Still, molecular

The new fibers were scientifically interesting—and they eventually laid the foundation for the synthetic textile industry—but at the time they seemed practically worthless. The first polyester fibers resembled those produced by the lowly silk worm, but Carothers did not think that the discovery would be commercially valuable. The polymer chains made in Hill s molecular still were still not long enough to make robust fibers. The filaments melted at such a low temperature and were so soluble that they could not be ironed or washed in dry cleaning fluid or hot water. Carothers knew he would have to make longer polymers if he hoped to make a marketable fiber. Instead, Carothers dramatized the romance of Hill s discovery by quoting the seventeenth-century microscopist, Robert Hooke, who had dreamed of making synthetic silk even better than that Excrement made by silk worms. 

By July 21, 1930, Hill was back at work heating a superpolyamide in the molecular still. To his great frustration, he could not make any fibers. Only much later was it discovered that it would indeed have produced fibers, if only he had known the proper technique to use. 

Wallace H. Carothers. Early History of Polyamide Fibers, addressed to Arthur P. Tanberg, Feb. 19, 1936, is the source for the discovery of superpolymer in the molecular still It should be noted that... obvious next step putting amides on backburner was foolish, but gives reasons and Coffman s discovery. HML 1784, Box 18. 

Herman Mark and G. Whitby, eds. Collected Papers of Wallace Hume Carothers on High Polymeric Substances. New York Interscience, 1940. This contains Roger Adams obituary of Carothers. The source for Carothers conducting few experiments discovering superpolymer in molecular still physical behavior of a molecular. . . and Carothers description of cold drawing and making fibers. 

John K. Smith. The Ten-Year Invention Neoprene and DuPont Research, 1930-1939. Technology and Culture. 26 (Jan. 1985) 34-55. Source for discovery of superpolymer in molecular still rubber as addition polymer others condensation Nieuwland Collins assigned DVA problem marketing Neoprene and new products in Depression. 

The 1,5-naphthalenedithiol can be further purified to a melting point of 120-121° by sublimation under high vacuum in a molecular still, followed by reprecipitation of the water-soluble disodium salt of the sublimate from excess hydrochloric acid. The pure compound obtained from 9.1 g. of product weighs 8.6 g. (76%). 

By reacting dicarboxylic acids with 5 % excess of diols, Carothers and Arvin obtained a range of polyesters with molecular weights up to about 4000 [19]. One of the collaborators in this work was J. W. Hill, who constructed a molecular still attached to a mercury diffusion pump that was capable of reducing the pressure in the reaction vessel to 10 5 mm of mercury [20], He made a polyester by reacting... 

To a mixture of Mg turnings (2 g, 83 mmol) and 1,2-dibromocthane (200 pL) in refluxing THE (60 mL) was added over 30 min l-chloro-3-ethoxy-l-phenyl-2,2,4,4-tetramethylcyclobutane (71 19.4 g, 73 mmol). The mixture was refluxed for 5 h, cooled, and poured into H2() (600 mL) containing sat. aq NaHC03 (200 mL). It was then extracted with petroleum ether (4 x) and then dried. Removal of the solvent and distillation of the residue in a molecular still gave the product, which was purified by redistillation through a 15-cm spinning-band column yield 5.5 g (40%) bp 34-36 C (0.1 Torr). 

Attempted isolation of diethyl hydroxymethyl phosphonate by standard vacuum distillation technique is accompanied by extensive decomposition. The use of Kugelrohr apparatus allows the isolation to be accomplished at a lower temperature, and therefore the product is obtained in higher yield. Alternately, the checkers found that distillation using a 2 wiped-film molecular still (Pope Scientific, Inc.) significantly raised product yields, especially when the reaction was performed on a larger scale (Notes 3 and 6). 

The checkers found that reactions run on up to four tiroes the present scale and rectified using a molecular still (wall temperature 110-120°C, 0.10 mm) gave yields of 89-94%. Warning-. On this larger scale (i.e., four times the present scale) a brief run-away was experienced and some material which escaped from the condenser was caught in a trap however, the yield was still excellent (94%). 

The evaporator of Figure 13.30(d) is for service intermediate between those of ordinary film evaporators and molecular stills, with greater clearances and higher operating pressures than in the latter equipment. The rotating action permits handling much more viscous materials than possible in film evaporators. 

Figure 13.30. Molecular distillation and related kinds of equipment, (a) Principle of the operation of the falling film still (Chemical Engineers Handbook, McGraw-Hill, New York, 1973). (b) Thin-layer evaporator with rigid wiper blades (Luwa Co., Switzerland), (c) The Liprotherm rotating thin film evaporator, for performance intermediate to those of film evaporators and molecular stills (Sibtec Co., Stockholm), (d) Centrifugal molecular still [Hickman, Ind. Eng. Chem. 39, 686 (1947)].

Molecular Distillation. The pentane extract from the Athabasca sands and the other oils without any treatment were distilled in an Arthur F. Smith molecular still at pressure ranges of 75-250/ and tem-... 

Distillation from a brush-type molecular still separated the isolated lignins into three fractions containing alkyl-substituted monomeric phenols in the most volatile fraction, a mixture of monomeric phenolic alcohols and alkyl-substituted dimeric phenols in the intermediate fraction, and nonvolatiles which presumably contained dimeric phenolic alcohols and higher molecular weight material. Unfortunately, separation of monomeric alcohols and alkyl-sbustituted dimers was not complete, and this greatly hampered separation of the alkyl-substituted dimers in later chromatographic separations. 

P. Ridgeway Watt (1963). Molecular Stills. London Chapman Hall. 

Distillations. The upgraded coal liquids were distilled with a metal-mesh-spinning-band still under the conditions shown in Figure 1 to produce cuts at 200°, 325°, and 425° C. Asphaltenes were then precipitated from each >425° C residuum dissolved in benzene by addition of 50 volumes of normal pentane (15). Further distillations on the asphaltene-free materials, at 202° C and 4 micron pressure using a wiped-wall molecular still, produced 425° to 540° C distillate cuts and residua fractions. 

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