How to ease the plight of polyester fiber industry from the scarcity of resources? Seen from the current situation, the feasible way is to seek resources from both ends of the chain: first one is the raw materials sector, striving to develop biological raw material and biomass fiber, and enhancing the use of renewable resources such as waste plastic bottles; the second one is in the terminal part to strengthen the recycling use of textile waste.
— to gradually replace the synthetic polyester system
China is a country short of petroleum. According to the current industry program, if in the future the basic chemical raw materials which the growth of the domestic chemical industry depends on still rely on imported crude oil processing, the development of the industry would be difficult to get rid of the predicament of over a barrel as well as ups and downs. Without innovation, it would be difficult to improve self-sufficiency rate of chemical fiber raw materials in the short term. Abundant biomass resources is the future for green chemical raw materials; more and more chemical products are available through biomass resources, especially bio-technology based on agriculture and forestry by-products and waste, which will achieve many things at one stroke: addressing the problem of resources, avoiding the problem of food competition, and increasing the farmers' income.
As early as 2005, in “Guideline for the Chemical Fiber Industry’ Eleventh Five-Year Program", the "biological polyol technology research and development" was included in the focus of chemical fiber biomass engineering development, striving to take biological propanediol (PDO), ethylene glycol (EG), butanediol (BG), etc. as key points to achieve industrial breakthrough and built China's chemical fiber industry chain around bio-based polyol. During "Twelfth Five-Year Program" period, the industry put forward that biomass fibers and biochemical raw materials are necessary to focus on the development of the total volume but also focus on the targets of technology and product as well as the industrial structure.
Of course, bio-based polyol is only a starting point for bio-chemical technology. In the future, based on the understanding of the molecular structure of carbohydrates, we can develop relevant multi-acid and polyol, and achieve industrial upgrading of such several links as raw materials development and processing, equipment design and manufacturing, product design and processing, and product packaging and applications, which will eventually form a similar closed biochemical fiber chain based on petrochemical raw materials.
After over two years of exploration and research, a research institution combined by Donghua University and Dacheng Group has completed the test experiments of bio-based ethylene glycol’s entire industrial process from polymerization, spinning, texturing, weaving, dyeing to garment. Since the biological-raw-material based synthesis polyester and spinning have achieved results of the current stage, the polyester directly synthesized by bio-based ethylene glycol owns better spinning and dyeing properties than the existing one. Especially the bio-based ethylene glycol containing multi-component diatomic alcohol of about 2% mass fraction such as propanediol, butanediol, pentanediol, and sorbitol, plays a copolymerization modification effect, thus such fiber is soft, bright staining with visible moisture regain and anti-static performance, enjoying a substantial application prospects.
In 2000, DuPont introduced biomass PTT resin made from corn-made biomass 1,3 - propanediol (PDO) instead of malthenes PDO as raw material. Through cooperation in terms of manufacturing, studying, scientific research, and applications, Donghua University, Fujian Haitian Textile Group, Shing Hong Group and other units developed new copolyester preparation techniques that PTT-PET, CDPTT can be dyed under high-speed spinning-level temperature and pressure, establishing proprietary technologies of independent intellectual property such as polymerization, spinning, and weaving, integrating and developing PTT chips, fibers, fabrics, and products, and taking the lead in forming an industrial chain of PTT polymerization, spinning, weaving, dyeing & finishing, and fabric products.
In addition, more and more attention has been paid to the production of 1, 3–propanediol from the ferment of hogwash oil, in which manufacturing 1, 3–propanediol through the fermentation of glycerol which is as the substrate has initially achieved kiloton pilot production. 2, 5–furan dioctyl phthalate has the similar nature with PTA, therefore, polydiethylene–2, 5–furfuralat (PEF) can be produced from the raw material of 2, 5–furan dioctyl phthalate and ethylene glycol, which may form whole bio-based polyester to completely change the dependence on petroleum resources. Extracting 2, 5–furan dioctyl phthalate from plant stalks like corn has been achieved in the world. 1.dioctyl phthalate
R & D of bio-polyester products is both opportunities and challenges. The former refers to the sustainable resources, low carbon products, large market space, and being in line with current social trends; the latter is a long industrial chain, technical difficulties and engineering development for a long time. First is the establishment of raw material system which has to form large-scale biosynthesis logistics, biotechnology, and device systems; second is the separation and aggregation system which must overcome the biomass feedstock volatile issue and develop related catalytic technology and build the product and application system according to its composition characteristics. However, what is sure is that in China biomass polyester will gradually replace synthetic polyester system after ten to twenty years or more.
Recycled chemical fibers
– to be supported by polices and technologies
Strongly advocating the development of circular economy and building a "resource-saving and environment-friendly" society is a major strategic decision made by the CPC Central Committee as well as a basic national policy. The Party's 17th People’s Congress also proposed "to build ecological civilization, basically establishing an industrial structure, growth mode, and consumption pattern to save energy resources and protect the ecological environment" and taking the "formation of large-scale circular economy" as a goal to realize a comprehensive well-off society. Recycled terylene industry as a typical green, circular economy on behalf of industry has outstanding advantages in energy conservation and environmental protection, recycling one-ton fiber and reducing more than three tons of carbon dioxide emissions.
China has the world's largest recycled polyester industry with production of seven million to eight million tons. Currently, the industry mainly takes the recycled bottle flakes as raw material and spinning waste silk, and blocks pulp as supplement; products are mainly recycled terylene staple fiber as well as such recycled filament as POY, DTY, FDY, BCF carpet yarn and industrial yarn used in cotton spinning and filling material, which will be processed into clothing, non-woven fabric, toy filling materials and other products.
International recycled terylene recycling and processing technology has been improved, breaking the previous gulf between large and small chemical fibers. Gradually improved quality of recycled products has by and by weakened the advantages of original fiber spinning; besides, the input-output ratio of recycled terylene industry is lower than that of original one, thus the recycled products will race to control the original terylene market. Recycled terylene products’ applications currently cover carpets, home textiles, automotive textiles, and other fields with hundreds of species.
In recent years, the frequent appearance of terylene staple fiber imitating large chemical fibers, recycled filament, bosilun, microfiber, feather-like fiber, flame-retardant textile fibers, and other renewable textile high-end products, has greatly enriched the recycled chemical fiber market, so that the downstream market is more and more diversified with increased sales channels and volume. However at the same time, supply of raw materials is becoming increasingly tight.
Opposite to the tight recycled textile raw materials is the waste of used and waste textile products. China’s annual output of polyester fibers is about 30 million tons, and there are nearly 20 million tons used and waste textiles each year, most of which have not been reused.
What are the reasons?
On the one hand, waste textiles regeneration technology is not mature. As for the recycled products obtained through the use of physical methods to recycle polyester fiber, the quality is poor; economic value is not high; the method of chemical degradation requires long processes and high costs. On the other hand, the waste and used textiles comprehensive utilization and the products have not won the support from the government to be included in the "Catalogue of Resources Comprehensive Utilization" and to enjoy preferential taxation policies.
In view of this, the polyester fiber regeneration is in an urgent need to be supported by advanced scientific and technological means to carry out key technology and equipment research of comprehensive utilization of waste textiles, breaking through the technology bottleneck in the process of comprehensive utilization and improving the comprehensive utilization of waste textiles.
To this end, organized by the industry associations, the General Logistics Department Quartermaster Equipment Institute, Donghua University, and Zhejiang Furun together conduct a joint research. They adopt different recycling methods for various polyester fiber products, and physical recycling technology is used in terylene products. As for the T/C products, depolymerization agent is used to break the ester linkage under certain conditions to alcoholysis high polymer into monomer or lower polymer. As for the wool-terylene products, mechanical separation is used for polyester fiber products, then carrying out draw-off, opening, and finally spinning.
Through key technology of pure terylene and T/C textile waste recycling, adjusting the quality and viscosity of the melt to study the digital design of recycled spinning equipment, improvements of recycled fiber dyeing, color compensation, nature changing of the blended fibers, recycled functional fabric weaving design and deep processing technology innovation and integration, we cannot only establish fiber (fiber with own proprietary intellectual property rights) recycling technology system, but also develop recycled polyester fiber based high-quality multi-functional fibers such as cotton-like fiber, anti-aging fiber, high color fastness fiber, colored fibers, flame-retardant fibers, and textile products, which will be applied in more advanced areas. Meanwhile, in each industrial chain links the industry model line should be constructed, and technical specifications should be developed aiming at new technologies and products, and technical standard system is to be established, gradually expanding the applications.
With the help of the government and the associations, it is worth expecting to gradually establish textile regeneration and application base among major cities all around the country, to establish a national network for recycling waste and used textiles, and to ultimately achieve resource conservation and environmental coordination and sustainable development in the textile industry.
It is predicted that, within next few years, the proportion of recycled polyester fiber will gradually increase in China. If the proportion of recycled textiles reaches 30%, it would provide ten million tons of raw materials for China’s chemical fiber industry, thus greatly easing the pressure on the nation’s fiber raw material supply chain.