Study of the effect of dye – resin complexation on the degree of dye absorption were carried out using Procion Blue MX-R to dye cotton fabric in the presence hexamethylol melamine (MR6) and its phosphate derivative (MPR4) for resination. The highest degree of dye exhaustion was obtained at 400C for 1 hour with the resinated fabric showing more affinity for the dye than the ordinary fibre. Improved fastness properties was recorded which show a relatively higher stability of dye – resin complex formed in the fibre.
Dyeing is a process of colouring materials, such as textile fabrics, leather, paper to mention but a few so that the colour becomes an integral part of the material [1]. This is because Dyes are soluble compounds that can be absorbed and retained by these materials or chemically combined because they often exhibit a natural affinity for them [2]. Cotton fabric is mostly made up of cellulose by analysis and the most widely used textile fabric accounting for more than 50% of the total consumption in the world [3]
i. ii. iii. iv.
Cotton fibre have affinity for several dyes namely vat, direct, reactive and sulphur but reactive dyes remain the most versatile class of dye used for cotton. It differs from other dye by their ability to react chemically with cotton fabric through the reactive group in it thus forming covalent bonds which is a strong binding force between molecule leading to the production of wide range of shades of good light fastness and excellent wash fastness.
Reactive dyes are widely used for the exhaustion dyeing of cotton and other cellulosic fibres, but studies have reveals that one of the problems associated with reactive dyeing is the dye uptake by the fibre which is hardly up to 70%. A major reason advanced for this low utilization degree compared to other types of dyestuff is that the dye can react not only with the fibre nucleophile (cellulosate anion) but also with the nucleophiles (common hydroxyl ions) present in the dyebath (since dyeing are carried out under aqueous alkaline medium) and bonding with water, thus creating hydrolysis
Good dye exhaustion depend on promoting fiber – dye reaction while suppressing hydrolysis of the dye. Previously control of pH have been helpful, but the use of dye-fixative to improve the dyeing properties of the dye on the fibre become inevitable to improve exhaustion. Resin dye-fixative techniques
infra red fixation ii. reactive resin dye fixative technique are employed [4, 5]. These could be valuable in reducing the environmental impact of unfixed dyes added to the dyeing assistants that are release as effluent from the dyeing house. i.
i. ii. iii. iv.
Conditions under which the dyeing was carried out remain important as this may enable researcher to draw out or improve conditions that will bring about optimum result in terms of substantivity of the dye in the fibre temperature of dyeing , time of dyeing, pH of dyeing resin application (more recent) may affect
fastness properties economy of dyeing and dye uptake which have direct impact on quantity of dye in effluent discharged from dye house and posing environmental risk.
The hydroxyl groups in the methylol resin react with a reactive group in the dye molecule forming dye – resin complex. There is a possibility of the dye being simultaneously absorbed by the fiber while reacting with the resin during dyeing and resination. The dyeing and resination will produce a network of fiber-dye-resin structure which may lead to improve dyeing properties.
A plain woven 100% cotton fabric obtained from Kwari market in Kano, Nigeria was used. This was cut to 10cm by 10cm dimension A reactive dye, Procion Blue MX-R supplied by Zayo-Sigma Chemicals was used in this work Hexamethylol melamine (MR6) prepolymers the phosphate derivative (MPR4) synthesized and characterized [6] was used for the resination. All the reagents used are analytical grade and need no further purification.
CH 2OH
HOH2C N N
N CH 2OH
HOH2C N
(MR6)
N
N
CH 2OH
CH 2OH
O
H +
H N
H O
N
N
-
P OH OH CH 2OH
HOH2C N
CH 2OH
CH 2OH
O
(MPR4)
N
N
NH 2 SO3H Cl
O
HN
H N
N N N Cl
SO3H
Procion Blue MX-R (Zigma)
Fabric Purification A plain woven 100% cotton fabric was used. The fabric was cut to 10cm x10cm dimension and purified by process of mercerization [7]. This involved treating the fabrics in 10% aqueous ammonia (L.R 1:50) at 5oC for 30min then neutralized in 1% acetic acid, rinsed with water and dried for 24hrs.
Fabrics Resination and Dyeing Application of the resins involves treating the pieces of cotton fabrics by impregination with 1.0g of MR6 and MPR4 separately. The fabrics were then dyed and cured at 1000C for 15 minutes.
Dyeing was carried out as described by [8]. 2% dyeing was carried out at goods to liquor ratio of 1:50 0.5g NaCl, 0.15g Na2CO3 and 2% NaOH as dye assistants. A dyeing temperatures maintained while varying the time of dyeing e.g. 400C at 10 – 60 min., 500C at 10 – 60 min Temperature was initially held for 30 minutes after which 2ml of 2% NaOH was added gradually to maintain pH within 10 - 11. Dyeing continue for another 30 minutes The final dyed fabrics were rinsed with water for 5 minutes at 300C and 10 minutes at 600C so that final rinsed water was colourless
Samples of dye-bath exhaust were collected for studying dye exhaustion and fixation Calibration curve was obtained by taking portions of 0.25, 0.5, 0.75 and 1.00 ml of freshly prepared dye-bath before dyeing commenced and diluting to 100ml in a volumetric flask and absorbance readings taken on UV – Visible spectrometer Model CE 3040. During dyeing, 1 ml portion of sample of dye liquor was taken at given time intervals of 10 minutes, transferred into 50ml volumetric flask, diluted to the mark and the absorbance reading taken as well.
The percent exhaustion or dye uptake was estimated using equation % Dye uptake = (A0 – At)/A0 x 100 Where A0 is absorbance before dyeing, At is absorbance at time „t‟ The affinity of the dye for the fibre was adopted from the thermodynamic expression ∆μf = RT ln [Df]/[Ds] Where [Df] is concentration of dye in fibre [Ds] is concentration of dye in solution
Light fastness BS1006 1978 light fastness test [9] was carried out in an improvised fadeometer. Wash fastness ISO TEST 2 wash fastness test [10] was carried out in a lauderometer at liquor ratio 1:50
HOH2C
Cl
+
Cell-OH
N Dye
Cellulose
+
N N
Cl
CH2OH
N
N N
N
Reactive Dye
+
Cell-OH
N CH2OH
HOH2C
N
Dye
Cellulose
N
HOH2C
O NH3O P OH +
Cl
+
N N
Cl
N
OH
N
CH2OH
HOH2C
N
N
Reactive Dye
N
HOH2C
CH2OH
CH2OH Modified Resin
2NaOH
2NaOH
HOH2C
N
N N
N
N
3
N
Crosslinked
N CH2OCH2
CH2OH
N
N
N N
N
CH2 O - Cell
O
N
Cell
N
2NaCl
+ 2H2O
N N
Dye
O
N
N
OH2C
OH2C
SCHEME 1: Formation of Resin – Dye Complex in Cotton fibre using MR6
OH N
Crosslinked
N CH2OCH2
CH2OH
N
N
CH2 O - Cell
OH2C
N
O
N
Cell Dye
+
N
N
N
Cell
Cellulose - Dye - Resin Complex
3
N CH2 O - Cell
HOH2C
N N
O NH O P OH +
OH
Dye
+
O NH O P OH +
CH2OH
N
OH2C
Dye
HOH2C CH2 O - Cell
HOH2C
N
CH2OH
2NaCl
+ 2H2O
N N
O
Cell
Cellulose - Dye - Resin Complex
SCHEME 2: Formation of Dye - Resin Complex in Cotton fibre using MPR4
90
70
80 60
70 Dyeing without resination
60 40'C
40
50'C 60'C
30
70'C 80'C
20
0'C
10
Exhaustion (%)
Exhaustion (%)
50
50 Dyeing with MR6 Application
40 30
Dyeing with MPR4 Application
20 10
0
0 0
10
20
30
40
50
60
0
Time (min)
FIG. 1:
Effect of time and temperature on the degree of exhaustion of Procion Blue MX-R on Cotton Fabric
10
20
30
40
50
60
Time (mins)
FIG. 2: MPR4
Effect resination of Cotton fabric with and MR6 on degree of exhaustion of Procion Blue MX-R at optimum dyeing
-------------------------------------------------------------------------------------------------------Fabric Treatments Wash Fastness Light Fastness Dyed Stained Stained Fabric Cotton Polyester --------------------------------------------------------------------------------------------------------Cotton fabric Dyed without resin application
4
4/5
5
4
Cotton fabric Dyed with MPR4 application
4
4/5
5
6
Cotton fabric Dyed with MR6 application 5 4/5 5 6 ---------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------Method of Dyeing % Exhaustion Affinity of Fibre for the dye /kj mol-1 -------------------------------------------------------------------------------------------------------------Dyeing without resin application 64.0 0.150
Dyeing with MPR4 application
81.0
0.377
Dyeing with MR6 application 76.5 0.307 --------------------------------------------------------------------------------------------------------------
percentage exhaustion increase with increase in time of dyeing, attaining equilibrium at in about an hour (fig. 1) It was expected that equilibrium exhaustion are always attained at higher time than at lower temperature in most cases of dyeing The least exhaustion occurs at 00C and increased to maximum at about 400C. At 00C, the kinetic energy of dye may be insufficient to transport the dye molecules from the fiber inter- phase to the internal structure. It is also possible that at 00C pores of the fiber may have not expanded enough to allow sufficient dye absorption by the fiber Noticeable reduction in the degree of exhaustion at temperature above 400C may be because dyeing is an exothermic process; therefore increasing the dyeing temperature may lead to lowering the affinity and reduction in equilibrium absorption At relatively higher temperature there increase in the rate of hydrolysis of the halogenated triazine dyes in alkaline medium at the expense of the dye uptake
The numerical values of affinities obtained at optimum dyeing temperature and dye exhaustion of the resinated fibre (table 2 and fig. 2) shows that the dye has more affinity for the resinated cotton fabrics There is possibility of the dye, which is bifunctional with two chloro groups forming covalent bond by nucleophilic substitution with the cellulosate ion from the fiber using one of the chloro group and the possibility of the resins reacting with the other chloro group thus producing a fiber – dye – resin complex leading to a better dye uptake, increased colour strength and good fastness properties.
Looking at the work carried out so far, we can see that the amount of dyes taken up by the fibre depends on the temperature and particularly resin application. The numerical estimate of affinity was obtained using thermodynamic principles. The results obtained shows an optimum dyeing temperature at 400C with higher affinity shown when dyeing and resination are carried out compared to dyeing without resination. This would equally reduce the quantity of unfixed dye
[1] H.X. Nguyen,„Dyeing‟ A Scholarly Contribution in Encarta Dictionary, Microsoft Corporation, 2008 [2] C.H. Giles, „A Laboratory Course in Dyeing‟ 3rd Edition, Society of Dyers and Colorist,Bradford, 1974, pp. 35 [3] K.E. Duckett, Surface Properties of Cotton Fibres. In: Surface Characteristic of Fibres andTextile. Fibre Science Series. Schick, M.J. (Ed), Mercel Dekker, Inc, NY,1975, pp. 67 [4] P.E. Burch, The Chemistry of Dyeing: The Reactive Dyes. www.wikipedia.com/dyeing Jan., 2003 [5] Y. Yikai and Z. Yuejun. “Review of Study on Resin Dye – Fixatives on Cotton Fabrics”. Modern Applied Science. Vol. 3. No. 10, 2009, pp. 9 – 12 [6] N.A. Ayeni, “Effect of Dye-Resin Complexation on Flame Retardant and Dyeing Properties Of Cellulose Fibre” Ph.D. Thesis, Abubakar Tafawa Balewa University, Bauchi, Nigeria, 2011 [7] J.O. Ajayi, K.A. Bello and F.F. Boyede, “Effect of Liquid Ammonia Pre-treatments On the Crease Recovery Properties of Resinated Cellulose Fabrics”. J. Chem. Soc. Nigeria. Vol. 26 (1). 2001, pp. 120 – 122 [8] M.M. Dalai and K.R. Desai, “Dyeing Effect of Bifunctional Reactive Dyes on Knitted CottonFabrics”, American Dyestuff Reporters April 1996, pp. 22 – 25 [9] BS 1006 Light Fastness Test [10] ISO Test 2 Wash Fastness Test