Paper sheet-forming process

For production of woodfree uncoated and coated fine papers up to 40 kg starch per ton of paper are applied. 3 to 10 kg starch is added at the wet end, with the aim of internal strength improvement and retention increase. The major share of the starch is added to the sheet in surface treatment. A mass balance on a typical fine paper machine has shown, that more than 90% of the added starch is retained in the final paper product. Losses occur mainly during the sheet forming process in the wire section due to insufficient retention. Starch which is not held back in the paper is discharged with the process effluents to the waste water treatment plant, where a complete biodegradation process follows. 

The retention of fillers in the sheet during the forming process is important. Both hydrodynamic mechanisms and colloidal or coflocculation phenomena are significant in determining filler retention (7). Polymeric retention aids are used to bridge between filler particles and fibers. Talc is sometimes used with mechanical pulp furnishes in order to reduce the deposition of pitch-like materials onto paper machinery. 

The pulp and paper additives enter the process first through a dump chest in their concentrated form. Adjustments are then made to the concentration in the stock chest just prior to transfer onto the Fourdrinier wire where the paper sheet is produced. Surface additives are sprayed after sheet formation and the final sheet is dried at high temperatures in dryers. The water from the wire is removed into underground tanks and in most cases, recirculated and reused. 

Procedure Prepare the chromatogrphic tank by lining the walls with sheets of filter paper pour the mobile-phase into the tank, saturating the filter paper in the process, to a depth of 5 to 10 mm, close the tank and allow it to stand at 20° to 25 °C for 1 hour for equilibration of the mobile-phase in the chromatank. Apply separately to the TLC plate 5 (il of each of two solutions (1) and (2) of apomorphine hydrochloride and (3) of morphine in the form of circular spots about 2 to 6 mm in diameter, and 15 to 20 mm from one end of the plate and not nearer than 10 mm to the sides the two spots must be at least 10 mm apart. Mark the sides of the plate 15 cm from the line of application. Allow the solvent to evaporate and place in the chromatank,... 

Chemists are heavily involved in the manufacture of our currency. In fact, in a very real way, the money industry depends on chemistry and finding substances with the correct properties. The most common paper currency in the United States is the dollar bill. Chemistry is used to form the ink and paper and in processes used to defeat counterfeiters. The ink used on currency has to do a variety of things. It must be just the right consistency to fill the fine lines of the printing plate and release onto the paper without smearing. The ink must dry almost immediately, since the sheets of currency fly out of the press and into stacks 10,000 sheets tall. The pressure at the bottom of the stack is large, and the ink must not stick to the back of the sheet above it. 

Cellophanes. Cellophane looks and acts like a hydrocarbon-based plastic material, but is not one. The viscose process is used to extract cellulose as cellulose xanthate, which is then treated and processed to regenerate the cellulose as Rayon, a material used extensively as fibers. The same material, however, can be made in sheet form, in which it is essentially a modified cellulose paper. 

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