Cellophane is Born (May, 1938)
Cellophane is Born
By A. P. PECK
1. From forest giant to Cellophane is a long stride made possible by chemical research. For the manufacture of Cellophane, the Du Pont Company buys wood pulp—purified cellulose—in square sheets, soaks them in a caustic soda solution (above); the result is “alkali cellulose”.
2. Damp alkali cellulose is shredded into small fluffy particles, aged for two to three days in order that later steps in production may be carried out successfully. Above: Unloading ground-up chemically treated cellulose from shredder.
3. Aged alkali cellulose is treated with carbon disulfide, result of the reaction being cellulose xanthate. This compound, dissolved in caustic soda, becomes viscose, which in turn is aged or ripened in battery of tanks shown above.
4 Viscose ripened under controlled conditions, checked to insure uniformity, is filtered and re-filtered to remove all solid particles. Ripened viscose emerges from a narrow slot in a casting machine as a thin, weak sheet (right), is treated with dilute sulfuric acid and sodium sulfate.
5. Viscose regenerated in one or more acid baths becomes cellulose again, gains strength in sheet form. After several washing and bleaching operations to remove all chemicals, the sheet passes through a glycerin and water bath and through heavy squeeze rolls (above). In the last bath the film absorbs enough glycerin to keep it pliable.
6. If colored Cellophane is being produced, the sheet is dyed before the glycerin bath. Above: The finished Cellophane film being wound on large cores. Winding was proceeding at full speed when photograph was taken. The next step is cutting the finished film to length.
7. Rolls of Cellophane are run off onto huge drums (below) and then cut to length. Moisture-proof Cellophane is produced by passing a moist film through a moisture-proofing solution and drying. Both sides of the Cellophane are so treated simultaneously.
8 Cellophane wrapped in Cellophane (below), to protect the rolls from moisture. The film may be embossed between pressure rolls in any desired design.
9. Keen-eyed girls (right) are employed to assort and inspect sheets of Cellophane, cut from long strips made by the process described, at the Richmond, Virginia, plant of E. I. du Pont de Nemours and Company. Cellophane film is usually made about .0009 or .0013 of an inch thick, some being made .0018 of an inch thick. Thicker sheets than this are made by cementing several thin sheets together, since it is difficult in production to make a single sheet thicker than .0018 of an inch.