Production of staple fibres

The dried polyester polymer is transported to extruders where it is melted, and piunped to spinning packs held in a spin manifold. The spin packs contain spiimeiets with a large number of fine holes through which the melted polymer flows to form filaments. Any contaminants in the polymer are removed by filtration prior to the spinneret. Different spinneret designs enable a wide range of fibre cross-sections to be produced including solid round, hollow and trilobal. 

The hot filaments are cooled by blowing air through the filament bundle and are combined together into a tow band, which is deposited into a can. The fibre thickness is determined by the wind-up speed of the denier setter . Spin draw finish is applied as an aid to subsequent processing. 

The spim tows are combined at the creel and drawn to optimise the tensile properties of the fibres. The tow is then crimped to give it the necessary bulk characteristics for different end uses. The crimped tow is dried and a final finish is applied to suit customer requirements. The tow is cut to the required fibre length, up to 150 mm, before being baled ready for dispatch. 

Filament yams are produced from PET chips. They are blended to ensure uniformity, prior to being pre-crystallised, and dried ready for melting. In the extruder, the polymer chips are melted, and then fed into a special manifold where the melt is distributed. 

From there, the melted polymer is passed through spinnerets to produce thread lines. The thread lines are drawn, dressed with processing aids, and intermingled to give the yam its excellent mechanical properties. They are then wound up onto packages called cheeses . 

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The Nomex family products consists of staple fibres, continuous filament yarns, paper, woven, hydroentangled and coated fabrics, and they are used in firefighter garments insulation in fire resistant thermal protective apparel and apparel fabrics to protect against flash fire and electric arc exposure. Examples of DuPont Nomex fibres suitable for protective clothing are summarized in Table 3.3 below. 

Approximately 2.5 million t of viscose process regenerated ceUulose fibers were produced in 1990 (Table 1). Measured by production capacity in 1990, the leading producers of filament yams in 1990 were the Soviet Union state-owned factories (255,000 t capacity) and Akzo Fibres in Europe (100,000 t). The leading producers of staple fiber and tow were Courtaulds with 180,000 t capacity spUt between the UK and North America Formosa Chemicals and Fibres Co. with 150,000 t in Taiwan Tenzing with 125,000 t in Austria, and a 40% stake in South Pacific Viscose s 37,000 t Indonesian plant and Grasim Industries in India (125,000 t). BASF s U.S. capacity of 50,000 t was acquired by Tenzing in 1992. 

Other uses of HCI are legion and range from the purification of fine silica for the ceramics industry, and the refining of oils, fats and waxes, to the manufacture of chloroprene mbbers, PVC plastics, industrial solvents and organic intermediates, the production of viscose rayon yam and staple fibre, and the wet processing of textiles (where hydrochloric acid is used as a sour to neutralize residual alkali and remove metallic and other impurities). 

The total PET world production capacity amounted to 30 megatonnes per year (Mt/y) in the year 2000. This total production includes 8.5Mt/y of packaging resins, comprising 93 % of bottle-grade PET and 7 % of film-grade PET. The staple fibre and textile filament capacities have been 9.1 Mt/y and 11.1 Mt/y, respectively, while the industrial yarn capacity has been 1.2 Mt/y. Typical plant capacities are 240-600 t/d for bottle resin production, 100-200 t/d for staple fibres and 100-300 t/d for filament-spinning textile grades. Batch plants for the production of industrial yams have typical capacities of 20-40 t/d [2],... 

Slitting is necessary when making continuous yams, but for staple fibre it is sometimes possible to avoid slitting and to stretch the full width of the sheet or tube because the product is afterwards cut to the desired staple length and the cards or garnets will disintegrate the product to a more or less individual fibre state. 

As for viscose fibres, these are mostly produced as staple fibres for textile and nonwoven applications. In 2011, world production was 3.246 million tons [49] while filament yam for textile and technical applications reached 332 000 tons in 2011 [49] with a share of technical yarns of 56 000 tons. Technical viscose fibres, also called rayon or viscose rayon, are used mainly as carcass reinforcing fibres in fast-running and run-flat tyres. Lyocell fibres are produced only as staple and virtually exclusively by Lenzing AG, Austria, with a production capacity of 140 000 tons in 2011 [50]. 

By producing fabrics with different components in warp and weft, it may be possible to create a stmcture that utiUses the best features of each. The most popular combinations in this respect are multifilament warp and staple-fibre weft yams (Fig. 3.24) and monofilament warp and multifilament weft yams. In both cases the ratio of warp to weft threads is at least 2 1 and usually considerably higher. This facilitates the production of fabrics with a smooth warp-faced surface for efficient cake release. 

Ring spinning is a long established technique used for manufacturing yams from staple fibres such as cotton, flax, wool, etc. The ring spinning system is the most flexible system, and is the most dominant method of yam production when using staple fibres. Several literatures describe its operation and process control. ... 

As stated above, conventional synthetic fibres may be rendered inherently flame retardant during production by either incorporation of a flame retardant additive in the polymer melt or solution prior to extrusion or by copolymeric modification before, during, or immediately after processing into filaments or staple fibres. Major problems of compatibility, especially at the high tanperatures used to extrude melt-extruded fibres like polyamide, polyester, and polypropylene and in reactive polymer solutions such as viscose dope and acrylic solutions, have ensured that only a few such fibres are commercially available. A major problem in developing successful inherently flame retardant fibres based on conventional fibre chemistries is that any modification, if present at a concentration much above 10wt% (whether as additive or comonomer), may seriously reduce tensile properties as well as the other desirable textile properties of dyeability, lustre and appearance, and handle, to mention but a few. 

The fiber cloth is the deciding ctor in the success or failure of all press operations. In view of the wide range of process variables involved in the filtration process, it is virtually in ossible to select a filter medium that will satisfy all process requirements and the usual limited time scale available for cloth selection is used to find an acceptable medium, i.e. one that will satisfy most, if not all of the requirements. In this reject, one particular requirement (e.g. filtrate clarity) may have to be relaxed, if other specifications (e.g. filtrate rate, absence of blinding) are to be maximised. Thus the more open weave Mcs will be superior in nonblinding characteristics, but may have poor particle retention. The latter will in rove in the order monofilament < muldfilament < staple fibre. Tabulated information is presented in Tables 4.2,4.3 and 4.4 below on the effect of yam properties, weave patterns, etc. on the processes of cake release, productivity, resistance to blinding, etc.. 

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