Chemical processes

Paper  is a thin material produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. Paper is a versatile material with many uses. Whilst the most common is for writing and printing upon, it is also widely used as a packaging material, in many cleaning products, in a number of industrial and construction processes, and even as a food ingredient – particularly in Asian cultures.

Paper, and the pulp papermaking process, was said to be developed in China during the early 2nd century AD, possibly as early as the year 105 A. D. , by the Han court eunuch Cai Lun, although the earliest archaeological fragments of paper derive from the 2nd century BC in China. Paper spread from China through the Middle East to medieval Europe in the 13th century, where the first water-powered paper mills were built. [3] In the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts.

In 1844, Canadian inventor Charles Fenerty and German F. G. Keller independently developed processes for pulping wood fibers. The oldest known archaeological fragments of the immediate precursor to modern paper date to 2nd century BC in China. The pulp papermaking process is ascribed to Cai Lun, a 2nd-century AD Han court eunuch. With paper an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age. ————————————————- Etymology

The word “paper” is etymologically derived from Latin papyrus, which comes from the Greek(papuros), the word for the Cyperus papyrus plant. Papyrus is a thick, paper-like material produced from the pith of the Cyperus papyrus plant which was used in ancient Egypt and otherMediterranean cultures for writing before the introduction of paper into the Middle East and Europe. Papyrus is a “lamination of natural plants, while paper is manufactured from fibres whose properties have been changed by maceration or disintegration ———————————————— Papermaking Chemical pulping: To make pulp from wood, a chemical pulping process  separates  lignin  from cellulose fibers. This is accomplished by dissolving lignin in a cooking liquor, so that it may be washed from thecellulose fibers. This preserves the length of the cellulose fibers. Paper made from chemical pulps are also known as wood-free papers–not to be confused with tree-free paper. This is because they do not contain lignin, which deteriorates over time.

The pulp can also be bleached to produce white paper, but this consumes 5% of the fibers. Chemical pulping processes are not used to make paper made from cotton, which is already 90% cellulose. There are three main chemical pulping processes: * sulfite process *  kraft process *  Soda pulping * sulfite process: The sulfite process dates back to the 1840s, and it was the dominant process before the second world war. * kraft process: The kraft process, invented in the 1870s and first used in the 1890s, is now the most commonly practiced strategy.

One advantage is a chemical reaction with lignin produces heat, which can be used to run a generator. Most pulping operations using the kraft process are net contributors to the electricity grid or use the electricity to run an adjacent paper-mill. Another advantage is the process recovers and reuses all inorganic chemical reagents. *  Soda pulping: Soda pulping is a specialty process used to pulp straws, bagasse, andhardwoods with high silicate content.

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