SOLVENT SPINNING

Polyimides for use ia molded products and high temperature films can be produced by the reaction of pyromelHtic dianhydride [89-32-7] and 4,4 -diaminodiphenyl ether [13174-32-8] ia DMAC to form a polyamide that can be converted iato a polyimide (13). DMAC can also be used as a spinning solvent for polyimides. AdditionaUy, polymers containing over 50% vinyHdene chloride are soluble up to 20% at elevated temperatures ia DMAC. Such solutions are useful ia preparing fibers (14). 

Stabilizers, pigments, and other additives are milled in spinning solvent, normally along with small amounts of the urethane polymer to improve dispersion stabiUty this dispersion is then blended to the desired concentration with polymer solution after chain extension. Most producers combine prepolymerization, chain extension, and additive addition and blending into a single integrated continuous production line. 

Water is continuously added to the last extraction bath and flows countercurrenfly to filament travel from bath to bath. Maximum solvent concentration of 15—30% is reached in the coagulation bath and maintained constant by continuously removing the solvent—water mixture for solvent recovery. Spinning solvent is generally recovered by a two-stage process in which the excess water is initially removed by distillation followed by transfer of cmde solvent to a second column where it is distilled and transferred for reuse in polymer manufacture. 

Polymerization and Spinning Solvent. Dimethyl sulfoxide is used as a solvent for the polymerization of acrylonitrile and other vinyl monomers, eg, methyl methacrylate and styrene (82,83). The low incidence of transfer from the growing chain to DMSO leads to high molecular weights. Copolymerization reactions of acrylonitrile with other vinyl monomers are also mn in DMSO. Monomer mixtures of acrylonitrile, styrene, vinyUdene chloride, methallylsulfonic acid, styrenesulfonic acid, etc, are polymerized in DMSO—water (84). In some cases, the fibers are spun from the reaction solutions into DMSO—water baths. 

Uses. The largest use for sodium thiocyanate is as the 50—60 wt % aqueous solution, as a component of the spinning solvent for acryUc fibers (see Fibers, acrylic Acrylonitrile polymers). Other textile appHcations are as a fiber swelling agent and as a dyeing and printing assist. A newer commercial use for sodium thiocyanate is as an additive to cement in order to impart early strength to concrete (376). 

Table I describes the resins that were evaluated. Films of the resins were applied to topographic substrates by spin coating from concentrated solutions of the resins in volatile spinning solvents using a Headway Research Model EC101 spin coater. After 2 minutes of spinning the coated substrates were transferred to a hot plate for baking. The temperature of the hotplate was measured with a surface thermometer.

The wavelength range for which each polymer undergoes photodimerization, the wavelength at which each polymer displays maximal sensitivity, and the sensitivity (E the minimum incident input energy per unit area required to produce an insolubilized film of the same thickness as the the initial film) are listed in Table I. Polymer sensitivities were determined for the wavelength where each polymer displays maximum sensitivity. All formulations employed the same spinning solvent and the same developer. 

Use Chemicals (methyl isobutyl ketone methyl isobutyl carbinol methyl methacrylate bisphenol-A) paint, varnish, and lacquer solvent cellulose acetate, especially as spinning solvent to clean and dry parts of precision equipment solvent for potassium iodide and permanganate delusterant for cellulose acetate fibers specification testing of vulcanized rubber products. 

Use Solvent extraction, plasticizer, organic synthesis, natural gas purification, synthetic fiber spinning solvent. 

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