Solvent nylon

Paper may not be chemically inert to organic solvents. Nylon, on the other hand, is inert to organic solvents. 

Because of its extremely low solubility in low-boiling and inexpensive organic solvents, nylon 66 required a new technique for converting the solid polymer into fibers hence the development of melt spinning, the third basic method for producing manufactured fibers. The following description refers essentially to nylon 66 because it was the first to use the method, but the process applies, in general, to all melt-spun manufactured fibers. 

C, b.p. 81"C. Manufactured by the reduction of benzene with hydrogen in the presence of a nickel catalyst and recovered from natural gase.s. It is inflammable. Used as an intermediate in the preparation of nylon [6] and [66] via caprolactam and as a solvent for oils, fats and waxes, and also as a paint remover. For stereochemistry of cyclohexane see conformation. U.S. production 1980 1 megatonne. 

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

Caprolactam Extraction. A high degree of purification is necessary for fiber-grade caprolactam, the monomer for nylon-6 (see Polyamides). Cmde aqueous caprolactam is purified by solvent extractions using aromatic hydrocarbons such as toluene as the solvent (233). Many of the well-known types of column contactors have been used a detailed description of the process is available (234). 

Poly(vinylidene chloride). Poly(viayHdene chloride) [9002-85-1] (PVDC), most of which is produced by Dow Chemical, is best known in its saran or PVC-copolymerized form (see Vinylidene chloride and poly(VINYLIDENE chloride)). As solvent or emulsion coating, PVDC imparts high oxygen, fat, aroma, and water-vapor resistance to substrates such as ceUophane, oriented polypropylene, polyester, and nylon. 

Stereochemistry. Cyclohexane can exist ia two molecular conformations the chair and boat forms. Conversion from one conformation to the other iavolves rotations about carbon—carbon single bonds. Energy barriers associated with this type of rotation are low and transition from one form to the other is rapid. The predominant stereochemistry of cyclohexane has no influence ia its use as a raw material for nylon manufacture or as a solvent. 

The United States accounts for about a third of the world s consumption of cyclohexane, or 3.785 x 10 m /yr (about 1 biUion gallons per year). U.S. producers and their 1990 capacities are Hsted in Table 13. Texaco has aimounced that it is leaving the cyclohexane business, but the timing is not yet certain. Over 90% of all cyclohexane goes to the production of nylon through either adipic acid (qv) or caprolactam (qv). The balance is used to produce 1,6-hexamethylenediamine [124-09-4] (HMD A) and for various solvent uses (see Diamines and higher amines, aliphatic Polyamides). 

Almost all of the cyclohexane that is produced in concentrated form is used as a raw material in the first step of nylon-6 and nylon-6,6 manufacture. Cyclohexane also is an excellent solvent for cellulose ethers, resins, waxes (qv), fats, oils, bitumen, and mbber (see Cellulose ethers Resins, natural Fats AND FATTY OILS Rubber, NATURAL). When used as a solvent, it usually is in admixture with other hydrocarbons. However, a small amount is used as a reaction diluent in polymer processes. 

Ketones are an important class of industrial chemicals that have found widespread use as solvents and chemical intermediates. Acetone (qv) is the simplest and most important ketone and finds ubiquitous use as a solvent. Higher members of the aUphatic methyl ketone series (eg, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone) are also industrially significant solvents. Cyclohexanone is the most important cycHc ketone and is primarily used in the manufacture of y-caprolactam for nylon-6 (see Cyclohexanoland cyclohexanone). Other ketones find appHcation in fields as diverse as fragrance formulation and metals extraction. Although the industrially important ketones are reviewed herein, the laboratory preparation of ketones is covered elsewhere (1). 

Many polymers, including polyethylene, polypropylene, and nylons, do not dissolve in suitable casting solvents. In the laboratory, membranes can be made from such polymers by melt pressing, in which the polymer is sandwiched at high pressure between two heated plates. A pressure of 13.8—34.5 MPa (2000—5000 psi) is appHed for 0.5 to 5 minutes, at a plate temperature just above the melting point of the polymer. Melt forming is commonly used to make dense films for packaging appHcations, either by extmsion as a sheet from a die or as blown film. 

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