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MARCIAC. BONNEA; SUNY-Cortland Cortland. NY 13045
The Chemistry of Fabric Reactive Dyes Marcia C. Bonneau SUNY-Cortland Cortland, NY 13045 Developing a n activity t h a t can relate chemistry concepts to t h a t which i s interesting and relevant to high school students is a challenging one, but tie dyeing i s one of those phenomena that has been found to be very popular and successful in many high schools. Even though it appears to be a n "arts and crafts" project, the activity can be justified in a high school chemistry course if the chemistry involved in tie dyeing can be related to the organic chemistry unit. The objective of this article is to describe the method of application and the chemistry of the most popular fiber reactive dyes, roci ion' MX dyes, used i n tie dyeing. The Dyes Procion MX i s the commercial name for dichlorotriazine dyes. They are the most reactive and versatile of the fiber reactive dyes, which means that the dye molecule actually reacts with fabric molecules. These dyes can be used on cotton, silk, wool, rayon, linen, paper, and wood but not on
a. Procion Brilliant Yellow M-6G (ICI)('CI Reactive Yellow 1)
b. Procion Brilliant Red M-2B (ICI)(CI Reactive Red 1)
c. Procion Brilliant Blue M-R (ICI)(CI Reactive Blue 4) Figure 2. Three common dichlorotriazine dyes. 'CI refers to the Colour Index. Published jointly by the American Association of Textile Chemists and Colorists, Research Triangle Park, NC, and The Society of Dyers and Colourists, Bradford, England.
Figure 1. Procion MX (dichlorotriazine). synthetic fibers. The reactive group is shown below in Figure 1( I ) . The " D represents the color-forming or chromophore part of the molecule attached to the reactive group. Examples of three of these common dyes are given i n Figure 2
(21. Mixing the Dyes Caution: The dyes are sold in the form of a powder and are considered to be nontoxic. Common sense should be used in handline- anv, chemical. however. Proloneed inhalation of the dw powder ran muw sn d l l c w c rtatllun in somc pwplc A dust mark and ruhher gloves should be worn to mix the rhcmicnls, and mixing should he done in a hood. Approximately 10-20 mL of dye may be mixed with 250 mL of warm water or urea solution. Hot water up to 120' F may be used to dissolve the less soluble dyes, but the dye solution should be cold when the alkali is present to prevent premature reaction with water (3). Urea solution, made by mixing 125 mL of urea i n a liter of water (2 cups per gallon), is optional. It helps to dissolve the less soluble 'Procion is a trade mark of Zeneca Colours formerly ICI (Imperial Chemical Industries)
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Journal of Chemical Education
dyes and, being hydrophilic, keeps the fabric damp during the processing time. Urea also "drives" the dye into the fabric during the heat-fixing process so t h a t the colors come out brighter. Once the dye powders are mixed with water or urea solution, they have a shelf-life of four to five days. Liquid fiber reactive dyes by Createx Colors have a shelf-life of two years and may he used a s an alternative to the powdered dye. Some sources for fiber reactive dyes are listed a t the end of the article. The Application of the Dye Refore dye is ndded to the f:ihric, the fabric is washed in a mild drrrrarnt or rh(, commtwi.ll product called Ssnthrapol S P t{remove sizing and other-chemicals that may interfere with the dve. Plastic doves, aprons, and safety goggles must be wain, and tnblrs should 116: covtwd with plastic. 'l'hc fal~ricis sw~kc,din a sodium carbonate soda i s h ) solution for a t least 15 min. The solution is made by adding 60 mL of sodium carbonate per liter of water (one cup per gallon). The sodium carbonate i s used to "activate" or weaken the bond between the "H" and the "0"on the "OH" (hydroxyl) group of the cellulose molecule. Cellulose is ionized under these alkaline conditions. The solution of soda ash has a pH of 10.6 and also will neutralize the HC1 formed during the reaction (4). The fabric is wrung out to remove excess solution and folded, twisted, and tied. The methods of folding and tying
ond chlorine becomes much less reactive once the first hecomes combined with the fiber a s shown i n Figure 4. During the hot wash-off process, the second chlorine either reacts with water (hydrolyzes) or reacts with the cellulose a s shown in Figure 5. The reaction of the excess dye with water i s also sequential due to the lower reactivity of the second chlorine. The first chlorine group may be substituted after dyeing a t low temperature followed by substitution of the less reactive chlorine after washing a t a high temperature (7, 8). The loss of the dye by hydrolysis during dyeing varies over a range of 15 to 40%. Because the dye is so rapidly absorbed by the fiber, the reactive groups in the dye and fiber are brought into close proximity and the heterogeneous reaction with the fiber predominates over the homogeneous reaction with the water molecules (9). The hig advantage of using these dyes is that once the fabric is washed i n hot water, the colors will not run or fade easily unless exposed to bleach or bright sunlight.
Simplified Version can be represented as: HO-Cellulose
Figure 3. Cellulose represented as poly-l.4D-glucopyranose
D-C:
HOH
N
CI
P CI
Sources of Fiber Reactive Dyes PRO Chemical and Dye Ine., 6.0.Box 14, Somerset, MA02726;
,OH
+ N=C,
+ HCI
HO- cellulose- alkali D-C, IOW T
!'%,N N-c:
+ HCI
Tel. (508) 676-3838.
Createx Colors, ColarCRAFT Ltd., 14 Airport Park Rd., East Granhv. CT 06026: Tel. (2031 653-6225. Grateful d i e s , Inc., 2139 S. Sheridan Blvd., Denver, CO. 80227; Tel.(303) 753-8774.
CI
Figure 4. Two possible reactions of the dyes at low temperature.
Acknowledgment I would like to t h a n k Elnore Grow of Horizon High School, Brighton, Colorado, for sharing her expertise on tie dyeing, and Peter J. Dolby of Dolby Dyeing Systems, Charlotte, NC, formerly of ICI- America for sharing his knowledge of dyes.
can be found i n many sources such a s arts and crafts books and, therefore, not included in this article. The dye may be applied by means of squirt bottles or jumbo pipets to the fabric. The dyed fabric should be allowed to drain preferably on a rack over the sink or dishpan before i t wrapped i n newspaper or paper toweling. The dyed fabric is placed i n a plastic bag, tied tightly, and allowed to set for a t least four hours (24 hours for ereen or turauoise) before i t is rinsed thoroughly i n cold water to remove the hydrolyzed dve. I t is then untied and washed in verv hot water with a mild dc,tc,rgent or Synrhnpol. The hbric"is then drred i n a hut drver, so the heat will "fix" the dve which is then colorfast (5). The Chemistry of the Dyeing Process Cellulose i s a complex molecule shown as poly-1,4-D-glucopyranosei n Figure 3. The structural formula of cellulose can be simplified to show that i t is a large molecule with a n active " O H end. Under alkaline conditions, D -C, the dye reacts with the 6-hydroxyl position of NC ', the glucopyranose ring (6). The dye c a n react with cellulose and/or water. T h e dyes all contain two chlorines which combine with the hydrogen from the "OH" on the cellulose molecule or the " H on the water molecule to form HC1. When the dye r e a d s with the cellulose, one chlorine reacts a t the low temperature of application. The sec- ~i~~~~ 5,
Literature Cited
7. Dolby P J. Tezlile Chemist ond Colorist. 1880.12 .(9),74. 8. Dolby P d., Personal communication, 199%. 9. Allen. R. L. M., p 203
O- cellulose 0
, CI
+
HOH high T
N-c,'
D-6
O- cellulose N
+ HCI
ossible reactions of the dye after washing at high temperature.
Volume 72 Number 8 August 1995
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