Highlights and topics
Carbon fibers from cellulose
Nonwoven production technologies with pulp
Production technologies
The environmental development of viscose and lyocell fibers
Recycling cotton and PET/cotton cellulose for viscose raw material
Chemical recycling of waste textiles
Alternative feedstocks for cellulose fibers
Functional viscose fibers and composites
Cell-cultivated cotton materials
Carbon fibers from cellulose
Cellulose as the raw material for carbon fibers has been studied since Edison, who used cotton yarns as the conductive fibers in electrical vacuum class bulb lamps for lightning. Problems with cellulose-based carbon fibers generate from the orientation of starting polymer, and low carbon and high oxygen content result in complex pyrolyzing chemistry. As the result, yields of carbon fibers and their properties are much lower compared to pitch and polyacrylonitrile.
The Denkendorf research team (Vocht, Ota, Hermanutz, Buchmeiser) at DITF receives the award at the Cellulose3 Conference for the development of carbon fibers from cellulose. The process uses an ionic liquid solvent for wood and non-wood cellulosic materials for manufacturing carbon fibers with adaptable fiber properties. The oriented cellulose fibers are suitable in the formation of the high tenacity carbon fiber structure at 1400°C using continuous lab-scale processing at high carbon yield.
The invention may result in manifold applications in composite technology, which is applied in aerospace, transportation, sports, and car industries all over the world.
Nonwoven production technologies with pulp
Amid the growth of nonwovens production reaching 18 mill tons of cellulose fibers for the sustainable product as increased their share. Single-use nonwovens (such as wipes) are becoming more and more popular. Their main production technologies based on spunlace (hydroentangling), and needle-punching is often use the classic material mix of polyester and viscose. Air-laid technology allows the use of fluff pulp with a binder as reinforcing the structure. Glass fibers and short-staple viscose fibers are used in the wet-laid process combined with a binder.
Production technologies
The 3rd Cellulose Fibre Conference in Cologne was secondly organized during Covid19 restricted conditions. It didn´t limit the number of participation due to the interesting program covering sustainability, recycling, and alternative feedstocks as well as the latest development in pulp, cellulose fibers, and textiles. Some new technical application areas of non-woven, packaging, and composites were discussed, as well. With increased production dominated by viscose, capacities of more than 7 million tonnes of cellulose fiber products are expanding in technical hygiene and textiles. Due to their possibility to reach extra high tensile properties, alternatives for carbon fibers for lightweight applications are under development.
Future opportunities and challenges, presented by Afry, for novel textile fibers based on the increased demand powered by an increased share of middle-class consumers. The present production of 115 mills. tonnes could be increased during some decade future up to 150-200 mill. tonnes. It consists of viscose and lyocell fibers made from dissolving pulp, polyester, and recycled rPET from packaging waste, paper pulp using MFC process, and of residues of agricultural materials. In the case of recycled textile building the logistics and infrastructure needs to be further developed. Recycled cotton and viscose textiles will be used as such and as a component for the production of r-cellulose fibers.
MFC is using cheaper paper pulp in the value chain, but hemicellulose can pose problems. Sappi´s Stijfs was highlighting MFC´s importance in phasing out (micro)plastics, while contributing to sustainable development and reducing synthetic ingredients overall. The potential is high in replacing present additives in rheology modifications, water retention, imparting lightweight strength and sustainable alternative to plastics.
Environmental issues, circular economy, and biorefinery
Viscose and lyocell textiles are biodegradable and show marine degradation within 1 month without any harmful degradation products in sea surface and sea floor conditions. They also maintain or even improve performance in comparison to existing commercial fossil-based products. Lenzing has shown a solution for the hydrophobic properties of lyocell fibers – comparable to PET fibers – which is maintained after carded hydroentangling (spunlaced) processing.
Canopy, is an environmental not-for-profit service established 21 years ago. The activities have been focused on direct purchasing power and market leverage, supporting brands and retailers to embrace sustainability, seek systemic solutions to protect forests and biodiversity, and climate- Up to 2021 total of 455 global brands committed to sustainability criteria and received green shirt designations. The companies’ combined revenue was US$791 billion. In 2021 about half of the global production capacity, 13 MMCF producers earned ’green shirt’ designations, and only two producers maintain the ranking of ’dark green shirt. Many producers are testing, trialing, and/or prototyping with a strong interest in China, and are commercially manufacturing MMCF with pre-and post-consumer waste cotton textiles.
According to Metsä Biorefineries, systems allow highly efficient and cost-effective processing of biological feedstocks into a range of bio-based products and offer a platform for partnerships & collaboration. In many cases, this happens in conjunction with the production of bioenergy. Optimization of the system, i.e., several material & energy streams parallelly and the whole is more than the sum of its parts. The multiple actors in the value chain should play as a team and optimize the ‘system’ together: in an ideal circular economy material, energy, value, and information flows are optimized.
Important to recognize that from waste to product ‘Cascading in time’ and ‘Biorefinery’ are complementary concepts. Cascading in function is co-production, which can be achieved by using biorefinery. Co-production is the production of different functional streams from one biomass stream, maximizing total functional use. Traditional wood-based products consist of 7 products from wood biorefinery. New approaches include 8 additional products, mainly chemicals, and a new pulp-based environmentally sound textile fiber.
The environmental development of viscose and lyocell fibers
Lenzing, one of the world’s top 3 producers of viscose and lyocell fibers, actively increases self-sufficiency for steam and heat production and increased utilization of biomass for energy production. Air purification plants produce steam that is converted into electricity and the necessary rest is bought from renewable grid energy. Biorefinery is used in factories such as pulp mills using cleaner pulp and producing side chemicals and in Lyocell process by recycling the solvent. Decreased steam demand and higher energy efficiency through capacity increase are achieved. For the viscose process, an additional air purification plant reduces GHG emissions. Recycled cellulose from textile waste is used depending on availability and product properties.
The part of Indian conglomerate Aditya Birlas´Cellulose aims to net zero carbon emissions across all its operations by 2040 and achieve a 50% reduction in its greenhouse gas emissions intensity by 2030. Birla Cellulose targets to scale recycled fibers to 100,000 tons by 2024 and reduce sulfur release to air by 70% at all fiber sites with novel recovery units by the year 2022. Plans include the reduction in water intensity by 50% in VSF manufacturing by the year 2025. The sustainability performance of key suppliers will be stressed by the year 2025 including the use of alternative feedstock such as pre-and post-consumer waste into fiber.
Dr. Hassi from Scitech of Finland states that customers of fiber suppliers now have recycling, sustainability, and transparency at the top of both their strategic and operative agendas. The fashion value chain has transformed into active, networks with initiatives and development projects with objectives needed to meet the targets in time. Active players in the MMCF industry can certainly strengthen their competitive position and their products can gain market share. Forest-based MMCFs’ existing integration with the global carbon cycle is to be better recognized to take full, the justified benefit of their recyclability.
Recycling cotton and PET/cotton cellulose for viscose raw material
The estimated 166 mills. tons textile fiber consumption in 2030 is based mainly on the growth of PET production, however, pushes up regenerated cellulose up to 8% of the total, which makes 13 mills. tons. Claesson and Weilach presented the common viscose/lyocell recycling project of Södra and Lenzing. The idea is to collect used cotton and PET/cotton textiles for purification and blending with dissolving pulp. The target is to produce 25 kt/a textiles capacity when recycled content in pulp is 50%. The development includes sorting and quality of raw materials, and flexible processes, e.g. decolorization and handling of non-cellulosic, non-polyester contents (elastane, rubber). A similar type of project was presented by Crnoja-Cosic from Kelheim and Cavalli-Björkman from Renewcell, a Swedish cotton recycling project to produce viscose fibers. It has been developed over the course of a decade by researchers at KTH producing multiple global patents. The target of cooperation Renewcell and Kelheim is the development of large-scale production of high-quality viscose fibers from up to 10,000 tons per year of Renewcell’s 100% textile recycled row material Circulose®.
Chemical recycling of waste textiles
Sebastiá was presenting the possibilities to utilize pulp mill processing in the chemical recycling of textile waste. The idea is based on the big share of cellulose material (cotton, viscose, lyocell, cotton/polyester, flax) for depolymerization and decrystallization for further treatments, e.g. enzymatic hydrolysis. Existing technology can be used in bleaching, pre-treatment with internal streams in the mill, and energy integration. Thus, reduction of capital and operational costs as well as mitigate risks during scale-up. There are ongoing research projects to explore sugar production from waste textiles with Lund University and RISE. Several chemicals are reported to be produced, e.g. 1.4-butanediol, caprolactam (from PA 6), furan derivatives, and ethanol. Techno-economic studies to explore potential bottlenecks and risks are going on in industrial collaborations with partners along the value chain, both upstream and downstream.
Alternative feedstocks for cellulose fibers
Antje Ota and the team from DITF Denkendorf presented an EU-financed HEREWEAR project developing Cellulose fibers from alternative feedstocks. The aim is to use of bio-based materials as well as reuse and recycle used materials of the textile sector. The project aims the creation of a European ecosystem for locally produced circular textiles and clothing made from bio-based resources. DITF is responsible for the wet spinning of cellulosic filaments from bio-based waste streams and marine waste. Establishing the textile circular economy based on the DITF Digital Textile Micro factory structure for new local/regional circular sustainable spinning technology for cellulose filaments. The funding from 2020 to 2024 comes from a € 7 million budget with a consortium of 6 research organizations, 8 SMEs, and 1 large enterprise from 9 different EU countries, and 1 US.
According to the presentation of Meister, hemp straw conversed to high purity dissolving pulp grades for Lyocell fiber manufacturing and textile processing. An adjusted soda cooking process followed by additional pulp bleaching and washing steps for being compatible to the Lyocell process requirements. A laboratory-scale NMMO process and prepared dopes exhibited satisfying properties for air-gap spinning producing Lyohemp fibers and filaments well sufficient mechanical properties for further textile processing.
Carlo Centonze of HeiQ reported that the global textile apparel market amounts to US$1,7 trillion in 2022 growing annually by 3.39%. The fashion industry is estimated to be responsible for 8-10% of all global greenhouse gas emissions according to the UN between 3 to 3.5 billion tonnes of CO2 into the atmosphere every year Worldwide. Due to decreases in the average number of times a garment is worn before discarding and the per capita ownership of textiles, 26% of the global carbon emissions will be caused by 2050. HeiQ invests in a pilot plant of 100 tons annual capacity of cellulose filaments in 2022 continuing a mass manufacturing plant with up to 30’000 tons annual capacity in 2024. HeiQ AeoniQ is a continuous cellulosic filament yarn, which can be recycled eternally without loss of performance
LIST technology, based on a new type of kneading-extrusion machinery for CMMF innovations, has proved to be an essential part of developing high-performance polymers into fibers. According to Manuel Steiner, it suits a wide range of types of celluloses producing high-quality for spinning solutions with higher capacity per line. Being robust and scalable, it can be utilized easily from lab to industrial projects
Functional viscose fibers and composites
Dominik Mayer of Kelheim Fibers presented the functional fiber (CELLIANT®), which contains a blend of natural, thermo-reactive minerals of silicon dioxide and aluminum oxide. Aluminum oxide is the molecular foundation of the corundum family of gemstones and helps reflect energy. The functional fiber captures, converts, and reflects heat back as infrared (IR) energy, which increases local circulation and cell oxygenation. Functional viscose, CELLIANT® is designated as a Class 1 Medical Device in Australia, Canada, the European Union, Japan, New Zealand, and the United Kingdom. It is clear to market in China, India, Indonesia, Korea, Mexico, Peru, Philippines, Russia, Singapore, Thailand, and Taiwan, with more countries and regions to follow
Taina Kamppuri from VTT Finland showed results of chemical modifications, cationization, and allylation carried out to kraft pulps. The reaction efficiency of cationization and allylation reactions was found to be rather low, < 5 %, however, substitution was kept low to avoid solubility in water and to achieve regeneration. Hemicelluloses, especially xylan, seem to be more reactive compared to cellulose in the derivatization reactions. Reaction optimization and/or reaction conditions where hemicelluloses could be retained on the surface of modified fibers might solve the loss of hemicelluloses. Reactive groups were found to be stable during dissolution and regeneration. This opens up possibilities to post-treat the fibers to obtain different functionalities and improved technical, e.g. dyeing, properties.
Except of traditional multiple proven carded/spunlaced products from cellulose/PET fibers Germany´s Trütschler has developed carded/pulp technologies in cooperation with Voith Paper. Such are wet-laid/spunlaced) from paper-grade pulp and viscose/lyocell fibers carded/pulp from paper-grade pulp and viscose/lyocell fibers. Pulp-based nonwovens wetlaid-spunlace and carded pulp processes. First plants are already in service and the machinery has proven equipment and proven production processes as well as well-accepted final products for wiping applications.
According to Nina Graupner, University of Bremen, regenerated cellulose fibers have comparable mechanical properties to many types of natural fibers with considerably higher toughness. They are well suited for applications requiring high-impact resistance and are completely degradable in combination with a biodegradable matrix. Research activities have increased significantly in recent years, however, there are only a few industrial applications in the composites sector. BFT company transforms raw bast fibers from hemp and flax plants to meet the exacting standards required by nonwoven customers. In the transition away from synthetics, natural fibers are vitally important to produce truly sustainable nonwovens, as well.
Demand for wood is accelerating as packaging, nonwovens, and textiles replace plastic with viscose and pulp. Deforestation is associated with biodiversity loss, soil erosion, increased GHG emissions, and climate change. Viscose simply replaces one problem with another. BFT allows nonwoven companies to accelerate sustainability goals and work towards a circular, zero-waste future. Fibers are carefully individualized and standardized to meet converters’ requirements. BFT applies proprietary performance enhancements to the fiber to be more suitable for composites, especially regarding uniformity of fiber length, and hydrophobic adhesion properties.
Cell-cultivated cotton materials
Kuperman and Natalio from Weizmann Institute reported studies on biologically fabricated cotton fibers with tailored properties. Growing fertilized cotton ovules in vitro were producing complex biomaterials with tailored properties using biological system (cotton) plant physiology and biochemistry and transport mechanism.