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Package Dyeing

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					                           Package Dyeing

The dyeing of yarn in package form is called as package dyed. The advantages
claimed for package dyed over hank dyeing include the following:

           Elimination of hank reeling
           Reduction in waste
           Faster back winding speeds
           More controllable dyeing process with
            better levelness and the use of faster
            dyes
           Savings in water, energy ,dyes and
            chemicals due to the lower liquor ratio
            use
           Less space required
           Less labor handling
           More production from a machine of a given size
           High temperature dyeing possible and rapid drying
           Readily automated processes

The success of package dyeing in terms of both levelness and yarn quality is
greatly influenced by the degree of care taken in the preparation of the yarn
packages. The density of package may be controlled during the winding process
by adjusting the yarn tension and the winding speed.

Rockets, cones, springs, plastic tubes and non woven fabric centers have all
found favor. The springs have been widely used for dyeing high bulk acrylic yarn,
since they allow a certain amount of shrinkage to occur in the package due to
compression of the spring in both width and length. As with most stainless steel
formers, cost can be a serious problem, especially if a large number is required,
due to their use in supply packages. Both metal and plastic formers can be used
and this is perhaps most widely recognized in the case of cones. Metal formers
although expensive are obviously more durable and easy to clean. Plastic
formers are less expensive, but have a shorter life and can be heavily stained by
certain dyes which can cause contamination problems.

Package dyeing can be applied on different types of yarn of some are:

   1)   Texturized yarns
   2)   Staple yarns
   3)   High bulk acrylic yarns
   4)   Carpet yarns
   5)   Knit –Deknit yarn
1) Texturized yarns:-

Texturized yarns are traditionally package dyed. The main advantage of of all
packages for texturized yarn is that they are prepared on the texturizing machine,
thereby eliminating winding process.

2) Staple yarns:-

Staple yarns have conventionally been delivered to the package dyer on
perforated cones ready for dyeing. This method has the advantage that a winding
process is eliminated, but the dyer has little control over the package densities
produced. Furthermore, expensive pacing devices are required and, even with
these; cones can slip on the dyeing machine spindle giving rise to liquor
channeling and the risk of unlevel dyeing. The payload with cones is less than
that with other forms of package.

3) High bulk acrylic yarns:-

Prepration of high bulk yarn packages by the dyer is justified since the
continuous relaxation of the yarn is carried out at the same time.
High bulk acrylic yarns were conventionally dyed in hank form to allow for
approximately20% shrinkage which occurs due to the relaxation of the yarn in
water at about 85c(and above).

Various machines have been developed for the continuous relaxation of the yartn
using steam or dry heat. The principle of the operation is to unwind the unrelaxed
yarn from cones through the relaxation chamber, the yarn then being wound on
suitable packages for dyeing.

4) Carpet yarns:-

Staple carpet yarns can be package dyed, since the yarn can be wound onto dye
packages from spinner’s tube, thereby eliminating a winding operation.
Continuous filament can be handled on springs which are prepared by the fiber
producer.

5) Knit-Deknit yarn:-

Continuous filament yarn for the production of crinkle type fabrics is knitted into
tabular fabric approximately 8 cm in diameter. Rolls of the fabric can be handled
as dye packages on spindle machines and after wet processing are deknitted.
This type of package is handled in essentially the same way as the others.
Preparation for dyeing:-
Scouring is not readily carried out in package dyeing machines, largely due to the
filtration effects produced by the yarns. Thus excessively dirty yarns can cause
problems in package dyeing and most yarns are either dry spun or are spun with
a self scouring.

Machines:-
Dyeing machines for packages can be sub divided into four basic configuration
types:

   1)   Rectangular dyeing machines
   2)   Beam type dyeing machines
   3)   Circular dyeing machines
   4)   Vertical spindle carriers

1) Rectangular dyeing machines:-

It is usually designed for hank dyeing, which have been adapted or further
improved to accommodate package frames: these are usually horizontal spindle
machines. The outstanding example is Pegg GSH.

This is usually as economical machine to install and allows hank machines to be
converted to dye packages. Flow rates may be low, so that package density has
to be reduced.

2) Beam type dyeing machines:-

They have been designed to take horizontal package carriers. They are high
temperature machines.

3) Circular dyeing machines:-

They are designed to take a number of different types of carriers. These can be
used with horizontal spindles

4) Vertical spindle carriers:-

Operation can be at high temperature, high and often variable flow rate. They are
most expensive, but also the most versatile type of machine.

The last machine seen is said to be the best type of all package dyed machines.
Products of package dyeing:-
        Texturized yarns for both weaving and knitting
        Sewing threads
        Regular acrylic yarns
        Weaving yarns in wool and acrylic fibers fot apparel or furnishing
        High bulk acrylic yarns for machine knitting
        Cellulosic yarns for weaving or machine knitting

Characteristics of package dyeing:-

        Leaner yarn but the yarn gives better fabric definition
        Larger payloads for a machine of a given size
        Faster back winding and less waste generation
        High degree of levelness and reproducibility, with the possibility of using
          dyes of high fastness
        Savings in energy, water etc.


                               Dye selection
Reactive dyes:-
Reactive dyes are well established for dyeing all types of cotton materials,
including sewing threads, yarn packages or woven fabrics. These units are
controlled by fully or semi automatic systems, wholly or partially programmed to
regulate temperature, process time, flow direction cycles, dye bath additions,
dosage rates and sequence changes. Machine functions and substrate form
determine not only the quality of dyeing but also the dyeing procedure.

The more thorough the access of dye liquor to the material, the better the
levelness and penetration. Rapid dyeing cycles required uniform liquor
circulation, which in turn depends on the efficiency of machine loading and the
quality of package winding. If circulation is poor or non uniform good quality
dyeing might still be possible but relatively long dyeing cycles would be
necessary, particularly at the critical stages of the leveling in the salt solution and
alkali dosage. Feasible chemical additions should be made when the liquor is
circulating from outside to inside. Special care is necessary with yarns for plain
weaving or knitting as opposed to effect threads in a colored woven or knitted
design.

At some places, where penetration problems are anticipated, as in certain
mercerized high twist or multi ply yarns, it is advisable to use low reactivity dyes
at temperature above 70c with holding the alkali addition until atleast 30min after
the final addition of salt.
Sulphur dyes:-
The most suitable dyes are either the water soluble sulphur dyes, which are
applied in a nn substantive form to to obtain uniform penetration of the package,
followed by reduction, or the pre-reduced liquid brands, which require no pre-
boiling and may be more easily added to the vessel, in portions if desired. The
preparation of packages suitable for dyeing is quite critical. For package dyeing
the essential requirement is for consistent winding as variations in tightness in
packages within a dye lot will lead to an uneven dyeing
A typical method for the pre-reduced brands after wetting out or scouring would
be as follows

1) Set the bath at 40C with 1 gm sodium sulphide flakes 60%, I gm sequestering
agent and 1ml anti oxidant and then circulate for 10 min.
2) Add the dye in one to four portions over 10 min then raise to 75-95c and
circulate for 10 min.
3) Add 5-20gm salt slowly over 20 min and run for further 10 min.


Important Control Parameters:-
      Use of dyeing machines at standard loadings and liquor levels
      Characterization of dye ability to substrate
      Rationalization of dye ranges
      Use of standardized dyes
      Dispensing facilities
      Standard application techniques




Reference:-

Fiber to fabric by B.P.CORBMAN

Fabric science by ARTHUR PRICE

www.htpunitex.com/NewFiles/tmbi.html
Textile Institute of Pakistan
Txch-458




                        “Package Dyeing”




Submitted to Aslam Khan
Submitted by M.Farrukh Rangoonia ( TS4A)   Dated: 01.04.2008

				
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