Synthetic polyamides

Reaction of hydroxylamine with ketones or aldehydes yields oximes, aldoximes RHC=NOH, or ketoximes R2C=NOH. Almost all the hydroxylamine production (95%) is used for the production of either cyclohexanone oxime or caprolactam, both of which are intermediates for polyamide synthetics. The remainder of the hydroxylamine production is used as an anticreaming agent in paints and coatings, as an auxiliary in refining fats for soap production, as a regulator or inhibitor for various polymerizations, as a stabilizer for developers, and as an additive for color emulsions. Oximes are also used as pharmaceuticals or in crop protection. 

Copolymers are produced by the simultaneous polymerization of two or more dissimilar molecules. Examples include polyvinyl acetate, polyesters, and polyamides. Synthetic elastomers (such as SBR synthetic rubber, made from styrene and butadiene) are also copolymers. This pattern continues with the ter-polymers (such as acrylonitrile-butadiene-styrene (ABS)), which consist of three different monomers. 

Step-growth condensation reactions may be carried out in organic solvents, interfacially, in bulk, microheterogeneously, or on a solid support. Active esters are often employed in solution methods at relatively low temperatures to yield water-soluble polyesters or polyamides. Synthetic polypeptides, polynucleotides, and polysaccharides are commonly made by sequential addition of protected monomer imits onto polymer supports. 

Sebacic acid is used to stabilize alkyd resins in the coatings industry. It is also used to make low-temperature lubricants and polyamide synthetic fibers. 

Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

We only need to recall the trade name of synthetic polyamides, nylon, to recognize the importance of these polymers and the reactions employed to prepare them. Remember from Sec. 1.5 the nylon system for naming these... 

However, because of the low melting poiats and poor hydrolytic stabiUty of polyesters from available iatermediates, Carothers shifted his attention to linear ahphatic polyamides and created nylon as the first commercial synthetic fiber. It was nearly 10 years before. R. Whinfield and J. T. Dickson were to discover the merits of poly(ethylene terephthalate) [25038-59-9] (PET) made from aromatic terephthaUc acid [100-21-0] (TA) and ethylene glycol [107-21-1] (2G). 

The materials of attention in promoting fire safety are generally organic polymers, both natural, such as wood (qv) and wool (qv), and synthetic, nylon (see Polyamides), vinyl, and mbber (qv). Less fire-prone products generally have either inherently more stable polymeric stmctures or fire-retardant additives. 

PyraZolines. l,3-Diphenyl-2-pyia2olines (7) (Table 2) aie obtainable from appiopiiately substituted phenyUiydiazines by the Knoii reaction with either P-chloro- or P-dimethylaminopropiophenones (30,31). They are employed for brightening synthetic fibers such as polyamides, cellulose acetates, and polyacrylonitriles. 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

V. V. Korshak and T. M. Emnze, Synthetic Hetero-Chain Polyamides, Israel Program for Scientific Translation, Jemsalem, Israel, 1968, pp. 87—93. 

Eatty bisamides are used primarily to kicrease sHp, reduce blocking, and reduce static ki polymeric systems. Other specialty appHcations kiclude cosolvents or coupling agents for polyamide reskis, fillers for electrical kisulation coatings, additives for asphalt to reduce cold flow, and synthetic waxes for textile treatments (68). Bisamides have been used ki all the traditional primary amide appHcations to kicrease lubricity and have become the amide of choice because of thek better efficiency. Bisamides have the highest commercial value ki the amide market. 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

Sulfur dyes are used mainly for dyeing textile ceUulosic materials or blends of ceUulosic fibers (qv) with synthetic fibers such as acryUc fibers, polyamides (nylons), and polyesters. They are also used for sHk (qv) and paper (qv) in limited quantities for specific appHcations. Solubilized sulfur dyes are used on certain types of leathers (qv). 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

Oxidized castor oils are excellent nonmigrating, nonvolatile plasticizers (qv) for ceUulosic resins, poly(vinyl butyral), polyamides, shellac, and natural and synthetic mbber (see Rubber, natural). The high viscosity products are also used as tackifiers in gasket compounds and adhesives (qv) because of good oil and solvent resistance. They also serve as excellent pigment grinding media and as a base for inks (qv), lubricating oils, and hydrauHc oils (62). 

The primary driving forces behind investigation of new solvents include environmental concerns and the abiUty to form Hquid crystals in the new solvent systems. By analogy with Kevlar, a synthetic aromatic polyamide fiber, spinning from a Hquid crystalline solution should yield cellulose fibers with improved strength, as has been demonstrated in laboratory experiments. 

The most important coating appHcation for the nonreactive polyamide resins is in producing thixotropy. Typical coating resins such as alkyds, modified alkyds, natural and synthetic ester oils, varnishes, and natural vegetable oils can be made thixotropic by the addition of dimer acid-based polyamide resins (see Alkyd resins). Specialty high performance coating appHcations often requite the properties imparted by dimer acid components. 

It is difficult for dye solutions in water to penetrate synthetic fibers such as polyester, cellulose triacetate, polyamides, and polyacryUcs which are somewhat hydrophobic. The rate of water imbibition differs with each fiber as shown in Table 1 as compared to viscose (see Fibers, regenerated CELLULOSics), which imbibes water at the rate of 100% (1). The low imbibition rate is attributed to the high T obtained when the polymeric fibers are drawn. During this drawing operation the polymer chains become highly oriented and tightly packed, forming a stmcture practically free of voids. 

Disperse dyes are water-iasoluble, aqueous dispersed materials that are used for dyeiag hydrophobic synthetic fibers, including polyester, acetate, and polyamide. 

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