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11.2 Types of Paper, Board and Cardboard Paper and board are planar products made essentially from fibers that are mostly of plant origin, and different portions of fillers. Fillers are mainly inorganic sub¬stances, their content in the product may vary from zero to about 40 %. Paper and board are formed by draining a fiber suspension through a sieve. The resulting fiber web is subsequently compacted and dried.
There are approximately 3000 kinds of paper and board products [11]. Most products with a basis weight up to 225 g m2 are defined as paper. Above 225 g m2, these products are usually called board, but the naming overlaps.
Depending on their use the paper and board grades can be divided into four main groups:
1. 1. graphic papers
2. 2. packaging paper and board grades
3. 3. hygienic papers
4. 4. specialty paper and board grades. This classification has also been largely adopted by the Statistisches Bundesamt (Federal Statistical Office) of Germany in Chapter 48 of the “Commodity index for foreign trade statistics” [12]. The basis of this systematology is a “harmonized system for the marking and coding of merchandise” of the “council for tariff co¬operation”. 11.2.1
Graphic Papers
The term graphic papers refers to a large range of different papers that are suitable for printing and writing and are made from virgin or recycled fibers or mixtures of them.
11.2.1.1 Printing and Press Papers [13]
Printing and press papers are divided into the following four subgroups:
1. 1. newsprint
2. 2. wood-containing natural printing papers
3. 3. Wood-free natural printing papers
4. 4. Coated printing papers (wood-containing and wood-free). 11.2.1.1.1 Newsprint
Newsprint represents an important subgroup. It consists primarily of a mixture of primary and secondary fibers (0–100 %). The primary fibers include groundwood and small amounts of chemical pulp, which are used to increase strength. The main field of application is newspaper production. Other uses are, e. g., paper¬backs, calculating-machine rolls, and interleafing paper.
Newsprint has a basis weight of 40–49 (in certain cases up to 54) g m–2. It is machine-finished or supercalendered. Standard newsprint should have an ISO brightness of 57–60 %.
Improved newsprint has a high filler content and is calendered to obtain a more closed surface. It is used, e. g., for book and offset printing. The ISO brightness is about 10 units higher than the mean brightness of standard newsprint [14]. 11.2.1.1.2 Wood-containing Natural Printing Papers
The term wood-containing indicates that these printing papers consist mainly of mechanical pulp along with chemical pulp, while “natural” refers to the fact that they are not coated. Fillers, e. g. kaolin or calcium carbonate, are used to produce high smoothness and good opacity. This important group of printing and press papers includes gravure printing paper, also called SC paper (supercalendered). Here SC-A+, SC-A, SC-B and SC-C are the subgrades (with decreasing quality demands).
Natural magazine papers have high lignin content, are filled and highly super¬calendered. Their main use is the production of magazines and catalogs. Gravure papers (SC-A. SC-A+) have the same properties as natural magazine paper, they are specially suited to gravure printing. ISO brightness is > 67 %.
Improved newsprint (SC-B, SC-C), improved for gravure printing containing up to 25–30 % recycled pulp has the same properties as natural magazine paper; ISO brightness is < 67 %.
SC offset paper has the same properties as natural magazine paper. The ISO brightness is > 67 % and the surface strength is optimized for offset printing.
Wood-containing thin printing papers have a basis weight of ) 45gm–2. They are used for telephone, railroad timetables, and address books.
Book papers are used in the production of books. They have a groundwood con¬tent of 5–20 %. The filler content depends on the desired specific volume.
Voluminous book papers are produced with a * 1.4-fold specific volume compared with book papers. 11.2 Types of Paper, Board and Cardboard
Supercalendered writing papers are wood-containing natural papers that are sized and supercalendered. They can also be made from recycled fibers.
Machine-finished offset papers are supplied in sheets or rolls.
Wood-containing coating base papers and boards are intended to be further proc¬essed into coated papers or boards.
11.2.1.1.3 Wood-free Natural Printing Papers
Wood-free natural printing papers consist almost exclusively of chemical pulp. The proportion of fibers from mechanical pulp should not exceed 5 %. Wood-free print¬ing papers do not yellow to any appreciable extent and have a high strength. This is the main difference between these papers and the wood-containing grades de¬scribed above. The papers are uncoated and normally leave the paper machine in a machine-finished state. For certain printing processes these papers can be ma-chine-finished or further calendered on a supercalender. This group of papers includes:
Wood-free, machine-finished natural printing papers with basis weights of ) 80gm–2 (Group 1), 81–149 g m–2 (Group 2) and * 150gm–2 (Group 3).
Wood-free, supercalendered natural printing papers with basis weights as described for machine-finished papers.
Letterpress printing papers are particularly suitable for books (specific volume is
* 1.4 fold).
Wood-free bible, thin printing papers and thin letter papers can be rag-containing or rag-free. They are highly filled to give good opacity. The basis weight is in the range below 40 g m–2.
Coating base papers for printing papers and boards are intended to be further proc¬essed into coated papers or boards.
11.2.1.1.4 Coated Printing Papers
These represent the largest group within the printing and press papers. Here the base paper is finished by the application of one or more layers of coating color to both sides of the paper web, which imparts a closed surface to the printing papers (see Chapter 7). These papers are supercalendered and supplied with a dull or glossy surface. They are described as wood-containing or wood-free, depending on the raw materials used. The wood-containing, coated printing papers represent the largest part and the LWC papers (light weight coated), in turn, make up the main part of this subgroup. Basis weight varies for LWC from 35–80 g m–2, for MWC (medium weight coated) from 70–130 g m–2 and for HWC (high weight coated) from 130–170 g m–2 (basis weight figures include base paper plus coating weights if not stated differently).
Examples include:
Wood-containing, two-sided coated papers. Typical coating application is 5–13 g m–2 per side. Base paper basis weight is 29–36 g m–2. Main areas of appli¬cation are magazines, catalogs, and job printing with total basis weight of 39 g m–2 (ULWC).
Wood-containing LWC paper is coated on both sides; basis weight is ) 80gm–2. It is suitable for gravure printing and roller offset printing.
High weight coated (HWC) papers differ from other coated, mechanical pulp dom¬inated paper grades in their higher coat weight. Traditionally they are produced at a basis weight of 100–135 g m–2. They compete with coated fine papers in such end use areas as high-quality magazines, catalogs, and magazine covers as well as in the area of direct advertising. HWC papers can be double or triple coated.
Wood-containing consumer papers, coated on both sides have a minimum ground¬wood content of 50 % and typical coat weight of 3–14 g m–2.
Wood-free, two-sided coated papers (WFC). The coating application is 3–14 gm–2 per side and the basis weights vary between 55 and 170 g m–2. The fields of appli¬cation are magazines, catalogs, books, direct mail, labels.
Wood-free medium weight coated paper (MWC) is coated on both sides and has a basis weight of 72–120 g m–2 and typical coat weight of 12–25 g m–2.
Art papers represent one of the highest quality printing papers and are used for illustrated books, calendars, and brochures. The basis weight varies from 100 to 230gm–2. Art papers are produced with matt or glossy finish. The coat weight varies from 20 to > 40 g m–2 per side. Art papers are almost exclusively available in sheets. They are triple coated, usually first with a precoater and thereafter with a double blade coater.
Pigmented papers, film coated offset (FCO), have a coat application of 5–10 g m–2 per side and basis weights of 45–65 g m–2. Wood-containing or wood-free coating base paper can be used for their manufacture.
11.2.1.2 Office and Administration Papers
These papers offer a wide spectrum for very different areas of use, e. g., writing papers, papers for data printing, papers for forms, copy and duplicating papers, envelope paper, postcard board, self printing papers, refined papers for offset printing, blueprint papers, work drawing paper, bank notes, documents, and map paper. These printing and writing papers and the corresponding base papers are the papers that are used predominantly in offices, administration, and schools.
Examples are:
Data papers and boards are used for the manual, mechanical, electronic, and magnetic recording of data and its input and output.
Bookkeeping transparent paper is made from a highly beaten stock and is there¬fore transparent.
Account book paper or paper for bookkeeping machines is wood-free, highly su¬percalendered, and fully sized.
Paper for continuous forms is wood-containing or wood-free and often contains recycled fibers, usually machine-finished reeled paper.
Index board is wood-containing or wood-free, supercalendered, single-layered board that can also contain recycled fibers.
Writing papers are used almost exclusively for manual writing. They are super¬calendered and can contain varying amounts of rags. This group also includes handmade papers, moldmade papers, bond, and air mail papers.
11.2 Types of Paper, Board and Cardboard
School writing paper is a machine-finished, highly sized paper with a basis weight of 60–80 g m–2.
Air mail paper is light-weight (25–30 g m–2) wood-free, often rag-containing pa¬per with high opacity.
Carbon copy paper is well sized, has a basis weight between 23 and 30 g m–2 and is used in the copying of letters and manuscripts.
Carbonless copy papers contain color forming reagents, which produce a contour-true copy when subjected to pressure (exerted on underlying sheets).
Correspondence envelope paper can be made from a wide range of stocks, from 100 % recycled fibers to 100 % virgin fibers. This paper is used exclusively in the production of envelopes and mailing bags.
Kraft paper is used to make envelopes and mailing bags and is made from unbleached or bleached kraft pulp.
Envelope lining tissue is an intensely colored, sometimes dip dyed, wood-free tissue paper with a basis weight of 22–30 g m–2. It is used for the lining of ex¬pensive envelopes.
Base paper for diazotype is wood-free, has a basis weight of 55 to > 200 g m–2 and is used in the making of blueprint papers.
Copying papers are used for copying and nonimpact printing. Basis weight varies between 70 and 90 g m–2 and ISO brightness between 80 and 96 %. The most important properties for a copying paper are smooth run in a copy machine and good dimensional stability. It must not show curling or cockling and retain dust when copying. It is mainly made of 90–100 % virgin chemical pulp fibers, but it may contain recycled fibers up to 100 %. The recycled fibers used are mainly from recovered newspaper, magazines and copying paper. Total filler content varies be¬tween 10 and 25 %.
Digital printing papers (synonymous with electronic printing papers) are a rapidly growing group predominantly made from chemical pulp. They are mainly un¬coated, but increasingly coated, fine paper grades. The bulk of this paper is deliv¬ered in sheets.
The major categories of nonimpact printing the papers have to suit are electrical charge based methods, magnetic methods, thermal methods and ink-jet methods. The requirements vary by printing method. In electrophotography, the runnability of the paper is critical. The electrical conductivity as well as the electrical resistivity of the paper should be sufficient. Moisture content and friction are also important properties. Other required characteristics are good dimensional stability to avoid curl and cockle for example, surface strength and surface smoothness, especially for high resolution printing. Chemical properties of the paper surface such as surface energy are important for fixing the toners to the paper. In ink-jet printing, papers require characteristics that are matched with the inks and the ink drop size. First, ink-jet papers must be smooth. They must have sufficient and uniform po¬rosity, with small pores, in order to absorb the solvent quickly and to counteract the spreading tendency. Dimensional stability is also important to avoid cockling and curling. Typical uses for digitally printed products are manuals, price lists, and various direct mail materials, but also low-volume paperbacks and hard-cover books. Black-and-white applications cover more than 80 % of digital paper needs at present. Basis weights vary a lot, from 40 to as much as 400 g m–2 [10].
Copy base papers are wood-free. They can be finished to e. g., thermocopy, and photocopy papers with a wide basis weight range of 50 to 180 g m–2.
Base papers for offset films are predominantly wood-free papers that are used for making paper offset plates.
Carbonizing base papers are carrier papers for a wax-bearing color mass. They are used for the production of carbon and blue papers (basis weight range of the coating is 10 to 14 g m–2).
One-time carbon (OTC) base paper is used in the production of one-time carbon paper (basis weight range is 16 to 24 g m–2).
Multiple carbon base papers are used in the production of multiple carbon or blue papers.
Base papers for nonimpact printing processes are predominantly wood-free and are specially suitable for nonimpact printing processes (thermosensitive, electrosensi¬tive, thermostatic papers). Basis weights range from 50 to 180 g m–2.
Blotting papers are wood-containing or wood-free, white or colored, and some¬times have veined fibers. They possess a very high absorbency and wetability. Basis weight range is from 35 to 350 g m–2.
Security, banknote, and archival papers are wood-free and/or rag-containing or linters-containing. These heavyduty, nonaging papers are suitable for color print¬ing and can be made resistant to forgery, e. g., by means of a watermark. Basis weights range from 60 to 80 g m–2.
Map and nautical chart papers are wood-free, dimensionally stable, and are used for printing of maps and sea charts (basis weights from 70 to 120 g m–2).
Letterpress board is wood-containing or wood-free and may contain recycled fib¬ers. It has a basis weight of > 150 g m–2 and is supercalendered.
Picture postcard board is wood-containing or wood-free and is used for picture postcards (basis weights from 150 to 300 g m–2).
Letter file cardboard is solid fiber board used in the production of files. It is multi¬layered, vat-lined or unlined and has a basis weight of 1000–2000 g m–2. Special requirements are that it should be exactly planar, and have a precisely maintained moisture level.
Filing board is a special, tough board which is usually colored and supercalen¬dered (basis weights from 130 to 900 g m–2).
Ticket board is wood-containing or wood-free and often colored. It is used, e. g., for streetcar tickets, entrance and weighing tickets. Ticket board is produced in accordance with regulations issued by the railroad authorities.
Fancy cardboard can be pasted or unpasted and is often wood-free, e. g., ivory, bristol, and opaline board. It is used in the production of visiting cards, invitations etc. Basis weights range from 100 to 400 g m–2.
11.2 Types of Paper, Board and Cardboard
Packaging Paper and Board Grades
11.2.2.1 Overview
A large number of grades of paper and board are available for packaging and are employed for many different purposes.
Packaging paper grades range from simple wrapping paper (WP, made from mixed recovered paper) to kraft paper, and are predominantly supplied in rolls. They are made from various virgin pulps (sulfite/kraft pulp), from recycled fibers or from mixtures of chemical pulp and recycled fibers. These grades are employed in the production of bags, beer mats, carrier bags, gift wrapping paper, etc. Some examples are:
For the foodstuff sector, for instance, special types of paper and board are pro¬duced which must fulfil the requirements of the food laws. These papers are also widely used in the nonfood sector, e. g., as coating papers. The possibilities of combination with each other and with other materials (plastics) are numerous. In this way, special packing materials can be produced for most packaging purposes. Greaseproof papers, e. g., are used for the packaging of butter, margarine, meat, and sausage. These papers include vegetable parchment and glassyne, and are pro¬vided with barrier polymers.
Kraft liner or test liner, and corrugating medium are the base for corrugated board production. Depending on their intended purpose (for the smooth surface or the corrugated inner layer of corrugated board), these papers are produced with vary¬ing strength, stiffness, wet strength, and printability.
Folding boxboard is ideally suited for the production of folding boxes because of its properties, such as good scorability, creasing ability, groovability, and print¬ability. This board can be coated or uncoated; the former gives a better printed format.
Machine-made board (also solid fiber board) is produced almost exclusively from recycled fibers and is processed primarily into mailing boxes.
For all paper and board grades described above, the stock is adjusted to meet the requirements in each case.
11.2.2.2 Packaging Papers
11.2.2.2.1 Kraft Papers
In order to meet the high strength requirements, these papers consist of primary or a mixture of primary and secondary fibers of kraft pulp. They are used predom¬inantly for packaging purposes.
Kraft sack paper (60–115 g m–2), bleached and unbleached, includes kraft bag asphalt base paper which is used in the production of asphalt paper.
Extensible kraft sack paper (Clupak) corresponds to the kraft sack papers. It has a higher elongation (> 6 %) in the longitudinal direction. It can also be used as base paper for plastic coating (45–350 g m–2).
Secondary kraft sack paper (70–350 g m–2) is made from at least 50 % unbleached kraft primary fibers.
Kraft packing papers (40–350 g m–2), are made of slightly bleached, unbleached, or bleached fibers and must contain 80 % primary fibers.
Kraft tissue, bleached or unbleached, has a basis weight of < 30 g m–2. It is a one-sided smooth or fluted kraft paper that is employed for wrapping glass or metal goods; it is also suitable for packing fruit, e. g., oranges.
11.2.2.2.2 Sulfite Wrapping Paper (ZP)
The stock composition of this paper is on average 70 % primary fiber pulp and not more than 30 % fibers from recovered sulfite or kraft paper. The basis weight is >30gm–2.
Wrapping papers (WP) consist of mixed recycled fibers of varying composition; they may also contain chemical pulp (30 g/m2–350 g/m2).
Crepe packing material is a highly sized and creped packing paper of any stock composition (70–350 g m–2).
Mixed soda pulp-paper is made predominantly from secondary fibers and kraft pulp (70–35 g m–2).
Glassyne (20–40 g m–2) is a highly supercalendered paper made from strongly beaten pulp. It is largely greaseproof, but not water resistant. The high transpar¬ency is achieved by intensive supercalendering. It is frequently colored. This paper is used, e. g., as wrapping paper for chocolates, covering paper in photograph al¬bums, for dust jackets, envelope windows, and for packing high-quality pre¬serves.
Supercalendered base paper for waxing is designed to be waxed and frequently contains titanium dioxide as filler. The waxed paper is often used as wrapping paper for candies (30–150 g m–2).
Silicon base paper (30–160 g m–2) is a supercalendered paper to be used for sili¬conization.
Greaseproof paper (40–200 g m–2) is made resistant to grease primarily by using a special beating process (high fibrillation) and by the addition of auxiliary agents. In comparison with vegetable parchment, this paper is neither waterproof nor boil-proof.
Parchment base paper (35–200 g m–2) is unsized, highly absorptive and is made of 100 % chemical pulp fibers. It contains no chemical auxiliary agents and is employed in the production of parchment paper.
Vegetable parchment [15] is a highly waterproof, greaseproof, boilproof paper product of high purity. It is used in the packing of fats, also in combination with aluminum foil or with a plastic coating. Silicon-coated parchment paper has a wide range of applications, e. g., baking paper, antiadhesive papers, etc. Basis weight is 40–130 g m–2.
Coated papers are often coated on one side and are suitable for offset and gravure printing. They can be painted, bronzed, and punched. They are waterproof and alkali resistant to prevent the detachment of labels in washing machines. They are
11.2 Types of Paper, Board and Cardboard
used, e. g., as wrapping paper for chocolates, cigarettes, soap, and as dust jackets for books and records (70–20 g m–2 with a coat weight of 9–15 g m–2).
Coated packaging papers (80–200 g m–2) are bleached kraft papers having a one-sided matt or glossy coat and are suited for the production of bags and carrier bags.
11.2.2.2.3 Corrugated Papers
These papers include:
Kraft Liner (115–440 g m–2). This covering paper is made of at least 80 % kraft pulp, bleached or unbleached, and has a bursting strength per basis weight (burst-
–1
ing index) of 3.43 kPa m2 g.
Kraft-faced liner is a covering paper that does not have a specified stock composi¬tion, but it has guaranteed strength properties.
Two-layer paper is a double-layered covering paper.
Semichemical paper is corrugated paper made of at least 65 % semichemical pulp.
Fluting or corrugating medium (80–200 g m–2). The corrugated medium used for the production of corrugated board has no specified stock composition; however, definite strength properties are required.
11.2.2.3 Board and Cardboard
Paperboard grades can be classified into three categories: cartonboards, container-boards, and specialty boards. The classification used is shown in Fig. 11.1.
As stated in the introduction the terms paper and board overlap as regards basis weight, so many linerboard and corrugating medium grades have a basis weight lower than 100 g m–2, and recently even down to 80 g m–2 and less. Products with basis weight > 600 g m–2 are usually called cardboards. Most of the paperboard grades are multiply products like folding boxboard and liquid packaging board whereas corrugating medium is very often a single-ply product.
Paperboards are very often used for packaging, but again there are exceptions like plasterboard. Because of their function in the packages, strength properties are most often very important for paperboards. Cartonboards are mainly used for consumer product packaging such as food, cigarettes, milk, and pharmaceuticals. Containerboards (corrugated boxes) are used in many packaging applications start¬ing from simple transportation containers and ending with multicolor printed display containers for stores.
The following board types are included in the group of folding boxboard:
Coated pulp board made from bleached chemical pulp is usually used for folding boxes.
Cast coated pulp board is used for high-grade packaging and for folding boxes, fine pasteboard boxes, paperback covers, etc.
Chromo board, chromo duplex board, chromo triplex board have very different stock compositions, depending on their intended purpose.
Artificial chromo board, triplex board, a gray core can also be used in this case.
Other machine-made boards in the cartonboard group include:
Mechanical pulp board which has a light or gray core. It is used, e. g., in the production of paper plates and round cheese boxes.
Brown mechanical pulp board is made predominantly from recycled fibers and has a brown colored cover and reverse. It is used for the production of mailing boxes.
Chipboard consists predominantly of recycled fibers and is employed for the production of mailing boxes, box lining, etc.
Pasted board consists of two or more layers of mill board that have been pasted together in the dry state.
Sheet-lined board is made from mill board. It may also be pasted, is lined on one or both sides with paper, and is used for high-grade packaging.
Mill board is made by winding one or several fiber webs on a press roll. Thus, high basis weights and the production of especially stable packaging material are possible.
Cartridge papers and boards are usually made from recycled fibers and are used in the production of cartridges, special cartridges, cardboard tubes, and containers such as detergent drums.
Board for cups is a single layered hard board consisting of bleached pulp and is used for the production of drinking cups, etc.
11.2 Types of Paper, Board and Cardboard
Hygienic Papers
The major component of all hygienic papers is tissue. The term “tissue” describes products made from lightweight, dry creped (sometimes wet-creped or noncreped) papers such as toilet paper, kitchen towels, handkerchiefs, facials, napkins, hand towels, wipes. Such kind of products are made from a one-ply, semi-finished, wet-laid tissue base paper, that is predominantly composed of natural fibers. The origin of the fibers may be virgin or recycled. Usually the basis weight of the base paper before creping is 10–20 g m–2 which is increased during creping by 10–20 %. Tis¬sue is usually used in multiple layers because of its low basis weight. Cellulose wadding and crepe paper also belong to the group of tissue papers whereas non¬wovens (predominantly air-laid products) do not.
11.2.3.1 Cellulose Wadding
This is a loosely structured, highly absorbent fiber product. It is made from virgin fibers. Its use includes the production of sanitary towels, surgical artificial cotton, patients’ sheets, and packing cotton.
11.2.3.2 Tissue
Tissue is made of virgin or recycled fibers (or a mixture), with fine, soft creping and closed formation. The basis weight is < 27 g m–2. Tissue has to meet a wide variety of requirements, for instance surface softness, liquid absorbency, tensile energy absorption as shown below. The highest quality tissue is made on machines with a through-air drying system (TAD, Section 6.11.4) or other soft tissue produc¬ing systems. Tissue is employed in the production of :
Toilet paper (bathroom tissue) is the biggest single product made from tissue. It is made in one, two, three or five plys with or without moderate wet strength, be¬cause this type of tissue has to disintegrate in the sewage system. Toilet paper should be smooth and can be embossed, unprinted or patterned, tinted, purely white or off-white.
Kitchen towels are the second biggest product for the consumer sector. Kitchen towels usually have a basis weight of 20–24 g m–2. Sheets are 220–280 mm wide and 250–280 mm long. The number of sheets to a roll is normally between 54 and 100.
Most kitchen towels are two-ply. Good wet strength and high water absorbency behavior are the most important functionalities.
Facial tissue and handkerchiefs have the lowest basis weight of 14–18 g m–2. The surface is often made smoother by light calendering or softening additives. Facial tissue is usually two-ply while handkerchiefs are two- or three-ply. Because of the high quality requirements, the base tissue for most facial tissues and handker¬chiefs is made either entirely from pure chemical pulp or from a mixture of pure chemical pulp and selected recycled fiber. Handkerchiefs can be one-, two-, three-, or four-ply and must have good air permeability, absorbency, wet-strength and burst strength.
Serviettes can be one-, two-, three- or four-ply. The size and type of fold vary greatly.
Diapers and sanitary towels covers have additive functionalities which are sup¬ported by a special water absorber.
11.2.3.3 Crepe Paper
Crepe paper is a single-layered, highly absorbent hygienic paper made from groundwood and/or secondary fibers. The basis weight is > 27 g m–2. The most important uses are toilet paper, paper handkerchiefs, and cleaning rolls.
11.2.4
Paper and Board for Technical and Specialty Uses
This group of paper and board covers a wide range of grades. The most important subgroups comprise base papers for decor, priming and barrier foils, body, coating and soakage base papers and base papers for wallpaper, papers for electrotechnical purposes, drawing paper, photographic base paper, cigarette paper, filters and filter layers and special cardboards for the various branches of industry, e. g., pressboard (pressspan), car body and shoe cardboard. All these papers and boards have a common requirement; they must exactly fulfill defined quality criteria according to the use. Chromatography papers are porous, absorbent special papers made from linters without the addition of sizing or filling agents. They are often acid washed and contain silicon compounds to render them hydrophobic.
Reagent and indicator papers are high-grade special papers used for impregnation with test reagents and indicator dyes.
Household filter papers are wood-free special papers that give a defined rate of filtration. They must comply with food laws. They are used, e. g., for coffee filters. The rate of filtration and the separating ability depend on the degree of fiber beating.
Analytical and industrial filter papers are usually made from cotton, dissolving pulps, glass microfibers or other artificial fibers. They possess a uniform stock distribution and, thus, a homogeneous pore size. Analytical filters are acid washed and are made without paper making additives. Filter layers with a basis weight of up to about 750 g m–2 are produced to withstand special stress, e. g., in the bev¬erage industry. Filter layers of this type, that are also used for sterilization filtration, must comply with food laws. For industrial use, the paper and filter layers may also be impregnated with melamine-urea resins or similar compounds.
Filter mass is made from soft-cooked, highly bleached pulps or from rags or linters and is used in the form of flocks for industrial filtration.
Cable and condenser paper (capacitor tissue paper) is stiff, nonporous paper made from pulp and is usually impregnated with artificial resins. These papers contain neither fillers, metal impurities, nor salts. The absence of pores is achieved by fine
11.2 Types of Paper, Board and Cardboard
beating of the pulp fibers and by supercalendering. Cable paper must exhibit high strength in the longitudinal direction. The thickness of condenser paper is 0.006–0.012 mm and the basis weight is 6–7 g m–2. These papers must meet IEC regulations [16].
Pressspan is a single-layered, highly rigid product that is made from pure pulp and couched in the wet state. When used in the electrical industry, the pulp must be produced with a high degree of electrochemical purity.
Building papers and boards include: roofing felt base, a wool-felt board (reclaimed wool) impregnated with tar/bitumen and used to produce roofing sheets. Felt and wool-felt board made from recycled fibers and rags. They are used as the base material for textile floor coverings and as insulating material in various fields, predominantly in the automobile industry. They are also employed as separating layers on flat roofs that are covered with a plastic foil. Gypsum liner board used for the production of gypsum wallboards (building plates).
Covering papers and cardboards, this general term describes various papers and cardboards that are used as protective coverings. These single-layered or multi¬layered materials can be made from various raw materials. They are used, e. g., as covering papers in road construction.
Substrate papers, saturating base papers, and coating base papers. Substrate papers are used in many different technical systems as manufacturing aids. They are frequently removed from the finished product at the end of the production proc¬ess, rewound and reused in the same process. Saturating base papers must be absorbent and have wet-strength and often also resistance to organic solvents. Coating base papers must be moisture resistant and stable to organic solvents. One or both sides of the paper are treated with various solutions or dispersions, which represent the requirement for the desired coating.
Raw material for artificial leather is tough kraft paper that is not dyed and is usually moisture resistant. It forms the web base for the production of artificial leather.
Base paper of vulcanized fiber is absorbent, voluminous paper made from cotton rags, cotton linters, and refined pulps.
Photographic base paper. A suitable base paper for the production of photographic paper is a moisture resistant, dimensionally stable, chemically neutral chemical pulp paper that is free from traces of iron or copper. Today, papers coated with a thin polyethylene foil on both sides have replaced barite paper. This paper is used for the uptake of light-sensitive emulsions.
Saturating base paper (overlay paper) is made from special pulp and has basis weights of 15–40 g m–2. It is highly porous, free of dirt, and protects the under¬lying decor in the production of laminated products.
Decor base paper is a soakage base paper made from bleached or unbleached kraft pulp; it is used for resin absorption in the production of laminated plates.
Base papers for abrasive papers are tough, sized papers made from kraft pulp and are coated with an abrasive.
Calender bowl paper is strong, compressible, heat-resistant paper used for the manufacture of calender bowls.
Technical drawing paper. This group includes the following: Opaque drawing pa¬pers are fine look-through papers made from pulp and have good sizing and hard¬ness. Erasability is the most exacting demand. Translucent drawing paper. A distinc¬tion is made between natural transparent paper and paper made transparent by chemical treatment. Natural transparent papers are made from pulp, linters, or mixtures of the two by intensive beating of the fibers. They are well sized and exhibit good surface smoothness and look-through. Opaque papers are rendered transparent by soaking them in a solution of synthetic resin. Sketching papers are wood-containing or wood-free, machine finished, sized natural papers with a basis weight * 80gm–2. Art drawing papers and board are suited to special drawing and painting techniques, e. g., watercolor paper. The latter has a rough surface which accepts water colors but does not allow their penetration. This material also has good erasability.
Base paper and board for wallpaper. This is the general name for papers and boards that are suitable for the production of wallpaper [17]. They can be single- or multilayered, couched or pasted, wood-containing or wood-free, coated or uncoa¬ted. They may contain recycled fibers and may have a woodchip coat. Strip-off wallpapers or preglued wallpapers can also be produced.
Papers for tobacco products. Imitation cork paper is a brownish yellow colored paper used for the production of cigarette tips. It has an imitation cork imprint and joins the filter to the tobacco stick. Filter encasing paper is used for the production of acetate and/or cellulose filters. Cigarette paper has a high filler content and a basis weight of 18–28 g m–2. To control the smoking properties, this paper has a porosity that is suited to the type of tobacco and contains additives that regulate burning. Cigar or cigarillo casing paper holds the chopped tobacco together and serves as the inner casing.
Long-fiber paper is used for tea bags and artificial sausage skin and is made from fibers having an average length of > 3 mm. The addition of synthetic fibers is permitted.
Binding papers are tough, wood-free papers that are frequently embossed.
Cover paper and board is tough, elastic, durable, wood-free white paper or board that has a linen finish and is specially suited to the production of covers for bro¬chures, paperbacks or similar products.
Bookbinding board is press rolled or mill cardboard that is pasted or unpasted and has high rigidity, dimensional stability, and perfect lining ability.
Car body cardboard is a hard cardboard used predominantly as shaped parts in automobile manufacture; it is usually capable of being cupped.
Leather fiberboard is an especially tough hard cardboard that is flexible and resis¬tant to moisture.
Suitcase board is an embossed hard cardboard used in the production of lug¬gage.
Flong is a coated cardboard (solid board) made from very high-grade stocks (rags). It is processed with fillers and is completely knot-free and can be subjected to hot embossing. It is used to produce the matrices for high-pressure dry ster¬eotyping.
References
Cardboard for beer mats is a highly absorbent groundwood cardboard that may be pulp covered. It can be punched, embossed, and printed. Base papers for chart paper have a basis weight of 30–130 g m–2 and are usually filled and sized. They have a refined surface and good dimensional stability.
Gardener, flower, and decoration crepe. Gardener’s crepe is a white or colored, highly expandable paper that has longitudinal grooves and serves as decorative flowerpot wrappers. Flower crepe paper is wood-free and is used to make artificial flowers. Decoration crepe paper is flameproofed by impregnation with chemicals and is used for decorations of various types.
Board for playing cards is made of two or three layers pasted together. It is coated on both sides, has a supercalendered surface, and is sometimes linenized. The basis weight is 280-340 g m–2.
Album board is used for photograph, stamp, and other albums and is often wood-free and voluminous. Hot setting paper and hot sealing paper are coated on one side, become sticky on heating and can consequently be fixed to another material. Insect resistant or insecticide paper is resistant to insects. It can kill insects by means of volatile components or by contact. Antitarnish paper is an impregnated or coated paper that protects other materials against corrosion by releasing substances in the vapor phase or by direct contact.
Photographic protective wrapping (black photo) paper is lightproof, black-dyed, chemically neutral paper that can be folded without breaking and is suitable for wrapping photographic film.
Sterilization paper is a wood-free paper that, even when coated, can tolerate steril¬ization processes and is used for packing sterilized materials.
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