Saturday, November 7, 2020

Basic Dyes[1-2]
Art Resource

Marie-Therese Wisniowski

Preamble
This is the one hundredth and fifth post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.
Other posts in this series are:
Glossary of Cultural and Architectural Terms
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General
Woven Pile Fabrics
Chenille Yarn and Tufted Pile Fabrics
Knit-Pile Fabrics
Flocked Pile Fabrics and Other Pile Construction Processes
Glossary of Paper, Photography, Printing, Prints and Publication Terms
Napped Fabrics – Part I
Napped Fabrics – Part II
Double Cloth
Multicomponent Fabrics
Knit-Sew or Stitch Through Fabrics
Finishes - Overview
Finishes - Initial Fabric Cleaning
Mechanical Finishes - Part I
Mechanical Finishes - Part II
Additive Finishes
Chemical Finishes - Bleaching
Glossary of Scientific Terms
Chemical Finishes - Acid Finishes
Finishes: Mercerization
Finishes: Waterproof and Water-Repellent Fabrics
Finishes: Flame-Proofed Fabrics
Finishes to Prevent Attack by Insects and Micro-Organisms
Other Finishes
Shrinkage - Part I
Shrinkage - Part II
Progressive Shrinkage and Methods of Control
Durable Press and Wash-and-Wear Finishes - Part I
Durable Press and Wash-and-Wear Finishes - Part II
Durable Press and Wash-and-Wear Finishes - Part III
Durable Press and Wash-and-Wear Finishes - Part IV
Durable Press and Wash-and-Wear Finishes - Part V
The General Theory of Dyeing – Part I
The General Theory of Dyeing - Part II
Natural Dyes
Natural Dyes - Indigo
Mordant Dyes
Premetallized Dyes
Azoic Dyes
Basic Dyes
Acid Dyes
Disperse Dyes
Direct Dyes
Reactive Dyes
Sulfur Dyes
Blends – Fibers and Direct Dyeing
The General Theory of Printing

There are currently eight data bases on this blogspot, namely, the Glossary of Cultural and Architectural Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, the Glossary of Colors, Dyes, Inks, Pigments and Resins, the Glossary of Fabrics, Fibers, Finishes, Garments and Yarns, Glossary of Art, Artists, Art Motifs and Art Movements, Glossary of Paper, Photography, Printing, Prints and Publication Terms and the Glossary of Scientific Terms, which has been updated to Version 3.5. All data bases will be updated from time-to-time in the future.

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Introduction
Basic dyes are also called cationic dyes because in solution they ionize with the colored component bring a cation (i.e. a positively charge carrier). Also, the opposite to an acid is a base and because acidic dyes carry a negative charge in solution and cationic dyes carry a positive charge, the latter are also known as basic dyes. Note: The anion of the cationic dyes is usually a chloride anion, which assists these dyes to be water soluble.

Basic dyes were developed very early in the synthetic dye industry. For example, the basic dye Rosorcine Violet was developed in 1883. The chromophore (i.e. the group in the dye responsible for its color) is the -N(CH3)2+- chemical group. When they were first synthesized they were used to dye wool and silk, but as these colored textile materials possessed poor color fastness, they were displaced for these fibers by acidic dyes.

Basic (Cationic) Dyes.

The manner in which basic dyes bond to the fiber is not too dissimilar to acidic dyes, except using a reverse mechanism. That is, the basic dyes only attach to those in the fiber that can accept a negative charge from the acidic solution.

When acrylic fibers come to the fore, a modified form of the basic dyes was developed and appropriately named modified basic dyes. The descriptor “modified” has been dropped from this class of dyes, since they are now more prevalent in dyeing and printing, than the original basic dyes.

Synthetic acrylic and modacrylics are mostly dyed and printed using (modified) basic dyes. They work well with modified nylon or polyester fibers. They work with some plant fibers: reed, rafia, grasses and barks etc. They produce brilliant colors and so, they are sometimes used as topping colors in overdyeing to increase the brilliance of the fabric.

Basic dyes yield brilliant colored dyed and printed textiles.


Dyeing With Basic Dyes
Basic dyes are applied to acrylic fibers using slightly acidic dye liquor. Basic dyes have good substantivity for acrylic fibers and exhaust well within narrow limits of temperatures. Care must be taken when applying basic dyes to acrylic fibers in order to avoid unlevel dyeing. This is achieved by introducing a retarder and by carefully regulating the temperature of the dye liquor during dyeing (see below).

The color component of the basic dye is the cation. The dyeing process can be represented as follows.

Reaction equation for dyeing on an acrylic fiber.
Courtesy of reference [1].
Basic dyes only attaches to those sites in the fiber that can accept a negative charge from the acidic solution.

Fiber polymer system becomes negatively charged by the acid solution.
Note: The negative charge carriers that are loose (in the mildly acidic solution that contains the basic dyes) are attracted to specific sites on the fiber surfaces and the fiber polymer system.

Positively charged dye is attractive to the negative site on the fiber surface and within the fiber polymer system.
Note: Sites on the fiber surface are now negatively charged and so will attract the positive dye molecules in solution.

Ionic attraction (shown) and van der Waals forces of attraction (not shown) bond cationic dyes to fiber sites.

The complete bonding mechanism is a mixture of ionic attraction (positive dye ion attracted to a negative ion on fiber sites) and van der Waals forces (i.e. intermolecular forces).

To prevent unlevel dyeing of the acrylic fibers, a cationic retarder is added to the dye liquor. It has the same charge as the dye molecule and so effectively competes with it for the negatively charged sites, preventing the dye from rushing onto the fiber. Nevertheless, because the cationic dye has a greater substantivity for the acrylic fiber polymer system than the cationic retarder, it will slowly replace the cationic retarder and so ensure a more levelling dyeing process.


Printing with Basic Dyes
When basic dyes are applied to acrylic fibers by printing, steaming is required to enlarge the voids in the amorphous region of the polymer system in order to enable greater penetration by the cationic dyes into the fiber polymer system. The steam also provides the kinetic energy for the cationic dyes to attach themselves to the negative fiber sites within the fiber polymer system.

Properties of Basic Dyes
Light Fastness
Dyed and printed textile materials using basic dyes have a light fastness rating of about 6-7, which translates to excellent light fastness. This is attributed to the acrylic fibers, which are hydrophobic and so minimizes their absorption of water, and also because of their natural excellent resistance to sunlight.

Wash Fastness
Acrylic textiles dyed and printed with cationic dyes have a good wash fastness with a rating of about 4-5. This is attributed to the hydrophobic nature of acrylic fibers, which in effect has a natural tendency to repel water.

Bright Colors
Basic dyes are characterized by their brilliance and intense hues. The bright colors achieved using basic dyes do not usually occur for other dye classes. The reason for this lies within the chromophores and their interaction with the incident light.


References:
[1] A Fritz and J. Cant, Consumer Textiles, Oxford University Press, Melbourne (1986).

[2] E.P.G. Gohl and L.D. Vilensky, Textile Science, Longman Cheshire, Melbourne (1989).

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