Bio-based fiber "new star" - PTT fiber
The bio-based fiber with the largest output in the world is bio-based polyester fiber. Among them, bio-based PTT and PDT fibers have developed rapidly in recent years due to their excellent performance and application, and have received high attention.
1. Bio-based PTT fiber
PTT fiber is the abbreviation of Polytrimethylene terephthalate fiber. It is a new type of polyester spinning polymer with excellent performance first developed by the Dutch Shell company. It is made of terephthalic acid (or Dimethyl terephthalate) and 1,3-propanediol undergo esterification (transesterification) and polycondensation reactions to obtain polyester, and then melt spinning to obtain fibers. The chemical structure and three-dimensional structure of PTT are as follows:
The bio-based PTT fiber uses 1,3-propanediol from biomass conversion, which is more environmentally friendly. DuPont has used the biological method to produce the bio-based PTT product Sorona® with grains as raw materials, and further produced fibers, which are used in clothing, carpets, etc., as shown in the figure below. Fangyuan Chemical Fiber Co., Ltd. uses DuPont Sorona® to produce PTT fiber with the trade name "Somalor", which is used in the fields of clothing, automobiles, interior decoration and home textiles.
Bio-based PTT fiber combines the excellent properties of other fibers such as polyester and nylon, and has become a new star of bio-based fiber, attracting global attention.
1. Raw materials
The difference between bio-based PTT fiber and petroleum-based PTT fiber is that 1,3-PDO produced by biological method is used. The total cost of this method is 25% cheaper than the preparation of petroleum-based 1,3-PDO. With the excessive use of limited petroleum resources and the gradual increase of petroleum prices, the production of 1,3-PDO by biosynthesis has attracted worldwide attention. Compared with traditional chemical synthesis methods, biological methods have the advantages of renewable raw material sources, mild reaction conditions, good selectivity, less by-products, and less environmental pollution.
DuPont and Genencor cooperated to prepare bio-based 1,3-PDO by microbial fermentation and successfully put it into production. Various domestic enterprises and universities have also begun to invest in the research and development of bio-based 1,3-PDO technology, such as Tsinghua University, Dalian University of Technology, East China University of Science and Technology, Jiangnan University, etc., and have achieved phased results. At present, there are several methods for preparing 1,3-PDO by biological method:
(1) Glycerol conversion method
The glycerol conversion method is to convert glycerol into 1,3-PDO under anaerobic conditions and fungi (such as citric bacteria, Clostridium butyricum, Klebsiella pneumoniae, Lactobacillus, etc.). However, in countries where the price of glycerol is relatively high, the cost of directly preparing 1,3-PDO from glycerol is relatively high. Therefore, lower cost methods such as using glucose as a substrate or biodiesel conversion have emerged.
(2) Glucose conversion method
① One-step method: DuPont and Genencor have jointly developed a one-step method for the production of bio-based 1,3-PDO. Glucose is used as a substrate to convert 1,3-PDO under the action of genetically engineered bacteria. This method improves production efficiency , can greatly reduce production costs.
② Two-step method: Tsinghua University proposed a production process using glycerol as the base material and glucose as the auxiliary substrate. Glucose is converted into glycerol under the action of hypertonic yeast, and then converted into 1 by Klebsiella pneumoniae. ,3-PDO. Dalian University of Technology uses corn as raw material to produce 1,3-PDO through two-step fermentation.
③Biodiesel conversion method
About 100kg of glycerol is by-produced per ton of biodiesel, so the production of 1,3-PDO from crude glycerol obtained from biodiesel through bio-fermentation has a certain cost advantage. In 2011, Jiangsu Shenghong Group cooperated with Tsinghua University to produce 1,3-PDO using biodiesel by-product glycerin as raw material, and built a production facility of 30,000 tons per year.
2. Synthesis process
Bio-based PTT is obtained by polymerizing dimethyl terephthalate (DMT) or purified terephthalic acid (PTA) and bio-based 1,3-PDO, and then melt spinning or electrospinning to obtain bio-based PTT fibers. The polyester synthesis process can be roughly divided into the following two types:
① Direct esterification method (PTA method): This method uses PTA and 1,3-PDO as raw materials, and an esterification reaction occurs under the action of a catalyst to obtain the intermediate product BHPT, and then further undergoes polycondensation reaction to obtain PTT.
② transesterification method (DMT method): dimethyl terephthalate (DMT) is transesterified with 1,3-PDO, the transesterification is carried out at 140 ~ 220 ° C, using a Ti-based catalyst, first removing methanol, heating To 270 ° C and reduced pressure to 5kPa for polycondensation, prepared PTT.
Compared with the DMT method, the production cost of the PTA method is lower, the process is mature and reasonable, and the production efficiency is high. The water produced in the production process is easier to handle than methanol, the recovery process is simpler, and it can reduce environmental pollution. Therefore, the direct esterification method is the main method for large-scale preparation of PTT.
