dye bath Bath modulus Duration, h
Temperature, *C Duration, h
Temperature, *C Duration, h
Different methods of adding dyes to the polymer in fabrication of transparent polyamide 6 (PA 6) and polyamide 66 (PA 66) monofdaments are compared in the present article. Three methods were investigated: dyeing crumb from water baths, dusting polymer crumb in an apparatus of the "tumbler" type, and mixing granulate with the dye in a high-speed centrifugal mixer.
We previously described the results of studies on fabrication of transparent polyamide monofilaments by incorporation of special modifiers in the polymer. The character of the effect of the chemical nature and amount of modifier, on the structure and transparency of the monofilaments, methods of incorporating the modifier in the polymer, and the effect of the technological parameters on the transparency and physicomechanieal indexes of the finisbed thread were investigated [3-7].
As Table 2 shows, dyeing in all cases decreased the specific tenacity by 3.0-6.5%, and the greatest decrease occurred as a result of dusting. The reaction of the active groups of the dyes, SO3 and SO2 - NH2, for example, with the end groups of the polymer macromolecules could be the cause of this as it would decrease their length due to reamidation of amide bonds [11]. The transparency of the dyed monofilaments was on the level of or better than the transparency of undyed samples.
We can hypothesize that this change is due to the physical hindrances to motion of the polymer chains by the dye molecules [12]. The increase in transparency is also due to the dye's blocking of active sites in the macromolecules of PA 6 and PA 66 capable of reacting with water, causing the formation of large supermolecular formations which worsen the transparency of the monofilaments.
Dyes capable of absorbing undesirable wavelengths of visible light and passing the others are used to give polyamide monofilaments color without altering their transparency. Such dyes should either be dissolved in the polymer or added in the form of freely disperse particles in order to prevent light scattering [8]. Caprosols, which are soluble in a polyamide melt, were selected as such dyes [9].
Temperatur 4-5 1:2 1,0
98-100 1,0
50-60 1,0
30-40
[
PA 66
0,075 - 0,132
3-4 1:2 5,0
98-100 1,0
50-60 1,0
3040
TABLE 2. Comparative Characteristics of Dyed (numerator) and Undyed (denominator) PA 6 and PA 66 Monof'daments
Polymer
Method of dyeing
PA 6 PA 66
Dusting From water baths In a centrifugalmixer Dusting
The method of dyeing crumb from water baths allows uniformly dyeing the polymer granules. Dyeing is conducted according to the regimes reported in Table I.