Chapter 3
Synthetic Fibers from Renewable Resources Downloaded by UNIV OF HOUSTON MAIN on November 25, 2014 | http://pubs.acs.org Publication Date (Web): October 21, 2014 | doi: 10.1021/bk-2014-1175.ch003
Li Shen* Group Energy and Resources, Copernicus Institute of Sustainable Development, Utrecht University, Heidelberg 2, 3584CS Utrecht, The Netherlands *Tel: +31-30253-7600. Fax: +31-30-253-7601. E-mail:
[email protected].
Synthetic fibers from renewable resources account for only a small fraction in the world fiber market. Due to the concerns of limited fossil resources, the environment and climate change, materials made from renewable resources have attracted much attention in the past decades. In the meantime, biobased polymers have experienced a renaissance. Many traditional synthetic polymers, such as PET, PTT and PA have been, or can be potentially made from renewable resources. The historical use of biomass for material production shows that biobased polymers are neither fictional nor new. If emerging biobased polymers, such as PLA, biobased PET, biobased PTT and biobased PA, succeed in following this example, they could possibly replace their petrochemical counterparts in large quantities in the future.
Introduction The production of fibers has undergone dramatic changes in the last century. Prior to the industrial revolution in the 19th century, natural materials such as cotton, wool and silk had been used for thousands of years. In the first decades of the twentieth century, cotton accounted for 70% of all textile raw materials in the world. It was not until the 1930s that the first man-made fiber, viscose, became one of the principal fibers. Figure 1 shows the global fiber production in the past one hundred years. Before World War II, one of the most important motivations for the research and development of man-made fibers was to find the alternatives of cotton. After World War II the production of man-made cellulosic kept increasing, until in the 1960s synthetic fibers “swept” the whole textile market. © 2014 American Chemical Society In Lightweight Materials from Biopolymers and Biofibers; Yu, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
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Figure 1. World fiber production 1920 – 2005 (1, 2).
Man-made fibers can be made from inorganic origin, petrochemical feedstocks and renewable resources. Within man-made fibers from renewable resources, two categories can be distinguished: 1) man-made fibers by transforming natural polymers (e.g. viscose), and 2) synthetic fibers based on emerging biobased polymers which are equivalent to the petroleum-based counterparts (see Figure 2). Man-made cellulose fibers are produced via the transformation of natural polymers, for example, regenerated cellulose or cellulose esters. The most important man-made cellulose fiber is viscose fiber, which has been produced at industrial scale since the 1930s. Today approximately 3 Mt (million metric tonnes) of viscose fiber are produced per year. In the meantime, emerging biobased polymers have gained much attention due to the concern of environment, limited fossil fuels and climate change. Some of these biobased polymers are novel polymers, e.g. PLA (polylactic acid or polylactide); others are chemically identical with their petroleum-based counterparts, e.g. biobased PET (polyethylene terephthalate) and biobased PA (polyamide). Today, PLA has been produced at industrial scale and are used for textile fiber. Partially biobased PET polymer has been used to make beverage bottles. Biobased PAs are still in the research and development phase. 38 In Lightweight Materials from Biopolymers and Biofibers; Yu, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
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Figure 2. Classification of fibers based on polymer origin. *Generic fiber names according to BISFA (3). **Fibers covered in this chapter.
Biomass Resources for Emerging Biobased Polymers Polymers abound in nature. Wood, leaves, fruits, seeds and animal furs all contain natural polymers. Biobased polymers have been used for food, furniture and clothing for thousands of years. Every year about 170 billion tonnes (1 billion = 109) of biomass are produced by nature, of which only 3.5% (6 billion tonnes) are utilised by mankind. Most of these 6 billion tonnes are used for food, about one third is for energy, paper, furniture and construction, and only 5% (300 million tonnes) are consumed for other non-food purposes such as chemicals and clothing (4). Like biofuels, biobased polymers can be produced from first or second generation biomass. First generation biomass originates from sugar crops such as sugarcane and sugar beet, from starch crops such as corn, wheat and tapioca, or from animal fats and vegetable oils. Platform chemicals, such as ethanol and lactic acid, can be produced by directly fermenting sugar or starch via enzymes and microorganisms. Second generation biomass refers to non-food crops (e.g. switch grass), agricultural and forest residues (e.g. stems and husks), or industrial/municipal waste (e.g. woodchips and municipal waste water streams). Second generation technology aims to use cellulose, lignocellulose or lignin as the feedstock instead of sugar or starch, to produce biofuels and biochemicals. Pre-treatment (e.g. hydrolysis) is necessary to obtain fermentable sugar from lingo-cellulosic feedstock. Today nearly all emerging biobased polymers are produced from first generation crops. Much R&D effort has been focused on cellulosic feedstock; but so far no commercial product is available. Emerging biobased polymers still have a very small share in the work market. The global production capacity was 1.2 Mt in 2011 (5), which is about 0.5% of total plastic production. It is projected 39 In Lightweight Materials from Biopolymers and Biofibers; Yu, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
that by 2020 the world capacity of emerging biobased polymers will increase to 3.5 Mt (6). Approximately million hectares of arable land would be required if all of these biobased polymer would be produced from first generation crops; this land use is, however, less than 0.3% of the arable land in Europe or 0.06% worldwide (7). As a consequence, no interference with food supply needs to be feared for the short to medium term.
Biobased Polyesters Downloaded by UNIV OF HOUSTON MAIN on November 25, 2014 | http://pubs.acs.org Publication Date (Web): October 21, 2014 | doi: 10.1021/bk-2014-1175.ch003
PLA PLA (see Figure 3) is an aliphatic polyester produced via polymerization of lactic acid or lactide, which are sugar fermentation products. With the start of the NatureWork LLC’s manufacturing plant in 2002, PLA became the first biobased plastic produced on a large scale (name plate capacity 150 kt p.a. in 2009). In 2007, the world’s largest lactic acid producer Corbion/PURAC started to produce lactide, which is a precursor of PLA, for technical applications (capacity 75 kt p.a. lactide in 2008, plant located in Thailand).
Figure 3. PLA molecule. Lactic acid, 2-hydroxypropionic acid, is the simplest hydroxycarboxylic acid with an asymmetrical carbon atom. Lactic acid may be produced by anaerobic fermentation of carbon substrates, either pure (e.g. glucose and sucrose) or impure (e.g. starch). NatureWorks’ PLA is produced from corn and PURAC’s lactides are produced from cane sugar, potato starch and tapioca starch. In the future, it is expected that cellulosic biomass can be used to produce PLA. Lactic acid produced by fermentation is optically active; specific production of either L (+) or D (–) lactic acid can be achieved by using an appropriate lactobacillus (8). Polymerization of L-lactide results in PLLA and polymerization of D-lactide results in PDLA. The majority of current commercial PLA is poly (meso-lactide), which is a mix of L-lactide (> 95%) and D-lactide (
