The History of Papermaking
The history of papermaking can be traced back to about ad 105, when Ts’ai-Loun created a sheet of paper using old rags and plant tissues. In its slow travel westwards, the art of papermaking reached Arabia in the middle of the eighth century, from where it entered Europe via Spain in the 11th century. By the 14th century, a
number of paper mills existed in Europe, particularly in Spain, France, and Germany. For centuries, paper had been made from linen, hemp and cotton rags. After cleaning, sorting and cutting, these were boiled with potash or soda ash to remove the remaining dirt and color. The operation was continued in a “breaking engine” by adding fresh water until the cloth was separated into single fibers.
Ts’ai Loun (Cai Lun)
Until the paper machine was constructed in 1799 by Louis-Nicholas Robert, the final sheet-formation process was carried out manually.
Throughout the 18th century the papermaking process remained essentially unchanged, with linen and cotton rags furnishing the basic fiber source. However, the increasing demand for paper during the first half of the 19th century could no longer be satisfied by the waste from the textile industry.
“paper machine” “Louis-Nicholas Robert”
Friedrich Gottlob Keller
Thus, it was evident that a process for utilizing a more abundant material was needed. Consequently, major efforts were undertaken to find alternative supplies for making pulp. As a result, both mechanical and chemical methods were developed for the efficient production of paper from wood. Mechanical wood pulping was initiated in 1840 by the German Friedrich Gottlob Keller.
The wood-pulp grinding machine was first commercialized in Germany in 1852 (Heidenheim) on the basis of an improved technology developed by Voelter and Voith. However, mechanical pulping did not come into extensive use until about 1870 when the process was modified by a steam pretreatment which softens the inter-fiber lignin.
Paper made from mechanical wood pulp contains all the components of wood and thus is not suitable for papers in which high brightness, strength, and permanence are required. The clear deficiencies compared to paper made from cotton rags made it necessary to strengthen the development of chemical wood pulping processes, focusing on the removal of accessorial wood components such as lignin and extractives.
The first chemical pulping process was the soda process, so-named because it uses caustic soda as the cooking agent. This process was developed in 1851 by Hugh Burgess and Charles Watt in England, who secured an American patent in 1854. A year later, the first commercial soda mill using poplar as raw material was built on the Schuylkill River near Philadelphia under the direction of Burgess, who served as manager of the mill for almost 40 years. Because this process consumed relatively large quantities of soda, papermakers devised methods for recovering soda from the spent cooking liquor through evaporation and combustion of the waste liquor and recausticizing of the sodium carbonate formed.
To compensate for the losses, sodium carbonate had to be added to the causticizing unit.Since the preparation of sodium carbonate from sodium sulfate was rather expensive by using the Leblanc process, Carl Dahl in Danzig tried to introduce sodium sulfate directly in place of soda ash in a soda pulping recovery system. This substitution produced a cooking liquor that contained sodium sulfide along with caustic soda. Fortunately, the pulp so produced was stronger than soda pulp and was called “Kraft” pulp, so named from the Swedish word for “strong”. The process, which was patented in 1884 by Dahl, has also been termed the sulfate process because of the use of sodium sulfate (salt cake) in the chemical make-up. As a consequence, many soda mills were converted to Kraft mills because of the greater strength of the pulp. Kraft pulp, however, was dark in color and difficult to bleach compared to the competing sulfite pulp. Thus, for many years the growth of the process was slow because of its limitation to papers for which color and brightness were unimportant. With the development of the Tomlinson [7,8] combustion furnace in the early 1930s, and with the discovery of new bleaching techniques, par ticularly using sodium chlorite (1930) and later chlorine dioxide (1946), bleached Kraft became commercially important. The availability of pulp of high brightness and high strength and the expanding demand for unbleached Kraft in packaging resulted in rapid growth of the process, making Kraft the predominant wood-pulping method.
In 1857, shortly after the discovery of the soda pulping process, Benjamin Tilghman, a US chemist, invented acid sulfite pulping. In 1867, the US patent was granted to Tilghman on the acid sulfite cooking process, using solutions of sulfur dioxide and hydrogen sulfite ions at elevated temperature and pressure. Tilghman observed that the presence of a base such as calcium (to form hydrogen sulfite ions) was important in preventing the formation of burned or discolored pulp.
His invention, however, did not result in commercial use due to severe technical difficulties (leakages, etc.), although the product he obtained was satisfactory.
In 1870, Fry and Ekman in Sweden carried these studies further and their improved process, which came into use in 1874, used rotary digesters and indirect heating to produce magnesium-based sulfite pulp. This process was applied in the first American mill, the Richmond Paper Co., built in 1882 at East Providence, Rhode Island, with a capacity of about 15 tons of book and newsprint per day.
Immediately after the German/French war of 1870/1871, Alexander Mitscherlich began to work on the development of calcium hydrogen sulfite cooking with an excess of dissolved sulfur dioxide. The process was characterized by its low temperature (ca. 110 °C), low pressure and long retention time, thus producing rather strong fibers. Heating was carried out indirectly by means of steam in copper coils within the digester. The German sulfite pulping industry was built 1880 on the basis of the Mitscherlich process. In 1887, the first commercially successful sulfite mill in America was built by G. N. Fletcher in Alpena, Michigan. This mill continued in active production until 1940. Between 1878 and 1882, the Austrians Ritter and Kellner developed an acid calcium-based hydrogen sulfite process using upright digesters with direct steaming.
The time of cooking was considerably reduced by applying high temperature and high pressure (“quick cook” process). The patent rights for the Ritter–Kellner process which covered the digester, the method of making the acid cooking liquor, and all features of the system were acquired about 1886 by the American Sulfite Pulp Co. Following the introduction of the upright digesters, progress was rapid and sulfite pulping became the leading cooking process using spruce and fir as the preferred species. The good bleachability and low costs of the applied chemicals were the main reasons for the advantage over the soda and kraft processes. In 1925, the total production of chemical wood pulp showed a distribution of 20% soda, 20% kraft and 60% unbleached and bleached sulfite pulps. While for sulfite pulp manufacture, a single-stage treatment of pulp at low consistency, using calcium hypochlorite satisfied most requirements, this simple bleaching treatment was not practical for kraft that is difficult to bleach, nor can it retain maximum strength.
