Molten adipic acid

Waste nylon-6,6 was washed in a diluted commercial detergent solution at 100°C for 0.5 h and then rinsed twice with water to remove any finishes present. The washed nylon-6,6 was then reacted with molten adipic acid for 1.5 h or more at a temperature of 175°C with a weight ratio of nylon-to-adipic acid of 0.15 1. The molten product was then exposed to steam at a temperature of 230-233°C to remove any stabilizers present. The acidolysis product was then hydrolyzed with water at a temperature of 204°C under autogenous pressure for 0.5 h or longer with a ratio of water to acidolysis product of 0.50 1 (w/w). The hot solution was then filtered at 100°C to remove any titanium dioxide present. The filtered product was then mixed with HMDA to neutralize any excess acid present. The solution was then filtered to remove any solids. A 50% by weight aqueous solution of HMDA was added to the filtrate, and under standard polymerization conditions, polyhexamethylene adipamide (nylon-6,6) was produced. 

HEXANEDIOIC acid KYSELINA ADIPOVA(CZECH) MOLTEN ADIPIC ACID... 

The molten mixture of iodo-acid and silver is maintained at 100°—120° until it thickens and the temperature is then raised to 150°—160°. After remaining at this temperature for two or three hours the mixture is cooled and then extracted with boiling water, The aqueous extract, on evaporation, deposits a considerable crust of adipic acid which is separated. A further quantity of adipic acid is obtained by evaporating the mother-liquor, and the whole may be recrystallised from hot water. Colourless crystals m.p, 148°-149°,... 

Nylon is the common name for polyamides. Polyamides are generally made from reactions of diacids with diamines. The most common polyamide is called nylon 6,6 because it is made by reaction of a six-carbon diacid (adipic acid) with a six-carbon diamine. The six-carbon diamine, systematically named hexane-1,6-diamine, is commonly called hexamethylene diamine. When adipic acid is mixed with hexamethylene diamine, a proton-transfer reaction gives a white solid called nylon salt. When nylon salt is heated to 250 °C, water is driven off as a gas, and molten nylon results. Molten nylon is cast into a solid shape or extruded through a spinneret to produce a fiber. 

Nylon. In 1939 the DuPont Company introduced the first truly synthetic textile fiber. Dr. Wallace Carothers invented nylon as a result of his basic research into polymer science. Chemically, nylon is a polyamide fiber. The two major types of nylon polymer are used in textiles type 6,6 which is made by using hexam-ethylene glycol and adipic acid, and type 6, which is made by polymerizing e-caprolactam. Nylon fibers are made by melt-spinning the molten polymer. The result is a continuous filament fiber of indeterminate length. It is spun in many deniers, with its diameter varying from 10 to 50 microns. The cross-section usually is round, trilobal, or square with hollow channels when used as carpet fiber. 

In the first step, phenol is hydrogenated in the molten state to cyclohexanol, in the presence of a nickel catalyst The operation takes place at around 150°C and 03 -106 Pa absolute. Once-through conversion of phenol is up to 99.5 per cent The second step consists in oxidizing the cyclohexanol to adipic acid by nitric add, in the presence of a... 

In the earlier vapor phase process, a mixture consisting of ammonia and adipic acid in a volumetric ratio of 20/1 was sent between 300 and 350 C to a catalyst bed based on phosphoric acid and boron. The thermal decomposition which occurred upon the vaporization of adipic acid limited the dinitrile molar selectivity to 80 per cent. The new liquid phase process, developed by IC1 (Imperial Chemical Industries) and Monsanto, operates in the molten acid between 200 and 300°C. in the presence of phosphoric acid. The selectivity to adiponitrile, purified by distillation and recrystallization, is 90 molar per cent. 

Nylon 6,6 may also be prepared by direct amidation of adipic acid and hexamethylene diamine. In this process, the molten monomers are added to a vessel in approximately stoichiometric proportions, but usually with a slight excess of acid. The exothermic salt formation produces sufficient heat to raise the batch temperature to approximately 200 °C, so polymerization proceeds rapidly. As the polymerization proceeds, the stoichiometry is adjusted to exactly equal molar portions of diacid and diamine, and the autoclave temperature and pressure are raised to 275 C and 250 Ib/in., respectively. After a specified heating time, pressure is reduced, and the temperature is maintained to complete polymerization. 

In the preparation of nylon-6,6 salt, DuPont discloses a process for making highly concentrated solutions of nylon salt at maximum solubility [192], In the first step of this process, a concentrated salt solution for nylon-6,6 is made with 73.5-77.5 wt% of adipic acid and 22.5-26.5 wt% of hexamethylene diamine at 55-60°C. The solution contains 60-69.5 wt% solute as compared to an ordinarily stoichiometric solution containing 56% diacid and 44% diamine with a maximum solute concentration of about 59 wt%i. The second step is to remove water from the solution by evaporation to a solution concentration of 93-96 wt%. When the concentrated solution is ready to be polymerized, addition hexamethylene diamine is added to complete the reaction. A process with similar reaction modifications is developed to prepare an essentially anhydrous mixture of adipic acid and hexamethylene diamine [193], The reaction mixture is heated to 120-135°C to allow evaporation of water while reacting. The resulting product has a ratio of adipic acid to hexamethylene diamine of 81 19. The molten acid-rich mixture is withdrawn in a continuous process. 

Polyamides are formed by the polymerization of a diamine and a dicar-boxyhc acid and are commonly known as nylons. Among the various nylons, nylon 66 and nylon 6 are commercially important polymers. It is shown here that in these cases the application of the equal reactivity hypothesis is no more than an approximation. Nylon 66 is prepared in two stages. In the first stage, the monomers hexamethylene diamine [NH2—(CH2)g—NH2] and adipic acid [COOH—(CH2)—COOH)] are reacted to form hexamethylene adipamide (sometimes called nylon 66 salt). It is known that the amino and carboxylic groups ionise in the molten state and the ionised species do not participate in the step-growth polymerization [7,31-33]. In other words, the polymerization can be... 

The type of process used also indicates the addition of polymer modifiers. Blow-molding requires that the polymer flows easily, while retaining good cohesive strength when molten, to avoid tears and voids. Melt flow modifiers are typically used for this purpose and include fatty acid esters, oleoamides, and adipates. Compounds of this type often also serve to prevent blocking (adhesion of one side of a bag to the other). 

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