5. What are the sizing methods?
Answer: according to the different sizing effects, the sizing method is divided into internal sizing and surface sizing. Internal sizing is to add the size to the pulp, and then make paper and paperboard with hydrophobicity. Commonly used compounds are rosin compound and synthetic compound. Surface sizing is to apply a thin layer of sizing material on the surface of the paper so that the paper has hydrophobic properties. Commonly used rubber materials are starch, animal glue, and synthetic rubber. Surface sizing is mainly used for offset paper, writing paper, and packaging paper, and paperboard with hydrophobicity requirements.
6. What are the effects of surface sizing on the properties of printing paper?
A: ① increase the water resistance and surface strength of the paper, can reduce the phenomenon of paper in offset printing; ② improve the printability, if the surface glue is too little, the paper will absorb too much binder in the printing ink, resulting in matte imprinting. On the contrary, if there are too many surface sizing materials, it will slow down the drying rate of the ink, resulting in rubbing and bright stains; ③ increase the paper's abradability, surface sizing can reduce the penetration of the ink, so it is easy to wipe off the ink, increasing the anti-wear ability of the paper surface; ④ increase the paper's strength, such as bursting strength, folding strength and tensile strength; ⑤ reduce the two side difference and deformation of the paper.
7. What is the function of filler?
A: filler is to make the paper obtain specific properties, such as whiteness, opacity, smoothness, etc. at the same time, the addition of filler makes the gap inside the paper smaller and thinner, so as to increase the ink absorption of the paper and make the ink absorption more uniform. The content of insoluble or slightly soluble minerals in the pulp is about 10% - 25% in the printing paper. The amount of minerals added to different papers is different and may vary greatly
8. What are the characteristics of printing paper filler?
A: the filler of printing paper should have high whiteness, high refractive index, fine particles, low water solubility, low density, and good chemical stability. In addition, it is better to have rich resources and low prices.
9. What are the common fillers for printing paper?
A: 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, and organic synthetic filler is some high molecular material.