Step of viscose manufacturing process

Viscose

Viscose is a regenerated natural fiber that is produced from cellulose fiber. In other words, viscose is a semi-synthetic type of rayon fabric made from wood pulp that is used as a silk substitute, as it has a similar drape and smooth feel to the luxury material. The molecular structure of the viscose is the same as that of cotton and linen, except that the molecular chains are shorter and do not form as many small crystals. Different types and grades of viscose fibers can mimic the feel and texture of natural fibers such as silk, wool, cotton, and linen. Fiber is used to make textiles for clothing and other needs.

History of viscose

Viscose is the earliest regenerated fiber that was first patented in 1855 by the Swiss chemist Georges Audemars. It was also called artificial silk. Sir Joseph Swann, an English chemist, was inspired by Thomas Edison's incandescent electric lamp to make filaments for electric light. His fibers were used in Edison's discovery and in 1885 his wife in an exhibition of textiles crushed from his new fiber. Artificial silk was also exhibited at the Paris Exhibition in 1889 by the French chemist Count Hilaire de Chardonnet who is known as the "father of the rayon industry" Because he built the first plant for commercial production of chardonnet silk in Besancon, France in 1905, Cortalds Lee. The USA produced the first commercial Viscose Rayon which was the very first economically viable "Artificial Silk".

Viscose fiber properties

There are two types, such as-

a. Physical properties

1. Viscose is a regenerated natural fiber that is made from cellulosic wood pulp.

2. The drape and slipperiness of viscose textiles are often more like nylon.

3.  The hand feels and texture of viscose like silk, wool, cotton, and linen.

4. Viscose fibers are easily dyed in a wide range of colors.

5. Viscose fabrics are soft, smooth, cool, comfortable, and highly absorbent.

6. The durability and appearance retention of regular viscose is low, especially when it wet.

7. Viscose has the lowest elastic recovery of any other fiber.

8. Regular rayon has lengthwise lines called striations and its cross-section is an indented circular shape.

9. Staple fibers range from 1.5 to 15 deniers and are mechanically or chemically crimped.

10.  Rayon fibers are naturally very bright.

11. Moisture Regain 11-13%

12. It becomes weak when heated above 150 °C.

b. Chemical properties

1. Viscose is damaged by strong acids but it is moderate with weak acids.

2.  It has good resistance to weak alkali but strong alkali damage the viscose.

3. Strong oxidizing agent damage the viscose fiber.

4. It has a high ability to protect various solvents.

5. Mildew damage the viscose fiber.

6. Various insects attacked the viscose fiber.

Chemical composition of viscose

Viscose is 100% cellulose and has the same chemical composition as the natural cell. The molecular structure of viscose is the same as that of cotton and linen, except that the molecular chains are shorter and do not form as many small crystals.

 

Spinning bath chemicals

Below chemical solvent is used in spinning bath-

H₂SO₄ – 10%

Na₂SO₄ – 18%

Glucose – 02%

ZnSO₄ – 01%

Water – 69%

Viscose manufacturing process

The viscose manufacturing process can use wood as a source of cellulose, whereas other routes to rayon require lignin-free cellulose as a starting material. The use of wood sources of cellulose made viscose cheaper, so it was traditionally used on a larger scale than other methods. Viscose fiber is produced from the ripened solutions by treatment with a mineral acid, such as sulfuric acid. In this step, the xanthate groups are hydrolyzed to regenerate cellulose and carbon disulfide.

Production begins with processed cellulose obtained from wood pulp and plant fibers. The cellulose content in the pulp should be about 87-97%.

The steps of the viscose manufacturing process-

1. At first, the cellulose content in the pulp is treated with caustic soda.

2. The treated cellulose is then pressed between rollers to remove excess liquid.

3. The pressed sheets are crumbled or shredded to produce what is known as a white crumb.

4. The white crumb is aged through exposure to oxygen. This is a depolymerization step and is avoided in the case of polynosics.

5. The aged white crumb is mixed in vats with carbon disulfide to form the xanthate. This step produces Orange-Yellow crumbs.

6. The yellow crumb is dissolved in a caustic solution to form viscose. Viscose lets it ripen, standing for a certain period of time. At this stage the molecular weight of the polymer changes.

7. After ripening, the viscose is filtered, degassed, and then extruded through a spinneret into a bath of sulfuric acid, resulting in the formation of viscose filaments. The acid is used as a regenerating agent. It converts cellulose xanthate back to cellulose. The regeneration step is fast which does not allow the correct direction of the cellulose molecules. So to delay the process of regeneration, zinc sulfate is used in the bath which converts cellulose xanthate to zinc cellulose xanthate thus providing time for proper orientation to take place before regeneration.

a. Spinning: The spinning of viscose fiber is done using a wet-spinning process. The filaments are allowed to pass through a coagulation bath after extrusion from the spinneret holes. The two-way mass transfer takes place.

b. Drawing: The viscose filaments are stretched, in a procedure known as drawing, to straighten out the fibers.

c. Washing: The fibers are then washed to remove any residual chemicals from them.

d. Cutting: If filament fibers are desired, then the process ends here. The filament shoots are cut while producing the main fiber shots.

Advantages of viscose

1. Viscose is a versatile and widely used fiber.

2. The drape and slipperiness of the viscose are good.

3.  Viscose fabrics are soft, smooth, cool, comfortable, and highly absorbent.

4. Stronger and exhibits higher durability and appearance retention.

5. Viscose can be machine-washed.

     

6. Viscose fibers are naturally very bright.

Disadvantages of viscose

1. Highly toxic carbon disulfide is used in the production of viscose.

2. Rates of disability in modern factories are unknown.

3. The more water-repellent the rayon-based fabric, the more slowly it will decompose.

4. Viscose is weak when it is wet.

5. Always recommended care for regular viscose rayon is dry-cleaning only.

6. Prone to stretching and bagging and often doesn’t recover

Conclusion

The future of viscose fabric is so bright. Not only is there a growing demand for viscose worldwide, but there are many new technologies that promise to make viscose even better and cheaper. Today there is a strong trend toward mixed fabrics. Blends offer the best of both worlds. With the present body of knowledge about the structure and chemical reactivity of cellulose, some scientists believe it may soon be possible to produce the cellulose molecule directly from sunlight, water, and carbon dioxide.