Q & A on the hottest printing paper 20

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Printing paper Knowledge Q & A (20

20. How can paper be simply classified?

answer: paper can be simply divided into non coated paper and coated paper. Uncoated paper is called non coated paper, such as paper, relief paper and offset paper; coated paper is called coated paper, such as copper coated paper, glass paperboard, etc.

21. What is the process flow of papermaking?

answer: the process flow of papermaking consists of the following links:

separation Fiber (pulping) → preparation of paper → papermaking → finishing and processing of paper

22. What is pulping

answer: pulping refers to the production process of color pulp or bleached pulp by using chemical or mechanical methods or a combination of both to dissociate plant fibers

23. What is chemical pulping

answer: chemical pulping is to use the aqueous solution of chemicals to treat plant fiber raw materials at a certain temperature and pressure, dissolve the lignin in the raw materials, and retain cellulose and hemicellulose to varying degrees as far as possible, so that the raw fibers can be separated from each other into pulp. Among the chemical methods, the most representative pulping methods are sulfate method and sulfite method

24. What is mechanical pulping

answer: mechanical pulping uses mechanical methods to treat fiber raw materials to dissociate fibers. Wood as raw material is called mechanical wood pulp, and grass as raw material is called mechanical straw pulp. The paper industry mainly uses mechanical wood pulp, also known as ground wood pulp. Mechanical pulp retains a large amount of lignin in raw materials, and the pulp yield is higher than that of chemical pulp

25. What is the purpose of bleaching pulp

answer: the pulp made by chemical and mechanical methods is called natural color pulp, which has a certain color. In order to meet the use requirements of paper, the pulp must be bleached to make the paper have a certain whiteness. Bleaching is to use appropriate bleach to dissolve the residual lignin in the pulp through oxidation, reduction or decomposition, or to fade the colored substances while retaining the lignin

26. What are the common methods of bleaching pulp

answer: there are two common methods of bleaching pulp:

one is oxidative bleaching, which uses Oxidative bleach to destroy the structure of lignin and dissolve it, so as to improve the purity and whiteness of pulp. Such bleaching agents include Cl2, ClO2 and hypochlorite. At present, oxidative bleaching is still the main bleaching method. Oxidative bleach will gradually be replaced by oxygen bleaching because of its serious pollution caused by chlorine bleaching

the other is reductive bleaching, which uses reductive bleach to change the structure of chromogenic groups and decolorize them. Because it will not cause the loss of fiber components and can maintain the characteristics of the raw pulp, it is especially suitable for the bleaching of high yield pulps such as ground wood pulp and chemical mechanical pulp. Such bleaches include zinc dithionite, sodium dithionite, hydrogen peroxide and sodium peroxide. The whiteness stability of the pulp bleached with VAT bleach is poor, and it will return to its original color after long-term illumination in the air

27. Why beating

answer: the pulp after cooking or mechanical grinding, washing, screening and bleaching cannot be directly used for paper making. Because the fibers in the pulp lack the necessary flexibility, and the connection performance between fibers is not good. If you use it to make paper, the paper will be loose, porous, rough surface, low strength, and can not meet the requirements of use. Beating is to use mechanical methods to treat the fibers in the pulp and make it broom, so as to meet the requirements of paper machine production, so that the produced paper can achieve the expected quality indicators

28. What are the methods of paper copying

answer: paper making methods can be divided into dry and wet methods. The main difference is that wet paper making takes water as the medium, while dry paper making takes air as the medium. At present, the vast majority of paper is made by wet method

29. What are the wet paper machines

answer: according to the structure of the paper forming part, wet paper machines are divided into three categories: long paper machines, round paper machines and folder paper machines. Long and round paper machines adopt single-sided dehydration when forming paper sheets, which will cause the difference between the two sides of the paper sheets; The paper clamping machine adopts spraying both sides and dehydration at the same time, which effectively reduces or eliminates the difference between the two sides of the paper sheet and improves the evenness of the paper

30. What is the process of copying paper

answer: take the long paper machine, which is currently the most widely used, as an example to introduce the process of paper making:

the paper machine is composed of two parts: the wet end and the cadre, and the wet end includes the headbox, the head and the press; Cadres include drying department, calendering department and paper reeling machine. The paper suspension sent by the purification system is sprayed onto the surface at a uniform and stable speed through the headbox. After forming and removing most of the water through the part, it is sent to the pressing part for further dehydration, improving the performance of the paper and increasing the tightness and surface smoothness of the paper. After the paper is mechanically dehydrated by the press department, it is sent to the drying department to further dehydrate with heat energy to meet the water content requirements of the finished paper. The surface of offset paper should also be treated with sizing in the drying section to improve the surface strength of the paper and meet the requirements of high-speed printing. Converting the elongation into the tensile value, the surface of the paper coming out of the drying section is still very rough, which cannot meet the requirements of printing and writing. In order to improve the smoothness of the paper and adjust the thickness of the paper, the paper must also be calendered by one or several metal rollers. The paper passing through the calender is rolled into a reel at the outlet of the paper machine, and finally divided into flat paper by the paper cutter or rolled into a reel by the rewinder

31. Why do we need paper coating processing

answer: after calendering, the paper fibers are no longer loosely arranged, but have a certain degree of tightness, but the smoothness of the surface still cannot meet the requirements of high-end fine printing. The surface uniformity of non coated paper is poor, the ink color is uneven after printing, and the gloss is low, which cannot restore small points, resulting in the loss of layers, and the uniformity of the field part of the image is reduced, which affects the printing reproduction effect. Therefore, the paper for fine printing must be coated and processed to further improve the surface performance of the paper

32. What is the purpose of paper coating processing

answer: the purpose of paper coating processing is to cover a layer of coating composed of fine particles with good absorption of ink on the surface of the uneven and porous ordinary paper formed by fibers, so as to obtain a paper surface with good uniformity and smoothness. Coating can also improve the gloss of the paper and improve the stability and opacity of the paper. These characteristics increase with the increase of the coating amount

33. What are the types of printing coating paper

answer: printing coated paper can generally be divided into two categories: ordinary coated paper and special coated paper. Ordinary coated paper is coated on the surface of base paper by ordinary coating method, and then calendered after drying, and finally cut or rewound into flat paper or web paper, such as coated paper, light-weight coated paper, etc; Special coated paper refers to printing coated paper made with special coating or special processing methods, such as cast coated paper (glass paperboard), embossed paper and matte coated paper

34. Today, the production flow of printing coating paper has become an important field to stimulate consumption and improve economic growth in the universal tensile testing machine industry

answer: the production process of printing coating paper is as follows:

selection of base paper → coating preparation → coating by coater → drying → calendering or surface finishing → slitting or rewinding

35. How to classify the coating process

answer: coating operation is divided into in-machine type and out of machine type according to the relationship between coating machine and paper machine, and it is divided into single-layer coating and double-layer coating according to the coating times. In machine coating is to install a coating machine on the paper machine, so that papermaking and coating can be carried out continuously; Out of machine coating is the relative separation of coating machine and paper machine, and papermaking and coating are carried out independently. Double coated paper has better printability than single-layer coated paper, which can improve the quality of coated paper. There are three kinds of coaters used in coating operation: roll coater, air knife coater and scraper coater

36. What are the drying methods of coated paper

answer: after the coating is coated on the surface of the base paper, it cannot be dried directly with the dryer like non coated paper. Because the coating is still in a wet state, direct contact drying will make the coating stick to the surface of the dryer. Generally, infrared drying or hot air drying should be used, or these drying methods should be used to dry to a certain dryness, and then contact drying with drying cylinder

37. What is the surface calendering effect of coated paper

answer; There are also some bumps on the surface of the base paper after coating, which can make the display self repair slightly, and can not meet the gloss required by printing. Therefore, surface calendering treatment must be carried out. The most commonly used calendering method is super calendering. The super calender is composed of a plurality of metal rollers and paper meal rollers. The paper passes between the rollers under the action of pressure and friction to produce gloss. Matte coated paper does not need to be super calendered. The printer contains "printing materials" such as liquid or powder, or only slightly calendered

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