Question

Hygroscopic agents used as printing auxiliaries are:
(A) Urea
(B) Glycerin
(C) Sodium lactate
(D) Turkey red oil
(E) Potassium ferrocyanide
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (C), (D) and (E) only.
• D. (B), (C) and (D) only.

Hint:

Urea and glycerin are the most common humectants used in textile wet processing.
They ensure the print paste remains moist during the initial stages of steaming, which is essential for uniform dye fixation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In textile printing, hygroscopic agents (humectants) are added to the printing paste.
These agents absorb moisture during the steaming process, helping to swell the fiber and dissolve the dye for better fixation.

Step 2: Detailed Explanation:
Let us evaluate each printing auxiliary:
- (A) Urea: A widely used organic compound in printing pastes.
It is highly hygroscopic, absorbing moisture during steaming, and also acts as a solvent for disperse and reactive dyes. Thus, (A) is correct.
- (B) Glycerin: A clear, viscous liquid that is highly hygroscopic.
It is used in printing pastes to prevent them from drying out and to absorb moisture during steaming. Thus, (B) is correct.
- (C) Sodium lactate: A sodium salt of lactic acid.
It is highly hygroscopic and is used as a humectant in specialized textile printing and finishing formulations. Thus, (C) is correct.
- (D) Turkey red oil: This is sulfonated castor oil.
It is used primarily as an emulsifier and wetting agent to help disperse the dye, not as a hygroscopic agent. Thus, (D) is incorrect.
- (E) Potassium ferrocyanide: A chemical reagent used as an oxidizing agent or catalyst, not as a humectant. Thus, (E) is incorrect.
Therefore, urea (A), glycerin (B), and sodium lactate (C) are the hygroscopic agents.

Step 3: Final Answer:
The hygroscopic printing auxiliaries among the options are Urea, Glycerin, and Sodium lactate, corresponding to option (A).