Suzhou Zhanheng intelligent analysis: International microfiber development trends and development trends 

 Manufacturing process of microfiber The varieties of microfiber are super fine viscose, super fine polyamide, super fine polyester, super fine polypropylene and so on. Using different technologies, microfibers of different sizes, types and uses can be produced. Its production technology and manufacturing process can be roughly divided into direct spinning improvement method, high polymer cross-spinning method, stripping composite spinning method, multilayer composite spinning method, blending segmentation method and island method. 

 1. Direct Improved Spinning (DSP) Direct spinning improvement method, also known as conventional spinning improvement method, refers to the method of directly manufacturing microfibers by improving its process equipment with conventional spinning methods. At present, POY or FDY spinning machines can be used, and a slight improvement in process design can be applied to microfiber production:

 (1) The screw extruder should have a low temperature mixing head (LTM) to ensure the uniformity of the melt; 

 (2) There must be a high quality, pure melt that does not contain gel particles and granular impurities, so there must be a melt pre-filter;

 (3) Components are required to be mounted under to prevent chimney effect and ensure uniform temperature of spinneret components; 

 (4) In the design of spinneret, pay attention to the hole spacing and arrangement of "no turbulence"; 

 (5) The wire should be fully and evenly cooled to reduce the Uster value; 

 (6) The distance from the surface of the spinneret to the side blow is as short as possible;

 ⑺ The oil system is about 300~600mm below the spinneret; 

 (8) The spinning channel is shorter than the conventional fiber, generally 300~500mm, to reduce the tension of the spinning process; 

 (9) The spindle-type winding head is used for spinning POY grooved cylinder, and the FDY is used for double-rotor transverse device; 

 (10) The silk path between the heater and the false twist shaper should be straight, otherwise it will cause filaments and reduce fiber strength; (11) The friction disc should be polyurethane to reduce fiber surface wear. Using POY and FDY spinning machine to produce microfibers, the biggest advantage is that a single component of microfibers can be directly obtained, and there is no need to strip or dissolve two components like composite spinning or blending silk, generally stable production of 0.7 to 1.0dtex fibers, so the cost is low. If the melt quality and machine performance are good, microfibers up to 0.44dtex can be produced. If the production of monofilament thinner than 0.44dtex fiber to use a composite spinning machine. 2. Direct Optimal Spinning (DSOM) By optimizing the spinning process to improve the traditional spinning method, it is necessary to properly reduce the polymer viscosity, improve the purity of the melt, reduce the ambient temperature under the spinneret to accelerate the cooling and improve the uniformity of the cooling wind. Using direct spinning without chemical or mechanical treatment can directly obtain a single component of microfiber, low production cost, stable product quality. At present, the thinnest commercial product produced by direct spinning is PET fiber with a linear density of 0.165dtex. Compared with the conventional spinning method, the spinning method of polyester ultra-slender yarn needs to be optimized and improved as follows: (1) Appropriate reduction of polymer viscosity. This can be achieved by reducing the molecular weight of the polymer or increasing the spinning temperature, which can prevent breaking of the wire due to droplet extrusion. (2) The spinneret holes on the spinneret plate should be uniformly arranged in concentric circles to cool the strips evenly. (3) Reduce the ambient temperature below the spinneret to cool the wire strips quickly, and cluster and wind at 20~70cm below the spinneret to obtain the unstretched wire. (4) Make the fiber withstand 4 to 6 times after stretching. It can be stretched 10-20 times under specific conditions, but the technical conditions are unstable and the range is narrow, so it has not been applied. (5) High precision filtration to improve the purity of the spinning melt. (6) Reduce the amount of melt extrusion. This DSOM process has high production efficiency and low cost, which is the main trend of microfiber development at present. Western Europe, the United States mainly uses this process to produce ultra-fine denier fiber. Used to make imitation silk and high-density fabrics (functional clothing). The most economical method in the POY process is the POY direct warping machine, that is, the WD or WDS method, which directly makes the large warp shaft of super fine denier. The Italian company ValLesina has used this process to manufacture microfibers with a monofilament size of 0.5dtex for silk mimics, but this is suitable for mass production. 3. Composite spinning method The use of composite spinning machine to produce microfibers was first developed in Japan. As early as 1970, microfibers were developed by Toray for use in suede imitation. In 1972, the clock textile company developed imitation silk fabric, in 1981, the clock textile company developed ultra-high-density fabric, in the same year, Toray company developed the second generation of imitation leather products, and in 1985, the clock textile company developed high-performance clean cloth. The composite spinning manufacturing of microfibers can be divided into two categories according to different processes: peel type and sea island type. The stripped microfiber is a composite spinning process which combines two kinds of incompatible polymer melt with similar melt viscosity. After weaving, dyeing and finishing the composite fiber, the stripped microfiber is obtained. The stripping methods include mechanical method, solvent dissolution method and dissolution method. Marine island-type microfiber is composed of two components, one group is divided into the sea, the other group is divided into islands, and the islands are distributed in the sea component. Sea component to choose soluble polymers, such as polystyrene, this fiber woven into the fabric with solvent to dissolve the sea component, leaving the island component, using this method can be prepared with a monofilament size of 0.001dtex microfiber. Complex spinning process, high technical requirements, a large number of composite melt streams composed of a microfiber, not only need to have a special technical design and complex melt distribution mode, but also the manufacture of spinning components and accessories must be configured accordingly, but also use two or more components of different physical and chemical properties of fibers. A variety of products can be obtained by different finishing methods after weaving. According to different processes, the composite spinning method can be divided into two categories: peel type and sea island type. A. mechanical stripping composite spinning method In this method, two kinds of polymer melts, which are completely different in chemical structure and have different affinity but similar melt viscosity, are prepared into orange petal, rice shaped, hollow shaped composite fibers by composite spinning according to a certain proportion, and microfibers are obtained by mechanical peeling using the characteristics of poor compatibility and interface adhesion of the two components. Stripping methods include mechanical method, solvent dissolution method and so on. The main process used by chemical fiber companies such as Jongmi and Teijin to make microfibers is the mechanical stripping composite spinning method. B. Island stripping composite spinning method The island stripping composite spinning method is also called "dissolution (or hydrolysis) stripping composite spinning method". This kind of ultrafine composite fiber is a new type of fiber developed in the early 1970s, from the cross section of the fiber is a fine and dispersed island component surrounded by another sea component, the sea component and the island component are continuous and uniform in the fiber axis, the composite fiber obtained by using a suitable solvent to dissolve or hydrolyze the sea component to remove the microfiber that only retains the island component. The early sea island composite fiber uses PET or PA as the island component, the sea component mostly uses PS or PE, and then uses benzene, toluene and other organic solvents to remove the sea component, but this has brought environmental pollution, flammable and explosive problems, limiting its development. Since the 1990s, people have been committed to the research of water-soluble polyester (COPET), using it as a sea component, which can be hydrolyzed in hot water or hot lye, avoiding the use of organic solvents and reducing environmental pollution. At present, there are two main processes of "fixed island type" and "indefinite island type" in the island stripping composite spinning method: a. Fixed-island composite spinning method Compared with the composite spinning method, the melt distribution system and spinning components of the fixed island method are more complex and have higher technical requirements. The "sea" component and the "island" component are melted by a separate screw extruder and then compounded to the spinning assembly. In the spinning process, the island is not separated, maintaining the monofilament shape, and the island components are not adhered to during the molding process (good separation between the island and the island in the monofilament). After composite spinning, it exists in a conventional size, that is, the core layer of the island component is surrounded by the skin core of the sea component. Only when the "sea" component is dissolved into the core layer of the "island" component, can the microfiber be truly made