How much do you know about bio-based PTT fiber?

The bio-based fiber with the largest production volume in the world is bio-based polyester fiber, among which bio-based PTT is due to its excellent performance and application It has developed rapidly in recent years and has received great attention.

PTT fiber is polytrimethylene terephthalate ( Polytrimethylene terephthalate) fiber is a new type of polyester spinning polymer with excellent performance first developed by the Dutch Shell Company. It is composed of terephthalic acid (or dimethyl terephthalate) and 1, 3-Propylene glycol undergoes esterification (ester exchange) and polycondensation reaction to obtain polyester, which is then melt-spun to obtain fiber. The chemical structure and three-dimensional structure of PTT are as follows:

Figure 1 The chemical structure (top) and three-dimensional structure of PTT (top) (Bottom)

The bio-based PTT fiber uses natural The material converted into 1,3-propanediol is more environmentally friendly. DuPont used biological methods to produce the bio-based PTT product Sorona® from grains as raw materials, and further produced fibers for use in clothing, carpets, etc., as shown below. Fangyuan Chemical Fiber Company uses DuPont Sorona® to produce PTT fiber with the trade name “Somalor”, which is used in clothing, automobiles, interior decoration and home fabrics and other fields.

Figure 2 DuPont Sorona® fiber production process

Bio-based PTT fiber combines the excellent properties of other fibers such as polyester and nylon, and is a recyclable and recyclable green fiber, becoming bio-based fiber Rising star, attracting global attention.

1. Raw materials

The difference between bio-based PTT fiber and petroleum-based PTT fiber is that it is produced by biological methods 1,3-PDO. The total cost of this method is 25% cheaper than preparing petroleum-based 1,3-PDO. With the overuse of limited petroleum resources and the gradual increase in petroleum prices, the biosynthetic production of 1,3-PDO has attracted global 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 cooperate to prepare it using microbial fermentation method Bio-based 1,3-PDO was successfully put into production. Various domestic enterprises and universities have also begun to invest in the technological research and development of bio-based 1,3-PDO, 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 mainly the following methods to prepare 1,3-PDO by biological methods:

(1) Glycerol conversion method

The glycerol conversion method is to convert glycerol into 1,3-PDO under anaerobic conditions and the action of fungi (such as Lemongrass, Clostridium butyricum, Pneumoniae, Lactobacillus, etc.). For countries with high glycerol prices, the cost of directly preparing 1,3-PDO using glycerol is higher. Therefore, lower-cost methods such as glucose-based or biodiesel conversion methods have emerged.

(2) Glucose conversion method

▲One-step method: DuPont and Genencor cooperated to develop the production of bio-based 1, The one-step method of 3-PDO uses glucose as the substrate and converts it into 1,3-PDO under the action of genetically engineered bacteria. This method improves production efficiency and can greatly reduce production costs.

▲Two-step method: Tsinghua University proposed using glycerol The production process uses glucose 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 1,3-PDO by Klebsiella pneumoniae. Dalian University of Technology uses corn as raw material and produces 1,3-PDO through two-step fermentation.

Figure 3 One-step and two-step conversion of glucose into 1,3-PDO

(3) Biodiesel conversion method

Each ton of biodiesel produces approximately 100kg of glycerol as a by-product. Therefore, the crude glycerol obtained from biodiesel and then biofermented to prepare 1,3-PDO has certain Cost advantage. In 2011, Jiangsu Shenghong Group cooperated with Tsinghua University to produce 1,3-PDO using biodiesel by-product glycerol as raw material, and built a 30,000-ton/year production device.

Figure 4 Preparation of 1,3-PDO by biodiesel conversion method

Table 1 Production companies and technology sources of bio-based 1,3-PDO:

2. Synthesis process

Figure 5 Synthesis process of bio-based PTT fiber

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. PTT fiber. Its 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 performs a polycondensation reaction to obtain PTT.

② Transesterification method (DMT method): p-benzene Dimethyl dicarboxylate (DMT) and 1,3-PDO are transesterified. The transesterification is carried out at 140-220°C. A Ti-based catalyst is used. Methanol is first removed, the temperature is raised to 270°C and the pressure is reduced to 5kPa for polycondensation. Got PTT.

Compared with the DMT method, the PTA method has lower production costs , the process is mature and reasonable, the production efficiency is high, the water produced during the production process is easier to handle than methanol, the recycling process is simpler, and it can reduce environmental pollution. Therefore, direct esterification is the main method for large-scale preparation of PTT.

3. Performance

The surface structure of PTT fiber is in the shape of a smooth strip, and the light reflection and refraction are strong. The fiber has a strong luster; there are gaps on the surface, and it has certain moisture conductivity, breathability and warmth retention; it can be made into fiber products with different cross-sectional shapes, and can also be directly processed into colored PTT fibers during the manufacturing process for easy selection.

The “Z” helical structure of PTT fiber makes it It has higher elasticity and good resilience than other fibers. Since PTT fiber has a low glass transition temperature, it can be dyed under normal pressure.TT’s special structure makes it easier for dyes to enter the fiber, so the dyeing performance is better than PET fiber. PTT fiber combines the advantages of various fibers, such as the stain resistance of polyester, the softness of nylon, and the bulkiness of acrylic. The elongation of PTT is as good as spandex, and it is easier to process than elastic fiber spandex, making it very suitable for use in textile clothing fabrics.

Figure 6 Excellent properties of Sorona® fiber

PTT fiber also has good thermal stability, wrinkle resistance, antistatic properties, UV resistance, etc. The performance comparison between PTT fiber and other fibers is shown in Table 2.

Table 2 PTT fiber and PET, PA6, PA66 fiber Performance comparison:

4. Application

The excellent properties of PTT fiber make it Very suitable for use on clothing fabrics. Its good dyeability and printing adaptability can be used to produce a variety of dyed fabrics. Its stain resistance can make clothes easier to care for and clean. Its soft feel and elasticity, low water absorption and good drape can Improve the wearing comfort of clothing. Products with better performance can be obtained by blending PTT fiber with other fibers. For example, PTT fiber is interwoven with cellulose fibers such as cotton, viscose, Tencel, and linen. It has good hand feel and pleat resistance and can be used in knitted underwear, woven fabrics, etc.

PTT is interwoven with mulberry silk for memory fabrics, which can Make up for the shortcomings of mulberry silk products that are difficult to care for. PTT fiber is used in memory fabrics to make them lighter, softer, skin-friendly, more sweat-absorbent and breathable.

Figure 7 Application of DuPont Sorona® in the clothing field

PTT has excellent anti-fouling properties and good anti-static properties, and can be used in the production of carpets. At the same time, PTT fiber is also a good material that can be used to prepare nonwoven fabrics, and can also be used in other fields, such as bedding, decorations, car mats, webbing, etc. At present, the unique properties and advantages of PTT fiber make it develop rapidly and have good development prospects. With the continuous deepening of research on PTT fiber processing and application, its application fields will become more diversified.

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