Thermosol dyeing of Poly-cotton fabric with reactives

hermosol-rangeschematic

Thermosol Dyeing – Polyester and Poly-cellulose blends
Thermosol dyeing is a continuous dyeing process for synthetic fibers and their blends.  Various auxiliaries are used in thermosol dyeing, including buffers, anti-migrants and wetting agents. 

  1. Thermosol Dyeing Process (polyester)
  • Padding with liquor containing disperse dyes, migration inhibitor and other required auxiliaries at pH 4.5-5 with Acetic Acid.
  • Intermediate drying at 110-130°C.
  • Thermosol treatment at 180-225°C for 30 - 90 seconds.
  • Rinsing and reduction clearing, similar to HT dyeing.
  1. Reactive thermofixation process:
  • Pad-Dry
  • Alkali Padding
  • Pre-Drying
  • Thermo-fixation (steaming)zz
  • Rinsing and Soaping

 

  1. Reactive Disperse/Dyestuff
  • Dyestuff Penetration
  • Pre-Drying
  • Thermosoling
  • Alkali padding
  • Steaming
  • Rinsing and Soaping

Disperse Dyes Suitable for Thermosol Dyeing:

High energy Disperse dyes):

  • Excellent sublimation fastness 
  • Suitable for print/pad/high temperature or high pressure steam fixation. 
  • Recommended for thermosol dyeing of polyester / blends. 

        Medium energy Disperse dyes 

  • Good sublimation fastness 
  •  Suitable for general applications on polyester / blends

Generally all HE and H (MCT) type of reactive dyes are suitable for thermo fixation process.

All Cotfix HE and P series can be used for thero fixation process:

General recipe for Disperse thermosoling:

    1. Disperse Dyestuff = X gpl
    2. Sodium Alginate = 2 gpl
    3. Nuseq Conc (sequestering agent) = 0.5 gpl
    4. Ammonum Sulphate = 1.0 gpl
    5. Formic Acid = 0.3 to 0.5 gpl
    6. Sodium Chlorate 0.2 gpl (optional)
  • Pad 2 dip/2 nip at room temperature – pick up = 60 to 65%
  • Dry at 950C on Hot flue and thermo fix in a 6 to 8 chamber oil heated stenter at 190 to 2100C for 60 to 30 seconds.
  •  

General recipe for thermofix process of Reactive Dyes:

  • Cotfix HE or Cotfix P dyestuff = X gpl
  • Urea = 50 gpl
  • Sodium Alginate = 2 gpl
  • Resist salt = 10 gpl
  • Sodium Bicarbonate = 20 to 40 gpl
    • Pad – 2 dip/2 nip = expression = 65%
    • Dry at 1100C
    • Thermofix at 1400C for 5 minutes
    • Cold wash/Cold wash/Soap @ 950C/ Soap @ 950C/Hot wash/Hot wash/cold wash/

 

thermosol-dyg
 Thermosol dyeing problems (Disperse dyeing)
 

 

1. Listing

 

 Causes

Countermeasures

 

- one-sided liquor feed into the trough

- check injection pipe or mount a distribution plate

 

- different nip roller pressure

- check rollers (pickup) regularly

 

- unlevel migration in intermediate drying

- check temperature and air current over the entire width in the drier
- avoid migration by using lowest possible pickup and a suitable migration inhibitor.
Select dyes with little tendency to migrate.

 

- uneven thermosolling or fixation of dyes due to temperature differences

- check fixation units regularly with thermopaper or temperature sensors
- use more reliable dyes with as little sensitivity as possible to temperature deviations

 

 

 

2. Two-sidedness

 Causes

Countermeasures

 

- deflecting roller touched on one side only

- check entry of goods, if necessary replace roller

 

- deflecting roller stationary

-set roller in motion

 

- pad rollers not the same

- check Shore hardness, if necessary re-cover rollers

 

- uneven drying from side to side

- check temperature and air current in drying machine

 

 

 

3. Dark or pale selvedges

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Causes

Countermeasures

- one-sided liquor feed into the trough

- check liquor feed

- narrow goods impregnated on a wide padder

- move to a suitable machine

- worn rollers, rollers bend due to over compensation

- check the nip pressure, reduce pressure if necessary, change rollers if necessary, chick hydraulics

- varying drying conditions over the width of the goods

- check the air jets and circulation

- alkali residues in the goods

- add acetic acid to the padliquor for pH 5-6

 

4. Barry dyeings

 

Causes

Countermeasures

- uneven jet pressure in the drier

- check the air jets

- inadequate evenness of tension in drier, crease formation

- check guidance of goods in drier

- alkali residues in the goods

- add acetic acid to padliquor for pH5-6

 

5. Spots, specks

 

Causes

Countermeasures

- pale marks due to condensation drops

- check driers and pad-steam units regularly
- overhead heating

- foam spots due to excessive foaming of the pad liquor

- avoid high turbulence in the padding trough, use low-foaming chemicals, if necessary add anti-foamers

- coloured specks due to incorrect preparation of the padliquor

- follow instructions for preparing the pad liquor exactly, filter padliquor before feeding into trough
- avoid drying out of liquid dyes due to incorrect storage

- alkali residues in the goods

- add acetic acid to pad liquor for pH5-6

 

 

6. Ending

 Causes

Countermeasures

 

- dye substantivity

- use a smaller volume of liquor
- dye at higher fabric speed

 

- dye sedimentation

- keep the liquor in motion
- keep the temperature below 35°C

 

 

 

7. Pale points of intersection

 

Causes

Countermeasures

- poor penetration

- add a wetting agent to the pad liquor
- change the pressure of the rollers
- increase impregnation time

- severe migration

- dry more slowly
- use special migration inhibitors

 

8. Foam formation

 

Causes

Countermeasures

- dispersants in the dye

- use defoamers

- residues of boiling off agent

- scour goods better before dyeing

 

9. Frosting

 

Causes

Countermeasures

- migration during thermosolling

- use special chemicals

- fibre tips not dyed (e.g. viscose)

- add Lyogen V
- change process, e.g. wet steaming

 

PAD THERMOSOL MACHINE – some useful details:
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/A
Production Speed               60-100m/min
Padder                                Kuster
Chambers                           5(3 for drying and 2 for curing)
Padder Capacity                 100-150liters
Scray Capacity                   400-600mters of fabric
Trough Capacity                50-60litres
VTG/Airing Zone              12m of fabric
Nominal Width                  130�?
Working Width                  120�?
Thread Length                   170m
IR drying units                   2
Drying units heating         Oil Heating System
IR Temperature Range      650-850’C
IR vertical tension             2-6bar
Liquor Change                  after 3-4min   

 Process Conditions for Polyester:
1st chamber     80’C
2nd chamber    100’C
3rd chamber    120’C
4th chamber    190’C
5th chamber     210’C
Speed              30m/min
Pressure          3.2, 2, and 3 in 1st, 2nd and 3rd chamber respectively
Pick up           70%

Main sections Of Machine:
1.     Let off section
2.     Padding Section
3.     VTG/Airing Zone
4.     IR(Infra red Dying)section
5.     Curing Section
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.

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.

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)

   
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.