Production methods and classification of island-type microfibers
The production methods of microfibers are There are many different production methods for fibers with different linear densities. The main production methods are shown in Figure 1-1.
Among the production methods of ultrafine fibers, direct spinning is the simplest, but it is difficult to spin fibers below 0.55dtex. Other methods include melt-blown method and flash evaporation method, which have major limitations. Although the melt-blown method is relatively simple, the fiber thickness and length are difficult to control, and it is mostly used for immediate net making and non-woven base fabric production. superior. The flash evaporation method relies on rapid evaporation of the solvent to form fibers, and it is difficult to uniformly and stably control the quality of the fibers. They belong to the spinning method of random ultrafine fibers.
The two-component spinning method is currently the most widely used and researched method. It can be roughly divided into two categories: composite spinning and blending spinning. Among them, the composite spinning method is used At most, there are different production processes and stripping methods according to the linear density requirements of the fibers. Bicomponent fibers are also called composite fibers or conjugate fibers. According to different cross-sectional distributions, there are many types such as side-by-side type, core-sheath type, and island type.
In parallel fibers, the two components can be divided into two or more clear areas along the length direction. The distribution area and shape of the two components vary greatly. The shapes vary; another more important variety of bicomponent fiber is the sheath-core type, in which the core component is completely surrounded by another component (skin), and the cross-sectional shape and area of the two components are also different. Same; bicomponent fibers also include sea-island fibers, also known as matrix-fibril fibers.
Sea-island fiber is compounded or blended of two thermodynamically incompatible polymers in a certain proportion. One component of the spun composite fiber is the dispersed phase (i.e., the separation component), and the other is the continuous phase (i.e., the sea component). The island component is contained in the sea component in the shape of ultrafine fibers. The cross sections of the ultrafine fibers are distributed in an island shape, and their long axis is parallel to the composite fiber. According to the different distribution patterns of islands, they can be divided into two types: fixed islands and adventitious islands.
The former island distribution is uniform and fixed, while the latter is not fixed and not uniform enough. The thickness varies greatly. The thinnest one is thinner than the fixed island type, but the thick one is It can be above 0.1dtex; the former generally uses composite spinning, and the latter uses blending spinning; the former can be spun into filaments, and short fibers of various lengths can also be made after cutting the filaments, while the latter generally Only short fibers of different thicknesses and lengths can be spun. At present, more composite spinning methods are used because it can produce various ultrafine fibers with stable properties.
Both components, sea and island, have certain requirements and there are many combinations.
At present, the island component is mostly made of PET or PA, and the sea component is made of polyester that can be dyed with cationic dyes ( COPET), PE, PA, PS and PET, etc. The number of islands of the fixed-island type is usually 16, 36, 37, 51, or 64. At present, ultrafine fibers with more than 100 islands can be produced. The island-type microfibers currently produced mainly include PET/COPET and PA/(COPET or PET). The former is mainly made into filament type and used for the production of various textiles. The latter is mainly made into short fiber type and used for production. Synthetic leather base fabric.
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