Regenerated Cellulose

Cellulose is used in many forms. Often it is modified chemically to render it soluble in organic solvents. In other modifications, it is treated in a manner that allows forming it into desired shapes, like films or fibers, followed by restoration of its chemically insoluble form. The material is then called regenerated cellulose. Several processes evolved for preparation of regenerated cellulose. One, developed as far back as 1884, converts it first to a nitrate ester. The nitrated material is dissolved in a mixture of ethyl alcohol and diethyl ether and extruded into fibers. The fibers are then denitrated by treatment with ammonium hydrogen sulfide at about 40C. The product is called Chardonnet silk. It appears that this process is no longer practiced anywhere. In another process cellulose is dissolved in ammoniacal cupric hydroxide (Cu (NH₃)₄(OH)₂). The solution is then spun as a fiber into a dilute sulfuric acid solution to regenerate the cellulose. The product is called Cuprammonium rayon.
The material may still be manufactured on a limited scale.. The third, probably major commercial process used today, forms a material that is known as Viscose rayon. The regenerated cellulose is prepared and sold as a fiber as well as a film, known as cellophane. The viscose, or more properly referred to as the xanthate process, consists of forming cellulose xanthate by reacting alkali cellulose with carbon disulfide:

In a typical procedure, cellulose is steeped in an approximately 20% aqueous sodium hydroxide solution at room temperature for anywhere from 20 min to a whole hour. It is believed that this treatment results in formation of sodium alcoholate at every hydroxymethyl group. The resultant material is pressed out to remove excess liquid, shredded, and aged for 2–3 days. The aging is known to cause some molecular weight reduction. After aging, the alkali cellulose is treated with carbon disulfide for 2–4 h to form cellulose xanthate. The amount of xanthate groups in the product average out to one per every two glucose units. The material is dissolved in a dilute sodium hydroxide solution and again aged for 2–5 days. During the aging period, some xanthate groups decompose. The solution is then spun into dilute sulfuric acid to regenerate the cellulose and form fibers:

The rayon fibers are washed, bleached, and submitted to other various treatments, like dyeing, etc., depending upon intended use. When cellulose xanthate is extruded through narrow slits into acid baths, cellophane films form. These films are usually plasticized by washing in baths containing some glycerin.

اخر الاخبار

اخبار العتبة العباسية المقدسة

العتبة العباسية المقدسة تختتم فعاليات حفل التكليف المركزي الثامن بمشاركة أكثر من 6 آلاف تلميذة

من الخيام إلى الفتوى.. عرض مسرحي ضمن فعاليات اليوم الثاني لحفل التكليف

ضمن فعاليات اليوم الثاني من حفل التكليف المركزي الثامن تلميذات مدارس كربلاء يرددن نشيد التكليف

عرض فيلم عن مشروع الورود الفاطمية ضمن فعاليات اليوم الثاني من حفل التكليف المركزي الثامن

المزيد

الآخبار الصحية

عوامل تضعف القدرات الإدراكية لدى الإنسان

طريقة جديدة لتجديد خلايا الدماغ

دراسة بريطانية: الأطعمة النباتية عالية الجودة تقلل خطر فشل القلب

7 أطعمة يومية "تسمم" جسمك بالبلاستيك دون أن تشعر

المزيد

الآخبار التكنلوجية

اكتشاف أثري في أوريغون الأمريكية قد يعيد كتابة تاريخ البشرية

اكتشاف كائن بحري مدرع بلسان "حديدي" في بحر اليابان

نظام كوكبي "مقلوب" يحير علماء الفلك

بسبب الذكاء الاصطناعي.. هذه الوظائف "ستختفي" بعد أشهر قليلة ؟!

المزيد

مواضيع ذات صلة

Structures and Chemistry of Proteins

Proteins

Polyisoprene

Lignin

Derivatives of Cellulose

Cellulose

Starch

Hemicelluloses

Dendrimers and Hyperbranched Polymers

Poly (arylene ether) s and Poly (arylene ether ketone) s

Double-Stranded Polymers

Cardo Polymers