Spandex: The supply and demand pattern ushered in marginal improvement, and the industry prosperity continued to pick up

1. Spandex production process

Polyurethane fiber is a chemical synthetic fiber with excellent performance, which has a large yield, low elastic modulus, good fatigue resistance and other excellent properties, adding a small amount of spandex (a general use content of 5%-25%) in chemical fiber products can significantly improve the elasticity and comfort of chemical fiber products, so it is known as "MSG type" fiber. Its price is also much higher than other varieties of synthetic fibers.

At present, there are four main production processes of spandex: solution dry method, solution wet method, chemical reaction method and melt spinning. Among them, dry spinning is the most widely used spandex spinning process in the world, and its output accounts for more than 80% of the world's total spandex production. The dry spinning technology is mainly represented by Invista (formerly DuPont) in the United States, Hyosung in South Korea, and Toyo Textile in Japan. Invista and Hyosung use continuous polymerization and high-speed spinning, which are better in quality than conventional batch polymerization and medium-speed spinning, and have high output and low cost. Toyo Textile uses batch polymerization and continuous spinning, which is adopted by some spandex enterprises in early production in China, such as Huafeng Chemical and Yantai Spandex. With the technological progress of domestic spandex enterprises, the production technology widely used in the new production capacity of domestic spandex is continuous polymerization dry spinning technology.

Continuous polymerization dry spinning technology is mainly to mix the main raw materials liquid PTMG and liquid MDI in a static mixer with a certain ratio, and then carry out the first reaction in a static reactor, and the reactant is called prepolymer; After stable storage for a period of time, the prepolymer was dissolved with solvent DMAC, and then a mixed organic amine solution consisting of chain extender and chain terminator was added to the reactor for a second reaction. In order to improve the characteristics of spandex stock solution, some additives are added to the polymer generated by the secondary reaction, and the current conventional additives are mainly antioxidants, heat resistant agents, matting agents, whitening agents, dye AIDS and so on. After aging, the stock liquid of this part is transported to the spinning process, squeezed by the metering pump to form a trickle of stock liquid into the spinning tube, in the high temperature of the tube, the solvent DMAC is evaporated to form a wire bundle, and the silk bundle is oiled and wound by the winding equipment to form a product.

Energy consumption is the core factor that causes the cost difference between different specifications of spandex. The measurement unit to characterize the thickness of spandex yarn is Denier, referred to as D, which refers to the weight of 9000 meters of fiber under standard conditions: if 9000 meters of fiber weighs 40 grams, it is defined as 40D. Spandex fine denier is mainly 10D-50D, medium/coarse denier is mainly 70D-570D and so on. The most common spandex models on the market are conventional and heat-resistant. The cost difference of different specifications of spandex is mainly in 1) raw and auxiliary materials: the main raw materials are the same, only slightly different in the oil agent, the thicker the silk, the less the oil dose. Therefore, the coarser the silk, the lower the cost; 2) Core factor energy consumption: the coarser the silk, the higher the capacity, the less energy consumption per unit capacity, and the lower the cost. In addition, a characteristic of dry spinning spandex is that the solvent DMAC is evaporated in the spinning tube, the coarser the silk, the more solvent contained in the spinning liquid (the amount of solid is the same), then the heat required for evaporation is higher, and the production cost will increase; 3) Packaging materials: different sizes of spandex wire are stored in different quantities in the carton. Such as 550 grams of products can put 60 volumes in a box, and 600 grams of a box can only put 48 volumes, the weight of the whole box of spandex wire will be different, the cost difference in this respect is about 200 yuan -2000 yuan/ton.

2, the epidemic catalyzed demand growth, spandex profitability significantly improved

Overseas demand is recovering, and demand for spandex is growing rapidly

The most important downstream demand for spandex is still from the textile and clothing category, more than 50% of the world's textiles and clothing contain spandex components, about 60% of the domestic export textiles and clothing contain spandex components, "ammonia-free cloth" will become the future of high-end textiles and clothing development direction. From the downstream of spandex, warp knitting and round knitting are mainly used for knitting underwear, socks, sportswear, swimsuits, etc. Wrapping yarn is mainly used for casual wear, jeans, etc. Lace is mainly used for decorative lace, elastic and so on. Wrapping yarn and circular machine are the main areas of spandex weaving demand, accounting for 33% and 31%.