Basic Textiles VI: Finishing
Dyeing
Basic terms
Finishing is about all processes in textile industry that are done to
render the substrate to customer requirement. The start is after
weaving/knitting/nonwoven and ends at inspection room.
Dyeing Completely immersing the fabric, yarn or fiber in an aqueous
dye bath.
Printing Apply color in the form of paste or ink to the surface of a
fabric, in a predetermined block.
Colorfastness Refers to the property of a dyed or printed textile to
resist color loss/fading and to resist color bleeding/staining.
Colorfastness can be tested for laundering, dry cleaning, sunlight,
bleach, perspiration, environmental gases, swimming pool chlorine.
Dyestuff s are capable of reacting and combining with the textile Setting = finishing
fiber molecule, usually when in a water solution, and usually with other auxiliary chemicals to enhance
the process.
Pigments are microscopic-sized, insoluble colored particles made to adhere to a fabric.
Solution dyeing
Solution dyeing is part of the process of manufacturing fibers. In this method, the coloring agent is
added to the liquid spinning solution manufactured fiber before it is extruded from a spinneret. For
man-made fibers (polyester, polyamide, etc.).
Dyeing steps
1. Dissolve/disperse in water bath.
2. Fiber/yarn/fabric in dye bath (wet).
3. Absorption: transfer dye from water to fiber (chemically bonding of dye with fiber).
4. Diffusion: dye penetrate into the fiber through amorphous regions.
5. Migration: dye migrates in areas where there is lower concentration of dye.
6. Rinse away non fixed dyes (save money by rinsing less).
Crystalline and amorphous
Fibers consist of polymers that are oriented in crystalline regions
(organized) or amorphous regions (unorganized). The relative
proportion and distribution of crystalline and amorphous regions
determines the dyeing behavior. More time = more proper dyeing.
Diffusion
More amorphous areas = more dyeability.
Levels of dye penetration
1. Absorption of dye on the surface of the fiber
, Basic Textiles VI: Finishing
2. Penetration into the fiber
3. Migration in the fiber
4. Fiber is completely dyed
Discontinuous dyeing
Exhaust dyeing (discontinuous): material stays for a longer period in the dye bath and is only
taken out when almost all dye is penetrated and fixed on the fiber. Takes more time than continuous
dyeing. (Jigger)
Study Textile Reference Book p. 41-48
Clear bath and dewatering
- Rope: squeeze and un-roping, followed by drying.
- Fabric width: vacuuming or squeezing, followed by drying.
Process parameters:
- Temperature
- Material to liquor ration (MLR)
- Time
- pH
- pick up ratio (continuous dyeing)
Top 4 for discontinuous dyeing. All 5 for continuous dyeing.
Continuous dyeing
Pad dyeing : a process in which material is only in contact with dye solution for short period. Dye is
penetrated and fixed on fiber while material is not in dye bath anymore. P. 75-76
Equipment depends on:
- Batch size
- Substrate
- Color fastness requirements
- Dye group selection
Equipment parts:
- Fabric entry
- Foulard/pad batch Squeezing rollers to distribute dye even over width of fabric.
- (Pre)drying section If necessary. Vertical drying, no contact to avoid stains. IR
(electric/gas)
- Sublimation section (thermosol) High temperature for disperse dyes on polyester. Stenter frame
for stabilization. Sublimation: transition solid to gas, no liquid.
<1 minute, 200 - 230 C
- Steamer No oxygen, water lock. Temp. 100 C (pressure). Guiding rollers.
- Rinsing Fabric dipped in rinsing liquor. Counter flow, meandering,
expander roller.
- Drum dryer Vertical holder with gas/steam. Poor residual moisture control.
Fresh air.
- Inspection table Sometimes immediately after dyeing. Fabric speed high for
accurate inspection. SMS (Side Mid Side) or BME (Begin Mid
End).
fiber dyeing
Gives good dye penetration but is more costly than yarn and fabric dyeing. Mostly used to
produce yarns with 2+ colors. (Discontinuous)
Dyeing
Basic terms
Finishing is about all processes in textile industry that are done to
render the substrate to customer requirement. The start is after
weaving/knitting/nonwoven and ends at inspection room.
Dyeing Completely immersing the fabric, yarn or fiber in an aqueous
dye bath.
Printing Apply color in the form of paste or ink to the surface of a
fabric, in a predetermined block.
Colorfastness Refers to the property of a dyed or printed textile to
resist color loss/fading and to resist color bleeding/staining.
Colorfastness can be tested for laundering, dry cleaning, sunlight,
bleach, perspiration, environmental gases, swimming pool chlorine.
Dyestuff s are capable of reacting and combining with the textile Setting = finishing
fiber molecule, usually when in a water solution, and usually with other auxiliary chemicals to enhance
the process.
Pigments are microscopic-sized, insoluble colored particles made to adhere to a fabric.
Solution dyeing
Solution dyeing is part of the process of manufacturing fibers. In this method, the coloring agent is
added to the liquid spinning solution manufactured fiber before it is extruded from a spinneret. For
man-made fibers (polyester, polyamide, etc.).
Dyeing steps
1. Dissolve/disperse in water bath.
2. Fiber/yarn/fabric in dye bath (wet).
3. Absorption: transfer dye from water to fiber (chemically bonding of dye with fiber).
4. Diffusion: dye penetrate into the fiber through amorphous regions.
5. Migration: dye migrates in areas where there is lower concentration of dye.
6. Rinse away non fixed dyes (save money by rinsing less).
Crystalline and amorphous
Fibers consist of polymers that are oriented in crystalline regions
(organized) or amorphous regions (unorganized). The relative
proportion and distribution of crystalline and amorphous regions
determines the dyeing behavior. More time = more proper dyeing.
Diffusion
More amorphous areas = more dyeability.
Levels of dye penetration
1. Absorption of dye on the surface of the fiber
, Basic Textiles VI: Finishing
2. Penetration into the fiber
3. Migration in the fiber
4. Fiber is completely dyed
Discontinuous dyeing
Exhaust dyeing (discontinuous): material stays for a longer period in the dye bath and is only
taken out when almost all dye is penetrated and fixed on the fiber. Takes more time than continuous
dyeing. (Jigger)
Study Textile Reference Book p. 41-48
Clear bath and dewatering
- Rope: squeeze and un-roping, followed by drying.
- Fabric width: vacuuming or squeezing, followed by drying.
Process parameters:
- Temperature
- Material to liquor ration (MLR)
- Time
- pH
- pick up ratio (continuous dyeing)
Top 4 for discontinuous dyeing. All 5 for continuous dyeing.
Continuous dyeing
Pad dyeing : a process in which material is only in contact with dye solution for short period. Dye is
penetrated and fixed on fiber while material is not in dye bath anymore. P. 75-76
Equipment depends on:
- Batch size
- Substrate
- Color fastness requirements
- Dye group selection
Equipment parts:
- Fabric entry
- Foulard/pad batch Squeezing rollers to distribute dye even over width of fabric.
- (Pre)drying section If necessary. Vertical drying, no contact to avoid stains. IR
(electric/gas)
- Sublimation section (thermosol) High temperature for disperse dyes on polyester. Stenter frame
for stabilization. Sublimation: transition solid to gas, no liquid.
<1 minute, 200 - 230 C
- Steamer No oxygen, water lock. Temp. 100 C (pressure). Guiding rollers.
- Rinsing Fabric dipped in rinsing liquor. Counter flow, meandering,
expander roller.
- Drum dryer Vertical holder with gas/steam. Poor residual moisture control.
Fresh air.
- Inspection table Sometimes immediately after dyeing. Fabric speed high for
accurate inspection. SMS (Side Mid Side) or BME (Begin Mid
End).
fiber dyeing
Gives good dye penetration but is more costly than yarn and fabric dyeing. Mostly used to
produce yarns with 2+ colors. (Discontinuous)
