Paper is one of the four major inventions in ancient China. It is a sheet-like fiber product used for writing, printing, painting, or packaging. It is generally composed of an aqueous suspension of plant fibers treated with pulp, interleaved on the Internet, and dehydrated. Pressed and dried.
1. The composition of the paper
Paper consists of plant fibers, fillers, rubber, pigments, etc.
(1) Plant fiber
Plant fibers are the basic components of paper. Plant fibers, which are used as raw materials for papermaking, must have a tendency to dissociate during pulping. The cellulose content in plant fibers is high and the content of wood cords is low; the strength, length, and width are satisfactory; there is sufficient Flexibility and interweaving capabilities; abundant sources and low costs, adapting to mass production and other conditions.
China's commonly used papermaking plant fibers are: rice straw, wheat straw, reeds, bamboo, wood, hemp, cotton, etc. Waste cotton, waste cloth, waste hemp, waste paper, etc. are also the main raw materials for papermaking.
In the process of manufacturing pulp, the plant fiber manager processes and removes other components such as lignin, pectin, resin, and fat contained in the plant fibers, leaving only active ingredients such as cellulose and hemicellulose.
The nature of the paper, under certain conditions, depends on the physical and chemical properties of the selected plant fiber, as well as the pulping method.
(2) packing
Fibers made of interwoven fibers have many voids and must be filled with fillers to increase flexibility, reduce the paper's transparency and stretchability, and make the surface even to suit the requirements of use.
Commonly used fillers include kaolin, talc, gypsum powder, carbonic acid, and barium sulfate. In general, talc is used for printing paper, and kaolin and barium sulfate are used for high-grade printing paper.
The amount of filler is generally about 20%. Too much filler will affect the quality of the paper, reduce the tensile strength and toughness, hinder the absorption of ink, easy to drop powder when printing.
(3) rubber compound
The glue is added to fill the gap on the surface of the paper, reduce the capillary effect in the paper, improve the water resistance of the paper, and can also improve the gloss and strength of the paper and prevent paper from fluffing after the sizing.
Commonly used rubber compounds are rosin, aluminum sulfate, alum, starch, water glass, and cheese acid.
According to the different requirements of various papers, there are various sizing methods, such as internal sizing, surface sizing, heavy sizing and light sizing. The amount of sizing varies widely, ranging from 0.25 to 9% of the slurry weight. Excessive sizing can also affect the ink absorption performance of the paper.
(4) color material
Plant fibers have a certain color. After bleaching, they are still not pure white, but are slightly yellowish or light green, which can not meet the requirements for making white paper. Therefore, coloring materials and whitening treatment should be added.
The colorants commonly used in the production of white paper are royal blue and ultramarine blue, and certain fluorescent whitening agents have to be added to make fine paper.
In the production of colored paper, it is also necessary to use pigments, most of which use inorganic pigments or organic dyes.
2. Kind of paper
There are various types of paper, and the Ministry of Light Industry in our country is divided into 17 categories based on the use of various papers (Paper 11 and Cardboard 6).
Paper 11 categories are: printing paper, writing paper, drawing, drawing paper, electrical insulating paper, cigarette paper, suction paper, gauge paper, photosensitive paper, transfer paper (base paper), industrial technical paper, wrapping paper.
Cardboard 6 categories are: stapled cardboard, boxed cardboard, insulated cardboard, industrial technology cardboard, construction cardboard, shoe cardboard.
3. Paper specifications
The specifications of the paper are generally calibrated according to the type, size, and weight.
(1) Type
The type of paper is divided into two types, flat paper and web in printing paper. Webs are used for high-speed web presses, and flat sheets are used mostly for printing.
(2) Size
According to the former national standard GB147-59, the original paper size for printing, writing and drawing is: the width of the web is set at 1575 (ie 2×787), 1092, 880, and 787 mm; the size of the base paper is set at 880 ×1230, 850×1168, 880×1092, 787×1092, 787×960, and 690×960 mm.
The national standard GB786-87 stipulates that books and magazines and their size standards will be printed on 880×l230, 900×280, and 1000×1400 millimeter uncut single paper sizes to suit international cultural exchanges. Adoption of international standards, and due to equipment, paper supply and other reasons, the original 787 × 1092 mm paper size, as the transition period (up to 2000 AD) can still be used, but a non-standard format to be phased out, that is, paper production Size specifications will transition to new national standards.
(3) Weight
The weight of the paper is expressed in theorems and weights. Usually expressed in quantitative terms.
Quantitative, also known as grammage, is the stipulated weight per square meter of paper, which is expressed in grams, ie grams per square meter (g/m2), eg: 60 grams per square meter,... 200 g/m2 (including 200 g/m2) is called paper, and 200 g/m2 is called cardboard.
The weight represents the total weight of 500 sheets. For example, 52 grams of paper 880 x l230 mm weighs more than 28 kilograms.
4. Printing paper
In printing paper, there are papers with different properties and characteristics, such as newsprint, letterpress printing paper, offset printing paper, offset printing coating paper, dictionary paper, map paper, sea drawings, gravure printing paper, weekly newspaper, Drawing newspapers, whiteboards, writing papers, etc.
(1) Newsprint
It is mainly used for printing newspapers and letterpress books. The paper is soft, has good elasticity and plasticity, and has strong ink absorption performance. The ink can be fixed on the paper faster. The paper surface is pressed by the calender and has smooth surfaces on both sides. Fleeting, both sides of the printing are relatively clear, there is a certain degree of mechanical strength, can be suitable for high-speed rotary printing, opacity is very good. Because the raw materials used are mainly mechanical pulp, containing essential elements and impurities, so the paper should not be stored for a long time, the paper tends to yellow and brittle, the paper absorbs strongly, the water resistance is poor, and the paper is easily damaged.
(2) Letterpress paper
It is mainly used for printing presses, classical works, general books, textbooks, magazines, etc. Its characteristics are similar to those of newsprint paper, and its quality is better than that of newsprint paper. The smoothness, water resistance, and whiteness of paper are better than those of newsprint. The ink absorption ability is not as good as that of newsprint, but the ink absorption is even.
(3) offset printing paper
It is mainly used for lithography color pictorials, albums, posters, color logos and some advanced publications.
Offset paper is divided into single-sided offset paper and double-sided offset paper. Single-sided seizures are often used in color posters, cigarette packs, and trademarks. Double-sided offset paper is used to print pictures, illustrations, maps, etc.
Offset paper should have low stretchability and strong water resistance to prevent paper deformation caused by multi-color overprinting. Overprinting is not allowed. It should not be napped or peeled off, and the texture should be tight so as to prevent the adhesion of the ink during multiple printing. Under the action, it will cause pulling and de-powdering phenomenon, which will cause white spots in the imprint and affect the quality of the printed product. The ink-absorption property should not be too high, it can hinder the penetration of the connecting material in the ink, and make the ink dry on the paper to form a film layer. The gloss of the product; the surface is smooth, the imprinting is guaranteed, and the paper cannot contain sand, etc. to prevent damage to the blanket and printing plate.
(4) offset printing coating paper
Also known as coated paper. It is coated with a layer of inorganic paint on the paper surface of the coating base paper, and then made by super calendering. The surface of the paper is smooth, and the whiteness is high. The monochromatic or multi-color art pictures, illustrations, and pictorials are exclusively used for offset printing. , albums, product trademarks, product samples, calendars, etc.
Coated paper has a high degree of smoothness. When printing, it can get very fine smooth and clean dots. It can reproduce the level and quality of originals. The paper should not be de-powdered and layered. The ink absorption of paper should not be too fast. If the ink is too fast, it will cause the print to be dull, and when it is serious, it will also cause imprinting.
(5) Dictionary paper
It is mainly used for the printing of dictionary printing, pocket manuals, reference books, scientific and technical materials, and high-grade prints. It has a light weight of 25-40 g/m2.
Dictionaries are light and must have good opacity (prevent printing), uniform fibrous tissue, flat paper, and uniform thickness. Dictionaries are soft and paper edges tend to curl.
(6) map paper and sea drawings
Map paper is suitable for offset multi-color topographic maps, maps, and atlases. It is divided into two special numbers and one number. Special numbers are used to print topographic maps, and number one is used to print maps and atlases. Sea drawings are suitable for offset printing of multi-color charts.
The map paper and sea drawings are white and have a small degree of dust. In particular, they cannot have black dust of more than 1 mm in length (to avoid confusion with map symbols). The two sides are smooth, the structure is tough, the flexibility is small, and they are flexible. Graphics, the degree of folding resistance is much higher than offset paper, and the length of cracks in sea drawings is also very high.
(7) Gravure printing paper
Mainly used in monochrome and color gravure printing pictorial, art pictures, illustrations and other paper.
Gravure paper requires a firm white paper with good smoothness and water resistance. It cannot have significant powder dropping during printing, and there is a phenomenon of overprinting during fluffing.
The original gravure printing paper includes printing paper money, stamps and other high-quality papers that are not easily imitated, and has now been individually separated from banknote paper and stamp paper.
(8) Whiteboard paper
It can be used for printing various kinds of goods packaging cartons and commodity mounting sheets, and it can also print various educational pictures.
The fibrous tissue of whiteboard paper is relatively uniform, the surface layer has filler and rubber composition, the surface is coated with a layer of coating material, and the surface of the paperboard is compacted by multi-roller calendering. The paper surface is generally whiter and smoother, and has more uniform ink absorption. , Surface de-powdering and lint-free phenomenon, the paper has a better degree of folding.
(9) Synthetic paper
It is mainly used for printing high-quality artwork, maps, and dictionaries.
Synthetic paper is a paper synthesized from chemical raw materials. It is generally made of hydrocarbons as the main raw material, and then added with some additives. It has a soft texture, strong tensile strength, good water resistance, light resistance, heat resistance, no mildew, and good stability. Etc. Features and resistance to chemical corrosion. In the temperature range of -60 ~ 60 °C, can be used as a variety of printing paper.
Synthetic paper is not only suitable for printing, but also because it is non-toxic, non-polluting, good ventilation, so it is also an ideal packaging material. It is clean and dustless, can not afford paper powder, is an ideal information industry paper, is now taking
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