Page 445 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

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250 Pulp and Paper

to make cellulosic products such as rayon, cellulose or any other allied product mentioned above, is a term
acetate, and nitrocellulose. These pulps are high alpha- used to describe pulp after a reconsolidation into sheet or
cellulose pulps containing a minimum of hemicellu- board form has occurred.
loses, lignin, and extractives depending on grade.
Fourdrinier screen (or wire) Endless belt woven of wire
suitable for use on the fourdrinier machine on which I. INTRODUCTION
pulp fibers are felted into paper or paperboard.
Furnish This is the mixture, and proportion thereof, of Pulp and paper refers to the processes employed to con-
fibrous and other materials being conditioned or pre- vert wood fiber into paper and allied products used in such
pared for the paper machine. It is also to refer to the applicationsas communications,packaging,and construc-
materials being put together. tion. Pulp and paper technologies or processes capitalize
Hemicellulose Group of carbohydrates found in the cell upon the anatomical, physical, and chemical properties
wall in more or less intimate contact with cellulose. of wood and, to a much lesser extent, other sources of
The hemicelluloses are more soluble than cellulose and biomass. The application of those technologies or pro-
much more readily hydrolyzed into sugars. cesses has led to the development of a highly capital in-
Holocellulose Total carbohydrate fraction of wood re- tensive industry with worldwide sales on the order of $100
maining after the removal of lignin and solvent ex- billion per year.
tractable substances.
Lignin One of the principal constituents of woody cell A. Dimensions of the Pulp and Paper Industry
walls, whose exact chemical composition is still un-
known. In general lignin is aromatic or hydroaromatic The U.S. pulp and paper industry produces almost 100
in nature containing phenyl–propane units and lacking million tonnes (metric tons) of paper annually. The pa-
fused polycyclic hydrocarbons such as napthalene or per finds its way into a wide variety of products including
anthracene. Lignin is sometimes considered to be the newsprint, tissue, printing and writing papers, unbleached
“glue” holding wood fibers together. kraft paper, bleached boxboard, unbleached kraft liner-
Paperboard One of the two broad subdivisions of paper board, corrugating medium, recycled paperboard, and nu-
(general term), the other being paper (specific term). merous other commodities. These paper products compete
The distinction between paperboard and paper is not with plastics in the packaging of consumer goods from
sharp but broadly speaking, paperboard is heavier in eggs to milk. They are also used in sanitary applications
basis weight, thicker, and more rigid than paper. In where disposability is highly desirable.
general, all sheets thicker than .012 in. are classified as The production of millions of tons of paper annually
paperboard. requires a capital intensive industry. A modern pulp and
Paper machine Machine on which paper or paperboard paper facility such as the Leaf River Mill shown in Fig. 1
is manufactured. The most common type is the four- can cost in excess of $800 million to construct. Pulp
drinier machine using the fourdrinier wire as a felting and paper manufacturing throughout the world is a vast
medium for the fibers. industry, with production levels approaching 300 mil-
Tear strength (tearing resistance) Force required to tear lion tonnes/year. The dominant pulp and paper produc-
a specimen under standardized conditions. The tearing ing countries include: Canada, Sweden, Finland, Japan,
resistance in grams (per sheet) multiplied by 100 and Brazil, and Russia. The pulp and paper industry is typi-
divided by the basis weight in grams per square meter cally located near convenient, low-cost sources of wood
equals the tear factor. as the raw material.
Wet strength Strength of a specimen of paper after it has
been wetted with water under specified conditions.
B. Historical Development of the Pulp
and Paper Industry

THE TERM PULPisusedtodescribetherawmaterialfor Paper has been produced since the dawn of civilization.
the production of paper and allied products such as paper- Raw material for early papers included old paper (recy-
board, fiberboard, and dissolving pulp for the subsequent cling), rags, and cotton linters. During the last half of the
manufacture of rayon, cellulose acetate, and other cel- 19th century and the first half of the 20th century, how-
lulose products. More specifically, pulp is wood or other ever, a series of inventions occurred that revolutionized
biomassmaterialthathasundergonesomedegreeofchem- the pulp and paper industry. These innovations are shown
ical or mechanical action to free the fibers either individu- in Table I, and are reviewed in detail elsewhere. These
ally or as fiber bundles from an enbodying matrix. Paper, developments made wood the desirable raw material