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Chemical Properties Nylon in the form of yarn, or otherwise, is difficultly soluble in most reagents. Phenols and formic acid are active solvents, but all the common dry cleaning solvents are without effect. While the resistance of nylon to mineral acids is not remarkable, i t is quite resistant to alkalies even in fairly concentrated solutions and a t elevated temperatures (Figure 9). Nylon yarn and fabrics are practically nonflammable. Nylon has been exhaustively tested for physiological activity. It is completely inert and has found use in the form of surgical sutures. It is resistant to enzymes, mildew, molds, and moths. While nylon shows affinity for a great many classes of dyestuffs, the best results to date have been obtained with the so-called acetate colors which were developed for the dyeing of cellulose acetate yarns AUTOCLAVESIN THE DU PONTNYLONPLANT,WHEREPOLYMERIZATION TAKESPLACE and fabrics. There is an infinite number of possible nylons, differing widely in and the moisture in the form of steam. These operations on their physical pro; ties . Nylon yarn as currently offered the natural fibers are much more easily reversible than has a high melting lint, 253” C. (487” F.). with nylon. A brief shower or even the heat and moisture Literature Cited of the body will remove creases from the best of suiting materials. (1) Astbury, W. T., Science Progress, 28, 210 (1933). The use of this setting treatment before dyeing adds to the (2) Marston and Barker, “Wool Quality”, p. 211, London, H. M. Stationery Office, 1931. beauty and clarity of stitch characteristic of nylon hosiery. (3) MeYer and Mark, “Der Aufbau der hochPolYmeren organisohen It possesses general application 60 that any woven or knitted Naturstoffe”, p. 92, Leipsig, Akademische Verlagsgesellnylon fabric can have its physical form established by an schaft. 1930. appropriate setting treatment. (4) Wilson and Fuwa, IND.ENG.CHEM.,1 4 , 913 (1922).
Vinyon FREDERIC BONNET American Viscose Corporation, Marcus Hook, Penna.
INYON is the new textile fiber made from an unplasticized vinyl resin which is a copolymer of vinyl chloride and vinyl acetate. S. D. Douglas1pointed out that these resins are prepared by polymerization rather than by a condensation reaction, as is the case with the phenolic, urea, and alkyd types. Moreover, the resulting molecular structure of these vinyl polymers is linear or straight chain, in which the monomers have reacted with one another a t the double bond to give high-molecular-weight molecules. Such a straight-chain structure seems to be most important if the resin is to find use as a textile fiber; and the longer the straight chain (i. e., the larger the molecules of the polymer), the stronger and more resilient will be the resulting fibers and textile yarns. This is also exemplified by the polyamide nylon which is a long straight-chain com1
IND.ENQ.CHBM., Sa, 315 (1940).
pound and, like “Vinyon”, must be stretched to give a serviceable yarn. Although “Vinyon” is made from vinyl chloride and vinyl acetate, it must not be assumed that it is a mere mixture of the two. Mixtures of the chloride and acetate polymers even when most thoroughly and carefully blended give only weak and indifferent results of little or no industrial interest. When, however, the monomers are mixed so that they m a y be copolymerized-i. e., polymerized together-a whole series of resins result whose properties depend not only upon the initial mixture of the monomers but also upon the degree of polymerization which has been allowed to take place. It is the degree of polymerization which determines the molecular weight or the length of the straight-chain molecules. This copolymerization is interesting in that the vinyl acetate seems to plasticize the vinyl chloride internally, a n d
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INDUSTRIAL AND ENGINEERIRG CHEMISTRY
ACETATE RAYON PLANTOF AMERICANVISCOSECORPORATION AT MEADVILLE,PENNA., WHEREVINYONIs h’ow
PRODUCTION
Vinyon is a copolymerized vinyl resin made of vinyl chloride and vinyl acetate. The vinyl acetate internally plasticizes the chloride, making the resin stable. The polymerization takes place a t the double bond and gives a straight-chain linkage which is important for a resin textile. The copolymer is dissolved in acetone and spun in air as is cellulose acetate. The spun yarn is not sirong but, after stretching several hundred per cent, may attain a strength of 80,000 pounds per square inch. The yarn is very resistant to strong acids and alkalies a t ordinary temperatures. It is practically water repellent and is as strong wet as it is dry. It can be dyed. It is thermoplastic, and shrinkage takes place if heated ahove 65’ C. Largest use a t present is in industrial filter cloth, hut many other uses are suggested by its remarkable properties.
no other plasticizer is necessary. The ordinary type of external plasticizers are high-boiling liquids, waxes, gnms, etc., and with many resins such plasticizers are still necessary; but resins so plasticized are always subject to a change in composition owing to a loss of plasticizer by evaporation, oxidation, or solvent extraction. In the case of these vinyl resins, where the polymers are actnally cornbined, such changes cannot take place, and the resins are stable, wliich is most important for a textile fiber. The resin used for “Vinyon” contains 55-90 per cent vinyl chloride and 12-10 per cent vinyl acetate with a molecnlar weight around 20,000.
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Spinning The copolymer resin, as a white Ruffy powder, is dissolved in acetone to get a rather heavy, viscous spinning dope containing about 25 per cent by weight of the resin in solution. This is filtered, deaerated, and spun downward in air through multiholed stainless-steel jets, jnst as is done in acetate spinning, the solvent acetone being removed by a current of warm air and recovered. After being conditioned on the take-up bobbin, the yarn is stretched either directly or after being plied with one or more ends. This stretching operation is of great importance in producing a serviceable yarn of good strength, extensibility, elasticity, and resiliency. For high strength the yarn is stretched several hundred per cent; for lower strengths but
OVERHEAD VIEW
OF MIXER USED I N VIYYUN
PhVUFhCIURE
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brittle or in any way lower in quality. For example, a yarn with 10 filaments but only 8 denier in size has filaments much finer than silk, yet such a yarn is strong enough to be knit on a regular circular stocking machine.
greater softness and more extensibility the stretching is correspondingly less. After stretching, the yarn is set by heating, while under tension, to about 9+100” C . This treatment makes the yarn stable as to shrinkage up to a t least 65” C., but when heated above this temperature, shrinkage of the yarn occuw with a corresponding reduction in tenacity and increase in elongation. This shrinkage is quite definite for the temperature to which i t may be subjected; e. g., a t 75” C . there is a shrinkage of about 12 per cent, a t 80” C. there is further shrinkage with a teltdency for the filaments to adhere to one another, while a t 155-140” C. definite tackiness develops. The yarn &s spun has comparatively large filaments which, in the stretching process, become smaller. In fact they can be reduced to gossamer fineness without the yarn becoming
Properties “Yinyon” yarn is definitely thermoplastic so that ii heated above 65’ C. it will shrink. Mineral acids and alkalies do not a t h c k i t a t room temperature, even in high concentrations. Thus 70 per cent nitric acid, aqua regia, hydrochloric and hydrofluoric acids a t maximum concentration do not affect it, nor do 30 per cent sodium hydroxide, 28 per cent ammonium hydroxide, salt solutions, or even copper ammonia solution, which is soeffeotive in dissolving cellulose. It is also unaffected by alcohols, glycols, or aliphatic hydrocarbans (gasoline, mineral oils, etc.). On the other hand, i t is dissolved by ketones, and softened or partly dissolved by esters, certain halogenated hydrocarbons, ethers, certain anlines, and aromatic hydrocarbons. “Vinyon” is unaffected by water; in fact,, it may be considered water repellent althonghits suriace may be wetted by using some of the commercial wetting agents. Neither bacteria, molds, nor other fungi grow on its surface so it is not subject t o so-called mildew of any kind; therefore i t should find use in damp climates. The yarn is not flammable nor will i t support combustion. When heated in a flame i t melts and then chars, but i t will not burn. The tenacity can be controlled within a range of 1 to 4 grams per denier, the higher strength having the lower extensibility and vice yersa. One to four grams per denier is roughly equivalent to 20,000 t o 80,000 pounds per square inch. Because it i s unaffected by water, this new yarn shows the same tenacity and elongation, bot6 dry and wet,. For comparison the following table shows the tenacity and elongation of various fibers:
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The largest use of “Vinyon” a t present is in the manufacture of industrial filter cloth because of its unusual properties, particularly its resistance to chemicals either acid or alkali, and its high strength both wet and dry. The weaving of the cloth offers no special difficulty; a gelatin size with an ordinary softener is suitable for warping, but weaving should he done a t high humidity t o avoid the production of static as much as possible. Some successful trials have recently been made with “Vinyon” fish nets and lines along the Florida coast. Not onlydid the Cnoss (left) AND LONGITUDINAL VIEWS OF VINYON( X 300) “Vinyon” nets catch twice as many fish as did the ordinary tarimpregnated cotton nets, but in a 6-month test they gave no sign of detenoration, whereas all the other types tested a t the Dry (Relative tiumidity. same time showed partial or complete disintegration. wet66%)Yarn Tenacity Elongation %enaoity Elongstion Other suggested uses, some of which are rapidly developG /denP e ant G/daw Pa cent h g , are for shower curtains, bathing suits, waterproof acidSilk (degummed) 4 22 16 3 4 26 3 and alkali-resistant clothing, full-fashioned. hosiery, fireVlsCOSe 2 00 18 1 0 25 Acetate 1 40 27 0 85 38 proof awnings, curtains, sailcloth, umbrella fabrics, tent and Vl”Y”n” tarpaulin materials, shoo Linings, braids, and various knit Hlgh-etretch .. .. 4 00 1s Medwmstreteh 2 30 25 fabrics, etc. However, in commeicially developing these Uoatretrhed .. 100 120 various uses, a policy of careful test and experimentation is being followed so that the new tcxtile shall be used only for such purposes and under such conditions as are ivarranted by The ordinary yarn is bright but, as with aoetate or Visoose, it may be dulled by incorporating pigments in the spinning i t s special properties. dope. Its specific gravlty is about the same as acetate or wool-namely, 1.34 to 1.36. It does not conduct electricity and, &s water does not affect it, is an excellent insulator which easily develops and retains a static charge. Its flexing strength and its stability to the action of sunlight are excellent. It has true elasticity. Aside from coloring the “Vinyon” by adding pigments t o the spinning dope, dyeing of the fibers or fabric seemed a t first to offer great difficulties because of the low dyeing temperature required and because it was so inert to water. However, investigation soon showed that “Vinyon” codd be dyed with water-insoluble acetate rayon dyestuffs in the presence of small m o u n t s of certain solid organic chemicalsfor example, c-hydroxydiphenyl-termed “assistants”. The ordinary amount of dyestuff can be used (e. g., 2 per cent) which in the presence of the assistant is satisfactorily exhausted. The choice of assistant is, however, quite important because it influencesthe fastness property of the dyestuff.
.. I .
Usee Small amounts id “Vlnyon” staple have been successfully used m makmr! cotton. wool, and glass felts; the ther&oplastic resin functions as a binder which not only gives added strength but shortens the time of manufacture.
STEPS I-Y THE MANUFACTURE OF I‘irryo~ (2) mixer; (3) filter press: (4) insulated piping, indicating the importance of dose temperature control in (1) Vinylite resin as it arrives at the plant;
Vinyoii fiber produotion.
