Friday, November 8, 2019




Modal is a re-generated fibre. It is the next generation of rayon fibre. This fibre is made using wood chips of "beech tree" (European Schneider Zelkova tree). It is "high wet modulus fibre" made by using a modified viscose process with a higher degree of polymerisation and modified precipitating baths. The modal fibres have improved wet strength over standard viscose fibres. It has abrasion-resistant yet soft to handle. It also has good draping properties.  This process leads to improving fibre properties such as better wear, higher dry and wet strengths and better dimensional stability. The modal fibre contains modified cellulose obtained from a beech tree. 



Modal fibre is produced by using the viscose process. Wooden chips of beech trees are crushed and pure cellulose is obtained by processing them. The whole process takes place in the following steps:

The source of Cellulose: 

“wooden chips of beech tree are taken”. These chips contain cellulose and other substances like lignin, hemicellulose, wax and fat. These wooden chips get processed to remove impurities present in it. Thus pure cellulose is obtained. This cellulose is used to manufacture modal fibre. 

Formation of alkali cellulose: 

The cellulose obtained from the beech tree is dissolved in caustic soda (sodium hydroxide) solution. The alkali cellulose results after this process. The reaction follows below chemical equation:
Removal of excess sodium hydroxide:

The alkali cellulose solution gets passed between mechanical rollers. These rollers apply high pressure onto the alkali cellulose. The excess amount of sodium hydroxide gets removed in this process. A sheet of alkali cellulose results after pressing.

Shredding of pressed sheet:

The pressed sheets are crumbled or shredded to produce what is known as “white crumb”. The pressed sheet of alkali cellulose is mechanically shredded to increase surface area. it is easy to process the crumbs.

Ageing of white crumbs:

The white crumbs are oxidized here. The oxygen of ambient air is allowed to make contact with white crumbs. The cellulose is partially oxidized and is degraded. The molecular weight gets lowered.
This degradation is controlled carefully to produce a sufficiently short length of chain to provide required viscosities in the spinning solution but chain length should be still long enough to provide good physical properties to the fibre. 

Xanthation of aged alkali cellulose solution:

The carbon disulphide gas is applied to an aged mixture of alkali cellulose. This process is called “Xanthation”. the aged alkali cellulose crumbs are placed in vats and are allowed to react with carbon disulphide at a temperature (20° to 30 °C). The cellulose xanthate (compound fell) results after this reaction. “This compound gell is referred to as yellow crumb”. The reaction follows the below chemical equation:
Formation of viscose solution: 

The “yellow crumb” is dissolved in a solution of sodium hydroxide. Viscose solution of yellow crumb results. 

Ripening of viscose solution: 

The viscose solution is allowed to ripen. “In this process, the viscose solution is set to stand for a period of time”. The chemical reaction goes like the following chemical equation:
Filteration of viscose solution: 

After ripening of the viscose solution, it is filtered to extract any undissolved particles from the solution.

Removal of air bubbles:

Any bubbles of air present in the viscose solution are removed by pressing.  This process is called degassing process. 

Extruding or wet spinning:

“The viscose solution is extruded through a spinneret”, which resembles a shower head with many small holes. As the viscose solution comes out from the spinneret, it passes through a bath of sulphuric acid. The fine filaments of modal fibres result during this process. 
Drawing of filaments:  

The filaments obtained after extruding are coarse. “They are passed through drawing rollers running at various speeds”. The filaments are stretched till the required fineness is achieved. This process is called “drawing”.
The fibres are then washed to remove any residual chemicals present in it. These filaments are wound onto bobbins. “When staple fibres are required, the filaments cut down into pieces”.



Modal fibre is used to get comfort and aesthetics, lustre, sheen, shine and naturality. Modal fibre is used to make the following products:
Sports wear. 
Towels and Bathrobes.

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  1. Sir please verify how does the wet strength of modal higher than its dry strength.

  2. The manufacturing process you described here is of viscose and not modal's. If my memory is correct modal manufacture does not have these two steps namely ageing and ripening to keep maximum possible Dp. Moreover, there is change in the coagulating bath chemical proportion of modal from viscose.


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