Nylon 66, Intermediates

Although nylon intermediates are aliphatic, the main starting materials are aromatic hydrocarbons. In the earliest processes, phenol was hydrogenated (over nickel or palladium) to cyclohexanone/ol mixtures, known as KA oil , which gave adipic (hexanedioic) acid on oxidation with nitric acid. Half of this adipic acid was converted to the dinitrile, by vapour phase reaction with ammonia. Finally the dinitrile was hydrogenated to hexamethylenediamine (1,6-diaminohexane). Nylon-6,6 is produced by the condensation of essentially equimolar quantities of adipic acid and the diamine. 

In subsequent processes, now predominating, benzene is hydrogenated to cyclohexane for aerial oxidation (cobalt catalysed) to KA oil (or Bashkirov oxidation to cyclohexanol). One or two companies appear to have substituted aerial oxidation of KA oil for the nitric acid oxidation process, while Celanese produce their 1,6-diaminohexane via 1,6-hexanediol, rather than adiponitrile. 

However, the most significant changes in nylon-6, 6 production lie in the newer routes to adiponitrile introduced by Monsanto and Du Pont into both the U.S.A. and Western Europe. The former entails the electroreductive dimerization of acrylonitrile, while Du Pont use the addition of HCN to 1,3-butadiene catalysed by Ni(0) complexes  

This process is by no means as simple as this equation implies, with the formation of several isomers, and hence the need for interconversions at each stage. Both processes take the pressure off benzene, from which the multistage processes gave poor yields of dinitrile (c. 50% of theory). In a somewhat similar manner, BASF have operated a semi-commercial plant to produce adipic acid by the bis-hydrocarboxylation of 1,3-butadiene  

Cyclohexanone alone is the main starting point for the newer nylon-6 the hydrogenation of phenol can be directed to give this material, but KA oil (or cyclohexanol) must be dehydrogenated. The sulphate or, more recently, phosphate of the oxime, formed by reaction with hydroxylamine (as its salt), undergoes the Beckmann rearrangement in the presence of oleum. (Excess acid is neutralized with ammonia for sale into fertilizers.) 

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Polyamide and Intermediates, Techcon (U.K.) Ltd., London pubHshed monthly Nylon Intermediates andFiber, PCI— Fibers Raw Materials, West Sussex, U.K. pubHshed monthly World Nylon 6 and 66 Supply and Demand Report, PCI— Fibers Raw Materials, West Sussex, U.K. pubHshed annually Chemical Economic Handbook, Stanford Research Institute, Menlo Park, Calif., pubHshed and updated periodically. 

As an example of coirelating plant costs, the cost data from a nylon intermediate plant constructed from stainless steel was accumulated and converted to factors as shown in Table 2. 

Separation of individual saturated hydrocarbons from the petroleum fractions and subsequent conversion to more useful products. Important examples are n-butane to butadiene and cyclohexane to nylon intermediates. 

Acrylic textile fibers are primarily polymers of acrylonitrile. It is copolymerized with styrene and butadiene to make moldable plastics known as SA and ABS resins, respectively. Solutia and others electrolytically dimerize it to adiponitrile, a compound used to make a nylon intermediate. Reaction with water produces a chemical (acrylamide), which is an intermediate for the production of polyacrylamide used in water treatment and oil recovery. 

An explosion at a nylon-intermediates plant in England killed... 

INVISTA Nylon Intermediates Experimental Station, Wilmington, DE19880-0302... 

A Nylon recycle based on depolymerization via ammonolysis has been shown to be a technically feasible route for the recovery of high purity Nylon intermediates (1-6). In the ammonolysis process, the secondary amides of the Nylon (-6 and / or -6,6) fibers/polymers react with ammonia to break the Nylon chain and form a primary amide and an amine (Figure 1). The primary amide can subsequently be dehydrated to form a nitrile group. The net result is that the ammonolysis product is predominantly a mixture of four major components. 

Highly active, selective and stable catalysts for the production of MP [30-33] and DEK [33] with sterically demanding basic diphosphine ligands have also been developed. In addition, these type of catalysts selectively convert internal olefins to Unear esters for the production of detergents, plasticizers and nylon intermediates [32,34],... 

Uses Manufacture of ethylbenzene (preparation of styrene monomer), dodecylbenzene (for detergents), cyclohexane (for nylon), nitrobenzene, aniline, maleic anhydride, biphenyl, benzene hexachloride, benzene sulfonic acid, phenol, dichlorobenzenes, insecticides, pesticides, fumigants, explosives, aviation fuel, flavors, perfume, medicine, dyes, and many other organic chemicals paints, coatings, plastics and resins food processing photographic chemicals nylon intermediates paint removers rubber cement antiknock gasoline solvent for fats, waxes, resins, inks, oils, paints, plastics, and rubber. 

L. Shannon Davis is the director of Industrial Products Technology at Solutia, Inc., a specialty chemicals company. She received her B.S. from Georgia Southern College and her Ph.D. in inorganic chemistry from the University of Florida. She began her career in 1988 at Monsanto s Pensacola, Florida, site as a senior chemist in the nylon intermediates business unit, where she worked on processes for the... 

Although these nylon intermediates are derived mainly from cyclohexane, there are... 

The intermediate cyclohexane is a nylon intermediate. Economics depends on raw materials and selling price of cyclohexanone. 

Integrated Nylon nylon and acrylic fibres nylon 6,6 resins and nylon intermediates for third parties. 

Nylon intermediates by cyclohexane oxidation , British Chem. Engng, Process SuppL (Nov. 1967). 

Raney catalysts are used in a broad range of industrial hydrogenations. These include reductions of nitriles and dinitriles (e.g. for nylon intermediates), aldehydes (e.g. for sorbitol or alkane diols), olefins and alkynes (e.g. for monomer purification) and aromatic nitro compounds (e.g. for urethane intermediates). 

Polyamides. The first commercially produced synthetic polyamides were made from dibasic acids and diamines exemplified by polyhexameth-ylene adipamide (6,6-nylon). Adipic acid was first commercially produced by osdation of cyclohexanone produced from phenol, but today it is largely produced by oxidation of cyclohexane derived from either benzene or petroleum. Sebacic acid, another important nylon intermediate, is produced by caustic oxidation of ricinoleic acid from castor oil. 

DuPont Nylon Intermediates Specialties, PO Box 1089, Orange, TX, 77631-1089, USA (Tel 409-882-3720 800-231-0998 FAX 409-886-9100 E-mail NISP usa.dupont.com Internet www.dupont.com/intermediates)... 

Hazardous Decomp. Prods. Hydrogen cyanide heated to decomp., emits toxic fumes of CN NFPA Health 2, Flammability 2, Reactivity 1 Storage Store in a cool, dry, well-ventilated area out of direct sunlight Uses Intermediate in mfg. of nylon intermediate for hexamethylenediamine, mfg. of other chems. adipoguanamine resins as polar solvent... 

Thereafter, the operations of the petrochemical industry, or more accurately bulk organic chemical industry, centre on chemistry, with extensive use of catalysis to permit the use of the cheapest feedstock available and eliminate expensive reagents. However, potential changes in raw material availabilities and environmental pressures need a flexible response, possibly illustrated by the variety of production routes to acetic (ethanoic) acid and anhydride described in section 12.5. The remaining aliphatic chemical products are dealt with in carbon number sequence, followed by aromatics and nylon intermediates. 

Another early example was DuPont s nylon intermediates processes developed in the late 1930s. DuPont chose to commercialize nylon-66 because of the availability of benzene from coal as a feedstock. The benzene had to be hydrogenated to cyclohexane, which was oxidized in two steps to adipic acid. Originally, adipic acid was the precursor for the other intermediate, hexamethylene diamine. Production of nylon and other polymer intermediates would be an important field in homogeneous catalyst innovation in the post-war era (71). 

The elusive parent diisocyanate, 0=C=N—N=C=0, is only stable at —75°C, and therefore it is not suitable as a monomer for polyurethanes (23). The least costly aliphatic diisocyanate is hexamethylene diisocyanate (HDI), which is obtained by phosgenating the nylon intermediate hexamethylenediamine (HDA). Because of its low boiling point, HDI is mostly used in the form of its derivatives, such as biurets, allophanates, dimers, or trimers (24). Isophorone diisocyanate (IPDI) and its derivatives are also used in the formulation of rigid coatings, while hydrogenated MDI (HMDI) and cyclohexane diisocyanate (CHDI) are used in the formulation of flexible coatings and polyurethane elastomers. 

Acrylonitrile Adiponitrile Nippon Petrochem. Nylon intermediates... 

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