Acrylic fiber preparation

Highly colored, they have been used to dye cellulose acetate (552) and acrylic fibers (553). Cationic dyes prepared from 2-azothiazoles by simple alkylation on the ring nitrogen (552) have been used increasingly with the introduction of polyacrylonitrile fibers with basic sites that can be colored with such dyes (554). 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

An important nitrile is acrylonitrile H2C=CHCN It is prepared industrially from propene ammonia and oxygen m the presence of a special catalyst Polymers of acryl omtrile have many applications the most prominent being their use m the preparation of acrylic fibers... 

Vinyl Bromide. Vinyl bromide [593-60-2] is prepared by the base-promoted dehydrobromination of ethylene dibromide [106-93 ]. It is used as a comonomer in the production of acrylic fibers. 

Benzotrichloride Method. The central carbon atom of the dye is supplied by the trichloromcthyl group from p-chlorobenzotrichJoridc. Both symmetrical and unsymmetrical triphenylmethane dyes suitable for acrylic fibers are prepared by this method. 

Benzotrichloride Method. The central carbon atom of the dye is supplied by the trichloromethyl group fromy>-chlorobenzotrichloride. Both symmetrical and unsymmetrical triphenylmethane dyes suitable for acrylic fibers are prepared by this method. 4-Chlorobenzotrichloride is condensed with excess chlorobenzene in the presence of a Lewis acid such as aluminium chloride to produce the intermediate aluminium chloride complex of 4,4, 4"-trichlorotriphenylmethyl chloride (18). Stepwise nucleophilic substitution of the chlorine atoms of this intermediate is achieved by successive reactions with different a.rylamines to give both symmetrical (51) and unsymmetrical dyes (52), eg, N-(2-chlorophenyl)-4-[(4-chlorophenyl) [4-[(3-methylphenyl)imino]-2,5-cyclohexadien-l-yhdene]methyl]benzenaminemonohydrochloride [85356-86-1] (19) from / -toluidine and a-chloroaniline. 

Aminopyridine is prepared conventionally by the substitution of the pyridine ring via the so-called Chichibabin reaction using sodium amide in dimethylaniline [36]. 2-Aminopyridine is used in the manufacture of several chemotherapeutics and of dyes for acrylic fibers, and as an additive for lubricants [37]. Alkyl thiocyanates react [38] to give 2-alkylthiopyridines (eq. (12)) which are otherwise accessible only by multistep synthetic pathways [39]. The catalytic reaction (eq. (12)) seems to offer on easy entry into the pyrithione systems. 

NMR spectroscopy has been applied to investigate the behavior under uniaxially mechanical deformation. A study of drawn fibers prepared from an isotactic polypropylene modified by an ethylene-aminoalkyl acrylate copo-l)uner has been done using the broad line of H NMR. NMR spectra were measured on the set of fibers prepared with a draw ratio X from q to 5.5 at two temperatures, one of them corresponding to the onset of segmental motion and the other one is the middle of the temperature interval as determined by decrease of the second moment 2D time-domain H NMR was used to... 

Fibers prepared from straight polyacrylonitrile are difficult to dye. To improve dyeabiUty, manufacturers invariably add to monomer feed minor amounts of one or two comonomers, such as methyl acrylate, methyl methacrylate, vinyl acetate, and 2-vinyl-pyridine. Small amounts of ionic monomers (sodium styrene sulfonate) are often included for better dyeability. ModacryKc fibers are composed of 35-85% acrylonitrile and contain comonomers, such as vinyl chloride, to improve fire retardancy. 

A sheep grows a wool fiber that possesses a corkscrew crimp in the dry state and affords the animal a bulky insulation blanket. When it rains, the fiber becomes wet and loses the crimp the wool strands then bed down to form a close-packed, rain-tight covering capable of reducing the loss of body heat in the damp conditions. This evolutionary wool fiber, whose properties are derived from its bicomponent nature, was simulated in the laboratory by preparing a two-component acrylic fiber. 

Dry Spinning. This was the process first employed commercially by DuPont in 1950. It is shown schematically in Figure 8. For acrylic fibers, the only dry-spinning solvent used commercially is DMF. The DMF spin dope coming from the dope preparation unit is filtered and then heated to approximately... 

The flake is then dissolved in acetone and water to prepare the concentrated spinning solution or dope at a concentration of 15-30% solids. As with acrylic fibers, titanium oxide may be added as a delustrant, as well as pigments to color the fibers. The dope is subsequently filtered and de-aer-ated using varied filtration technologies to remove impurities. 

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