Nylon acid hydrolysis

Important solvolysis reactions for nylons are hydrolysis, methanolysis, glycolysis, aminolysis, ammonolysis, transamidation, and acidolysis.17 Hydrolysis of nylon-6 with steam in the presence of an acid catalyst to form caprolactam is tlie preferred depolymerization approach. However, when recycling carpet face fibers, file fillers in the polymer may react with file acid catalyst and lower the efficiency of the catalyst. 

This problem has been confirmed recently in a study of the mechanism of covalent reaction between nylon 6.6 and the sulpha toe thylsulphone dye Cl Reactive Blue 19 (7.37). Acid hydrolysis of the dyed fibre and HPLC analysis of the hydrolysate yielded the 6-aminohexylaminoethylsulphonyl derivative of Blue 19. Even when the dyeing procedure was optimised to achieve maximal exhaustion and fixation to the fibre [128], only about 30% of the N-terminal amino groups in the nylon 6.6 were accessible because of mutual blocking effects between these bulky anionic dye molecules. 

Amide urethane, and ester groups in the polymer chain, such as those present in nylons and polyesters may be hydrolyzed by acids to produce lower-molecular-weight products. Polyacetals are also degraded by acid hydrolysis, but ethers, such as polyphenylene oxide (PPO), are resistant to attack by acids. 

Chemical depolymerization of polyamides is mainly carried out by hydrolysis. Acid hydrolysis of nylon-6 allows the starting monomer, e-caprolactam, to be recovered. Likewise, basic hydrolysis of nylon-6,6 leads to hexamethylene diamine and adipic acid. Degradation of polyamides by ammonolysis has also been reported as an interesting alternative for the chemical recycling of nylon-6 and nylon-6,6 mixtures. 

Acid hydrolysis of nylon 6 wastes [21, 22] in the presence of superheated steam has been used to produce aminocaproic acid, which under acid conditions is converted to e-caprolactam, and several patents have been obtained by BASF [23, 24]. Acids used for the depolymerization of nylon 6 include inorganic or organic acids such as nitric acid, formic acid, benzoic acid, and hydrochloric acid [23, 25]. Orthophosphoric acid [24] and boric acid are typically used as catalysts at temperatures of 250-350°C. In a typical process, superheated steam is passed through the molten nylon 6 waste at 250-300°C in the presence of phosphoric acid. The resulting solution underwent a multistage chemical purification before concentration to 70% liquor, which was fractionally distilled in the presence of base to recover pure e-caprolactam. Boric acid (1%) may be used to depolymerize nylon 6 at 400°C under ambient pressure. A recovery of 93-95% e-caprolactam was obtained by passing superheated steam through molten nylon 6 at 250-350°C [23]. 

The alternative method for eluting a protein from an SDS gel involves transfer of the protein to a membrane. Nitrocellulose, nylon, and Immobilon-P membranes can all be used to carry out subsequent proteolytic digestion, but only nitrocellulose is suitable for CNBr digestion, and for acid hydrolysis only Immobilon-P can be used. 

Almost 250 million lb of butadiene are converted into raw materials for nylon manufacture. Butadiene reacts with hydrogen cyanide in a two-step process to give adiponitrile, which then is hydrogenated to produce hexamethylenediamine. It also can be reacted with carbon monoxide and methanol to give first a pentene ester and then the dimethyl ester of adipic acid. Hydrolysis of the ester then gives the free acid. 

Now let s see what happens in the dark, dank, slightly bubbly interior of your stomach when you eat meat or, if that doesn t appeal, then protein of some kind. As I remarked in Reaction 14, proteins are elaborate forms of nylon. You could think of a protein as a bundled string of pearls, each pearl being a special group of atoms and the links between them are peptide links , -CONH-, 5.1 shall deal with real proteins later (Reaction 27) to keep things simple at this stage, I shall describe how the peptide link is broken down by acid hydrolysis, but will use a very parsimonious string of just two pearls, 6. 

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)... 

The pelargonic acid by-product is already a useful item of commerce, making the overall process a commercial possibiUty. The 13-carbon polyamides appear to have many of the properties of nylon-11, nylon-12, or nylon-12,12 toughness, moisture resistance, dimensional stabiUty, increased resistance to hydrolysis, moderate melt point, and melt processibiUty. Thus, these nylons could be useful in similar markets, eg, automotive parts, coatings, fibers, or films. Properties for nylon-13,13 are = 56 (7 and = 183 (7 (179). 

Polyamides (nylons) The main types of nylon are oil and petrol resistant, but on the other hand susceptible to high water absorption and to hydrolysis. There are a few solvents such as phenol, cresol and formic acid. Special grades include a water-soluble nylon, amorphous copolymers and low molecular weight grades used in conjunction with epoxide resins. Transparent amorphous polyamides are also now available. 

In a patent granted to the DuPont Company in 1946, Myers8 described the hydrolysis of nylon-6,6 with concentrated sulfuric acid which led to the crystallization of AA from the solution. HMDA was recovered from the neutralized solution by distillation. In a later patent assigned to the DuPont Company by Miller9, a process was described for hydrolyzing nylon-6,6 waste with aqueous sodium hydroxide in isopropanol at 180°C and 305 psi pressure. After distillation of die residue, HMDA was isolated, and on acidification of the aqueous phase, AA was obtained in 92% yield. 

Adipic acid and HMDA are obtained from nylon-6,6 by die hydrolysis of die polymer in concentrated sulfuric acid (Fig. 10.7). The AA is purified by recrystallization and the HMDA is recovered by distillation after neutralizing die acid. This process is inefficient for treating large amounts of waste because of die required recrystallization of AA after repeated batch hydrolyses of nylon-6,6 waste. In a continuous process,5 nylon-6,6 waste is hydrolyzed with an aqueous mineral acid of 30-70% concentration and the resulting hydrolysate is fed to a crystallization zone. The AA crystallizes and the crystals are continuously removed from the hydrolysate. Calcium hydroxide is added to neutralize the modier liquor and liberate the HMDA for subsequent distillation. 

The depolymerization of nylon-6,6 and nylon-4,6 involves hydrolysis of the amide linkages, which are vulnerable to both acid- and base-catalyzed hydrolysis. In a DuPont patent,9 waste nylon-6,6 was depolymerized at a temperature... 

Acid-Catalyzed Hydrolysis of Nylon-6 in Carpet Waste74... 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

Nylon-6, 136, 530, 531. See also PA-6 acid-catalyzed hydrolysis of, 567-568 chemistry and catalysis of, 546 depolymerized, 532-534, 557-558 hydrolysis of, 535, 552 neutral hydrolysis of, 566-567 Nylon-6 waste, 543... 

Nylon-6,6, 2, 136, 530. See also PA-6,6 acid-catalyzed hydrolysis of, 568 acidolysis of, 568 alkaline hydrolysis of, 568-569 ammonolysis of, 555, 570 chemistry and catalysis of, 546 creation of, 1 hydrogen bonding in, 539 hydrolysis of, 531, 544, 552-555 phase-transfer-catalyzed alkaline hydrolysis of, 569-570... 

Phase-separated polymers, 215 Phase separation, 217-222 Phase transfer catalysts, 288, 563-564 Phase-transfer-catalyzed alkaline hydrolysis of nylon-4,6, 570 of nylon-6,6, 569-570 PHB. See Poly(3-hydroxybutanoic acid) (PHB)... 

Perhaps the most interesting finding of our synthetic studies was that the interfacial preparation of poly(iminocarbonates) is possible in spite of the pronounced hydrolytic instability of the cyanate moiety (see Illustrative Procedure 3). Hydrolysis of the chemically reactive monomer is usually a highly undesirable side reaction during interfacial polymerizations. During the preparation of nylons, for example, the hydrolysis of the acid chloride component to an inert carboxylic acid represents a wasteful loss. 

Pure xylan is not employed in industry. but crude xylan or pentosans are of industrial importance. Xylan has been proposed as a textile size but is not employed as yet for this purpose.130 Perhaps the largest use of pentosans is in their conversion to furfural, which has many applications and serves as the source of other furan derivatives. At the present time, large quantities of furfural are used in the extractive purification of petroleum products, and recently a large plant has been constructed to convert furfural by a series of reactions to adipic acid and hexamethylene-diamine, basic ingredients in the synthesis of nylon. In commercial furfural manufacture, rough ground corn cobs are subjected to steam distillation in the presence of hydrochloric acid. As mentioned above, direct preferential hydrolysis of the pentosan in cobs or other pentosan-bearing products could be used for the commercial manufacture of D-xylose. 

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