Editor: Pertti Nousiainen, Professor Emeritus, Tampere University

Man-made bio-based fibre products

Everything you need to know about texile applications of wood — clothing, hygienic and medical applications.



Textile fibre production has exceeded 100 million tonnes during 120 years of its history due to population growth and rising living standards. Fibres based on synthetic polymers have been responsible to the growth since 1950´s, because bio-based cultured fibres, especially cotton, couldn´t increase the production responding the growth of 1 mill. annual tons of textile fibres. Bio-based man-made fibres mainly produced from dissolving cellulose, such as viscose CV, cupro CU, and acetate CA have shown increased figures due to their hydrophilic character, which is important in clothing, hygienic and medical applications. The growth of viscose fibre production up to more than 6 % of total fibre production has increased rapidly the demand of dissolving pulp including sulphite and new modified Kraft pulp processes, as well.

The environmental concern on carbon dioxide, chemical and micro-plastics pollution in textile chain is favouring viscose and other cellulose-based fibres. The aim has been to develop aqueous viscose fibre technology as low-sulphur process by recycling of chemicals and as sulphur-free by enzymes, which are used for making cellulose soluble without derivatization. Increased amount, around 0,5 % of total fibre production are lyocell cellulose fibres produced by combination of solvent NMMO with water and recycling NMMO after spinning the fibre. Novel production processes based on ionic solvents are piloted in Finland. A new process for transforming pulp directly to fibres with water and without any chemicals is in piloting stage, as well.

Cellulose carbamate technology has been applied in 1980´s to produce viscose-like fibres, however, has not been competitive enough to replace viscose. Instead of virgin fibre production, carbamate technology has been developed to regenerate waste cellulose raw materials, such as cotton denim and paper waste.

Polyester is currently produced as a semi-bio-based (PTT) by the production of trimethylene glycol from agricultural waste by fermentation, which then polymerizes with oil-based terephthalic acid. The replacement of terephthalic acid with bio-based furan dicarboxylic acid is being developed, which would allow the production of 100% bio-based polyester (PEF) showing similar properties with current polyester (PET).

Due to the dominance of synthetic man-made fibres, there is a lack of cellulose fibres in the fibre production that can be satisfied with (regenerated) cellulose fibres. It seems that the global production of fibres reaches 150-200 million tonnes in 2050, cellulose fibres are needed in addition to cotton in the magnitude of 15 million tonnes. Thus, increased amount of dissolving pulp is demanded giving opportunities for forest biorefining. It is advantageous to develop different methods for obtaining different fibre products for the needs of clothing, hygiene products, home textiles and technical textiles.

The utilization of wood-based cellulose as the raw material for fibres leads to carbon-neutral cycle, whereby carbon dioxide, which binds to the tree, is transported with the product and decomposes back into the atmosphere as a result of burning or biodegradation. The share of cut trees for 15 million tons of dissolving pulp is small in comparison with other trees, green fields and oceans to absorb carbon dioxide.

Several lifecycle surveys conducted on cellulose fibres (viscose, lyocell) show that impacts on land use and emissions are lower than cotton, allowing more farmland to be used for food production. The new methods being developed can further reduce emissions from the production of cellulose fibres. Proper forest management (4 times planting and precise harvesting of up to 80%) can ensure their sustainable use. Eucalyptus wood fields are used to avoid large-scale use of rainforests for fibre production.

In outlining this theme, a simple structure with six chapters was selected. The purpose of the Chapter 1 is to describe the big picture of the textile and fibre industries: the position and outlook, major trends and drivers, a brief history of fibrous materials, production statistics of fibres, fashion and design, technical applications and composites. Thereafter are the presentations of various textile fibres: natural fibres, man-made regenerated fibres, man-made synthetic fibres and man-made synthetic fibres based on bio-monomers. Sustainability and environmental considerations are presented at the end of Chapter 1 with a specific focus on EU standardization and legislation.

Chapter 2 includes the presentation of man-made biobased fibre products and their end-uses. As the introduction main raw materials are discussed in the connection with fractionation of lignocellulosic biomass (dissolving pulp). Main regenerated (solution spun) fibres, viscose, lyocell, cupro, modal, polynosic and bacterial cellulose are described. Main features of cellulose carbamate are presented, even if the technology has only been piloted, but not found further interest. More rare fibres, such as alginate, chitosan and casein fibres are presented. In case of chemical cellulose derivatives, the presentation includes only specific forms of carboxymethyl cellulose fibres. Man-made biobased synthetic fibres are finding increasing interest and additional to polylactic fibres, PHA, PHB, PHBV and PEF are described.

In Chapter 3 processing of textile fibres into end-uses and the definitions are described for different fibre types of staple & filaments, profiled and functional fibres, followed by nonwovens and yarn spinning. High performance and speciality fibres are presented for technical applications and composites including regenerated cellulose, synthetics and carbon fibres made from cellulose. The chapter contains the mechanical, chemical and aesthetical requirements of fibres for textile and clothing applications, interior and household textiles. A review of standardization of fibres and textile products and methods of fibre and textile testing are presented at the end of the chapter.

Chapter 4 focuses on key aspects of the down-stream conversion processes. It starts on mechanical processing to fabrics: nonwovens forming & bonding, yarn spinning, knitting, braiding, weaving and sewing. Advanced mechanical processes in weaving and 3D structures and production of fibre-reinforced composites is included. Chemical textile processing from fabrics via pre-treatment, dyeing, finishing and washing are presented using latest developments of machinery. Clothing manufacture from ready fabric to different types of clothing are described.

Manufacturing processes of bio-based man-made fibres are described in detail in Chapter 5 with the various technologies of regenerate dissolving pulp into cellulose fibres. The emphasis is on description processes for viscose, modal and polynosic fibres, Lyocell fibres and cupro fibres. Others are cellulose acetates and ethers, mainly carboxymethyl cellulose CMC, alginate fibres, cellulose-based carbon fibres and regenerated protein fibres. Melt spinning of biobased polymers includes production of polylactic fibres PLA, which are the main synthetic bio-based fibres. The transversion of polyamides and polyesters into bio-based fibres and the potential of other polymers, such as PHA, PHB, PHBV is discussed.

Scientific principles of polymer fibre formation and properties is presented in Chapter 6. General elementary theory for polymer fibre forming and maximum values of their mechanical and thermal characteristics is described. Characteristics of fibrous structures using spinneret technique, copolymeric and polyblend fibres, multicomponent, micro- and nanofibres are presented. Additionally, general theories (phase separation, orientation, crystallization in solutions and melts), spinning of thermotropic and lyotropic polymers, anisotropic polymers and liquid crystals for separation is presented. Degradation and stabilization of polymers for fibre applications and respective additives are highlighted. Factors affecting on the properties of fibres is followed by the high-speed spinning technology.

As alternative and emerging processes for cellulose fibres, ionic liquid processing is presented, as well as novel processing with urea to cellulose carbamate and mechanical-enzymatic activation of cellulose to dissolve pulp for spinning cellulose fibres. Fibres and yarns manufactured from pulp fibres and nanocellulose is a novel method for textile fibres without any chemicals added to water.

Alternative and emerging processes for bio-based synthetic fibres describes the development of bio-based monomers for plastics and fibres using furan dicarboxylic acid for PEF and ricin and soya acids for polyamides. Finally, examples of methods for regenerated protein polymer fibres and spider silk related filaments are given.