Basic Dyes, Cationic Color for Acrylic & Modified Fibers

I can certainly provide a concise title and a detailed description for basic dyes.Basic Dye Title and DescriptionTitle (40 characters max)Cationic Color for Acrylic & Modified FibersDescriptionBasic dyes, also known as cationic dyes, are a class of synthetic organic dyes characterized by having a positive electrical charge in their chromophoric group (the part of the molecule responsible for color).1 These dyes are typically soluble in water and ionize in solution to form colored cations (2$\text{Dye}^{+}$).3 They are historically significant due to their exceptionally brilliant and intense colors, making them the most vibrant class of synthetic dyes available.4Primary Application: Acrylic FibersThe most crucial and widespread application of basic dyes today is the dyeing of polyacrylonitrile fibers (acrylics). Acrylic fibers are synthetically modified during manufacturing to contain anionic sites (negative charges, such as sulfo groups $\text{-SO}_{3}^{-}$ or carboxyl groups $\text{-COO}^{-}$) which are chemically incorporated into the polymer chain.The dyeing mechanism is based on a strong electrostatic attraction (ionic bond) between the positively charged dye cation ($\text{Dye}^{+}$) and the negatively charged sites on the acrylic fiber. This attraction is incredibly strong, leading to high dye exhaustion, deep shades, and excellent wet fastness (resistance to bleeding or running when washed). The strength of this bond is why basic dyes are the primary choice for coloring acrylics.Historical and Secondary UsesWhile their use on acrylics is primary, basic dyes have secondary applications:5Protein Fibers (Wool, Silk): Basic dyes can color these fibers, but the fastness properties are typically poor, and they are prone to fading and washing out.Tannin-Mordanted Cellulosics: Historically, before the development of modern direct and reactive dyes, basic dyes were used on cellulosic fibers like cotton and linen by first applying a tannin mordant. The tannin substance provides the negative charge sites necessary for the basic dye to attach, but this process is complex and rarely used commercially today.Paper and Leather: Basic dyes are still commonly used for non-textile applications, such as coloring paper, printing inks, and certain types of leather, where lightfastness is less critical than color intensity.6Advantages and DisadvantagesAdvantages:Exceptional Brilliance: They produce the brightest colors of any dye class.High Fastness on Acrylic: They provide excellent light and wash fastness on acrylic and modacrylic fibers.7High Exhaustion: Nearly all the dye is consumed by the fiber, minimizing dye waste in the effluent.8Disadvantages:Poor Fastness on Cellulosics/Proteins: Without chemical modification or a mordant, their fastness on natural fibers is low.Leveling Issues: Due to the high affinity, the dyes are quickly absorbed by the fiber, making it difficult to achieve level (even) dyeing, especially in pale shades. In summary, basic dyes are

1. WET PROCESSING -I
(Basic Dyes)
Emran Hossain
Assistant Professor, DoWPE, BUTEX

2. Basic Dyes
Why Basic dye is so called?
Basicdyesarecalledsosincetheyaresaltsoforganicbases.
Basicdyesarealsocalledcationicdyesbecauseinsolutionthe
basicdyemoleculeionizes,causingitscoloredcomponentto
becomeanactionofpositivelychargedradical.Basicdyesare
usedfordyeingwool,silk,andacrylicandmod-acrylicfibres.

3. General properties of Basic dyes
❑Many of the basic dyes are sparingly soluble in water.
❑The addition of glacial acetic acid helps to dissolve the basic dye quickly in water.
❑Basic dyes are readily soluble in alcohol or mentholated spirit.
❑It is cationic in nature.
❑Dyed in acidic condition.
❑Basic dyes shows affinity towards wool , silk and cationic dye able acrylic.
❑Basic dyes do not have affinity for cotton. The use of basic dyes on cotton involves
the troublesome process of mordantingwith tannic acid.
❑Jute is dyed with basic dye.
❑Basic dyes are also used for making inks, typewriter ribbons and dyeing leather.
❑The basicdyestuffwill combine with direct or sulphuror some acid dyestuffs. So
they cannot be used together in the same bath
❑Color fastness properties-average.
❑Environmentally not unfriendly.

4. Dyeing mechanism of Basic dye
Basedonthechemicalstructureofwool,itmaybesimply
representedasH
2N–W–COOH,where‘W’denotesthemain
non-reactingbodyofthewoolstructure.Whenwoolis
immersedinwater,thefollowingreactiontakesplace–

5. Dyeing of Acrylic with Basic Dyes
Themostcommonanionicgroupattachedtoacrylicpolymersisthe
sulphonategroup,-SO3-,closelyfollowedbythecarboxylategroup,
-CO2-.Theseareeitherintroducedasaresultofco-polymerisation,
orastheresiduesofanionicpolymerisationinhibitors.Itisthis
anionicpropertywhichmakesacrylicssuitablefordyeingwith
cationicdyes,sincetherewillbeastrongionicinteractionbetween
dyeandpolymer(ineffect,theoppositeoftheaciddye-protein
fibreinteraction).

6. Dyeing Recipe
Basic dyes : x% owf
Wetting agent : 0.5-1 g/l
Sequestering agent : 0.5-1 g/l
Levelling agent : 0.5-1 g/l
Acetic acid : 1 g/l
Sodium acetate : 1 g/l
Glubar salt : 1 g/l
Temperature : 90⁰C
Time : 60 minutes
M:L : 1:6

7. Dyeingof Cotton
Sequence of dyeing
Fabric preparation
↓
Mordanting
↓
Dyeing
↓
After treatment

8. Mordanting
1
st
step
CottonistreatedwithTannicacid(4%)at100⁰Cfor30
minutes.
2
nd
step
Thenthematerialistreatedwithtartaricacid(2%)atroom
temperaturefor30minutes.

11. Advantages of Basic Dyes
▪HighTinctorialstrength
▪Moderatesubstantivity
▪Relativelyeconomical
▪Wideshaderange
▪Includessomeofthemostbrilliantsyntheticdyes
▪Showsgoodbrightness
Limitations of Basic Dyes
▪Poorshadestability
▪Highacidcontent
▪Colouredbackwaters
▪Verypoorlightfastness
▪Preferentialdyeing