Improved dyeability of acrylic fibre with cationic and disperse dyes

Size: px

Start display at page:

Download "Improved dyeability of acrylic fibre with cationic and disperse dyes"

Roland Tucker
6 years ago
Views:

1 Indian Journal of Fibre & Textile Research Vol. 23, December 1998, pp Improved dyeability of acrylic fibre with cationic and disperse dyes A K Mukherjee & S D Bhattacharya' Department of Textile Technology, Indian Institute of Technology, New Delhi , India and R Varadarajan Department of Chemistry, Indian Institute of Technology, New Delhi 1\0 016, India Received 6 June 1997; revised received 9 March 1998; accepted 23 March 1998 Acrylic fibres were hydrolysed with sodium hydroxide of different concentrations at 50 C for different durations and then dyed separately with cationic dyes (C!. Basic Red 18 and C!. Basic Blue 3) and disperse dyes (C!. Disperse Orange 3 and C.I. Disperse Red 17) in different per cent of shades. The dyeing performance of these hydrolysed acrylic fibres was studied taking into account the structural transformation occurred due to hydrolysis process. It has been observed that the hydrolysed fibres always exhibit higher dye uptake than the untreated ones. Hydrolysed fibres also have higher diffusion coefficients than the untreated fibres. Cationic dyes show better dyeing performance than the disperse dyes. The wash fastness of dyed samples is quite satisfactory at all levels of dyeing. Keywords: Acrylic fibre, Cationic dyes, Diffusion coefficient, Disperse dyes, Dyeing, Dye uptake 1 Introduction Acrylic fibres have poor dyeability because of the compactness of their structure. Therefore, the commercial acrylic fibres always contain one or more comonomers which enhance their dyeability by providing more dye receptive sites. A number of studiesv" pertaining to the manufacture of acrylic fibres with higher water sorption and good dye uptake have been reported. Khamrakulov et al.. I3 reported the development of acrylic fibres from a blend of polyacrylonitrile (PAN) and hydrolysed PAN waste which showed better dyeing performance as compared to the unmodified acrylic fibres. Zbigneva" prepared acrylic fibres from acrylonitrile with hydrolysed waste ~hich showed a significant increase in sorption and fixation of cationic dyes. However, no detailed work has been reported on commercial acrylic fibres modified by hydrolysis and their dyeing behaviour with different dyestuffs. The commercial acrylic fibres exhibit unlevel dyeing 'Present address: Department of Textile Chemistry, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara , India. To whom all the correspondence should be addressed. with some restriction to shades. Therefore, in the present work, a commercial acrylic fibre was first hydrolysed to different degrees and then the hydrolysed fibres were dyed with cationic and disperse dyes under identical conditions and their dyeing behaviour studied. The diffusion of dye into the hydrolysed fibre structure and the equilibrium dye uptake of both the dyes on hydrolysed acrylic fibres have also been. investigated. 2 Materials and Methods 2.1 Materials A commercial acrylic fibre (acrylonitrile, 92%; methyl acrylate, 7% and sodium methyllyl sulphonate, 1%) was hydrolysed with sodium hydroxide solution of different concentrations (5%, 10% and 15%) at 50 C for different time periods. Different hydrolysed acrylic fibres were selected on the basis of their complex structure developed due to the hydrolysis process. For a particular sodium hydroxide concentration, three hydrolysed fibres having highest, medium and lowest nitrogen content at 50 C were chosen. Hydrolysed fibres at this temperature exhibit minimum strength loss

262 INDIAN 1. FIBRE TEXT. RES., DECEMBER 1998 and contribute to all possible structural changes in the fibre at a reasonably good level. Two cationic dyes, namely C.I. Basic Red 18(BI) and C.

2 262 INDIAN 1. FIBRE TEXT. RES., DECEMBER 1998 and contribute to all possible structural changes in the fibre at a reasonably good level. Two cationic dyes, namely C.I. Basic Red 18(BI) and C. 1 Basic Blue 3(BII), and two disperse dyes, namely c.i. Disperse Orange 3(DI) and c.i. Disperse Red 17(DII) were used. These dyestuffs were selected on the basis of the difference in their molecular weights. Cationic dyes were purified by recrystallizing in methanol and drying in an oven at 30 C for 2h. Disperse dyes were first refluxed using soxhlet apparatus for 72h in acetone, recrystallized and then dried at 30 C for 2h. 2.2 Methods Dyeing A mixture of 0.1 % acetic acid (ph 3.5) and 0.1 % cationic retarder (Acifix TD) was added to the 1.0% dye solution/dispersion. About g of fibres were then put into it, maintaining the material-to-liquor ratio at I :50. Dispersing agent (Lyocol 01) was used in case of dyeing with disperse dyes. Dyeing was carried out in a closed system (Beaker Dyeing Machine) with tlifferent depth of shades, viz 0.5%, 1.0%, 2.0%, 3.0% and 5.0%. The dyeing temperature was raised from 70 C to 100 C at the rate of 10 C/min. After dyeing for a required period of time, the sample was taken out, cooled slowly, washed with distilled water, soaped at boil for 20 min, dried and conditioned at 65% RH and 20 C. Dye uptake was measured on a UV -visible spectrophotometer (Perkin-Elmer, Lamda 3B) Calculation of Diffusion Coefficient The apparent diffusion coefficient (Da) was calculated using the method of Hiil 15 by measuring the dye uptake of fibre with the time intervals of t from an infinite dyebath Wasb Fastness Test Wash fastness of different dyed samples was assessed by ISO test method No.3. 3 Results and Discussion 3.1 Effect of Hydrolysis on Dyeing Performance of Acrylic Fibres Tables I and 2 indicate that the hydrolysed acrylic fibre can successfully be dyed with both cationic and disperse dyes. The dye uptake of all the hydrolysed acrylic fibres increases with increase in dyebath concentration (i.e. shade percentage) and decreases- with the decrease in nitrogen content in fibres, irrespective of the concentration of sodium hydroxide. At all the levels of dyeing, the dye uptake of hydrolysed Table I-Dyeing performance of hydrolysed acrylic fibres [Hydrolysis temp., 50 C) NaOH cone, Nitrogen Dye uptake, rng/g of fibre <lnd content in B I (C I Basic Red 18) B II (C I Basic Blue 3) treatment hydrolysed Shade%~O time fibre, % Contr.ol (U ntreated) 5% NaOH 0.5 h h h % NaOH 0.5 h h h % NaOH 0.5 h h h

MUKHERJEE et al.: IMPROVED DYEABILITY OF ACRYLIC FIBRE 263 Table 2-Dyeing performance of hydrolysed acrylic fibres [Hydrolysis temp., 50 C] NaOH cone.

3 MUKHERJEE et al.: IMPROVED DYEABILITY OF ACRYLIC FIBRE 263 Table 2-Dyeing performance of hydrolysed acrylic fibres [Hydrolysis temp., 50 C] NaOH cone. Nitrogen Dye uptake, mg/g of fibre and content in 01 (C I Disperse Orange 3) n II (C I Disperse Red 11) treatment hydrolysed Shade% ~ time fibre, % Control \ (U ntreated) 5% NaOH 0.5 h h h % NaOH 0.5 h h h % NaOH 0.5 h h h \ fibres is higher than that of the untreated fibre. As the concentration of sodium hydroxide increases, the dye uptake in the hydrolysed fibre increases, depending on the degree of hydrolysis. The degree of hydrolysis, as indicated by the nitrogen content values, does not reveal any relationship with dye uptake. For example, the fibres hydrolysed with 10% NaOH for 30 min and having 19.4% nitrogen content show the dye uptake of 44.2 mg/g and 40.1 mg/g of fibre with dyes BI.and BII respectively, and 33.4 mg/g and 31.6 mg/g of fibre with dyes DI and DII respectively at 5% shade. Again, fhe fibre hydrolysed with 15% NaOH for 30 min and having 18.4% nitrogen content shows the dye uptake of 46.2 mg/g and 42.1 mg/g of fibre with dyes BI and BII respectively, and 34.7 mg/g and 31.7 mg/g of fibres with dyes DI and DII respectively. This reveals that the hydrolysed fibres may have almost the same nitrogen content values but they may not exhibit the same dye uptake. This is possibly due to the fact that different reaction conditions (hydrolysis) develop different structural transformations in the macromolecular polymeric chains. The sample which is hydrolysed to the maximum extent (N2 content, 7.8%) also shows higher dye uptake compared to untreated fibre but the improvement is less as compared to that for other hydrolysed samples. This may be due to the structural changes that occur due to the hydrolysis process. These changes can be envisaged from the X-ray analysis. Dye molecules penetrate the amorphous and disoriented region of the fibres". The extent of hydrolysis, which changes the morphology of the polymeric chains, together with the dyeing temperature (above the TJ help the dye molecules to migrate into the fibre matrix to a greater extent for level dyeing. Among the two cationic dyes, the dyeing performance of dye BI is better than that of dye BII. This may be due to the difference in their molecular weights. The dye uptake values for the disperse dyes are comparatively lower than those for the cationic dyes at all levels of dyeing. For example, for untreated acrylic fibres, the dye uptake with cationic dye BI is 7.2 mg/g of fibre and that with disperse dye DI is 6.2 mg/g of fibre at 1%.shade. The same behaviour is observed for the fibres hydrolysed to the same extent and dyed with disperse and cationic dyes. This may be due to the fact that basic or cationic dyes are attracted by the electronegative groups present in the fibres" apart from the dispersion forces, common to both disperse and cationic dyes, that hold the dye molecules in the fibre.

264 INDIAN J. FIBRE TEXT. RES., DECEMBER 1998 3.

4 264 INDIAN J. FIBRE TEXT. RES., DECEMBER Equilibrium Dyeiug of Hydrolysed Acrylic Fibres The equilibrium dye uptake of cationic and disperse dyes on the fibres hydrolysed with different concentrations of sodium hydroxide at 50 C for different time periods is reported in Table 3. It is observed that the equilibrium dye uptake of cationic dyes is always higher than that of disperse dyes at all levels of dyeing. Similarly, the hydrolysed fibres always show higher equilibrium dye uptake than the untreated acrylic fibres in case of both cationic and disperse dyes. This may be due to the presence of more electronegative groups in the hydrolysed fibres, apart from the dispersion forces, common to both disperse and cationic dyes, that hold the dye molecules in the fibre The higher dye uptake on the hydrolysed acrylic fibres compared to untreated fibres may be explained on the basis of following facts: - Hydrolysis loosens the compact structure of acrylic fibres, thereby leading to higher penetration of dye molecules into the fibre structure. The effect is more pronounced at a higher degree of hydrolysis. - The presence of more voids/amorphous regions in the hydrolysed fibres and less orientation may also give more dye uptake to the hydrolysed fibre. This effect will be more pronounced with higher extent of hydrolysis (i.e. with less N2 content). - Due to hydrolysis, the polymeric chains become shortened, as indicated by the lower viscosity data. This offers comparatively more number of dye sites in the fibres, thereby increasing the dye uptake. - The structural development due to hydrolysis may also offer more dye receptive groups, facilitating higher dye uptake. 3.3 Dye Diffusion on Hydrolysed Acrylic Fibres Figs I and 2 show the dye uptake and the ratio of dye absorbed at time t to that after infinite time (C/C a ) respectively for untreated and hydrolysed acrylic fibres. It is observed that the untreated acrylic fibres attain the maximum dye uptake in 100 min, whereas the hydrolysed fibres with nitrogen contents 18.4% and 12.4% take 90 min and that with 7.8% nitrogen content takes 80 min. As the structure of acrylic fibre is compact and rigid, it requires longer time for the dye molecules to diffuse and migrate into the fibre". The diffusion of dyes into the acrylic fibres is controlled by the segmental mobility of the polymer chain", void structure and, to a considerable extent, molecular size of the dye molecules", The apparent diffusion coefficients (Da) (Table 4) are also higher for the hydrolysed acrylic fibres compared to the untreated acrylic fibres. For a particular dye, the Da values of different hydrolysed fibres gradually decrease with the increase in degree of hydrolysis. The diffusion of dye into the fibre is influenced by the polymer composition, porous structure and molecular size Table 3-Equilibrium dye uptake of cationic and disperse dyes on hydrolysed acrylic fibres [Hydrolysis temp., 50 C] NaOH cone. and Nitrogen content in Equilibrium dye uptake, mg/g of fibre treatment time hydrolysed fibre, % BI BII Nil (untreated) 5% NaOH 0.5h h h % NaOH 0.5 h h h % NaOH 0.5 h h h

5 MUKHERJEE et al.: IMPROVED DYEABILITY OF ACRYLIC FIBRE 'r ~ Q 10 go go E O~U_~ C.I. Bosic R~ 18(81) L_~~ L_~_L~! e Q. ~ 40 >- o 30 c.i aes«81u~3 (B II) C.I Disp~rn R~d 17( D II) ItO &0 Tim., min Fig. I--Dye uptake vs dyeing time for cationic and disperse dyes at 100 C [untreated acrylic fibre (-e-), and hydrolysed acrylic fibres with 18.4% (-0-), 12.4% (-d-) and 7.8 % (-x-) nitrogen content] 1 0 of the dye molecules":". In the cationic dyes, dye BII has higher Da value (2.47xlO 9 ern's") than the 0" dye BI (1.82xlO 9 em's"), whereas in disperse dyes, dye 01 has higher Da value (2.0x ern's") 0 6 than dye 011 (1.93xlo 9 em's"). This may be attributed to the molecular size of the dye molecule. As the molecular size of the dye increases, the diffusion coefficient decreases under 0,' identical conditions of dyeing. 'd 0 u v 1 0 0' C.I.Basic R.d 18(81) r: Fig. 2-qC a vs Ji for cationic and disperse dyes [untreated acrylic fibre (-e-), and hydrolysed acrylic fibres with 18.4% (-0-), 12.4% (-d-) and 7.8% (-x-) nitrogen content] o Wash Fastness of Dyed Fibres It has been observed that the untreated acrylic fibres dyed with cationic and disperse dyes show better wash fastness property at all levels of dyeing. Among the dyes studied, the cationic dyes show comparatively better wash fastness than the disperse dyes. In various hydrolysed acrylic fibres, the wash fastness is very good (5 for cationic dyes and 4-5 for disperse dyes) up to 2% of shade. For higher per cent of shade, the wash fastness rating varies from 4-5 to 4 with cationic dyes and from 4 to 3-4 with disperse dyes. In cationic dyes, the dye BI shows better wash fastness. The compact structure of untreated acrylic fibres needs higher activation energy, compared to the hydrolysed acrylic fibres, for the dye molecules to migrate. This makes the dye molecules difficult to remove

6 266 INDIAN J. FIBRE TEXT. RES., DECEMBER 1998 Table 4-Diffusion coefficients of hydrolysed acrylic fibres dyed with cationic and disperse dyes [Hydrolysis condition: 15% NaOH at 50"C for different time periods] Dye Mol. wt. of Diffusion coefficientx I0 9, ern's" dye Untreated fibre Hydrolysed fibre (23.7% N 2 ) 18.4% N z 12.4% N2 7.8% N2 BI BII DI DII from the acrylic fibres and hence the high wash fastness. Disperse dyed fibres (both untreated and hydrolysed) exhibit lower wash fastness than the cationic dyed fibres. This may be due to the absence of strong dye-fibre interaction between the disperse dyes and the fibre. The physical and chemical changes in the structure of the fibres might also affect the wet fastness properties. 4 Conclusions The hydrolysed acrylic fibres show higher dye uptake, depending on the extent of hydrolysis, at all levels of dyeing than the untreated acrylic fibre. Hydrolysed acrylic fibres also exhibit higher dye uptake at equilibrium of dyeing and have higher diffusion coefficients (Da) than the untreated acrylic fibres. The higher Da values for hydrolysed acrylic fibres depend on the molecular size of the dye used. With the increase in dye concentration, dye uptake increases and it depends on the degree of hydrolysis. The wash fastness of the dyed fibres is quite satisfactory. The dyeing performance of the hydrolysed acrylic fibres (in terms of dye uptake, Da and wash fastness) is always better with cationic dyes than disperse dyes. References I Sadaham A, J Soc Dyers Colour, 107 (1991) Mishra S P & Elangovan S P, Text Dyer Printer, 24(25) (\ 99\) Mishra S P &Elangovan S P, Text Dyer Printer, 25(1) (1992) Shukla S R, Hundekar R V & Saligram A N, J Soc Dyers Colour. 107 (1991) Kamat S Y, Alat D V & Murthy P K, Colourage, 38(3) (1991) Thorburn B D, McGuigan A A & Fresenius J, Anal Chem, 34(6) (1991) Khamraev A L, Abdukarimova M Z, Ibragimova G I & Zaved I V, Tekhnol Tekst Promst, 5 (1991) Yang Y & Ladisch C M, Text Res J, 62(9) (1992) Rizovska V, Todorova I, Karkinska M & Lashovski S, G/as Hem Techno/ Maked, 10(1) (1991) Giorgi De, Rita M, Risano C A & Ruggero C, Melliand Textilber, 70(7) (1989) 526. II Cegarra K, Pucute P & Castro B, Tinctoria, 85(9) (1988) Milyavskaya I Kh, Zakirov I Z & Ergashev K E, Khim Volokna, I (1987) Khamrakulov G, Milyavskaya IE, Zakirov I Z, Ergashev I Z & Mironova T S, Uzb Khim Zh, 5( 1990) Zbigneva Zh A, Khim Khim Tekhnol, 36(5)(1993) Harwood R J, McGregor R & Peters R H, J Soc Dyers Colour, 88(1972) Flath H J, Moritz R & Badawich J, Textiltech, 28 (\978) Herbulot G, J Soc Dyers Colour, 82 (1966) Beevers R B, Macromol Rev, 3 (1968) Rosenbaum S,J Polym Sci, Part A, 3 (1965) Flath H J, Moritz R, Kasten K & Mietz ~, Textilveredlung, 13 (1978) Flath H J & Moritz R, Textilveredlung, 15 (1980) Voltz J J, Text Chem Color, 9 (1977) 113.

DYEING OF PA 6.6 FIBRES:EFFECT ON PROPERTIES AND BEHAVIOUR OF THERMAL TREATMENT AND SOLVENTS. Azurém Guimarães - Portugal

DYEING OF PA 6.6 FIBRES:EFFECT ON PROPERTIES AND BEHAVIOUR OF THERMAL TREATMENT AND SOLVENTS M. S. Queirós Domingues a, J. I. N. Rocha Gomes a, J. A. Martins b a Universidade do Minho - Departamento de