How is modal made?
Modal is a regenerated fiber with cellulosic raw material extracted from hardwood trees like birch and oak. Modal is an alternative to viscose rayon for it requires less harmful chemicals in its production. Let us now understand the production process of the modal.
• Extraction and Preparation of raw material: The raw material that forms the basis of the modal fabric is cellulose which is extracted from the pulp of hardwood trees such as oak and birch. The pulp is a blend of various trees selected on the basis of their cellulose composition.
• After cultivation the trees are harvested and taken to mill. The outer bark of the tree is then removed. The bark is then loaded into the chipper machine which crushes the bark into small square chips. The chips are then purified to derive the cellulosic matter.
• Steeping: The cellulose matter so obtained is then formed into sheets. The cellulosic sheets are then transferred in a contained wherein they are steeped in an alkaline solution of caustic soda i.e. sodium hydroxide which converts them into alkali cellulose sheets. Also, the amount of sodium hydroxide used in the modal manufacturing step is quite less than the viscose rayon and thus less harmful chemical effluent is released.
• Shredding: The alkali cellulose sheets are then dried and shredded into a crumb form referred to as ‘white crumb’ using a shredder machine. After shredding the process of ageing is eliminated in case of the modal. Further, the process of xanthation is carried out in which the crumbs are churned in carbon disulphide which results in the formation of sodium cellulose xanthate that is bright orange in colour.
• The last step involves soaking the sodium cellulose xanthate in sodium hydroxide to obtain a solution which is then extruded through the spinneret (sieve-like device having small holes at the base) and the resultant filament fiber is extracted.
• The filament fibers are then soaked in sulphuric acid, stretched and straightened and made into yarns. After the yarns are extracted, they are washed and dried and rolled onto the spool. Lastly, as per the end-use, the finishes may be applied and yarns are then woven into the fabric.