GATE (TF) Textile 2012 Question Paper Solution | GATE/2012/TF/02

Question 02 (Textile Engineering & Fibre Science)

The chemical that is used to convert soda to sodium cellulose xanthate in the manufacture of viscose rayon is

(A)Carbon disulphide
(B)Sodium xanthate
(C)Sodium sulphide
(D)Sodium hydroxide
Answer / Solution
[Show Answer]

Option A

Frequently Asked Questions | FAQs

What is the method of preparation of rayon?

Rayon is a man-made fiber that is derived from natural sources, such as wood pulp or cotton. The process of making rayon involves the following steps:
Preparation of Cellulose: Cellulose is the main raw material used in the production of rayon. It is obtained by treating wood pulp or cotton with chemicals to remove impurities and break down the fibers.
Dissolving the Cellulose: The purified cellulose is then dissolved in a solvent such as sodium hydroxide to form a viscous solution called “dope.”
Extrusion: The dope is then forced through a spinneret, which is a device that contains small holes. The spinneret is immersed in a chemical bath, where the cellulose regenerates into solid fibers.
Washing: The fibers are then washed in water to remove any residual chemicals and impurities.
Bleaching: The fibers may be bleached to obtain the desired color and brightness.
Stretching: The fibers are stretched to improve their strength and durability.
Finishing: The finished fibers may be treated with chemicals or dyes to improve their appearance and performance.
The resulting rayon fibers can be used in the production of textiles, clothing, and other products.

What is the process of xanthation?

The process of xanthation is a crucial step in the production of viscose rayon. It involves the following steps:
Purification of Cellulose: The raw material, such as wood pulp, is purified by treating it with chemicals to remove impurities and break down the fibers.
Aging: The purified cellulose is aged for several days in a solution of caustic soda to increase its reactivity.
Xanthation: The aged cellulose is then treated with carbon disulfide (CS2) to form a substance called cellulose xanthate. The reaction takes place in an airtight container equipped with a mixer. CS2 is added to the cellulose slurry while stirring at a controlled temperature and pressure.
Dissolving: The cellulose xanthate is dissolved in a dilute solution of caustic soda (NaOH) to form a viscous liquid called viscose. The dissolution reaction is exothermic, and the temperature must be controlled to avoid overheating, which can cause degradation of the viscose.
The xanthation process converts the cellulose into a derivative that can be dissolved in the alkaline solution, allowing the production of viscose. The resulting viscose solution can then be used in the extrusion process to produce viscose fibers, which are used in the production of textiles, clothing, and other products.

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