Carbide Unveils Vinyon Ν Plant A STAFF REPORT
V,
IN YON N, a promising s y n t h e t i c tex tile material, is now being produced b y Carbide and Carbon Chemicals Corp. in pilot plant quantities at a new d e m o n s t r a tion plant at Charleston, W. Va. T h e new fibers, consisting of a vinyl chloride-acrylunitrile copolymer, were de veloped during 1 he search for an improve m e n t over vinyl chloride-acetate .fibers. According to t h e company, Vinyon Ν h a s excellent properties, a m o n g which are high s t r e n g t h and toughness, nonilammahility, exceptional chemical resistance, negligible w a t e r absorption, and i m m a n i t y t o rot a n d mildew. T h e manufacturing process for the newfibers s t a r t s at t h e resin p l a n t , where vinyl chloride a n d acrylonitrile a r e copolymerized by an emulsion process similar t o o t h e r s involving vinyl chloride. Since the copolymerization ratio i s high in favor of acrylonitrile, it is necessary to feed acry lonitrile continuously d u r i n g t h e reaction in order to obtain resins of the degree of compositional uniformity required for fiber applications. Stainless steel or glass-line equipment is used t o avoid a metallic-contamination effect'on the color a n d color stability of the 3 7 arn, a n d t h e process is carried out with special regard for t h e resin's heat r e a c t i v i t y . T h e resin emerges from t h e polymerization unit in t h e form of a fine powder a n d c a n be con v e r t e d into a coherent, resinous mass with a density of approximately 1.30 byr fluxing on h e a t e d rolls a t 180 ° C. P o r t h e Vinyon Ν fibers t h e copolymer resin at t h e present t i m e contains 56 to 6 0 % of vinyl chloride a n d h a s a specific viscosity* (as measured In a 0 . 2 % cyclohexanone solution) of 0.25 to 0.3. T h e Vinyon Ν resin, which is made at t h e company's main C h a r l e s t o n plant, is
sent t o t h e new y a r n development building in 50-lb. p a p e r bags. Here, on t h e third floor, t h e bags are checkweighed a n d emptied into a conical-bottom hopper lo cated a b o v e t h e mixer. I n order to ensure uniformity, each batch is m a d e up by using bags from several blends. T h e next s t e p is the a c t u a l mixing of the " d o p e . " Resin from the hopper, ace tone from a second-floor weigh t a n k , a n d a small a m o u n t of stabilizer a r c added at room t e m p e r a t u r e to a mixer of t h e Pfieiderer t y p e on t h e first floor. T h e t e m p e r a ture is gradually raised while t h e dough like mix is agitated u n d e r a nitrogen a t mosphere. After a period of t i m e at the proper t e m p e r a t u r e , the solids content of the dope is checked and adjusted b y adding acetone. After t h e dope is mixed, it is transferred through a strainer, which removes foreign m a t t e r a n d gels of p a r t i a l l y dissolved resin, into a receiving t a n k on t h e first floor. F r o m t h i s t a n k t h e dope passes through t w o p l a t e and frame filter presses, where it is clarified by t h e r e m o v a l of mi nute suspended m a t t e r , a n d is t h e n p u m p e d t o a feed t a n k on t h e second floor. T h e filter presses are of stainless steel with p l a t e s cored for hot water. P a p e r has been found t o be the m o s t s u i t a b l e filter medium for this process. T h r o u g h t h e system, dope t e m p e r a t u r e s are m a i n t a i n e d between 75 ° a n d 90 ° C. as the fluidity of Vinyon N - a c e t o n e solutions is g r e a t l y enhanced a t elevated tempera tures, especially a t the concentrations of over 2 0 % solids which are used in this process. From, t h e feed t a n k t h e copolymer-aeetone d o p e is circulated t h r o u g h the spin ning machine header with from five t o ten times as m u c h being circulated back t o t h e
T. A. Feild, E. W. Rug&ley9 and George H. Fremon Carbide and Carbon Chemicals Corp. all took part
746
of in
the the
original development J. R. Kernan and
C H E M I C A L
t a n k as is consumed in spinning. The spinning machine has 56 spinning cells arranged in t w o b a n k s of 2S each. Each cell is fed an accurately controlled a m o u n t of dope through a gear p u m p takeoff on t h e main header. T h e filaments are formed by e x t r u d i n g the dope downward through the spinneret te a t t h e t o p of the cell and evaporating the acetone solvent into a hot a i r stream which t r a v e l s up ward through t h e cell. Vinj'on Ν spinning a p p a r a t u s differs from normal rayon dry spinning because of the acetone removal operation a n d the size of the 3'arn. Individual Vinyon Ν filaments are about 10 denier in size while t h e Vinyon filament m a y be 370 denier. T h e acetone removal necessitates a n un usually long cell, about 20 feet, a n d re quires temperature control of b o t h the drying air a n d the cell-jacket. As the filaments leave the b o t t o m of each cell, t h e y are gathered t o g e t h e r and lubricated in an oil-in-water emulsion be fore being wrapped a r o u n d a pair of godet wheels, whose speed determines t h e yarn take-up rate. F r o m the godets t h e yarn travels down, onto a bobbin, over a con ventional c a p type take-up device which puts ahout one t u r n per inch twist into the group of filaments, which a r e t h u s con verted into a thread of yarn. This spun yarn has relatively little strength, as t h e long chain molecules are scattered in all directions in t h e filament. T o obtain t h e desired s t r e n g t h , t h e yarn is stretched t o orient the molecules along the length of the y a r n . T h i s operation naturally reduces t h e denier of the yarn, sc t h a t by plying various numbers of yarn ends together and v a r y i n g t h e a m o u n t of stretch, a w i d e range of deniers m a y be ob tained. In t h e stretching o p e r a t i o n the of the new synthetic J. M. Stualm of the
AND
material. Charleston
ENGINEERING
Right. plant
NEWS
y a r n is fed off slow speed godets into a s t e a m t u b e , where the actual stretching takes place. It i« then taken u p on godets which r o t a t e at high speed to provide the tension which stretches the yarn. For one type of yarn a five-ply 370 denier spun y a r n is stretched
