Aliphatic polyamides adipic acid

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. 

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). 

Figure 18.10. Melting points of polyamides from aliphatic diamines A, with adipic acid, B, with sebacic acid. (After Coffmann et al )...

Polyamides from diamines and dibasic acids. The polyamides formed fi om aliphatic diamines (ethylene- to decamethylene-diamine) and aliphatic dibasic acids (oxalic to sebacic acid) possess the unusual property of forming strong fibres. By suitable treatment, the fibres may be obtained quite elastic and tough, and retain a high wet strength. These prpperties render them important from the commercial point of view polyamides of this type are called nylons . The Nylon of commerce (a 66 Nylon, nam after number of carbon atoms in the two components) is prepared by heating adipic acid and hexamethylenediamine in an autoclave ... 

Many hydrogenation and polymerization reactions in the chemical industry are carried out with liquid-phase reactants. An example is the hydrogenation of aliphatic dinitriles to produce diamines (108,109), which are subsequently converted with adipic acid in solution and polymerized to produce linear polyamides, including nylon 6,6. Recently, the development of wet-environmental transmission electron microscopy (wet-ETEM) for direct nanoscale probing of... 

It has become the custom to name linear aliphatic polyamides according to the number of carbon atoms of the diamine component (first named) and of the dicarboxylic acid. Thus, the condensation polymer from hexamethylenedi-amine and adipic acid is called polyamide-6,6 (or Nylon-6,6), while the corresponding polymer from hexamethylenediamine and sebacoic acid is called polyamide-6,10 (Nylon-6,10). Polyamides resulting from the polycondensation of an aminocarboxylic acid or from ring-opening polymerization of lactams are indicated by a single number thus polyamide-6 (Nylon-6) is the polymer from c-aminocaproic acid or from e-caprolactam. 

Many combinations of diacids—diamines and amino acids are recognized as isomorphic pairs (184), for example, adipic acid and terephthalic acid or 6-aminohexanoic acid and 4-aminocyclohexylacetic acid. In the type AABB copolymers the effect is dependent on the structure of the other comonomer forming the polyamide that is, adipic and terephthalic acids form an isomorphic pair with any of the linear, aliphatic C-6—C-12 diamines but not with -xylylenediamine (185). It is also possible to form nonrandom combinations of two polymers, eg, physical mixtures or blends (Fig. 10), block copolymers, and strictly alternating (187—188) or sequentially ordered copolymers (189), which show a variation in properties with composition differing from those of the random copolymer. Such combinations require care in their preparation and processing to maintain their nonrandom structure, because transamidation introduces significant randomization in a short time above the melting point. 

The three methyl groups, which account for about 11.5 and 10.5% of the weight, eliminate crystallinity completely, both for the adipic acid-based aliphatic polyamide and the terephthalic acid-based aromatic-aliphatic polyamide. 

The industrial production of hexamethylenediamine became important with the discovery of the use of polyamides as synthetic fibres, the most important being Nylon-6,6. This polymer, prepared from adipic acid and hexamethylenediamine, was commercialized by DuPont in 1938 and it was virtually the only consumer of the entire production of this diamine until the development of light-stable polyurethanes. Those polymers, e.g. Desmodur N (Bayer) used in paints, are based on aliphatic diisocyanates prepared from the corresponding aliphatic diamine. 

Polyamides are obtained either by the condensation of a dicarboxylic acid and an alkylene diamine or by the head-to-tail condensation between an amino carboxylic acid or the corresponding lactam. Polyamides may have aliphatic or aromatic chain backbones. Aliphatic polyamides (nylon) have the most important commercial applications, mainly in the manufacture of fibres. Nylon-6 and nylon-6,6 account for around 85% of all nylon currently used. Nylon-6 is derived from the polymerization of e-caprolactam, whereas nylon-6,6 is obtained by the condensation of hexamethylene diamine and adipic acid. 

Cyclohexanone, a six-membered carbon ring with a ketone as functional group, is almost exclusively applied as a precursor for the production of aliphatic polyamides. Pure cyclohexanone is mainly converted, via cyclohexanone oxime and caprolactam, to nylon-6 (also called polycaprolactam) [1]. Mixtures of cyclohexanone and cyclohexanol, often called K4 oil, are converted via oxidation into adipic acid that reacts with hexamethylene diamine (HMDA) to nylon-6,6 (poly-hexamethylene adipamide). Other applications of these products can be found in the field of polyurethane and polyester production. 

Y.-T. Chen. Composition comprising crystallizable polyamide from tere-phthalic acid, adipic acid, aliphatic diamine and m-xylylene diamine. US Patent 5 194 577, assigned to Amoco Corporation (Chicago, IL), March 16, 1993. 

STRUCTURE As described in several articles md patents/ this type of aromatic nylon resin is a polyamide consisting of varying portions of aliphatic and aromatic units. Hexamethylene diamine is the main aliphatic component, which may be augmented by various amounts of adipic acid. The main aromatic component is terephthalic acid, which may be augmented by lesser amounts of isophthalic acid. Depending on relative composition, Amodel (nylon 6,6 copolymer) resins can be regarded as co- and terpolymers consisting of repeat units of nylon 66, nylon 6T, and nylon 61 —poly (hexamethylene isophthalamide). The major potential difference of other aromatic nylons, such as Ultramid T from BASF, is the presence of the 61 component. 

Polyamides of this type are called nylon ( , m 2), where n is the number of carbons in the diamine monomer and m - - 2 is the number of carbons in the diacid. Nylon 6,6, the most commercially important aliphatic polyamide with this structure, is produced from hexamethylene diamine (HMD) ( = 6) and adipic acid (m- -2 = 6). Nylon 4,6, nylon 6,10 and nylon 6,12 are also produced commercially [1]. 

The two main commercial polyamides are nylon 6,6, produced by condensation polymerization of HMD and adipic acid (see Table 7.1), and nylon 6, an AB-type polymer, which is produced from caprolactam. Other commercial polyamides include nylons 4,6, nylon 6,12 (which are AA- and BB-type polymers) and nylon 11 and nylon 12 (which are AB polymers made from linear aliphatic amino acids containing 11 and 12 carbons, respectively) [1]. Polyamides are also produced using monomers with aromatic, rather than aliphatic segments. Polyamides that contain 85% or more of the amide bonds attached to aromatic rings are called aramids. Commercial examples include poly(p-phenyleneterephthalamide) or Kevlar and poly(m-phenyleneisoterephthalamide) or Nomex [23]. 

Polyester amides are synthesized from polyamides and aliphatic polyesters and are completely biodegradable and still exhibit the required processing and material properties. The raw materials include adipic acid, aminocapronic acid, and diols, i.e., common chemicals that form statistically structured polyester amides under normal esterification conditions during a polycondensation process. 

PEAs can be synthesized by statistical condensation copolymerization of polyamide monomers (PA 6 or PA 6.6), adipic acid, and 1,4-butanediol (Scheme 11.4). A variety of amino acids and aliphatic diols, poly(ethylene glycol), or cyclic diols like dianhydrosorbitol or dianhydromannitol have also been used to prepare PEAs [109,119, 120]. 

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