Long Way Education

By Eman Abdallah Kamel

Eman is a writer and engineer. She received her bachelor’s degree in textile science from the Faculty of Applied Arts, Egypt.

This article discusses the definition of viscose, its key production stages, environmental risks, and sustainable viscose initiatives and certifications.

Viscose

Viscose is a semi-synthetic fibre derived from wood pulp, which is a natural source of regenerated cellulose.

Some viscose fabrics mimic the feel of natural fibers such as linen, wool, cotton, and silk. Viscose rayon is a natural alternative to synthetic fabrics. Viscose absorbs dyes efficiently, producing rich, vibrant colors.

Viscose rayon is knitted or woven to make underwear, children’s clothing, shirts, skirts, and dresses. It can also be used to make bedsheets, tablecloths, towels, napkins, furniture covers, and curtains.

According to an article written on Textile Exchange, obtaining wood for viscose production poses environmental risks, including deforestation and negative impacts on biodiversity. The chemicals used in pulp and fiber production negatively impact worker safety and the surrounding environment due to emissions and wastewater discharges.

In 2023, global trade in viscose rayon yarn, multi-grade, not for retail sale, reached USD 127 million, a 4.19% decrease from USD 133 million in 2022.

In 2023, China ($69.3 million), the Czech Republic ($26 million), and Italy ($8.46 million) were the top exporters of non-retail, multi-purpose viscose rayon yarn. The top importers were Italy ($29.4 million), India ($27.4 million), and Turkey ($7.21 million).

Viscose Production Stages

There are three main stages for viscose manufacturing.

1. Wood Production
2. Pulp Production
3. Fiber Production

1. Wood Production

Hardwood forests are the primary source of cellulose used to produce viscose.

• First, the trees are harvested from the forest, peeled, and cut into logs, usually where they are grown.
• The logs are transported to the mill for debarking. Debarking can be wet or dry.
• Sometimes, the bark can be removed at the harvest site, as in the case of mature eucalyptus and fresh spruce bark.
• In chemical pulping, logs are converted into chips. If the wood chips are produced at the harvest site, they are then transported to the mill via conveyors.

Remember

In cold climates, it is necessary to remove snow from the logs to facilitate debarking. This can be done using special conveyors with warm water or by using steam and hot water at the inlet of the debarking cylinder.

Keep in Mind

The production of wood for viscose rayon fibers causes the following:

1. Deforestation and forest degradation, which in turn lead to the destruction of natural habitats for many animals, birds, and other species, disrupt the ecosystem. Deforestation also leads to climate change.
2. Chemicals used when removing bark cause water pollution.

2. Pulp Production

In pulp production,

• Wood chips go through a process of refining and separating wood fibers through a series of steps that require steam and chemicals such as sodium hydroxide, sulfur dioxide, or sodium sulfide.
• The resulting brown pulp is washed using a cold caustic extraction process.

Did you know?

The washing process produces a black liquor that is recovered for energy production. The black liquor is evaporated and then burned in a recovery boiler, generating steam used in turbines to generate electricity.

• After washing, the pulp is chemically bleached in two ways.

1. Through the use of bleaching sequences that contain chlorine dioxide, known as “elemental chlorine-free.”
2. By combining oxygen delignification with an ozone stage and peroxide stage, which is called “complete chlorine-free.”

What Is Happening to the Environment after Pulp Production?

1. Pulp factories produce significant emissions into the air and water due to the chemicals used, as well as the organic compounds found in the wood.
2. Air emissions include sulfur dioxide, nitrogen oxides, carbon monoxide, and dust. Chlorine compounds used in bleaching may also be released into the atmosphere.
3. Bleach plant wastewater contains bleaching chemicals that contain chlorine, contain halogenated organic compounds (AOX), and contain chlorate, which have toxic effects on water. Chlorine bleaching can also release dioxins, classified as persistent organic pollutants, which are highly toxic not only to the environment but to humans as well.

Did you know?

AOX is an abbreviation for “Adsorbable Organically Bound Halogens,” expressed as chloride. AOXs are substances that are adsorbed from water onto activated carbon. They may be volatile substances such as chlorophenol, trichloromethane, and chlorobenzene, or complex organic molecules such as furans and dioxins. Most AOXs are chlorine-containing molecules.

Source: European Environment Agency

Viscose Fiber Production

Viscose fiber production includes the following steps.

1. Steeping involves soaking cellulose pulp in an aqueous solution of 17–20% sodium hydroxide (NaOH) at 18–25°C to produce alkali cellulose.
2. Pressing process to remove excess water.
3. The mechanical shredding process of compressed alkali cellulose produces fine white crumbs.
4. The aging process involves the alkali cellulose being stored in small galvanized drums (for 48 hours, at 18–25°C) to decompose it to the desired degree of polymerization. Additionally, the average molecular weight of the original pulp is reduced to achieve cellulose concentration and viscosity.
5. The xanthate formation process involves placing the alkali cellulose crumbs in basins to react with carbon disulfide at 20 to 30°C, producing cellulose xanthate.
6. The dissolution process involves dissolving the crumbs in a caustic solution. The large xanthine substituents in the cellulose catalyze the separation of the chains, reducing the hydrogen bonds between them and allowing water molecules to dissolve and separate them, producing an insoluble cellulose solution.
7. During the ripening process, sodium cellulose xanthate is stored for two to five days at a temperature of 10-18°C. Viscosity first decreases and then rises.
8. The filtering process is to remove undissolved materials from the viscose.
9. In the deairation process, bubbles of air are removed from the viscose to avoid weak spots in the viscose threads.
10. In the spinning process, firstly, a solution of viscose is measured through a spinneret into a bath containing sulfuric acid, sodium sulfate, and zinc sulfate. Once the cellulose xanthate is neutralized and acidified, the viscose rayon filaments rapidly coagulate, followed by simultaneous expansion and hydrolysis of the cellulose xanthate to produce regenerated cellulose.

Remember,

1. Sulphur compounds, including hydrogen sulphide and carbon disulfide, are released into the air during the viscose fibre production process.
2. Oxygen-consuming organic matter from zinc sulfate used in viscose production causes water emissions. If bleaching is used on fibers, the effluent may contain chlorates and AOX, which can have toxic effects on the aquatic environment.

Certifications and Initiatives for Sustainable Viscose

Below are the most common certification systems for viscose production:

• The Forest Stewardship Council (FSC) Certification: FSC is an internationally recognized program that has established a certification system to ensure sustainable forest management worldwide.
• The Programme for the Endorsement of Forest Certification (PEFC): PEFC is the world’s leading coalition of national forest certification systems, promoting sustainable forest management through independent third-party certification. It is a non-governmental and non-profit organization.
• EU Ecolabel: The EU Ecolabel is a voluntary certification program. It promotes goods and services with a guaranteed low environmental impact throughout their life cycle. It helps consumers, retailers, and businesses make sustainable choices.
• The CanopyStyle Initiative: Canopy is a nonprofit environmental organization dedicated to protecting the world’s endangered forests, with a particular focus on the viscose pulp and paper industry. Canopy has been collaborating closely with viscose manufacturers, designers, and brands since 2012 to guarantee the sustainable sourcing of the wood required for viscose production.
• The Higg Materials Sustainability Index: It provides information on the production impacts of materials used in the clothing and home textile industries.

Sources

• Yarn of viscose rayon, multiple, nes, not retail.
• Water Footprint Network… Viscose Fibre Production—An Assessment of Sustainability Issues.pdf
• Aprayon.com

©Eman Abdallah Kamel, 2025

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The Long Way Education Site path is based on self-learning. Here, you will learn about science, education, and religion. You will also learn about fiber and its manufacture. And different disciplines of engineering, such as mechanical and industrial engineering.