Nylons preparation

Anionic ring opening polymerization of lactams to generate polyamides has been studied quite extensively by Sebenda [8-10], Sekiguchi [11], and Wichterle [12-13], among others, in academia, and by Gabbert and Hedrick [14] and by us [23-25] in industry. By far, caprolactam is the most studied lactam and the nylon 6 prepared by this route compares favorably in properties with that prepared by conventional hydrolytic polymerization. 

Fig. 16. Gel permeation chiomatt am (g.p.c.) of cyclics (NH(Ql2)5CO with x = 2—6 obtained from nylon-6 prepared by ring-chain equiMI ation in the melt at S2S K...

Fig. 19. Concentrations of cyclics M (in mol kg ) in a sample of nylon-6 prepared by polymerising e-caprolactam at 459 K and heating for a total of 36 days ( ). These values are compared with cyclic concentrations in a polymer prepared by ring-chain equilibration in the melt at 525 K (o)...

Nylon-6,6, discovered by Carothers in 1929, is by far the most important polyamide prepared by condensation polymerization. Nylon 6, prepared by the ring-opening (non-condensation) polymerization of e-caprolactam, will not be discussed in this chapter. Other commercially important polyamides prepared by condensation techniques include nylon-6,10, from hexamethylene diamine and sebacic acid, poly(/n-... 

The spectra of nylons are also sensitive to the crystalline conformation and the extent of hydrogen bonding. Figure 3.21 shows the N-CPMAS spectra of nylon-6 prepared in the y and a crystalline forms, and a mixture of the two conformations [22]. Clearly, the chemical shifts are a sensitive probe of the crystalline chain conformation in nitrogen-containing polymers. 

Figure 3.21 The N-CPMAS NMR spectra of nylon-6 prepared in (a) predominantly y-nylon-6, (b) a mixture of a- and y-nylon-b, and (c) predominantly a-nylon-6. Reprinted with permission...

The polymer-montmorillonite composites were produced with the same Haake twin-screw extruder and protocol that was successfully employed with the nylon 6 work described in Chapter 5. The test samples were prepared by injection molding and characterized by the same equipment and protocol described in the successful nylon 6 preparation of polymer-montmorillonite nanocomposites described in Chapter 5. The montmorillonite content in the composites was prepared at approximately 2, 4, and 5.5 wt.%. 

Gogolewski,S. and Pennings, A. (1985), High-modulus fibers of nylon-6 prepared by a dry-spinning method , Polymer, 26,1394-1400. 

AlliedSignal s Infinity, Forever Renewable Nylon, prepared by recycling of polyamide-6, is briefly described. The polyamide is treated by depolymerisation, purification of the caprolactam monomer and repolymerisation. The new resin is said to exhibit the same properties as those of virgin polyamide-6. ALLIEDSIGNAL... 

Other semicrystalline polymers, such as nylon prepared in Experiment 9. 

For nylon-6,10 the smallest cyclooligomer contains 18 atoms in a ring. However, for nylons prepared from amino-acids, much smaller rings are possible. Nylon-6 at 270°C contains about 8 wt. % of caprolactam, the cyclic monomer [81]. Nylon-4 degrades thermally to form the very stable cyclic monomer, pyrrolidone, and the attempted preparation of nylon-4 at conventional high temperatures produces very little polymer [86]. 

Nylons prepared from aromatic diamines and diacids (aramids) can lead to very high-heat amorphous nylons such as Du Font s Nomex materials [poly(m-phenyleneisophthalamide)], or the highly oriented crystalline Kevlar fibers [poly(p-phenyleneterephthalamide)] derived from liquid-crystalline technology. Both of these aramids are sold as fibers. They have excellent inherent flame-retardant properties, and Kevlar exhibits a very high modulus. 

The nylons are named by the number of carbon atoms in the repeat units. The materials formed by polymerizations of lactams therefore carry only one number in their names like, for instance, nylon 6 that is formed from caprolactam. By the same method of nomenclature, a nylon prepared by condensing a diamine with a dicarboxylic acid like, for example, hexamethylene diamine with adipic acid, is called nylon 6,6. It is customary for the first number to represent the number of carbons in the diamine and the second number to represent the number of carbons in the diacid. 

Background of an Industrial Polymer. The type of polymerization used in the nylon preparation described in this series of experiments is called "step-growth" polymerization. The technique uses two different difunctional monomers that undergo ordinary organic reactions. In the present case an add chloride is treated with an amine to produce an amide linkage. 

Since nylons prepared by various procedures, e. g. by the hydrolytic or alkaline polymerization, do not generally differ much either in molecular structure or in dilute solution properties, the method of preparation is not mentioned in the text The polymerization method is pointed out only in those cases where side reactions affect the structure of the product (e g., branching), or effects due to the nature of various end groups are operative. 

Nylons prepared from aromatic diamines and aromatic dicarboxylic acids can lead to very high-heat aromatic nylons (aramids). Poly (m-phenyleneisoph-thalamide), MPIA, is made from the condensation polymerization of m-phenylenediamine and isoph-thaloyl chloride and has a Tg of 280°C. Its structure is shown in Fig. 1.3. W. Sweeny, a scientist at DuPont was responsible for discoveries leading to the commercialization of MPIA and is available under the Nomex trade name. MPIA is used in fibers to make heat-resistant and flame-retardant apparel, electrical insulation, and composites. 

Ferroelectridty has been observed in nylon-7, nylon-11, nylon-75, nylon-77, fluor-inated nykm-3S, nylon-SS, nyloo-75 and nylon-95, as well as several alicyclic and aromatic nylons. Ferroelectridty has been observed in nylons prepared from m-xylylenedi-amine and aliphatic dicaiboxylic adds, referred as nylon-hOCDs. Alicyclic and aromatic nylons picpaied from 13-bis(aminamethyl)cyclobexane (BAC) and aliphatic dicarboxylk adds were also found to be ferroelectric. The newly developed fluoro-nylons having odd... 

Of the many nylons available, nylons 6.6, 6,11, and 12 are the most widely used. Nylons prepared from the terephthalic acids have very high melting points and are called aramides. The aramides are used in fiber applications where high thermal stability and high tensile strength are important. The repeating unit (R) can be derived from aliphatic or aromatic diamines. 

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. 

Polyamides from diamines and dibasic acids. The polyamides formed from abphatic diamines (ethylene- to decamethylene-diamine) and abphatic dibasic acids (oxabc 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 cabed nylons The Nylon of commerce (a 66 Nylon, named after number of carbon atoms in the two components) is prepared by heating adipic acid and hexamethylenediamine in an autoclave ... 

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... 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

A rack and frame press uses heavy nylon cloth positioned in a wooden frame inside a rack. A measured amount of apple or other fmit mash is added from a hopper above the frame. The mash is leveled with a hand trowel and the edges of the nylon cloth are folded over the mash to encase it and create a cheese. The frame is removed, and a second rack is placed on top of the first cheese the process is repeated until a stack of cheeses is prepared. A hydrauhc ram then appHes gradually increa sing pressure on the stack and expresses the juice. A high yield of juice (80%) is obtained and no press aid is required. Because this process is labor intensive (17), it is mostly used for small farm and pilot-plant operations. 

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). 

Enzymatic hydrolysis is also used for the preparation of L-amino acids. Racemic D- and L-amino acids and their acyl-derivatives obtained chemically can be resolved enzymatically to yield their natural L-forms. Aminoacylases such as that from Pispergillus OTj e specifically hydrolyze L-enantiomers of acyl-DL-amino acids. The resulting L-amino acid can be separated readily from the unchanged acyl-D form which is racemized and subjected to further hydrolysis. Several L-amino acids, eg, methionine [63-68-3], phenylalanine [63-91-2], tryptophan [73-22-3], and valine [72-18-4] have been manufactured by this process in Japan and production costs have been reduced by 40% through the appHcation of immobilized cell technology (75). Cyclohexane chloride, which is a by-product in nylon manufacture, is chemically converted to DL-amino-S-caprolactam [105-60-2] (23) which is resolved and/or racemized to (24)... 

If adipamide reacts with hexarnethylenediarnine, then nylon-6,6 can be prepared by aminolysis of the adipamide this could also be viewed as reverse ammonolysis. 

The diacids for these polymers are prepared via different processes. A2elaic acid [123-99-9] for nylon-6,9 [28757-63-3] is generally produced from naturally occurring fatty acids via oxidative cleavage of a double bond in the 9-position, eg, from oleic acid [112-80-1] ... 

Nylon-11. Nylon-11 [25035-04-5] made by the polycondensation of 11-aminoundecanoic acid [2432-99-7] was first prepared by Carothers in 1935 but was first produced commercially in 1955 in France under the trade name Kilsan (167) Kilsan is a registered trademark of Elf Atochem Company. The polymer is prepared in a continuous process using phosphoric or hypophosphoric acid as a catalyst under inert atmosphere at ambient pressure. The total extractable content is low (0.5%) compared to nylon-6 (168). The polymer is hydrophobic, with a low melt point (T = 190° C), and has excellent electrical insulating properties. The effect of formic acid on the swelling behavior of nylon-11 has been studied (169), and such a treatment is claimed to produce a hard elastic fiber (170). 

Its manufacture begins with the formation of dodecanedioic acid produced from the trimeri2ation of butadiene in a process identical to that used in the manufacture of nylon-6,12. The other starting material, 1,12-dodecanediamine, is prepared in a two-step process that first converts the dodecanedioic acid to a diamide, and then continues to dehydrate the diamide to the dinitrile. In the second step, the dinitrile is then hydrogenated to the diamine with hydrogen in the presence of a suitable catalyst. 

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