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Isbn: 3-527-30999-3

©2006 WILEY-VCHVerlag GmbH&Co .

Handbook of Pulp

Edited by Herbert Sixta

1

Introduction

Jьrgen Blechschmidt and Sabine Heinemann

There are two technological principles to produce paper pulp from wood, namely

mechanical processes or chemical processes. Whereas in chemical pulping the

yields are only about 45–55%, mechanical pulping uses about 80–95% of the fiber

wood. Whilst this represents a source for the economic potential of mechanical

pulps, the higher yield results in certain unfavorable properties compared to

chemical pulp. Thus, fromthe sameportion ofwood, a double quantity of mechanical

pulp is produced compared to chemical pulp. The increasing demand for paper and

board has led to a permanent increase in mechanical pulp production (Fig. 1.1).

Fig. 1.1 Worldwide development of mechanical pulp production [1].

Among the total amount of paper pulp produced, mechanical pulp accounts for

about 20%.

Although mechanical pulping is a thermomechanical process, chemical processes

may also play a certain role. The mechanical defibration of wood is carried

out in two different ways (Fig. 1.2), namely as a grinding process or as a refining

process. The following definitions have been formulated for the products of those

processes:

1071

Handbook of Pulp. Edited by Herbert Sixta

Copyright © 2006 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim

Isbn: 3-527-30999-3

_ Mechanical pulp: this is manufactured by mechanical defibration

using a variety of mechanical procedures.

_ Stone groundwood: this is manufactured from round logs in a

grinder.

_ Refiner mechanical pulp: this is manufactured by the mechanical

defibration of wood chips in a disc refiner.

Fig. 1.2 An overview of the basic mechanical pulping procedures.

1072 1 Introduction

1073

2

A Short History of Mechanical Pulping

Jьrgen Blechschmidt and Sabine Heinemann

Along with the development of mankind there has been an ever-increasing

demand for writing materials. It is said that papermaking was invented in China

in the year 105 AD and, after a long journey, the procedure arrived in Europe in

1144 (Spain) and finally in Germany in 1390 (Nuremberg). When Gutenberg

invented letterpress printing in 1445, to replace hand-written books with printed

books, the demand for paper increased immensely. During this evolution, the raw

materials used for paper have ranged from rags to hemp, and from flax and cotton

as well as worn-out hemp ropes.

Up until the end of the eighteenth century, paper was only made by hand, but

in 1799 Nicolas-Louis Robert developed the first papermaking machine in France

(Fig. 2.1).

Fig. 2.1 Papermaking machine, developed in 1799 by N.-L. Robert (1761–1826).

At about in the same time, in 1805, Bramah invented the cylinder machine in

England, and as a result of these inventions paper production was subsequently

increased during the following years. The problem was that this increased production

resulted in an increasing lack of raw materials.

In 1843, the Saxon weaver Friedrich Gottlob Keller (Fig. 2.2) successfully developed

the mechanical defibration of wood to produce groundwood. "Because this

Handbook of Pulp. Edited by Herbert Sixta

Copyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim