continuous dyeing range
TRANSCRIPT
Continuous Dyeing Range Thermefix 338
INFRARED PREDRYERS
Either electrically or gas heated High specific evaporation efficiency Variable radiation intensity and constant output High operational safety and reliability Low maintenance Several IR predryers can be arranged in-line to meet production speed
requirements
Pivoted quartz glass radiators with gold-plated reflectors. Edge zone shutdown for narrow fabric (option).
With ignition and operation monitoring system. With selvedge shutdown for adaption to the fabric width. Heating and cooling within 2 seconds. Unaffected by splashing water and fluctuating gas qualities.
DYEING PADDER
The Continuous Variable Crown (CVC) systemMatex Color padder has a roller system without hydraulic or pneumatic roller gap correction.The solid core steel rollers with “intelligent” contour enables
Linear squeeze gaps in the line pressure range from 20 to 50 daN/cm Individual adjustment “edge-edge” or “edge-middle-edge” High squeeze effect with slim rollers (smaller roller diameter) Limited up to B260 cm Drive roller is the press roller, and the driven roller can be shifted to the sides.Gap pressure higher on the left than on the right and in the middle
Gap pressure higher on the edges than in the middle
Gap pressure uniform over the whole roller width
Gap pressure higher on the right than on the left and in the middle
Gap pressure higher in the middle than on the edges
Thermefix System
Application
Thermefix hotflue for thermosoling and condensing Application as a predryer Pad/dry processThermefix hotflue for drying after dye application combined with infrared pre-drying zone
Expansion into a continuous thermosol range consisting of padder, air passage, infrared predrying zone, drying and thermosoling hotflues
Pad/batch process using an additional batching device
AIR CIRCULATION
For migration and crease-free drying and thermosoling Roller spacing only 960 mm, roller diameter 140 mm The lint filters can be pulled from outside the machine for cleaning without
interrupting production The two air circulation fans in each Thermefix unit are arranged symmetrically and designed to provide the perfect match for the various-likewise symmetrically arranged-heating systems used in the treatment processes drying thermosoling and curing.
CHAMBER CONSTRUCTION
Reproducible quality:
Uniform flow Uniform temperature Uniform fabric finish Migration free production thanks to Thermo-Cut system
Thermo-Cut system Migration protection thanks to heat dissipation in the selvedge area of the fabric.Homogeneous and gentle drying by using the looper chamber as drying zone with tangential airflow across the whole fabric web.
Thermo-Cut
HEATING SYSTEMS
All standard types of heating system can be employed The circulating air is always uniformly heated, irrespective of the heating system employed. The heating chamber extends over the whole width of the machine.
Direct gas burner heating -one burner at each side of the machine.
Steam or oil circulation heating - one heat exchanger per Thermefix unitElectric heating - one heat exchanger per Thermefix unit
Combined steam and electric al heating system
FABRIC OUTLET COMBINATIONS
Fabric outlet combination with cooling drum and folder/ surface-driven winder combination
Fabric outlet combination with cooling drum, fabric scray and folder/surface-driven winder combination
Fabric outlet combination with cooling drum, feed compensation device and folder/surface-driven winder combination
Pad Thermosol dyeing machine:Introduction:
Pad Thermosol is dyeing machine that helps in achieving the dark/deeper shades and also lighter/light shades on cotton, polyester, and on its blends (PC).
These dyeing on pad Thermosol can be carried out with disperse, reactive, and also with pigments.
Machine specifications:Manufacture Monforts Monotex (2001)Model VTG/2M/AProduction Speed 60-100m/minPadder KusterChambers 5(3 for drying and 2 for curing)Padder Capacity 100-150litersScray Capacity 400-600mters of fabricTrough Capacity 50-60litresVTG/Airing Zone 12m of fabricNominal Width 130”Working Width 120”Thread Length 170mIR drying units 2Drying units heating Oil Heating SystemIR Temperature Range 650-850’CIR vertical tension 2-6barLiquor Change after 3-4min Process Conditions for Polyester:
1st chamber 80’C2nd chamber 100’C3rd chamber 120’C4th chamber 190’C5th chamber 210’CSpeed 30m/minPressure 3.2, 2, and 3 in 1st, 2nd and 3rd chamber respectivelyPick up 70% Main sections Of Machine:
1. 1. Let off section2. 2. Padding Section3. 3. VTG/Airing Zone4. 4. IR(Infra red Dying)section5. 5. Curing Section
1. 1. Let Off Section Parts
Scray:There is scray in front of pad dry trough, that helps to give fabric in bed form/pilling form with waves in order to give enough time for stitching of fabric.The capacity of scray is about 400-600mtrs depending upon quality of fabric.Also it facilitates changing of batcher without stopping machine. It is also capable of moving fabric in reverse direction. Compensator:It ensures even speed running and fabric tension. Brake Roller:Its is used to increase/decrease fabric tension by increasing/decreasing the brake roller pressure. Cooling Rollers:There are two cooling rollers in the machine. Fabrics after passing through scray it pass from cooling rollers. Function of these two cooling rollers is to moderate the temperature of fabric, so that it will not raise the temperature of trough. Trough:Line washing is done from color kitchen up to the trough of pad dryer. Then according to the lab dip recipe, the dyestuff is pumped into the trough of pad dryer. But first we stitch the fabric with leading cloth, and when the leading
cloth passed thorough the trough of pad dryer, then we allow dyestuff recipe to go into the trough.
1. 2. Padding section:
Padders:These padders are used to avoid the LCR (shade difference in left, center and right) problem in fabric.Central pressure of Padder is hydraulic pressure (operated or effected by liquid for e.g.: water or oil) and left and right side pressure of padder are pneumatic (using air) pressures.The Kuster padder should be adjusted here in such a way that it its pick up % must be 70%. LCR Problem:Due to pressure difference onto the left, center and right of the padder can produce the shade variation which is known as LCR problem. VTG/Airing Zone Section:It consists of vertically placed guide roller. Their purpose is to give reasonable penetration time of the dye into fabric. Also these rollers are Teflon coated to avoid stains on the fabric due to rusting and stickiness of chemicals. If these rollers are not placed in the flow of fabric and directly sent to IR chamber, the dye will remain at the surface and will not be present at center of fabric, so poor wash fastness will be resulted.
1. 3. IR Chambers:
IR Chambers:There are two IR chambers in each pad dryer. Actually these do pre drying which are used to remove approximately 30% moisture of water from the fabric. The purpose of pre drying is to avoid the migration of dye stuff and it just affects water molecules rather than dyestuff because of its low energy and high wavelength.Note:We set IR temperature according to following parameters
Fabric Quality Recipe Shade(Light/Dark)
SHADE LIGHT MEDIUM DARK IR TEMP 650 700-750 800-850
4. Curing Chamber Section:Drying chambers:There are three drying chambers, in each chamber there is a radiator in which steam is flowing. Besides there is a water blower which sucks air from the atmosphere and circulates that air by centrifugal action in whole chamber.Also PLEVA is present in each chamber which shows humidity % within the chamber on the panel.There is a gauge on each dryer which is showing the balance of air inside the chamber.Also there is nozzle edge cover, which helps in circulating the hot air directly on the fabric top and bottom so to achieve uniform treatment. Note:
There are three drying units and each have different pressure and that is maintained with motors, those helps in air circulation
50, 50, 50 (cotton) 50, 50, 75 (polyester) Each drying chamber contain 3 small motors for drive of 6 Teflon coated
rollers 1 more motor equipped that decides the position of plate through which air
circulates
Curing Chambers:There are total two curing chamber i.e. used when dyeing with polyester or with disperse otherwise as a drying chamber.These chambers are used for high temperature dyes fix up especially for polyester. Process Specification:
Padding (anti migrating agent, dispersing agent, disperse dyes and acetic acid)
IR drying (residual moisture/semi dry up to 30%) Drying(120’C) Curing(200’C-210’C for 45 – 60sec) Polyester dyeing on pad Thermosol with disperse dye carried on 180-210’C
Process Specification (PC Blend):
Thermosol (padding) Thermosol (drying) Thermosol (curing) Pad steam (reduction clearing) Thermosol (reactive dyeing padding) Pad steam (fixation/developing)
Reactive Dyeing: (Pad Dry reactive)
Padding (Pad Thermosol) Drying (Pad Thermosol) Fixation (Pad steam) Washing (Pad steam)
Following Processes can be carried out on Pad Thermosol Dyeing Machine:
One bath reactive/disperse dyeing Disperse dyeing Two bath dyeing Stripping(exceptionally) Curing E-Control Process(Pad humidity fix by urea)
Pad Steam dyeing Machine:Pad steam is a machine used for dyeing of cellulose (cotton) materials Dyeing technique:Pad------ Steam (102’C) ------ Wash------ Dry Machine Specification:Manufacture Monforts MonotexNo of washers 7Steamer 1Cooling drums 4Washer capacity 25mtr fabricBanana rollers in each washer 1Drying rollers 16Rolls in one washer 23Rollers in steamer 78Heat exchanger 2 for washersPleva 1Machine width 110”
Main Sections of Machine:
1. Inlet Section.2. Padding Section.3. Steamer.4. Washer.5. Dryers.6. Outlet Section.
Inlet Section:Inlet consists on following parts.a) Plaiter/batcherb) Tensioner rollersc) Free guide rollerd) Stationary rollers. Padder: Pad steamer is used for the fixation of dye on to the fabric. There Addition of chemicals for developing or fixation of dye is held in the trough of padder. Liquor is picked in the fabric; afterwards the excessive liquor is squeezed out by means of padders at predetermined pick-up% set by applying pressure on the padders. Steamer:Here in steamer temperature required for the fixation is given to the fabric. This temperature is achieved by saturated steam. The purpose of using saturated steam is that the chemicals used for developing should not dry on the surface of fabric preventing fabric from stains. Here roof temperature is given to avoid water dropping that causes spotty dyeing. Here water is not given at the entry of steamer because to prevent developing chemicals that just applied before going into steamer so water lock is given at the end of steamer.
Steamer Temperature 101-102ºC Fabric’s dwell time 1minute. Roof temperature 102’C-105’C Fabric capacity 75meter fabric Water lock 1 (at the end)
Washing Boxes: Washing is carried out in order to remove unfixed dyes. After steamer fabric flows from 7 washers, Most commonly first to four washers are used
for washing of salt or chemicals which are being applied in trough of pad steamer. In 5th, 6th washer, oxidation is done if required. If oxidation is not required then soaping is done in 5th, 6th washers. Neutralization is done in 7th washer by using acetic acid. Drying Drums: In the last of the pad steam machine, there are three groups of drying cylinder for dry the fabric. Each group has 12 hot cylinders but last one has 10 hot and 2 cool cylinders. All the cylinders are Teflon coated. Their purpose is to remove water molecules from fabric. Following Processes can be carried out pad steam:
Reactive dyeing Pad batch dyeing Reduction Clearing Stripping Vat Development/vat dyeing Washing(Hot + Cold) HCl Pad(remove finish) Enzyme Pad(with enzyme “LECO Z”) Light bleach Mercerization Pad steam Wet chemical pad
Comparison between Pad Steam and Pad Thermosol:
Pad steam is suitable for achieving lighter shades, but pad Thermosol is best for achieving dark and medium shades
The main difference between them is of steamer that is in pad steam and because of that we can do reactive dyeing on pad steam but cant on pad Thermosol because it needs proper reaction time that we achieve in steamer.
There is water dropping problem in pad steam but that is not in pad Thermosol
Pad steam is best for the dyeing of cellulose, while pad Thermosol is best for polyester dyeing.
There is MAHLO present in pad steam but its not in pad Thermosol. Pad Thermosol is best for high temperature dyeing but pad steam for low
temperature dyeing
Wet treatment processes can be carried out on pad steam but can’t be on pad Thermosol.
In pad Thermosol drying and then curing takes place but on pad steam padding, drying, steaming and then drying again.
Pad Thermosol is used for the topping of reactive or pigment dyes. Enzymatic Desizing (Use of Hard Water) by Textile Engineers on Thursday, April 14, 2011 at 10:11pm
why we preffer hard water in enzymatic desizing?????
even we add some amount of Ca n Mg ions in soft water to make it
hard for enzymatic desizing
My question is that what actually hard water do with it r how it
increases rate of reaction
Salts and ions may have many different effects of the activity of an
enzyme.
For example, inorganic ions may bind to some of the ionic side chains
of a protein. This kind of interaction, although not affecting the three
dimensional shape of ...the enzyme in a substantial manner could
make it easier for a substrate molecule to locate or bind to the active
site of the enzyme. Thus the presence of the ion in optimum
concentrations could alter the rate of the reaction.
Many enzymes exist in two states, an inactive and an active state.
Usually these states differ in the conformation, or three-dimensional
shape,
of the enzyme. The balance between these two states provides a
means for
regulating the activi...ty of the enzyme, in effect, by turning it on or off.
Often the switch that controls which state the enzyme is in is provided
by a small molecule which binds to a receptor site somewhere on the
surface
of the enzyme. Such a small molecule is called an allosteric effector.
For
alpha-amylases from mammals, chloride ion is the allosteric effector.
These
amylases have a binding site for chloride ion, which contains a
positively
charged amino acid residue (lysine, which at physiological pH is in the
ammonium ion form). This positive charge assists binding of the
negatively
charged chloride ion, and the size of the binding pocket excludes
larger
negative ions.
Binding of chloride causes a conformational change to the amylase,
switching it to the more active state.
we use alpha amylase enzymes in desizing
Absorb/Absorption: Dissipation of the energy of electromagnetic waves into other
forms as a result of its interaction with matter; a decrease in directional transmittance of
incident radiation, resulting in a modification or conversion of the absorbed energy.
Additive Primaries: Red, green, and blue light. When all three additive primaries are combined at 100% intensity,
white light is produced. When these three are combined at varying intensities, a gamut of
different colors is produced. Combining two primaries at 100% produces a subtractive primary,
either cyan, magenta, or yellow: 100% red + 100% green = yellow; 100% red + 100% blue = magenta; 100% green + 100% blue = cyan See Subtractive Primaries. Appearance: Manifestation of the nature of objects and materials
through visual attributes such as size, shape, color, texture, glossiness, transparency,
opacity, etc. Attribute: Distinguishing characteristic of a sensation, perception or
mode of appearance. Colors are often described by their attributes of hue,
saturation or chroma, and lightness.
B Black: The absence of all reflected light; the color that is produced
when an object absorbs all wavelengths from the light source. When 100% cyan, magenta, and yellow colorants are combined, the
resulting colortheoretically- is black. In real-world applications, this combination produces a muddy
gray or brown. In four-color process printing, black is one of the process
inks. The letter “K” is used to represent Black in the CMYK acronym to avoid
confusion with Blue’s “B” in RGB. Brightness: The attribute of visual perception in accordance with
which an area appears to emit or reflect more or less light (this attribute of color is
used in the color model HSB—Hue, Saturation, Brightness). See Lightness. C Calibration: To check, adjust, or systematically standardize the
graduations of a device. Chroma: The attribute of visual perception in accordance with which
an area appears saturated with a particular color or hue-for example, a red apple is high
in chroma; pastel colors are low in chroma; black, white, and gray have no chroma (this
attribute of color is used in the color model L*C*H—Lightness, Chroma, Hue). Also referred
to as Saturation. The Color Guide and Glossary Chromaticity, Chromaticity Coordinates: Dimensions of a color
stimulus expressed in terms of hue and saturation, or redness-greenness and
yellowness-blueness, excluding the luminous intensity. Generally expressed as a point in a
plane of constant luminance. See CIE xy Chromaticity Diagram. CIE (Commission Internationale de l’Eclairage): A French name
that translates to International Commission on Illumination, the main
international organization
concerned with color and color measurement. CIE94: The CIE94 tolerancing method utilizes three-dimensional
ellipsoids as “containers” for color acceptance. CIE94 is conceptually similar to CMC2:1 but lacks
some of the hue and lightness adjustments. It is expected that CIE94 will evolve over
the next few years as additional studies are performed. CIELAB (or CIE L*a*b*, CIE Lab): Color space in which values L*, a*,
and b* are plotted at right angles to one another to form a three-dimensional
coordinate system. Equal distances in the space approximately represent equal color differences.
Value L* represents Lightness; value a* represents the Redness/Greenness axis; and value
b* represents the yellowness/blueness axis. CIELAB is a popular color space for use in
measuring reflective and transmissive objects. CIE Standard Illuminants: Known spectral data established by the
CIE for four different types of light sources.When using tristimulus data to describe
a color, the illuminant must also be defined. These standard illuminants are used in
place of actual measurements of the light source. CIE Standard Observer: A hypothetical observer having the
tristimulus color-mixture data recommended in 1931 by the CIE for a 2° viewing angle. A
supplementary observer for a larger angle of 10° was adopted in 1964. If not specified, the 2° Standard
Observer should be assumed. If the field of view is larger than 4°, the 10° Standard Observer should
be used. CIE xy Chromaticity Diagram: A two-dimensional graph of the
chromaticity coordinates, x as the abscissa and y as the ordinate, which shows the
spectrum locus (chromaticity coordinates of monochromatic light, 380-770nm). It has
many useful properties for comparing colors of both luminous and non-luminous
materials.
CIE Tristimulus Values: Amounts of the three components necessary
in a three-color additive mixture required for matching a color: in the CIE System, they
are designated as X, Y, and Z. The illuminant and standard observer color matching functions
used must be designated; if they are not, the assumption is made that the values are
for the 1931 CIE 2° Standard Observer and Illuminant C. CIE Chromaticity Coordinates: x and y values that specify the
location of a color within the CIE chromaticity diagram. CMC (Color Measurement Committee): Of the Society of Dyes and
Colourists in Great Britain. Developed a more logical, ellipse-based equation for
computing ÆE values as an alternative to the spherical regions of the CIELAB color space. CMY: The subtractive primaries cyan, magenta, and yellow.
See Subtractive Primaries. Color Management: Matching colors between an original image,
scanner, monitor, color printer and final press sheet. Color Matching Functions: Relative amounts of three additive
primaries required to match each wavelength of light. The term is generally used to refer
to the CIE Standard Observer color matching functions designated. See CIE Standard
Observer. Color Model: A color measurement scale or system that numerically
specifies the perceived attributes of color. Used in computer graphics applications
and by color measurement instruments. Color Separation: The conversion of the red, green, and blue color
information used in a computer into cyan, magenta, yellow, and black channels
that are used to make printing plates.
Color Space: A three-dimensional geometric representation of the
colors that can be seen and/or generated using a certain color model. Color Specification: Tristimulus values, chromaticity coordinates and
luminance value, or other color-scale values, used to designate a color
numerically in a specified color system. Color Temperature: A measurement of the color of light radiated by
an object while it is being heated. This measurement is expressed in terms of absolute
scale, or degrees Kelvin. Lower Kelvin temperatures such as 2400°K are red; higher
temperatures such as 9300°K are blue. Neutral temperature is gray, at 6504°K. Color Wheel: The visible spectrum’s continuum of colors arranged
into a circle, where complementary colors such as red and green are located directly
across from each other. Colorants: Materials used to create colors–dyes, pigments, toners,
phosphors. ColorSync: Built-in color management architecture for Apple
Macintosh computers. Third-party vendors utilize the ColorSync framework to provide device
calibration, device characterization, and device profile-building methods. Colorimeter: An optical measurement instrument that responds to
color in a manner similar to the human eye–by filtering reflected light into its dominant
regions of red, green, and blue. Colorimetric: Of or relating to values giving the amounts of three
colored lights or receptors–red, green, and blue. Contrast: The level of variation between light and dark areas in an
image.
Control Limits: The amount of acceptable variation in press capabilities over the
course of a press run. Cyan: One of the process ink colors for printing. Pure cyan is the
“redless” color; it absorbs all red wavelengths of light and reflects all blue and green
wavelengths. D D50: The CIE Standard Illuminant that represents a color temperature
of 5000°K. This is the color temperature that is most widely used in graphic arts industry viewing
booths. See Illuminants D. D65: The CIE Standard Illuminant that represents a color temperature
of 6504°K. Delta (Æ): A symbol used to indicate deviation or difference. Delta Error (ÆE): In color tolerancing, the symbol ÆE is used to
express Delta Error, the total color difference computed using a color difference equation. The color difference is generally calculated as the square root of the
combined squares of the chromaticity differences, Æa* and Æb*, and the Lightness difference,
ÆL. See CIE94. Densitometer: A sensitive, photoelectric instrument that measures
the density of images or colors. Density: The ability of a material to absorb light–the darker it is, the
higher the density. Device-Dependent: Describes a color space that can be defined only
by using information on the color-rendering capabilities of a specific device. For example,
the RGB color space must be generated by a monitor, a device which has specific
capabilities and limitations for achieving its gamut of colors. In addition, all monitors have
different capabilities and limitations, as do different scanners, printers, and printing presses. Device-Independent: Describes a color space that can be defined
using the full gamut
of human vision, as defined by a standard observer, independent of the color-rendering
capabilities of any specific device. Device Profile: Device-specific color information that is a
characterization of a device’s color rendering and reproduction capabilities.Monitor profiles, scanner
profiles, and printer profiles are utilized in a color management system such as Apple
ColorSync to help the devices communicate color information with each other. Profiles are
created by calibration and/or characterization method. Dye: A soluble colorant; as opposed to pigment, which is insoluble. Dynamic Range: An instruments range of measurable values, form
the lowest amount it can detect to the highest amount it can handle. E Electromagnetic Spectrum: The massive band of electromagnetic
waves that pass through the air in different sizes, as measured by wavelength.
Different wavelengths have different properties, but most are invisible–and some completely
undetectable–to human beings. Only wavelengths that are between 380 and 720
nanometers in size are visible, producing light. Invisible waves outside the visible spectrum
include gamma rays x-rays, microwaves and radio waves. Emissive Object: An object that emits light. Usually some sort of
chemical reaction, such as the burning gasses of the sun or the heated filament of a light
bulb. F Fluorescent Lamp: A glass tube filled with mercury gas and coated
on its inner surface with phosphors.When the gas is charged with an electrical
current, radiation is produced which in turn energizes the phosphors, causing the
phosphors to glow. Four-Color Process: Depositing combinations of the subtractive
primaries cyan, magenta,
yellow, and black on paper to achieve . These colorants are deposited as dots of different sizes, shapes,
and angles to create the illusion of different colors. See CMY, Subtractive Primaries.
G Gamut: The range of different colors that can be interpreted by a color
model or generated by a specific device. Gamut Compression: Or tonal range compression. The color space
coordinates of a color space with a larger gamut are reduced to accommodate the
smaller gamut of a destination color space. For example, the gamut of photographic film is
compressed for representation in the smaller CMYK gamut used for four-color process
printing. See Gamut. Gamut Mapping: Converting the coordinates of two or more color
spaces into a common color space. Often results in tonal range compression.
See Gamut Compression. H - I HiFi Printing: Process printing that expands the conventional four-
color process gamut using additional, special ink colors. Hue: The basic color of an object, such as “red,” “green,” “purple,”
etc. Defined by its angular position in a cylindrical color space, or on a Color Wheel. ICC (International Color Consortium): A group of hardware and
software companies dedicated to the development of a specification that is OS
independent and provides the digital imaging, printing and related industries with a data
format for defining the color and reproduction characteristics of devices and their
related media. Illuminant: Incident luminous energy specified by its spectral
distribution. Illuminant A (CIE): CIE Standard Illuminant for incandescent
illumination, yellow-orange in color, with a correlated color temperature of 2856°K.
Illuminant C (CIE): CIE Standard Illuminant for tungsten illumination
that simulates average daylight, bluish in color, with a correlated color temperature of
6774°K. Illuminants D (CIE): CIE Standard Illuminants for daylight, based on
actual spectral measurements of daylight. D65 with a correlated color temperature of
6504°K is most commonly used. Others include D50, D55, and D75. Illuminants F (CIE): CIE Standard Illuminant for fluorescent
illumination. F2 represents a cool white fluorescent lamp (4200 K), F7 represents a broad-band
daylight fluorescent lamp (6500 K), and F11 represents a narrow-band white flourescent
lamp (4000 K). Intensity: Saturation or reflective energy as related to visible
wavelengths of light. Reflectance of wavelengths at high intensity generates high saturation,
or chroma. IT8: Series of test targets and tools for color characterization
established by ANSI (American National Standards Institute) Committee IT8 for Digital Data
Exchange Standards. Different IT8 targets are used to characterize different
devices such as scanners and printers. K - L Kelvin (K): Unit of measurement for color temperature. The Kelvin
scale starts from absolute zero, which is -273° Celsius. L*C*H: A color space that is similar to CIELAB, except uses cylindrical
coordinates of lightness, chroma, and hue angle instead of rectangular coordinates. Light: Electromagnetic radiation in the spectral range detectable by
the human eye (approx. 380 to 720nm). Lightness: The attribute of visual perception in accordance with which
an area appears
to emit or reflect more or less light. Also refers to the perception by which white objects are
distinguished from gray objects and light-from dark-colored objects. M Magenta: One of the process ink colors for printing. Pure magenta is
the “greenless” color; it absorbs all wavelengths of green from light and reflects all red
and blue wavelengths. Metamerism, Metameric Pair: The phenomenon where two colors
appear to match under on light source, yet do not match under a different light
source. Two such colors are called a metameric pair. Monitor RGB: Same as RGB; monitor RGB simply refers specifically to
the color space that can be achieved by a particular monitor using combinations of red,
green, and blue light. Munsell Color Charts: A three-dimensional color system developed
by Albert Munsell that is based on the attributes Munsell Hue,Munsell Value, and
Munsell Chroma. N - O - P Nanometer (nm): Unit of length equal to 10-9 meter, or one millionth
of a milli-meter. Wavelengths are measured in nanometers. Overprint: On a press sheet color bar, overprints are color patches
where two process inks have been printed, one atop the other. Checking the density of
these patches allows press operators to determine trap value. The term Overprint also
applies to any object printed on top of other colors. Phosphors: Materials that emit light when irradiated by cathode rays,
or when placed in an electric field. The quantity of visible light is proportional to the
amount of excitation energy present. Photoelectric: Pertaining to the electrical effects of light or other
radiation–for example, emission of electrons.
Photoreceptor: The cone- and rod-shaped nuerons that cover the
retina of the eye. Photoreceptors are excited by visible wavelengths, then send signals
to the brain where the sensation of color is perceived. Pigment: An insoluble colorant; as opposed to a dye, which is soluble. Pixel: A tiny picture element that contains red, green, and blue
information for color rendering on a monitor or a scanner.When generating colors, pixels are
similar to dots of ink on paper. A monitor resolution description in terms of pixels-per-
inch (ppi) is similar to a printer resolution description in terms of dots-per-inch (dpi). Primary Colors: The dominant regions of the visible spectrum: red,
green, and blue; and their opposite colors cyan, magenta, and yellow. See Additive
Primaries, Subtractive Primaries. Prism: Triangular-shaped glass or other transparent material.When
light is passed through a prism, its wavelengths refract into a rainbow of colors. This
demonstrates that light is composed of color, and indicates the arrangement of colors in
the visible spectrum. See Visible Spectrum. Process Control: Using densitometric and colorimetric measurement
data from press sheet color bars to monitor press performance throughout the
press run. Data is analyzed in relation to established control limits. See Control Limits R Reflective Object: A solid object that returns some or all of the
wavelengths of light that strike its surface. A reflective object that returns 100% of all light
is called a perfect diffuser-a perfectly white surface. Reflectance: The percentage of light that is reflected from an object.
Spectrophotometers measure an object’s reflectance at various intervals along the visible
spectrum to determine the
object color’s spectral curve. See Spectral Curve, Spectral Data. RGB: The additive primaries red, green, and blue. See Additive
Primaries. S Saturation: The attribute of color perception that expresses the
amount of departure from the neutral gray of the same lightness. Also referred to as
chroma. Sequence: The order in which inks are deposited on paper by a
printing press. Spectral Curve: A color’s “fingerprint”— a visual representation of a
color’s spectral data. A spectral curve is plotted on a grid comprised of a vertical axis-
the level of reflectance intensity; and a horizontal axis-the visible spectrum of wavelengths.
The percentage of reflected light is plotted at each interval, resulting in points that form a curve. Spectral Data: The most precise description of the color of an object.
An object’s color appearance results from light being changed by an object and
reflected to a viewer. Spectral data is a description of how the reflected light was changed.
The percentage of reflected light is measured at several intervals across its spectrum of
wavelengths. This information can be visually represented as a spectral curve. Spectrophotometer: An instrument that measures the
characteristics of light reflected from or transmitted through an object, which is interpreted as
spectral data. Spectrum: Spatial arrangement of electromagnetic energy in order of
wavelength size. See Electromagnetic Spectrum, Visible Spectrum Standard: An established, approved reference against which
instrument measurements of samples are evaluated. Subtractive Primaries: Cyan,Magenta, and Yellow. Theoretically,
when all three
subtractive primaries are combined at 100% on white paper, black is produced.When these
three are combined at varying intensities, a gamut of different colors is produced. Combining
two primaries at 100% produces an additive primary, either red, green, or blue:
100% cyan + 100% magenta = blue; 100% cyan + 100% yellow = green;
100% magenta + 100% yellow = red T Tolerance: The amount of acceptable difference between a known
correct standard (usually the customer’s specifications) and a set of measured samples.
See Delta Error Transmissive Object: An object that allows light to pass through
from one side to the other. The color of a transmissive object results from the
manipulation of wavelengths of light as they pass through. Tristimulus: A method for communicating or generating a color using
three stimuli– either additive or subtractive colorants (such as RGB or CMY), or three
attributes (such as lightness, chroma, and hue). Tristimulus Data: The three tristimulus values that combine to define
or generate a specific color, such as R 255/G 255/B 0. Tristimulus data does not
completely describe a color–the illuminant must also be defined. Also, in device-dependent
color models such as RGB, the capabilities of the viewer or color-rendering device must also
be defined. See Device-Dependent. V - W - X - Y Viewing Booth: A enclosed area with controlled lighting that is used
in graphic arts studios, service bureaus, and printing companies as a stable
environment for evaluating proofs and press sheets. Viewing booths are generally illuminated
using graphic arts industry- standard D65 lighting, and are surfaced in neutral gray colors.
See D65.
Visible Spectrum: The region of the electromagnetic spectrum between 380 and
720 nanometers.Wavelengths inside this span create the sensation of color when they are
viewed by the human eye. The shorter wavelengths create the sensation of violets, purples,
and blues; the longer wavelengths create the sensation of oranges and reds.
Wave: A physical activity that rises and then falls periodically as it
travels through a medium. Wavelength: Light is made up of electromagnetic waves; wavelength
is the crest (peak)-to-crest distance between two adjacent waves. White Light: Theoretically, light that emits all wavelengths of the
visible spectrum at uniform intensity. In reality, most light sources cannot achieve such
perfection. Yellow: One of the process ink colors for printing. Pure yellow is the
“blueless” color; it absorbs all wavelengths of blue from light and reflects all red and
green wavelengths.
Color Physics (Shade sorting)by Textile Engineers on Sunday, April 10, 2011 at 3:36pm
SHADE SORTING
Color is the most important aspect of any garment. It would not
be an exaggeration to say that to many consumers color is quality
and the decision whether or not to buy a garment rests on its
color.
Also, in fabric form the marketability of any fabric
depends on its color, which again depends on dyeing and its
preparatory processes. Therefore, good color and excellent
color/shade matching, for suits or coordinates, and even between
panels within a garment, are extremely important for
profitability.
The shade of a color may vary from lot to lot or from bolt(a roll
of fabric) to bolt. Such variation may be due to one or more of
the following factors:
1. Variation in maturity of cotton fibers.
2. Changes in merges of synthetic fibers.
3. Variation in sizing formula.
4. Inconsistent bleaching.
5. Varying absorbency of the fabric due to a variation in the
process variables in mercerization.
6. Variation in the pressure, temperature, and/or chemical
concentrations of dyes in the dyeing process.
These are just few factors that affect shade uniformity.
Sorting methods are appropriate for use when the normal
color variation within a process is greater than a visible amount of
difference and this difference is unacceptable to a customer.
The dyeing of textile is a good example. Variation in temperature,
humidity, dye strength, and the dye uptake characteristics of
cloth can result in color variation that is visible and unacceptable
between cloth pieces used in a cut and sew shirt product.
Shade numbering, sorting, and tapering are used in many
industries, but particularly the textile industry.
Shade Numbering:
The shade numbering feature performs calculations on the sample
data and assigns each sample a shade number based on how close
its color is to the standard.
The Shade Sorting:
The Shade sorting is the process of assigning samples of the
same nominal color into groups having no significant color
variation. Use of modern spectrophotometers and color
measurement technology make it possible to obtain precise color
differences between samples. shade sorting feature calculates a
shade number for each sample based on how close its color is to
the standard, but ALSO has the ability to sort all samples into
shade groups and provide data on which samples belong to each
shade number. A shade coding to each sample read based on how
close it is to the product standard.
One of popular shade sorting system is the Simon
method, known as the 555 system. In this system each color is
given a three digit numeric shade sort code. Using the CIE
L*C*h* color space as an example, the first digit shows lightness
of the color as compared to the standard color. If the color is
lighter than the standard this digit will be above 5, and below 5 if
it is darker. If the color is more saturate than the standard color
the second digit will be above 5 and below 5 if it is duller than
the standard. Similarly, the third digit in the shade sort code
indicates the hue variation from the standard.
SSS SHADE SORTING SYSTEM:
In a color matching is a very reliable system and it is based upon
modification of shade with reference to bare color. The SSS
code sis assigned for standard sample and its value started from
111-999. This code is assigned for a sample
The shade tapering:
The shade tapering feature is also known as color sequencing. The
software performs calculations that arrange the samples from
lightest to darkest or dullest to brightest and report them in this
order so that each sample is as close as possible in shade to the
samples next to it.
Processing Labby Textile Engineers on Wednesday, January 5, 2011 at 12:07am
1. 1. Compleximative Titration(Ca and Mg testing)
a) Take 50 ml of water
b) Add 1 ml of buffer pH 10
c) Then pour down Erichrome Black T(indicator) to get purple color
d) Then add EDTA for titration
e) Less EDTA consume means less Ca and Mg ions present. But if more
EDTA consume then it means less Ca and Mg ions present.
Formula:
PPm= vol: of EDTA x 20 (1PPm = mg/ltr)
Weak bonding between Ca and Mg ions, EDTA creates strong bonding
EDTA creates hexa dentate medium
Barium Activity Test: (To check mercerize degree)
1. a. Take fabric of 5gm
2. b. Neutralize it with water
3. c. Left it for drying
4. d. Cut 2 gm of fabric
5. e. Take 30ml of 0.25 normal of Barium oxide.
6. f. Left it for 2 hr but shake it periodically with constant interval of
time
7. g. Titrate it with 0.1 normal solution of HCl (strong acid) 10ml of
solution of barium oxide(barium oxide) then add phenolphthalein it
shows pink color if alkali present
Formula: Blank reading – sample reading x 100
Blank reading – un mercerized reading
Qualitative test/Quick test method for Mercerization
1. a. Make 20% iodine solution
2. b. Take 3 x 15” fabric piece (mercerized and un mercerized)
3. Then dip fabric pieces in 20% solution then see color change after
washing
4. Dip mercerized and un mercerized fabric at a time
5. Darker the blue color (best mercerized)
6. Brownish color (low mercerized)
pH by Extraction Method
1. a. Take 125 ml of distill water
2. b. Take 5gm of fabric
3. c. Left 125 ml distill water for boil for 10 minutes.
4. d. Cut the fabric in small and in equal pieces so that easy rotation
obtained
5. e. Dip the pieces in boil water
6. f. Then again left it for boil about 10minutes
7. g. Left it after boiling for cooling
8. h. Pipette out 5ml of water in which fabric was dipped
9. i. Take reading at room temperature with pH electrode(pH
electrode must be calibrated to avoid any variation in result)
Ph By IKEA:
1. Take 100ml of distill water
2. Add 2 gm of fabric in 100 ml of water
3. Place it for 2hrs at room temp on stirrer
4. Note down pH after 2 hrs
Iron Testing of Greige Fabric:
1. Take A4 size fabric piece
2. Treat it with nitric 5%(acidic media) it will make complex in acidic
media
3. Potassium thiosynite 10% add in solution then it will indicate red color
where iron particle present
Formaldehyde test: AATCC 112/ISO 14184/1
1. Take 1 gm of fabric
2. Add that piece of fabric in 100ml of water for 40’c
3. Pipette out 5ml water then add 5ml of Nash agent in solution
4. Treat it for half an hour with Nash agent(Nash agent must be prepared
12hrs before starting the process)
5. Then check it on Morapex instrument for quantitative analysis
Formaldehyde Test with AATCC method:
1. Take 50 ml of water
2. Take 1 gm of fabric and prepare like a doll for hanging purpose
3. Left it for 65’c for 4hr’s
4. Take out 5ml of solution and add 5ml of Nash agent at 58’c for
6minutes
Baume Testing:
1. take the reading on room temperature 30 – 32’c, of any chemical
which you want
2. as temperature becomes 30’c, leave the baume meter in that chemical
it will go in chemical but to certain extent and the value shown as in
numbers (there is numbering from its upper surface to lower)
Specific Gravity Test:
1. a. pipette out 1ml of solution of any liquid of which you want to
know the specific gravity
2. b. Then weigh that 1ml liquid, the weight that it got it will be its
specific gravity
Solid Contents Test:
1. Take china dish and weigh it first
2. Then pour down liquid, and then again weigh the sample
3. Then left it on 110’c for 1 hr(solid content will remained behind)
Determine the %age of polyester and cotton in blend fabric:
1. Percentage of polyester and cotton and may be determined by dipping
the blend fabric in 70% concentrated solution of H2SO4.
2. The cotton portion will be dissolved and just polyester will be
remained. We will weight the fabric before dipping and then we will
weight again after drying. And we may calculate the %age of cotton or
polyester in the blend.
3. H2SO4 actually breaks the glucoside linkage present in cellulose
4. Remaining portion will said to be polyester percentage
Formula: Final wt x 100 (Polyester %)
Initial wt
Initial – Final wt x 100 (Cotton %)
Winch dyeing
The winch or beck dyeing machine is quite simple and serves for all scouring, bleaching, dyeing, washing-off and softening processes.
The machine contains a length of fabric with the ends sewn together, which is compressed to form a continuous rope. This rope passes from the dye bath over two elevated reels and then falls back into the bath
The first roller is free-running (jockey or fly roller). The second (winch reel) is driven and controls the rate of rope transport and the extent of pleating where the rope accumulates below and behind the winch.
The fabric rope is held on the winch by friction and its own weight. Covering the winch with polypropylene or polyester tape increases the friction.
Deep-draught winches have circular or only slightly elliptical winch reels, This type of winch is preferred when fabric stretching may occur.
Shallower machines have more elliptical winches and plait the fabric into the back of the machine.
A perforated baffle separates the liquor in the front of the machine from the remainder. This part of the machine is called the salting box. Both dyes and chemicals are added to it during dyeing and gradually mix into the remainder of the solution.
Heating is by steam injection from a perforated pipe running along the length of the salting box. Direct steam injection causes some bath dilution and can be quite noisy
The problem of non-uniform temperature in the bath, caused by the cooled fabric falling into the back of the bath, can be minimised by use of a pump to circulate the bath solution.
The liquor ratio is typically about 20:1.
The rate of dyeing is partly controlled by the rate of rope cycling and usually increases with increasing winch speed.
for all forms of rope dyeing, the fabric must be fairly resistant to lengthways creasing.
A wide variety of materials that do not readily crease can be dyed using the winch machine.
The good mechanical action promotes crimp in the yarns and improves the loop length of knitted materials. It gives thicker fabrics with a fuller handle.
Open-width threading of the fabric in a winch machine is possible for heavy materials such as carpets and for fabrics that might be crushed in rope form.
Several ropes of equal length (50–100 m) are usually dyed
Jig dyeing machines
The jig or jigger dyeing machine is one of the oldest types of machine for dyeing a variety of materials in full width.
It is useful for fabrics such as satins and taffetas that crease readily. The open-width fabric passes from one roller through the dyebath and then onto a driven take-up roller on the other side. When all the fabric has passed through the bath, the direction is reversed Each passage is called an end. Dyeing always involves an even number of ends.
The bath can be rapidly heated by live steam from an open perforated pipe. Closed-coil steam heating is slower but gives better temperature control during dyeing and avoids dilution of the liquor. In the widest machines, stirring the bath ensures uniformity of its temperature.
During dyeing, the machine lid/hat should be closed. This helps to maintain a high and uniform roll temperature and reduces heat loss and steam consumption.
Dyeing under pressure is also possible using jigs that roll into an end-opening autoclave.
The jig has a small bath containing the dye liquor (200 to 750 l) and gives a very low liquor-to-goods ratio of around 1:1.
It is therefore useful for those dyes used on cellulosic fibers that normally give only low to medium exhaustion.
Jig dyeing is a form of pad–roll dyeing repeated several times. The rate of dyeing depends on
1. the amount of liquor retained by the fabric,2. the degree of exhaustion in the dwell period, and3. the extent of liquor exchange during the next dip.
The roll of fabric may vary in length from 1000 to 5000 m.
A heavy line holds more dye solution and may transfer dye to adjacent layers of fabric that will show more deeply dyed stripes.
The modern jig often has both the take-off and take-up rollers driven to minimise lengthways tension.
Lengthways tension elongates the fabric and reduces its width. To promote uniform dyeing, and maintain a constant dip time in the bath,
the linear velocity of the fabric is maintained fairly constant by gradually changing the angular speeds of the rollers.
There is little mechanical action in a jig machine and it is less suitable where energetic scouring is required before dyeing.
The major problems are side-to-centre color variations, called listing, and lengthways colour variations, called ending.
Ending is more pronounced with slow dyeing or temperature-sensitive dyes. The fabric at the end of the roll receives two closely spaced dips in the dye bath and tends to be dyed paler with slowly exhausting dyes. The end of fabric close to the roller may also have a lower temperature. It is usual to add only half the dye solution at the beginning of the first end, the rest being added before the second.
Listing can arise from
1. non-uniform temperature across the width of the fabric, or2. from non-uniform pressure that squeezes the retained dye liquor
across the fabric width between the layers.
After dyeing, the roll of fabric slowly turns to avoid drainage of dye liquor into the lower layers of fabric
Jet dyeing machines
The first jet dyeing machine, based on a design by Burlington Industries in the USA, was introduced by the Gaston County company in 1961.
Dye liquor is injected at high speed from an annular/ring shaped orifice around a rope of fabric as it passes through a venturi tube(used to control fluid flow). This is a tube with a constriction(bottleneck).
The high linear velocity of the jet of liquid, and its flow around the fabric rope in the venturi, pull the fabric along towards the back of the machine.
Fabric speeds are usually about 200– 250 m/min but can be much higher. The fabric then falls into the back of machine and slowly moves to the front where it rises to the jet again.
A non-driven lifter roller, or a small driven winch, in front of the jet, guides the fabric into the venturi tube.
In Dye liquor that collects in the bottom of the vessel is pumped through a heat exchanger and back into the jet. Solutions of dyes and chemicals are added from a tank using a secondary pump.
This type of machine is usually fully enclosed and can be pressurised by heating the bath to temperatures above 100 °C or with compressed air.
Jet dyeing machines have proved particularly suitable for dyeing textured polyester fabrics under pressure at temperatures of 120–130 °C.
In the jet machine, the fabric being dyed and the dye liquor are in constant motion and the vigorous exchange between them results in rapid dyeing. Considerable dye adsorption can occur even during the short period of about 1 s that the fabric rope spends in the venturi tube.
Limitations:
sampling to check the shade is often difficult. The machines are usually quite expensive and are difficult to load and
unload. Because the interior of most jet machines is not easily accessible, they are
difficult to clean. In particular, polyester oligomer deposits may develop on the hot surfaces
and later shift. Cleaning with circulating NaOH and Na2 S2 O4 solution is common. The
inside surfaces must be smooth to avoid tears. Jet dyeing machines have liquor-to-goods ratios in the range from 5:1 to
15:1. The lowest liquor ratios require only partly filled machines and useful for
dyeing cotton knits with reactive dyes because of the lower quantities of chemicals consumed. Partly filled jet machines, however, tend to produce copious/rich amounts of foam from the turbulent passage of dye liquor and fabric through the venturi.
Even when low-foam chemicals are used in dyeing, an anti-foaming agent such as a silicone or fatty alcohol will be required.
For a given rope of fabric, too small jet produces more creases because the fabric rope is more compressed in the jet and may even jam.
Too large a jet gives inferior/deficient rope transport. Some jet machines have adjustable jets. Accurate positioning of the jet
avoids giving a circular motion to the liquor that might cause twisting of the rope and more creasing.
Rectangular jet machines Lifting the dripping rope from the base of the machine to the jet, cause longitudinal tension and creasing. This type of machine is not suitable for many delicate fabrics.
Fabrics from spun yarns of staple fibers may tend to become quite hairy in appearance because of abrasion.
Much gentler jet dyeing machines avoid some of these effects. Some limit the fabric tension by providing mechanical assistance in moving the plaited fabric through the machine and back to the jet.
Fully flooded jet machines are useful for more delicate fabrics. They will have a higher liquor ratio (15:1) the fabric rope is always immersed in the dye liquor.
The dye liquor is pumped from both ends of the storage tube to a heat exchanger and then to the jet.
In the so-called soft-flow machines, tension and creasing problems are minimised. The fabric rope is gently lifted over the short distance between the dyebath and the transport tube using a circular driven reel.
The tube supports the fabric and there is no tension. The tube is filled to overflowing with dye liquor.
A typical liquor ratio is about 15:1. Several machines may share heating and circulation systems.
For lightweight or narrow fabrics, dyeing with several parallel ropes in the same jet is not usually satisfactory because equal lengths are needed and they may give different degrees of shrinkage. The flyer method of dyeing is used. For this, lengths of fabric are stitched onto a main carrier rope by their leading edges. They are slightly shorter than the main rope. Ideally, the fibre of the carrier rope will not be dyed.
Beam dyeing machines
In principle, beam dyeing is similar to package dyeing but with a single large package.
As mentioned above, beams of warp yarns can be dyed by circulating dye liquor through the bed of yarns laid down on a perforated roller.
Beam dyeing of fabric involves
1. winding it onto a perforated beam and2. pumping dye liquor through this
This dyeing method is widely practised for those fabrics that might crease, extend or abrade when dyed in machines
Obviously, it is not appropriate for compact fabrics that severely limit the flow of dye liquor through the many layers on the roll.
The autoclave type with a horizontal beam is now more common. The autoclave allows higher dyeing temperatures and, if required, two-way flow through the roll of fabric.
Beam dyeing under pressure is easier than jig pressure dyeing. The winding of the fabric onto the beam is a critical step. The beam is
usually first wrapped with a few layers of cotton fabric. This provides a soft bed for the material, allows dispersion of the solution, and filters out any particles.
The fabric is then wound onto the beam at constant speed with a uniform but not excessive tension. It is essential to avoid creases and to have evenly aligned selvages without any curling.
A piece of polypropylene or calico is stitched to the end of the fabric, rolled around a few times and re-stitched. This prevents the centre of the roll from ballooning and keeps it clean.
Beam barrels/drums come in various diameters. They are about 20 cm at each end and the rest of the cylinder is perforated to allow good liquor flow. The perforations at the ends can be wrapped with flexible stainless steel sheets, to accommodate narrower fabrics.
If there is too much overlap, the selvages receive less dye solution, but if the overlap is too small, much dye liquor escapes out through the sides of the roll. Both give unlevel dyeing.
The fabric to be dyed must have good dimensional stability. If there is any length extension during dyeing, solution may leak out of the roll sideways between the layers of fabric giving unlevel edges.
Shrinkage along the length of the fabric during dyeing causes excessive pressure that can flatten the fabric.
Width shrinkage causes flow variations while width extension gives ballooning of the roll and reduced flow.
Prior to rolling up the beam, fabrics made from thermoplastic synthetic fibres are therefore pre-set, using hot air or water, to relax tensions and eliminate possible dimensional changes during dyeing.
The circulating pump forces water from the beam interior out through the layers of fabric.
A wetting agent helps to eliminate air bubbles within the fabric roll. De-aeration(remove air or gas) is essential to avoid paler dyed spots. The level in the expansion tank rises as the temperature increases. Solutions
of dyes and chemicals are added through this tank. From its bottom, the small pressure pump feeds the solution back into the machine.
Complete circulation of the liquor takes about 1–2min. The liquor ratio is usually around 10:1. The fabric will then usually be scoured but the beam machine does not
effectively remove solid impurities that are retained in the layers of fabric. Heating is by high-pressure steam passed through pipes running along the
bottom of the autoclave. Cooling is achieved using the same tubes. Fast, even liquor flow through the roll of fabric is essential. This is usually in
the
1. in-to-out direction, but it can be reversed.2. Out-to-in flow
Out to in flow can compress the material causing flattening and glazing, particularly on the inner layers.
The major disadvantage of in-to-out flow is the risk of unlevel dyeing, with the inner layers of fabric having a deeper color than those on the outside of the roll.
The rate of exhaustion must be below about 2% per cycle of liquor.
The flow rate should be as high as possible without disturbing the layers of fabric. It depends on the
1. pump,2. the fabric permeability, and3. the number of layers in the roll.
Unlevel dyeings are difficult to correct unless readily migrating dyes are used.
Sampling during beam dyeing remains a problem. In many cases, it may be necessary to cool, drain the liquor to storage, sample the roll and then refill with additional dye solution. This is expensive.
MACHINES FOR DYEING YARNHank dyeing
In a hank dyeing machine, the skeins of yarn usually hang from poles fitted into a frame that can be lowered into the dyebath. Rods inserted at the bottom of the frame keep the skeins fully extended.
The frame has a perforated top and bottom. The dye liquor gently circulates either down through the hanks, or in the
reverse direction if the machine is completely filled. At the front of the machine, a compartment, separated from the hank frame, contains the impeller circulating the dye liquor. The steam and cooling pipes are at the bottom of this compartment. Dyes and chemicals are also added here.
This type of dyeing machine is frequently referred to as a Hussong machine. For level dyeing, equal exposure of all the yarn in the skeins to the
circulating dye liquor requires even packing of the skeins. It is important that upward circulation of the liquor in the machine lifts the
yarns in contact with the upper poles, otherwise these will dye paler because of poor contact with the liquor.
The liquor ratio is usually in the range from 24:1 to 30:1. Such high liquor ratios require greater amounts of dyeing assistants and consume more steam than in package dyeing machines
The rates of heating and liquor circulation are low. Even though dyeing in a Hussong machine is less productive and less economic than dyeing yarn wound into bobbins, it is still widely used for dyeing skeins of wool and acrylic yarn.
The Hussong machine preserves the yarn bulk and handle. Acrylic yarns, in particular, may shrink in the hot dye bath.
Invariant downward flow of the dye liquor through the hanks keeps them extended so that bottom poles are not needed. In this case, the problem of contact between the solution and the yarns touching the upper poles can be avoided by pulsating the liquor flow.
In another method, the dye liquor circulates through upward-pointing holes in the poles holding the skeins. There may be occasional problems of unleveled dyeing.
A major reason for the decline of hank dyeing is the problem of unwinding. After dyeing, the wet hanks are centrifuged, hung on poles or hooks, and passed through a hot air oven. They must then be mounted on a rotating frame to unwind the yarn. After package dyeing, yarn can be more easily unwound at much higher speed by pulling it over the top of a stationary bobbin.
Package dyeing machines
A package dyeing machine is typically a cylindrical vessel, about 2 m high and 2 m wide, with a rounded bottom and lid.
The yarn is wound into cheeses, cones or cakes using perforated former tubes. The formers may be rigid or compressible, the latter allowing packages to be squeezed tightly together when mounted on top of each other in the machine.
Cheeses are cylindrical with parallel sides, with a diameter usually larger than the length. Cones taper with a small angle.
Cones allow easier over-the-top unwinding of the yarn than cheeses. High bulk acrylic yarn can be dyed in cake form. The packages of yarn are inserted onto vertical, perforated spindles in the
machine. Each spindle typically takes 8–10 packages but the vertical columns of packages do not touch.
The spindles screw into holes in the base of a hollow, circular frame, at the bottom of which is a connection fitting onto the pump (Figure 12.2). The spacing of the spindles and hence the maximum load depends on the frame diameter and package size
The dye liquor is pumped into the base of the frame and up through the perforated spindles.
the liquor flow through a cone is not usually as uniform as through a more regularly shaped cheese.
The dye liquor flows up the perforated spindle and flows outward through the packages of wound yarn. It then flows back down over the outside of the frame and back to the pump.
Heating is usually with super-heated steam in coils situated just below the frame carrying the spindles. The same coils, or a different set, can be used for cooling.
Fully filled, closed machines allow bi-directional flow that assists level dyeing.
Less level dyeing dyes, of higher washing fastness, are used than when dyeing hanks.
Package dyeing has many advantages over hank dyeing.
1. 1. It allows higher loads,2. 2. lower liquor ratios,3. 3. more rapid dyeing and easier unwinding of the dyed yarn.4. 4. Package preparation is a crucial step.
Some of the factors influencing the stability of a package and its permeability to dye solution are:
(1) the denier or tex of the yarns or filaments; (2) the degree of twist of the yarn; (3) the extent to which the yarn traverses the package (cross-winding) and its tension;(4) the degree of swelling or shrinkage that occurs in hot water;(5) the actual shape of the package.
The yarn tension throughout the package must be even and winding must be as uniform as possible.
The initial rate of dye liquor flow through a viscose filament package may drop sharply because of the fibre swelling that occurs in water.
Non-textured nylon or polyester filaments, that tend to shrink in hot water, may have to be initially relaxed and re- wound before dyeing.
Textured artificially made filaments give softer packages that do not require pre-shrinking and for which the permeability is much less dependent on yarn and filament characteristics.
A typical liquor-to-goods ratio for a package dyeing machine is around 10:1, Many machines have tank, this tank is used to add solutions of dyes and any
required dyeing assistants, which are then pumped back into the machine. In package dyeing, it is difficult to reproduce the liquor flow conditions from
batch to batch and the shade reproducibility is sometimes not completely satisfactory.
Drying packages has always been a problem. Centrifuging packages in a basket removes much of the loosely held water but complete drying requires a lengthy period in a hot air oven. This type of process often takes as long as 24 hours to completely dry the yarn, More recently, the use of radio frequency dryers has become popular. As much water as possible is removed by centrifuging and the packages then go into the RF dryer.
The oscillating electromagnetic field causes oscillation of the polar water molecules in the package at the field frequency. This generates much heat. The degree of heating depends on the amount of water at a given point in the package so that drying is more uniform than in hot air.
Face and Back Prolem(wet processing)
face and back problem is mainly encountered in dyeing of textiles.
Face and back is that problem in which shade of color of fabric face appears
to be different than fabric back shade its known as face and back problem.
This problem we mainly encounter due to following reasons;
1. High Temperature(continuous dyeing)
2. Less Reaction time(exhaust dyeing)
3. Unsuitable quantity of antimigrating agent
4. Uneven padder pressure(continuous dyeing)
5. Padder roller not cleaned(continuous dyeing)
6. Fast dosing of color(exhaust dyeing)
7. Fast dosing of auxiliaries(exhaust dyeing)
High Temperature:-
This problem we mostly face if we pad the fabric and bringing that directly to
drying chambers without the passing from IR drying.
As the fabric reaches in drying chamber, there is much temperature that
affects water molecules to escape out from fabric but this also results in
migration of dye with it because the dye didn’t get much penetrated in fabric
When we press our suit if we are pressing the fabric y pouring some drops of
water on fabric so as the iron comes in contact with fabric water molecules
escapes and jumps to another place
IR pre drying prevents from fore said problem and this only affects water
molecules but not dye molecules.
Remedy:
After padding to avoid face and back do IR pre drying.
Less Reaction Time:-
If the dyeing time is not given to dye for its proper penetration and reaction
its color will bleed and the dye don’t get enough well penetrated into its
whole structure so causing face and back problem
Remedy:-
Its remedy is to give proper time to dye for reaction to avoid face and back
and so many problem
Unsuitable quantity of antimigrating agent:-
Anti migrating agent(say for example sodium alginate) prevents dye dye
migration
If we will not add this auxiliary in dyeing process dye can go move within the
faric structure so creating shade variation and also results in face and ack
problem
Anti migrating agent prevents dye migration increasing its viscosity to some
extent and defines a proper place to each dye molecule.
Remedy:-
Use proper anti migrating agent and also its proper quantity
Uneven Padder Pressure:
If the padder pressure is uneven i.e. variable LCR pressure it causes face and
problem by giving dark and light shades throughout the fabric length and
width
Remedy:-
Use proper setting of padder pressure i.e. at three main positions L.C.R to
avoid problem.
Padder Roller not Cleaned:-
If any of padder is not cleaned properly it will effect the shade of fabric of its
respective side.
Say for example if there is some oil left behind on one padder while other
being properly cleaned, as we start padding oil will affect the shade of
respective side.
Remedy:-
To avoid this there must be proper cleaning of padder is done in order to
avoid face and back problem.
Fast dosing of color:-
In exhaust dyeing mostly we add dye solution before starting process and in
between the process also. So if by mistaken its dosing done fast and it
directs to some portion of fabric, this will give darker shade at that place
than the rest and also differ in face and back shade.
Remedy::-
Care an vigilance must e taken in dosing, and it must e done at suitable
dosing rates.
Fast dosing of Auxiliaries:-
If dosing of auxiliaries(alkali, anti migrating and salt etc) is done at fast and
with pressure. It also creates the same problem in dyeing y giving
darker/light shade at that proper place than that of rest
Remedy:-
Its remedy is that dosing rate must proper and suitable and not directs on
the surface of fabric