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J-box and Vapor lock unit for continuous scouring processing

Continuous process for polyester-cotton blends

One of the major advantages of the continuous process is the increased production in a textile chemical process House. 

In the case of polyester-cotton blends, the fabric is scoured continuously in a J-box or Vaporlok-type machine.

There are mainly two machines used for continuously scouring the processing of the fabric.

(1) J-Box
(2) Vapor lock unit

J-Box is for combined Scouring as well as bleaching process so, it will be explained during the combined Bleaching process however, the Vaporlok process is used for continuous Scouring of the polyester cotton blended fabric.


It consists of mainly two units-

(1) Scouring unit consists of a caustic saturator, pre-heater & j-box 

(2) Bleaching unit consists of a peroxide bleaching bath

J-Box is used for scouring & is termed as J-box because the shape of the machine is similar to the letter J. 

The fabric is treated with an alkali solution before it enters the J-Box. The fabric is passed in the rope form & evenly piled up & then treated with Steam for about 60 to 90 min.

Because the scouring duration is shorter, the alkali solution concentration can be as high as 4 to 5%. 

By taking out the scoured fabric from one end and simultaneously feeding up the unscoured fabric from the other, the j-box scouring process can be made continuous.

After being squeezed from the rollers, the fabric passes through a pre-heater, which warms the cold fabric to the machine's temperature, allowing for better scouring.

The fabric is impregnated with the scouring solution in the saturator.

The cloth is stacked uniformly in the J-U-shaped box's structure and exposed to steam for 60 to 90 minutes at 90 to 97°C.

Because of the steam, using a J-box set up the fabric, in the open-width State is padded through liquor containing 15-25 GPL soda ash and 2 to 3 GPL of a Detergent & then piled into a regular J-Box.

The scoured fabric then passes on to an open-width soaping machine in which it is successively & thoroughly given hot & cold washes.

Recipe -

Sr No



Sodium carbonate

15 to 25 GPL



2 to 3 GPL



95 to 99 °C



60 to 90 minutes

J- Box(scouring)
J- Box (scouring)

Vaporlok unit (continuous process)

It is made up of three parts: an impregnation zone, a Vaporlok unit, and a washing unit. In a saturator, the cloth is impregnated with a liquid comprising 6 to 12 GPL sodium hydroxide and 3 to 5 GPL detergent.

After impregnation, the fabric is steamed for 90 to 120 seconds in the Vaporlok chamber at 2 to 2.2 kg/cm2.

The polyester fibre in the blend is unaffected by the short steaming time.

The goods are subsequently transferred to an open soaper, where they are washed as usual.

This is a short technique that results in a cleanly scrubbed cloth with good absorbency.

Recipe -


Recipe and parameters


Sodium hydroxide

6 to 12 GPL



3 to 5 GPL



2 to 2.2 kg/cm2



90 to 120 sec

Questions -

  1. What is the continuous process used for polyester-cotton blend fabric for scouring?
  2. What is the role of J-box in fabric scouring processing?
  3. What is the role of vapour lock in fabric scouring processing?


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Further reading,

Part 1 Introduction of scouring processing.

Part 2 Scouring processing actions

Part 3 Scouring processes methods

Part 4 Kiers in scouring processing

Part 5 Process flow of scouring and it's testing

Part 6 Types of kiers

Part 7 Scouring of Cotton & coloured cotton goods (1)

Part 8 Scouring of Natural polyamide or protein fibres (2)

Part 9 Scouring of Man-made fibres (3)

Part 10 Scouring for Polyester cotton blends (4)

Part 11 J-box and Vapor lock unit for continuous scouring processing

Part 12 Machines used for yarn scouring

Part 13 Jigger machine for scouring processing

Part 14 Winch Scouring Machine

 - Rushikesh Patil (Textile Engineer)
(DKTE Society textile engineering college Ichalkaranji)
Email Id -

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