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paper,thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The term also includes various types of paperboardpaperboard,
material similiar in shape and composition to paper, but generally thicker, stronger, and more rigid. Paper machines, e.g., Fourdrinier machines, are used to make sheets of paperboard.
..... Click the link for more information. , such as cardboard and wallboard.
The Formulation of Paper
A quarter to a third of most new paper is made from waste paper. The body of paper is made up of matted cellulose fibers—since c.1860 derived principally from wood. Rags, mostly cotton cuttings from textile and garment factories, are used to make fine stationery and for such purposes as cigarette paper. For other special papers, or where wood is not available, manufacturers may use pressed sugarcane, bamboo, manila rope, cereal straws, esparto grass, or other fibers.
Preparation from Wood Pulp
Most paper is made from wood pulp. Mechanical pulp, or groundwood, prepared by grinding the wood, is used to make newsprint, tissue, towel, and other inexpensive papers. For paper whose whiteness is important, a chemical pulp must be prepared. Lignin, which holds wood fibers together, turns yellow in sunlight and therefore must be removed by alternating treatments with acid and alkaline solutions. The wood pulp, boiled under pressure and treated to dissolve the lignin binder, is thus turned into cellulose fiber. The mixture is then washed and bleached; because the resulting pulp is more than 90% water, the water is usually treated before mixing.
Once the wood pulp has been treated, washed, bleached, screened, and beaten, it is blended to achieve the characteristics required for the intended use. The pulp, suspended in water, is poured over a wire screen in one of two machines that differ mainly in the form of the screen: a belt screen is used in the Fourdrinier machine and a cylindrical one in the cylinder machine. As water drains through the screen, a layer of fibers forms, which in the Fourdrinier is shaken to turn the fibers in different directions so that they mat. A wet felt belt pressed against the screen picks up the paper for feeding through sets of drying rollers. During this stage a rubber roller may be used to imprint a watermark. At the end of the process the paper is passed through a calender (stack of iron rollers), which presses the paper and smooths its surface. Fillers—chiefly clay or starch—are used to improve the printing, texture, and wet and dry strength of paper and to produce other special properties.
Treatment for Special Properties
Book paper is any kind of printing paper except newsprint; in order to prevent rapid deterioration of the paper through a reaction between the acids in the pulp mixture and the humidity in the air, modern book paper is further treated to make it acid-free. For the best reproduction of illustrations, especially halftones, book paper is coated with a layer of mineral pigment, usually clay, mixed with an adhesive. All writing papers are "sized"; i.e., a water-resistant substance such as rosin is added to the pulp to prevent the spreading of writing ink. Hanging paper, or wallpaper, is soft and bulky; it is rosin-sized for water resistance and coated to take a printed design. Bag and wrapping papers are made of kraft paper, the product of the sulfate process, because of its strength.
The Introduction of Paper
Paper is believed to have been invented by Ts'ai Lun c.105 in China, where it reached an advanced state of development. Chinese paper was a mixture of bark and hemp. Papermaking spread to Japan c.610 and to Samarkand c.751, whence it was introduced by the Arabs into Egypt c.900 and by the Moors into Spain at Játiva c.1150. Mills were established in Italy c.1276; in France, c.1348; in Germany, 1390; and in England, 1495. European paper was usually made of flax and hemp. Primitive bark paper had been made in Mexico and Central America in pre-Columbian times. Paper was first produced in the American colonies in 1690 by William Rittenhouse at Germantown.
See J. P. Casey, Pulp and Paper (3d ed., 4 vol., 1983); J. R. Lavigne, Pulp and Paper Dictionary (1986); N. A. Basbanes, On Paper (2013).
a substance made of vegetable fibers appropriately processed and randomly united into a thin sheet, in which the fibers are held together by surface aggregative forces. The materials used to produce paper are cellulose of different types of trees and annual plants and wood pulp. In addition to the vegetable fibers, depending on the use for which the paper is intended, different admixtures (fillers) may be introduced into its composition, such as mineral substances (kaolin and talcum), which make the paper white, dense, smooth, and good for printing (opaque, dye-absorptive, and so on); pasting materials (rosin size, starches, resins, and others), which make paper impermeable to ink and increase the durability and density of the sheet; paper dyes; and chemical fibers for special types of paper.
Paper was obtained for the first time by Ts’ai Lun in China in the second century through precipitation of vegetable fibers on a screen from a water suspension. For a long time this method was kept secret, and only in the early sixth century was it exported to Japan. At about the same time (sixth through eighth centuries) paper production began to spread to other countries of Asia. Owing to lack of fresh vegetable fibers, which were the raw materials for making paper according to the Chinese method, other countries began making paper of hemp or flax rags on silk or hair screens fastened on a wooden frame. After the water was first squeezed out, the sheet would be placed between cloths, pressed, and then dried in air. Subsequently, the Arabs brought this method through Persia to North Africa and Cyprus and then to Spain, Morocco, and several other countries. Paper began gradually displacing papyrus and other materials used previously for writing. From Spain paper production spread to Italy and then (roughly in the tenth century) to all the other European states, including Russia. The development of paper production became especially rapid after the invention of book printing in the 15th and 16th centuries. However, the method itself was still labor consuming, productivity stayed low, and rags continued as before to be the basic raw material right up until the middle of the 19th century. Manufacture of paper by machine started abroad with the invention in Holland of a new beating apparatus called a hollander beater. This occurred at the turn of the 18th century and was encouraged by the proposal of the Frenchman N. L. Robert in 1799 of mechanized formation of paper through a hand-operated, continuously moving endless wire screen placed over a vat. Later, this primitive equipment was supplemented by continuously operating sections for pressing, drying, calendering, and winding paper into rolls. In the 1860’s the paper machine had basically the same parts as present-day machines. This was the first time in the history of industry that a continuously operating unit was used to manufacture a finished product from semifinished products. Subsequently, the designs of all the parts of the machine were improved. The width of the paper sheet was increased (more than 9 m on modern machines), and the rate of output increased dozens of times. Cellulose fibers derived from wood began replacing rags as raw material. The old beaters were gradually replaced by continuously operating beaters. Synthetic polymeric resins and fibers were used on an ever-wider scale, and the technology was becoming more refined.
There is a considerable increase in the relative proportion of new types of paper products, including fibrous filtering material for the fine purification of oils, motor fuel, and gasses; “Silkon” brand capacitor tissue paper; and special gasket board for automobiles. The further increase of production efficiency will be provided by the modernization of existing paper machines.
There are more than 600 types of paper. In a number of instances paper and cardboard successfully compete with the output of the textile, woodworking, and glass industries; they replace various metal products and may be used as structural, insulating, lining, filtering, and finishing materials, and so on. Depending on its use, paper is characterized by such factors as mass (of 1 sq m), from 4 to 250 grams; thickness, from 4 mm to 400 microns; and mechanical properties, including breaking length, fracture, puncturability, erasability, compressibility, curl, degree of sizing, ash content, moisture content, color, whiteness, smoothness, absorbency, nonconductability, and impermeability to air, steam, and fat. The properties of the paper may be varied by the choice of fibrous materials and the mode of beating them; by the introduction of additives to the paper pulp; by the conditions of forming, pressing, and drying the paper sheet; by the calendering operations and the final finishing; and by a special paper processing called refinement.
According to the classification accepted in the USSR, paper is divided into 11 classes.
(1) Paper for printing (including typographic paper, offset papers, illustration paper for deep impressions, cartographic paper, and coated paper), which is distinguished by great smoothness and whiteness and absorbs printing ink well. This class also includes newsprint of cheaper fibrous materials without sizing, without fillers, or with a lower proportion of fillers, as well as wallpaper.
(2) Paper for writing (including writing, letter, envelope, and postcard paper); it is distinguished by good sizing, low absorbency, and great smoothness. Paper of the first two classes is made from unbleached and bleached sulfate and sulfite cellulose, as well as with the use of rag pulp and ground wood.
(3) Drafting and drawing paper (includes drawing, drafting, transparent drafting, and tracing paper), which is usually made without fillers or with a low content of fillers and is well sized; the transparency of some of the kinds of this paper is achieved by thorough moistening and calendering under great pressure from the rolls. This paper is made from unbleached sulfate cellulose; for certain types of paper an admixture of wood, rag, and cotton pulp is used.
(4) Electrical insulating paper (includes capacitor tissue paper, cable paper, telephone cable paper, and insulating winding paper); it is distinguished by high mechanical durability, and good nonconductor qualities. It is usually made of unbleached sulfate cellulose of low ash content and high purity and without fillers or paper-sizing substances.
(5) Cigarette paper (mouthpiece paper, cigarette tissue paper, cigarette paper, smoking paper), which exhibits a great variety in composition, properties, and production technology. The raw material for this class of paper is bleached or unbleached sulfite cellulose with admixtures of bleached wood pulp or wastes from flax or hemp production (combings).
(6) Absorbing paper (filter, blotting, and impregnating paper), which is used in the production of hard-fiber paper, parchment, sanitary and hygienic products, and so on; it is highly porous and absorbs liquids well.
(7) Paper for equipment (telegraph tapes, Creed tapes, punched-card paper, and so on), which has an especially high degree of mechanical strength. It is made of unbleached sulfite or sulfate cellulose, the latter in the case of paper for accounting machines, with an admixture of wood pulp in some instances.
(8) Sensitized paper (base paper), which is photographic base paper that is used to make photographic paper, sensitized paper for photostatic copies, and so on; it has a high degree of mechanical strength, good sizing, and a number of other special properties. It is made of bleached or unbleached sulfite or sulfate cellulose.
(9) Transfer paper (transfer and carbon base paper and so on), which is specially processed.
(10) Wrapping paper, used for the packaging of food products and industrial goods including bag paper; paper for packaging tea, matches, bottles, and fruit; vegetable parchment; lightproof paper; and base paper for paraffin paper and reinforced paper. It is made of solid fibrous materials, as well as of industrial wastes; some kinds of paper of this class are bituminized, paraffined, or laminated (laminated structure paper production).
(11) Industrial and technical paper for different uses, which is the broadest class of paper, including ammunition paper, abrasive paper, diffuser paper, and paper for sound recordings and spinning. This class also includes so-called long-fibered paper (tissue waxing paper, asbestos, glass paper, and other kinds of paper), which are made of cotton fiber, asbestos, and artificial fibers through the usual method of paper production, as well as through so-called dry formation. This paper has high elasticity and mechanical strength.
The production of paper pulp includes beating the fibrous material; putting together the fiber composition; sizing, adding fillers, and dyeing the paper pulp; preparing slurries and solutions of sizing agents, fillers, and dyes; and processing the broke. Beating the fibrous materials is one of the basic operations in paper production. During beating, the fibers are shortened, combed, and split longitudinally into separate fragments. Beating is done by devices of intermittent (beaters) and continuous (cylinder and disk mills) operations. The necessary additives are introduced into the beaten fibrous slurry, and the paper pulp obtained is diluted in water to the required concentration, purified in centrifugal and sorting devices, and fed into the paper machine. Finishing the paper consists of putting the paper sheet into the form of the finished product, for which sheets, rolls, and coils are used. (This also includes the glazing of paper in supercalenders.) Some types of paper are specially processed (refined) by surface sizing; coating; applying protective emulsions, films, resins, and foil; laminating; creping; and other means.
REFERENCESIvanov, S. N. Tekhnologiia bumagi. Moscow-Leningrad, 1960.
Kozmál, F. Proizvodstvo bumagi v teorii i na praktike. Moscow, 1964. (Translated from Slovak.)
V. A. SMIRNOV
What does it mean when you dream about paper?
Dreaming about a blank sheet of paper can refer to something that is not expressed, something we have not “put down on paper,” which can be an idea or a communication. Wrapping paper can refer to a gift or to the outer impression something conveys. A dream about paper can also be alluding to the meaning of a familiar idiom, such as “paper tiger,” “paper over the cracks,” a “paper trail,” or “not worth the paper it’s written on.”
A flexible web or mat of fibers isolated from wood or other plants materials by the operation of pulping. Nonwovens are webs or mats made from synthetic polymers, such as high-strength polyethylene fibers, that substitute for paper in large envelopes and tote bags.
Paper is made with additives to control the process and modify the properties of the final product. The fibers may be whitened by bleaching, and the fibers are prepared for papermaking by the process of refining. Stock preparation involves removal of dirt from the fiber slurry and mixing of various additives to the pulp prior to papermaking. Papermaking is accomplished by applying a dilute slurry of fibers in water to a continuous wire or screen; the rest of the machine removes water from the fiber mat. The steps can be demonstrated by laboratory handsheet making, which is used for process control.
Although paper has numerous specialized uses in products as diverse as cigarettes, capacitors, and counter tops (resin-impregnated laminates), it is principally used in packaging (∼50%), printing (∼40%), and sanitary (∼7%) applications.
Material of basis weight greater than 200 g/m2 is classified as paperboard, while lighter material is called paper. Production by weight is about equal for these two classes. Paperboard is used in corrugated boxes; corrugated material consists of top and bottom layers of paperboard called linerboard, separated by fluted corrugating paper. Paperboard also includes chipboard (a solid material used in many cold-cereal boxes, shoe boxes, and the backs of paper tablets) and food containers.
Mechanical pulp is used in newsprint, catalog, and other short-lived papers; they are only moderately white, and yellow quickly with age because the lignin is not removed. A mild bleaching treatment (called brightening) with hydrogen peroxide or sodium dithionite (or both) masks some of the color of the lignin without lignin removal. Paper made with mechanical pulp and coated with clay to improve brightness and gloss is used in 70% of magazines and catalogs, and in some enamel grades. Bleached chemical pulps are used in higher grades of printing papers used for xerography, typing paper, tablets, and envelopes; these papers are termed uncoated wood-free (meaning free of mechanical pulp). Coated wood-free papers are of high to very high grade and are used in applications such as high-quality magazines and annual reports; they are coated with calcium carbonate, clay, or titanium dioxide.
Like wood, paper is a hygroscopic material; that is, it absorbs water from, and also releases water into, the air. It has an equilibrium moisture content of about 7–9% at room temperature and 50% relative humidity. In low humidities, paper is brittle; in high humidities, it has poor strength properties.
The heaviest grades of papers, such as chipboard, are made on multiformer (cylinder) machines that form three to eight layers of fiber mats. These fiber mats are combined prior to pressing and drying. The lightest grades of paper, tissues, cannot withstand numerous felt transfers and are dried on very large Yankee dryers.
Paper may be smoothed against a series of rolls made from metal or rubbery material to impart smoothness or gloss. Paper may also be coated with a paintlike material to give it high brightness and gloss. In addition, numerous other converting operations may be performed on paper.