1. What are the raw materials of modern papermaking?
Answer: The raw materials of modern papermaking include plant fibers (wood, bamboo, grass, etc.), mineral fibers (asbestos, glass fiber, etc.), other fibers (nylon, metal wire, etc.), and polymer materials obtained by cracking petroleum. At present, the paper used for writing, printing and packaging is still mainly made of plant fibers.
2. What are the types of plant fiber raw materials for papermaking?
Answer: At present, the plant fiber raw materials used in the paper industry can be divided into two categories:
Wood fiber raw materials: plant fibers obtained directly from trees.
Non-wood fiber raw materials: divided into grass fiber raw materials, bast fiber materials and seed hair fiber materials.
3. What are the composition and functions of commonly used auxiliary materials for paper?
Answer: Auxiliary materials refer to various additives added to paper to meet the different performance of paper. The auxiliary materials are composed of fillers, rubber materials, pigments and other chemical additives.
Fillers can improve the smoothness and opacity of paper; sizing materials can make paper have water resistance; pigments can increase the whiteness of paper; dyes can color paper; other chemical additives can change the properties of paper to provide Some special uses of paper.
4. What is the role of rubber?
Answer: Paper produced from plant fibers can absorb water or other liquids because of the large number of pores between the fibers themselves and the fibers, and the cellulose and hemicellulose that make up the fibers contain a large amount of hydrophilic hydroxyl groups. In order to prevent the paper from being infiltrated by water or other liquids, it is necessary to add liquid-resistant colloidal substances or film-forming substances, that is, sizing materials, to the paper to provide the paper with resistance to liquid penetration and diffusion. The process of applying size in the paper industry is called sizing.
5. What are the methods of sizing?
Answer: According to different sizing effects, sizing methods are divided into internal sizing and surface sizing. Internal sizing is to add sizing material into paper pulp, and then make it into liquid-repellent paper and cardboard. Commonly used rubbers include rosin rubber and synthetic rubber. Surface sizing is to coat a thin layer of sizing material on the surface of the paper to make the paper hydrophobic. Commonly used rubbers include starch, animal glue, and synthetic rubber. Surface sizing is mainly used for offset paper, writing paper, and packaging paper and cardboard that require liquid repellency.
6. What are the effects of surface sizing on the performance of printing paper?
Answer: ①Increase the water resistance and surface strength of the paper, which can reduce the lint of the paper in offset printing; ②Improve the printability. If the surface sizing material is too small, the paper will absorb too much binder in the ink during printing, resulting in The blot is dull. On the contrary, if the surface sizing material is too much, it will slow down the drying rate of the ink, resulting in smearing and bright stains; ③Increase the erasability of the paper, surface sizing can reduce the penetration of ink, so it is easy to wipe off the ink and increase The abrasion resistance of the paper surface; ④Increase the strength of the paper, such as bursting resistance, folding resistance and tensile strength; ⑤Reduce the difference and deformation of the paper.
7. What is the role of filler?
Answer: The filler is used to make the paper obtain specific properties, such as whiteness, opacity, smoothness, etc. At the same time, the addition of fillers makes the internal voids of the paper smaller and finer, thereby increasing the ink absorption of the paper and making the ink absorption change uniform. Usually added to the water-insoluble or slightly water-soluble minerals in the slurry, the content in the printing paper is about 10%-25%, and the amount of addition of different papers is different, and may vary greatly
8. What are the characteristics of printing paper fillers?
Answer: The filler for printing paper should have high whiteness, high refractive index, fine particles, low water solubility, low density and good chemical stability. In addition, it is best to have abundant resources and low price.
9. What are the commonly used fillers for printing paper?
Answer: The most commonly used inorganic fillers are talc, clay, titanium dioxide and calcium carbonate. Among them, titanium dioxide is an expensive and high-quality filler; organic synthetic fillers are some polymer substances.
10. What are the effects of fillers on the performance of printing paper?
Answer: Adding fillers to printing paper can improve the printability of the paper, such as increasing the whiteness, smoothness, opacity and stiffness of the paper. Improve the affinity, softness and stability of paper to ink, thereby contributing to the improvement of printing quality. Of course, adding too much filler to the paper also brings some undesirable effects, which are mainly manifested as the reduction of paper strength and the reduction of sizing effect. The phenomenon of powder and lint is easy to occur in printing, and the filler particles are transferred to the printing plate and rubber. Phenomena such as paste will occur on the cloth; due to the friction of the filler, the printing plate will also be worn, but the use of precipitated calcium carbonate (PCC) to fill the plate can minimize the wear of the printing plate (currently used by Jindong).
11. What is the opacity of paper?
Answer: Opacity refers to the opaque nature of paper. The opacity of paper depends on the light scattering ability of the paper, the number of light scattering interfaces inside the paper (ie the number of independent particles inside) and the difference in refractive index of the scattering interface. The more light scattering interfaces, the greater the refractive index difference between the scattering interfaces, the greater the light scattering ability of the paper and the higher the opacity.
12. How does the filler affect the opacity of the paper?
Answer: Paper without filler is composed of fiber and air. Air exists in the pores between the fibers. Due to the difference in refractive index between the fibers and air, when the light beam hits the surface of the paper, part of the light is scattered at the fiber-air interface, giving the paper a certain (lower) opacity , Reflected in printing, mainly manifested as extremely easy to see through. After adding a filler with a refractive index greater than that of cellulose to the paper, the number of light scattering interfaces inside the paper is increased, that is, there are three different interfaces between fiber and air, filler and fiber, and filler and air. Among them, the difference in refractive index between filler and air is larger. Therefore, the light gets the maximum scattering at the filler-air interface, resulting in an increase in opacity.
13. How does the filler improve the smoothness of the paper surface?
Answer: The network formed by the interweaving of fibers always has a large number of pores and surface unevenness. The addition of fine particle fillers can improve the softness and plasticity of the paper, and can be better calendered, thereby improving the calendered paper The smoothness.