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Dyeing & Finishing

Possibility of space dyeing in Bangladesh

Space dyeing/yarn printing is a process of dyeing of yarn in which multiple colours are applied along the length of each strand of yarn which may or may not repeat after a fixed interval. It is a technique used to give yarn a unique multi-coloured effect.

Figure 1: There is a various method of space dyeing on different forms of yarn.

Space dyeing yarn is sometimes referred to as dip dyed yarn. Space dyeing means the localised application of dyes and chemicals by any method which can produce a particular effect of colors on the yarn or onto a yarn package according to the design. It is also known as yarn printing. Although we cannot get fixed repeat as printing in space dyeing. A color melange effect is produced in space dyeing.

Hanks or skein printing: The ready to dye yarn in hank form is mounted on a stand or laid on a suitable surface and then different colours are applied by brush or by spraying at fixed places to achieve the desired multi-color effect. Though this method imparts controlled yarn coloration at specific points and desired length the process is cumbersome and time-consuming and is mainly suitable for short length fabric.

Hanks or skein printing

The space dyed yarns are used to produce beautiful effects after knitting, weaving, decorative stitching or embroidery. The coloured band pattern and their length depends upon the desired effect. The Bangladeshi manufacturers are mainly producing knit products besides woven, towel or carpet using space dyed yarn.

Hanks or skein printing

Day by day the market value of space dyed fabric is increasing. According to the data from KC Yarn Dyeing Ltd, a unit of KNIT CONCERN GROUP space dyed fabric production is gradually increasing. KC Yarn Dyeing started production of space dyed fabric/yarn from Sept.-2011 and still continuing. The yearly production report of space dyeing of KC Yarn Dyeing Ltd is given for understanding its popularity which is growing its place in world market.

Yearly production report of space dyeing
Year Production in kg
2011 1305
2012 2826
2013 47893
2014 114076
2015 80407
2016 248421
2017 195940
2018 143404
2019 Continuing

Space dyeing in package form: Depending on the machinery available and the effect desired, the yarn printing in package form is done by two methods.

Manual operation: Colours are injected by hand or machine at different places in the package using a syringe filled with the dye solution. The skillset developed by the technicians enableS them to inject the needle by hand or machine.

Manual operation

Another variant of this method is dip stick process. In this case different places of yarn package are dipped in different dye solutions so that multiple colors get applied at various places and with varying intensity which after the unwinding of yarn provides a unique fancy dyed effect.

dip stick process

Nowadays foreign buyers are intending to fancy fabrics. To survive and to create higher market value Bangladeshi manufacturers are also producing space dyed fabric. The most popular technique of space dyeing/ yarn printing is manual operation (inject dyeing). There are some factories in Bangladesh who are producing space dyed fabrics. Among them, KC Yarn Dyeing, a unit of KNIT CONCERN GROUP is the first and the largest space dyed fabrics/yarns supplier in this country. They are using bobbin inject dyeing technology of LAIP.

As the Bobbin Inject dyeing technique is the most popular technique in this country so a brief description of bobbin injects dyeing is given below.

Machine specifications:

Brand LAIP
Origin Italy
Capacity 2 Pkg (at a time)
Pkg weight 1 Kg (each)
Colour used Maximum 4 colors & minimum 2 colors
Mixing tank 4 (1 for each color)
Colour storage capacity 250ltr/Tank
Temperature (40-70) C
No. of storage cylinder 08
Cylinder storage capacity 1 ltr

space dying machine

Machine parts:

  • Dyes Tank
  • Storage Cylinder
  • Injecting Needle
  • Bobbin Holder
  • Hydraulic Pressure/ Oil box
  • Colour Suction Pump

Machine description: Space dyeing/yarn printing machine consists of dyes tanks, cylinder, oil box, injecting the needle, color suction pump, etc. Key parts of the machine are discussed below.

Dyes Tank: Preparing the dyes solution is the first task before injecting color. Machine contains 4 tanks where we can make a solution of 4 specific colors with all required chemicals for uniform dyeing. There is a stirring motor and steam line in each tank which helps in color mixing and heating as required.

Dyes Tank

Storage/Printing cylinder: There are 08 cylinders which are connected to injecting needle. Every two cylinder contains same colour from one dyes tank and distribute that colour in 08 different injecting needles of two head. Capacity of each cylinder is 1 ltr. Dyes solutions that have to be injected is temporary stored in the cylinder. For printing 2 pkg, 08 ltr dyes solution is used from 04 tanks through 08 cylinders. It almost works as syringe used in medical treatment.

Printing cylinder

Bobbin holder: There is a pressing head which press the pkg from upper part which keep the yarn package in firm space.

Bobbin holder

Needle head: It is adjusted with the colour supply pipe. For one package 04 needle head is used which covers the whole surface of the package. Each needle head contains 04 needles from top to bottom that penetrates discharged dyes into the package.

Needle head

Printing needle: The machine contains 32 needles which each needle contains 05 pores which pass the liquor from cylinder to package by hydraulic pressing of cylinder and air pressure.

Printing needle

Hydraulic pressing/oil box: All operation or movement of this machine is done by hydraulic pressure which is produced by an oil box. Oil box produce 100 Bar pressure to move the cylinder, needle pad and the bobbin holder.

Hydraulic pressing oil box

Suction pump: When dyes solution is injected through needle from cylinder by hydraulic press suction pump suck that solution from inner side of bobbin so that dyes solution can uniformly spread into package and do not bleed with another colour.

Suction pump

Note: Minimum 06 bar air pressure is needed for operating various types of sensors in this machine.

Space Dyeing Flow Chart:

Grey yarn

Soft Winding (DIGI)

Batching

Pre-treatment (Bleach/white)

Hydro Extractor

Dryer (Radio Frequency)

Re-soft winding (Precision)

Bobbin inject printing machine

Steaming/ Thermal fixing

Wash off

Fixing+Finishing

Quality check

Hydro Extractor

Dryer (Radio Frequency)

Hard winding

Packing section

Delivery

Note: Steamer is a supporting machine of bobbin inject dyeing machine where the thermal fixing of yarn is done. As usually thermal fixing of cotton yarn is done at (80-100)C for (30-60)minute and thermal fixing of polyester yarn is done at 130C for (30-60)minute. In steamer we can process 108pkg yarn at a time.

Steamer of supporting machine bobbin

  • No. of injection : single
  • Setting : 100% * 40 second(For 04 Colour)

: 90%*30 second (Containing white steak design)

: Double punch (70%*30 second & 30%*30 second For Polyester

  • Steaming : (80-100) C for (30-60) minute For cotton

:  130C for (30-60) minute for polyester

  • Pattern : It is depended on the number of colour

Variation of design in BID 04 colour space dyeing machine:

  • Different Design:

4 Different color

Different color

3 same colors & 1 another color

3 same colors & 1 another color

2 same colors & alternative color

2 same colors & alternative color

2 same colors & subsequently

2 same colors & subsequently

2 same colors & 2 Different colors (3 colors)

2 same colors & 2 Different colors (3 colors)

Horizontally same colors

Horizontally same colors

Vertically same colors

Vertically same colors

Costing: Cost analysis of yarn printing is higher than solid yarn dyeing. When a solid dyed T-shirt value is $2, then a T-shirt from dyed yarn is $5 But T-shirt from printed yarn is $10. Typical costing of space dyeing/yarn printing of KC Yarn Dyeing Ltd is given below.

Typical cost of yarn printing
Type of shade Cost in $/Kg
All types of shade

(For cotton)

3.80-4.00
All types of shade

(For polyester)

5.00-6.00

Problems of space dyeing/yarn printing: Besides new development new technologies have some limitations also. Space dyeing/yarn printing has also some limitations. Some limitations of space dyeing/yarn printing using BID machine are given below.

  • Yarn breakage may occur during knitting as 16 needles are injected inside the yarn package. The penetration of needles frequently weakens the yarn at the contact point.
  • As we dye two package at a time so package to package & layer to layer shade can vary(around 10%) in bulk quantity Batches.
  • A tertiary colour can be visible mostly in light colours at the contrast point of two different colours.
  • Sometimes some white spot may visible due to faulty needle and poor yarn absorbency.
  • As colours are injected so process loss of dyes is higher than as usual solid yarn dyeing. Yarn process loss is also high because the inner layer of the yarn packages does not absorb the required of dyes solutions.
  • Sometimes shade becomes lighter because dye solution (containing gluber salt, soda ash and all auxiliary chemicals) has to keep for 2 or 3 hours. So it has a great possibility of hydrolyse of dyes.
  • No re-process system can be done here. If we find any fault then we have to cut out the faulty part or use it for any other purpose. After wash-off, a lot of dyes are wasted away from coming and wastage of dyestuff occurs.

After wash off

This study reveals that there are many more horizons of technology and arts that helps fusion of many steps which cause hassle, instead these we can use the shortest potential one way- yarn printing. This is a modification of yarn dyeing process but replacement of other multifunctional printing system and gives a clear outline and contrast printing appearance. Garment using printed yarn is an empirical study of value addition to increase foreign currency by exporting ready-made clothing.

References:

Special Thanks to:

  • Md. Armanul Islam Khan, DGM, KC Yarn Dyeing Ltd.
  • Md. Ruhul Rahad Khan, Sr. Manager, KC Yarn Dyeing Ltd.
  • Md. Rakib Haider, AGM, Dong Bang Yarn Dyeing Ltd.
  • Md. Tuhin Molla, DGM, Zarjis Composite Knit Ind.
  • Saibal Chandra Majumder, DPM, KC Yarn Dyeing Ltd.
  • Md. Moksheduzzaman, Sr. Production officer, KC Yarn Dyeing Ltd.
  • Faruk Hossain, Sr. Planning Officer, KC Yarn Dyeing Ltd.

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