Acrylic fiber spinning

Hazardous Decomp. Prods. On decomp., emits toxic fumes of NO, NEPA Health 1, Flammability 2, Reactivity 0 Storage Store In cool, dry, well-ventilated area, out of direct sunlight Uses Solvent for llqs., gases. In vinyl resins, acetylene, butadiene, acid gases, paints, paint strippers, cleaners, zinc electroplating, acrylic fiber spinning, pharmaceuticals mfg. of polyacrylic fibers, butadiene. 

Diethylenetriamine Dimethyl formamide Tetraethylenepentamine solvent, acryl Methoxybutyl acetate solvent, acrylic coatings Hexyl acetate Methyl ethyl ketone solvent, acrylic copolymers Diethylene glycol propyl ether solvent, acrylic fiber spinning Dimethyl formamide Sodium thiocyanate solvent, acrylic high-solids coatings Butoxyethanol acetate solvent, acrylic paints C7-8 isoparaffin solvent, acrylic paints/coatings Ethoxyethanol acetate solvent, acrylic resins Xylene... 

Carbon and Graphite Fibers. Carbon and graphite fibers (qv) are valued for their unique combination of extremely high modulus and very low specific gravity. Acrylic precursors are made by standard spinning conditions, except that increased stretch orientation is required to produce precursors with higher tenacity and modulus. The first commercially feasible process was developed at the Royal Aircraft Fstablishment (RAF) in collaboration with the acrylic fiber producer, Courtaulds (88). In the RAF process the acrylic precursor is converted to carbon fiber in a two-step process. The use of PAN as a carbon fiber precursor has been reviewed (89,90). 

Cyanohydrins are used primarily as intermediates in the production of other chemicals. Manufacture of methyl methacrylate, used to make acrylic mol ding resins and clear sheet, eg, Plexiglas acrylic sheet, from acetone cyanohydrin is the most economically important cyanohydrin process (see Methacrylic polymers). Cyanohydrins are also used as solvents in appHcations including fiber-spinning and metals refining. Cyanohydrins and derivatives reportedly act as antiknock agents in fuel oil and motor fuels and serve as electrolytes in electrolytic capacitors. 

Capone, G. J., Wet-spinning technology. In Acrylic Fiber Technology and Applications, ed. J. C. Masson. Marcel-Dekker, New York, 1995, pp. 69 103. 

Deaths from cancer of the stomach were statistically elevated in one study of six manufacturing plants in the United Kingdom involved in the polymerization of acrylonitrile and the spinning of acrylic fibers (Werner and Carter 1981). No quantitative data on the exposure levels to acrylonitrile were given and the numbers of expected deaths was too small to provide confidence in the results. 

Doped silicon, conductivity in, 23 35 Doped/undoped electrochromic organic films, 6 580-582 Dope-dyeing, 9 197 Dope-making process, in acrylic fiber solution spinning, 11 204 Dope solids, in air gap spinning, 11 209 Doping, 23 838—839 calcium, 23 842-844 conducting polymers, 7 528-529... 

Uses. The largest use for sodium thiocyanate is as the 50—60 wt % aqueous solution, as a component of the spinning solvent for acrylic fibers (see Fibers, ACRYLIC Acrylonitrile polymers). Other textile applications are as a fiber swelling agent and as a dyeing and printing assist. A newer commercial use for sodium thiocyanate is as an additive to cement in order to impart early strength to concrete (376). 

Improved Comfort Properties. Wear comfort generally means cotton-like properties, The ability lo absorb moisture from the skin and ihe softness of cotton fabrics are considered to be the two key properties for comfort. The extremely line denier of cotton fibers accounts for its softness. Both properties can be achieved in acrylic fibers. Improved moisture retention can be achieved by incorporating hydrophilic comonomers that decrease ultimate fiher density, by modifying the fiber spinning process, ur by using after-treatments such as modified finishes. 

Bis-cationic dyes, which are usually used for spin dyeing polyacrylonitrile, are derived from thiazole [83], Compound 33 dyes acrylic fibers blue with good steamfastness [84],... 

Solutia, a firm created through a spin-offby Monsanto in 1997, also looks more like a conglomerate than like a specialty chemicals company because it retains large operations in nylon and acrylic fibers as well as in upstream... 

Fig. 12.19. Flow diagram for the manufacture of acrylic fiber (1) acrylonitrile (2) tank farm (3) polymerizer (4) comonomer and catalyst (5) centrifuge (6) waste liquid (7) dried polymer (8) grinding (9) polymer storage (10) dissolver (11) filter (12) solvent plant (13) spinnerette (13w) wet spinning (13d) dry spinning (14) roller dryer (15) additional treatment (16) crimper (17) cutter (18) acrylic fiber bale.

Acrylics. The DuPont Company introduced the first commercial acrylic fiber, Orion, in 1950. Acrylics are made from the polymerization of acrylonitrile and other co-monomers to allow dyeability and to open the internal structure. The fibers are produced by either solventspinning (Orion), or wet-spinning (Acrilan). In the solvent-spinning process, the polymer is... 

PAN homopolymer is not a true TP. It is a polar crystallizing polymer that undergoes chemical decomposition before crystalline melting at temperatures above 300C (572F). The almost pure homopolymer, however, can be processed into fiber (acrylic fibers) through its spinning from solutions (Chapter 6). PAN is also used as a base material... 

From the above it appears clear that the moisture transport takes jdace at the surface of the fiber (solid-liquid interface). The capadty of water retenticm, on the other hand, appears to reside primarily in macrovcMds within the fiber. Actually, acrylic fibers with high water retention can be (Stained, accordii to a recent patent by spinning a fiber from a blend of an acrylic copt maer and a hqjdy soluble con ronent (e. g., glycerine), which later is washed out in the further treatment, leaving behind voids and capillaries which provide the water retention. 

Transition metal compounds catalyze an infinite number of organic reactions. (For a recent review, see e.g. Ref. Most probably, these compounds will have an effect on the processes going on during the heat treatment of acrylic fibers, in particular on dehydrogenation reactions, provided they can be introduced into the fiber in a way such that they will not be washed out during the spinning process. 

Dimethylformamide (DMF) has been known since 1893, but since the 1950s, it has evolved as an important solvent. Its main uses are as a solvent for spinning acrylic fibers, polyurethane and polyamide coatings and films, PVC, polyacrylonitrile, extraction of aromatics from petroleum, selective solvent for removal of acid gases from natural gas, solvent for dyes, electrolyses in galvanization processes, and paint remover and cleaner [16]. By 1980, the worldwide production of DMF had grown equal to the production of formic acid at 220,000 metric tons per year [18]. By 1993 the U.S. production of formic acid was 30 to 35 mm pounds and DMF production had grown to 60 to 65 mm pounds. 

The situation changed dramatically when DuPont introduced the first commercial acrylic fiber under the trade name of Orion. This commercial development took place shortly after DuPont [12] and I.G. Farbenindustrie [13] simultaneously reported solvents suitable for spinning acrylonitrile fibers in 1942. Based on this solvent breakthrough, DuPont was able to develop a commercial process for producing acrylic fibers. The DuPont process was based on dry spinning with A,A-dimethylformamide (DMF) as the solvent. The product was introduced in 1944 as Orion. Shortly thereafter Chemstrand (later to become Monsanto Fibers and Intermediates Company) introduced Acrilan, Siiddeutsche Chemiefaser (Hoechst) introduced Dolan, and Bayer introduced Dralon. Developments in this fledgling industry occurred rapidly from that time on. 

Chemstrand s Acrilan process was based on a wet-spinning technology, which produces a fibrillar microstructure. As a result, early acrylic fiber products suffered from problems with abrasion originating with a lack of coherence in the fibrillar surface of the fibers. This was overcome by adding a steam-annealing step, which, combined with the presence of vinyl acetate as comonomer, makes the fibrils that compose each filament fuse together. 

We close this section with a few comments regarding the ultrahigh-modulus acrylic fibers. It is estimated that the theoretical crystalline modulus for polyethylene is 240 GPa hence there has been an intense effort over the last 10-15 years to develop spinning processes to exploit the high-modulus potential. This goal has been achieved by gel-spinning techniques [177]. Allen et al. [178] have estimated the theoretical modulus that might be obtained for... 

PAN by use of gel-spinning or other techniques to create a completely extended chain. Their estimate, based on a comparison of the rod-like PAN conformation with helical chain conformations of other polymers, is that the maximum tensile modulus of atactic PAN would be about 55 GPa. They conclude that PAN with ultrahigh modulus cannot be made by gel spinning, or by any other means, due to the intrinsic chain properties. It is proposed that the strong intramolecular nitrile repulsions that cause the PAN to adopt a rod-like, semiextended conformation do not allow the chain to unravel completely from its semiex-tended conformation. Attempts to develop gel-spinning processes in acrylic fibers are discussed in Section 12.5.4. 

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