Nylon, synthesis

A new commercial use for butadiene is its employment in the nylon synthesis joining furfural, benzene, and cyclohexane as raw materials for nylon salt components. Amother olefinic hydrocarbon, which has found large scale application in recent years, is propylene tetramer, widely employed in reaction with aromatic nuclei to yield an alkylated aromatic base used in synthetic detergent production. 

Example peptide bond (N-H + RCOOH), nylon synthesis, formation of polysaccharide... 

If you have been highlighting a polymer a week, the first four experiments in Section A— Free Radical Polymerization, Synthesis of Nylon, Synthesis of Polyesters in the Melt, and Synthesis of a Polyurethane Foam —are excellent demonstrations to intersperse with the content as it is presented. If you want your students to actually perform the experiments, it might be best to wait until the end of a first-year chemistry course when the students have developed their laboratory techniques to the greatest extent. Another use for the four experiments would be to introduce a different one each quarter and discuss the polymer produced in the experiment. This is a good way to use the information on polymer chemistry if time does not permit the presentation of a Polymer of the Week. 

The salts of hydrazoic acid, M+Ns, have already been discussed in Section 3.2.4, but a variety of other alkali pseudohalides exist. The most important of these are the cyanides M+CN , preparable by neutralization of HCN with the appropriate alkali base. NaCN and KCN reached such industrial importance that alternative bulk syntheses have been developed (e.g. equation 10). This Castner process fed the gold extraction industry and continued to feed the electroplating and nylon synthesis markets until cheaper routes directly to HCN were found. In cases where the alkali cyanides are still required, the simple neutralization route is now most economic. 

The second category, hydroxy- and epoxy-containing acyl groups (and their esters), have numerous applications as chemical feedstocks in lubricants, paints and coatings, food and cosmetics emulsifiers, nylon synthesis, laxatives, disinfectants, etc. The utility of ricino-leic acid and its derivatives, for instance, the most commonly recognized member of this category, has existed for at least a century, demonstrated by US patents issued nearly 100 years ago, and 577 patents issued between the years 1990 and 2004. 

Example 10.3. Oxidation of cyclohexane [63-65], Air oxidation of cyclohexane to a mixture of cyclohexanol and cyclohexanone is an important step in a process for production of adipic acid and caprolactam in du Pont s Nylon synthesis. The reaction is carried out in the presence of a small amount of a cobalt salt (typically naphthanate or 2-ethylhexanoate) at 140 to 165° C and moderate pressure (e.g., 10 atm). The primary reaction product is cyclohexyl hydroperoxide ... 

Of far-reaching and more lasting importance for the industrial use of benzene was the commencement of the production of styrene by IG Farbenindustrie in 1929, and the hydrogenation of benzene to cyclohexane as a feedstock for nylon production, after the discovery of nylon synthesis from hexamethylenediamine and adipic acid by Wallace H.Carothers of Du Pont in 1935. 

Nylon salt n. Any of the intermediates in nylon synthesis formed by the combination of one molecule of diamine and one of diacid, such as nylon-6/6 salt. 

No doubt the versatility of nylon synthesis has been responsible for a performance approximating that of all plastics from 1950 to 1975 in spite of the introduction of many new resins in that interval (U.S. data. Fig. MK-5). Moreover, in the last decade nylon has done somewhat better than all plastics (Fig. MK-5). As seen in Fig. MK-6, nylon plastics in the U.S. roughly paralleled the growth of fiber and amounted to 7 to 8 percent of the fiber up to 1966. Fiber growth since then has been erratic and slower overall than plastics such that plastics reached the 10 per cent level in 1975 and has since increased to almost 17 per cent in 1984. A similar experience at higher levels has characterized Western Europe where plastic use was 22.7% of 66-fiber use in 1982 [41]. Of interest is the per capita consumption in various countries (Table MK-3) which suggests that many areas, particularly the U.S., have some catching up to do. 

As improvements over P-methylumbeUiferone (55—57), 4-methyl-7-amino-coumarin [26093-31-2] (12a) and 7-dimethylamino-4-methylcoumarin [87-014] (12b) (58—61) were proposed. These compounds are used for brightening wool and nylon either in soap powders or detergents, or as salts under acid dyeing conditions. They are obtained by the Pechmaim synthesis from appropriately substituted phenols and P-ketocarboxyflc acid esters or nitriles in the presence of Lewis acid catalysts (see Coumarin). 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Another example is the du Pont process for the production of adiponitrile. Tetrakisarylphosphitenickel(0) compounds are used to affect the hydrocyanation of butadiene. A multistage reaction results in the synthesis of dinitrile, which is ultimately used in the commercial manufacture of nylon-6,6 (144-149). 

Nylon-6 [25038-54-4] was first made in 1899 by heating 6-aminohexanoic acid (143), but its commercially feasible synthesis from caprolactam was discovered by Paul Schlack at 1. G. Farbenindustrie in 1938. Like nylon-6,6, it is a tough, white translucent, semicrystalline sofld, but melts at a lower temperature (T = 230° C. The physical properties and primary producers of nylon-6 are Hsted in Tables 9 and 10, respectively. 

Ammonium sulfate is also recovered as a by-product in large amounts during the coking of coal, nickel refining, and organic monomer synthesis, particularly during production of caprolactam (qv). About four metric tons of ammonium sulfate are produced per ton of caprolactam which is an intermediate in the production of nylon. 

Polymer Plasticizer. Nylon, cellulose, and cellulose esters can be plasticized using sulfolane to improve flexibiUty and to increase elongation of the polymer (130,131). More importantly, sulfolane is a preferred plasticizer for the synthesis of cellulose hoUow fibers, which are used as permeabiUty membranes in reverse osmosis (qv) cells (131—133) (see Hollow-FIBERMEMBRANEs). In the preparation of the hoUow fibers, a molten mixture of sulfolane and cellulose triacetate is extmded through a die to form the hoUow fiber. The sulfolane is subsequently extracted from the fiber with water to give a permeable, plasticizer-free, hoUow fiber. 

Practical methods for synthesis and elucidation of the optimum physical forms were developed at Du Pont (13). The violets fill the void in the color gamut when the inorganics are inadequate. The quinacridones may be used in most resins except polymers such as nylon-6,6, polystyrene, and ABS. They are stable up to 275°C and show excellent weatherabiUty. One use is to shade phthalocyanines to match Indanthrone Blue. In carpeting, the quinacridones are recommended for polypropylene, acrylonitrile, polyester, and nylon-6 filaments. Predispersions in plastici2ers ate used in thermoset polyesters, urethanes, and epoxy resins (14). 

Nylon resins are made by numerous methods (53) ranging from ester amidation (54) to the Schotten-Baumann synthesis (55). The most commonly used method for making nylon-6,6 and related resins is the heat-induced condensation of monomeric salt complexes (56). In this process, stoichiometric amounts of diacid and diamine react in water to form salts. Water is removed and further heating converts the carboxylate functions to amide linkages. Chain lengths are controlled by small amounts of monofunctional reagents. The molten finished nylon resin can be dkectly extmded to pellets. 

The preparation of nylon resins from lactam precursors involves ring opening, which is facihtated by a controlled amount of water in the reaction mixture. The salt complex condenses internally to produce the polyamide (57). The synthesis of nylon-6 [25038-54-4] from S-caprolactam is as follows ... 

There has been only one major use for ozone today in the field of chemical synthesis the ozonation of oleic acid to produce azelaic acid. Oleic acid is obtained from either tallow, a by-product of meat-packing plants, or from tall oil, a byproduct of making paper from wood. Oleic acid is dissolved in about half its weight of pelargonic acid and is ozonized continuously in a reactor with approximately 2 percent ozone in oxygen it is oxidized for several hours. The pelargonic and azelaic acids are recovered by vacuum distillation. The acids are then esterified to yield a plasticizer for vinyl compounds or for the production of lubricants. Azelaic acid is also a starting material in the production of a nylon type of polymer. 

Fibers in which the basic chemical units have been formed by chemical synthesis, followed by fiber formation, are called synthetic fibers. Examples include nylon, carbon, boron fibers, organic fibers, ceramic fibers, and metallic fibers. Among all commercially available fibers, Kevlar fibers exhibit high strength and modulus. (Kevlar is a DuPont trademark for poly [p-phenylene diamine terephthalamide].) It is an aromatic polyamide (aramid) in which at least 85% of the... 

Butadiene is by far the most important monomer for synthetic rubber production. It can be polymerized to polybutadiene or copolymerized with styrene to styrene-butadiene rubber (SBR). Butadiene is an important intermediate for the synthesis of many chemicals such as hexa-methylenediamine and adipic acid. Both are monomers for producing nylon. Chloroprene is another butadiene derivative for the synthesis of neoprene rubber. 

Caprolactam, a white solid that melts at 69°C, can be obtained either in a fused or flaked form. It is soluble in water, ligroin, and chlorinated hydrocarbons. Caprolactam s main use is to produce nylon 6. Other minor uses are as a crosslinking agent for polyurethanes, in the plasticizer industry, and in the synthesis of lysine. 

Adiponitrile, a starting material used in the manufacture of nylon, can be prepared in three steps from 1,3-butadiene. How would you carry out this synthesis ... 

S. M. Aharoni, n-Nylons Their Synthesis, Structure and Properties, Wiley, New York, 1997. 

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