Globally, 4 billion pairs of sports shoes are sold annually, generating 1.5 million tons of shoe waste, over 70% of which cannot be recycled. Taiwan Industrial Technology Research Institute developed the world's first "full-cycle single polyester material low-carbon shoes" technology, using the innovative polyester elastomer material "rTPEE-G", combined with the integrated injection molding of the middle and large soles, the integrated weaving technology of the upper and Recycling and remanufacturing verification allows the most difficult to recycle midsoles, outsoles, and entire pairs of shoes to be recycled.
With the improvement of people's health awareness, the sales of sports shoes are booming, driving an annual output value of up to 80 billion U.S. dollars. Behind the huge output value, the waste generated by sports shoes is also considerable. Although the upper material is relatively easy to recycle, the midsole and outsole mostly use ethylene-vinyl acetate copolymer (EVA) foam and rubber materials obtained through the cross-linking process, although there are currently recyclable thermoplastic polyurethanes. (TPU) midsole foam material, but because the midsole and outsole are firmly bonded with adhesive, it is not easy to separate, which makes recycling more difficult.
According to the survey of Nike, a major sports brand manufacturer, most shoe waste can only be disposed of by incineration. Therefore, the average carbon emission of each pair of shoes from manufacturing to final disposal is as high as 13.6kgCO2e (kg carbon dioxide equivalent). fatal to the environment. In recent years, under the wave of sustainable development, brand shoe factories are actively seeking low-carbon emission and recyclable solutions. Taiwan Industrial Technology Research Institute is also actively investing in carbon reduction innovations in the supply chain.
Taiwan Industrial Technology Research Institute has been cultivating material polymerization technology for a long time. From clothing, auto parts to shoemaking materials, it is very familiar with the characteristics of upstream polyester monomers. With many years of material expertise, it has developed "full-cycle single polyester material low-carbon shoes" "Technology, its new materials have the advantages of high performance, recyclability, use of renewable and bio-based raw materials, low carbon, etc., and its research and development process is divided into three stages.
ITRI's exclusive innovation low-carbon polyester elastomer
The first is the successful development of new elastomeric materials. The Industrial Technology Research Institute uses recycled plastic bottles to obtain PBT or PET oligomers with alcoholysis technology, supplemented with bio-based raw materials such as castor oil, etc., refines monomers (PTMEG, Bio-PO3G) and then carries out copolymerization reactions, and finally develops High molecular weight low carbon polyester material "rTPEE-G". Then, based on the rTPEE-G single material, polyester materials with different hardness and properties were further developed to meet the performance requirements of different parts of the shoe. For example, it is made into yarn for weaving shoe uppers. With the design of weaving structure, the shoe uppers have the characteristics of good coverage, elasticity and comfort at the same time; the balance piece of the arch part is made of high hardness rTPEE-G injection, which has strong support Strength; the midsole adopts supercritical foam technology, which can take into account high rebound, comfort and support; the outsole is made of high wear-resistant and high anti-slip polyester material through the mixing process and is made with injection processing.
Integrated injection foaming process further lightweight and carbon reduction
The second stage is the innovation of the processing process, which is divided into two parts: the mid-sole and the upper. The non-melt adhesive integrated injection molding foaming technology developed by the Industrial Technology Research Institute uses rTPEE-G to make the midsole, melts the material and introduces supercritical CO2 or nitrogen at the same time, and foams in the mold at the same time as the injection to form a specific midsole. The shape of the bottom; because CO2 is used as the blowing agent, no carbon emissions are increased, and it is more environmentally friendly. Compared with the traditional EVA molding and foaming process, it has the advantages of faster processing, higher precision, and lightweight shoe body, so the carbon emission is extremely low. It is estimated that each pair of shoes will be lower than 2kgCO2e, which is lower than the average carbon dioxide of global sports shoes. The emissions are reduced by 80%, which is even lower than the current shoes with the lowest carbon emissions in the world.
In the design of the whole shoe, the principle of subtraction is adopted, and the unnecessary weight of the shoe is reduced by simplifying the design. In the upper part, the elastic yarn made of rTPEE-G is also used, and it is woven together with rPET recycled yarn from plastic bottles. Technology, can adjust different weaving density and strength, with elasticity and air permeability.
The third stage is waste shoe recycling technology. Based on the above two innovative processes, the Industrial Technology Research Institute has further started to develop the recycling and remanufacturing process of all shoes after aging, completing the last mile of circular economy. The full-cycle low-carbon shoes made of rTPEE-G, an innovative material, can be directly recycled and broken after aging due to the use of a single material, and reprocessed into sports products such as shoes, shoe parts or yoga mats, which are expected to be made into local characteristics in the near future The flip flops asked the city.
Started with 3 core patents the commercialization process is in sight
Wu Jinan, manager of the Institute of Materials and Chemical Engineering of the Taiwan Industrial Technology Research Institute, said frankly that the research and development process has encountered many bottlenecks. For example, it took nearly a year to depolymerize the upstream materials. The selection and dosage of the agent, which system and reaction time should be used as the reaction catalyst; in addition, a lot of time was spent exploring the change of the viscoelastic properties of the material in the selection of the monomer during the copolymerization process. In addition, the injection foaming process of one-piece molding has also encountered the challenge of unstable quality. It must be tried again and again to confirm the rheological properties of the material and the design of the midsole and outsole molds to produce the most appropriate midsole and outsole.
Overcoming all difficulties, it has successfully developed "full-cycle single polyester material low-carbon shoes" and won the Global Top 100 Science and Technology Research and Development Award (R&D 100 Awards) has formed a complete cycle from materials, shoemaking processes and recycling applications. The technology has matured, and three core patents will be obtained in 2022. In the future, we will join hands with shoe factories and supply chains to promote commercialization, whether it is to provide innovative materials or establish our own brands.
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