15. How does filler affect the bulk of paper?
Answer: the density of paper fiber is about 1g / cm3, while the density of filler is mostly 2.5-3.0g/cm3. Therefore, the addition of filler will reduce the loose thickness of the paper. But when the amount of filler is small, the loose thickness increases with the increase of filler, especially for short fiber paper.
16. How does filler affect paper stiffness?
A: paper stiffness is a function of paper thickness and elastic modulus. The influence of fillers on stiffness should be considered in combination with the influence of fillers on the loose thickness and tensile strength. When the amount of fillers is small, the addition of fillers does not affect the paper stiffness. When the amount of fillers increases, the paper stiffness decreases significantly with the increase of the number of fillers.
17. What is the role of color in the paper?
A: even the bleached pulp fiber is slightly yellow or gray. This is because the lignin in the pulp fiber tends to absorb violet and blue light with a wavelength of 400-500nm. The more lignin in the pulp, the darker the color. Therefore, in order to make the paper have higher whiteness, blue-purple or red-blue dyes are often added to the bleached pulp. The production of a colored paper must also be dyed.
18. What are the ingredients of pigments?
A: pigments are pigments and dyes used for paper dyeing and color matching. Pigments are mostly inorganic, and most of them are insoluble in water. Dyes can be divided into natural dyes and synthetic dyes. At present, synthetic dyes have completely replaced natural dyes, and most of them are soluble in water, or soluble in water after chemical treatment.
19. Other chemicals in paper accessories and their functions?
A: in order to meet the needs of some special uses of paper, various types of non-fiber additives are often used in pulp or paper. According to their uses, they can be roughly divided into the following categories:
① Wet strength agent. A wet strength agent is a kind of additive added to increase the wet strength of paper, such as urea-formaldehyde resin and phenolic resin.
② Dry strength agent. Such as cationic starch, polyacrylamide, etc.
③ Retention aids. Additives such as polyacrylamide, polyethylene oxide, and polyethyleneimine are added to reduce the loss of fillers and fines in a papermaking process.
④ Defoamer. It is used to eliminate foam in the papermaking process. Such as silicone oil, turpentine, tridecanol, tributyl phosphate, pentanol, and octanol.
⑤ Water-resistant agent. It is mainly used in paper with a high requirement of water resistance. Such as paraffin, metal soap, glyoxal, melamine resin, and dimethyl aminoethyl acrylate.
20. How to classify paper simply?
A: paper can be divided into cultural paper, industrial paper, household paper, and special paper according to its use. Cultural paper can be simply divided into uncoated paper and coated paper. Uncoated paper is called uncoated paper, such as newsprint, offset paper, xerographic paper, and writing paper; coated paper is called coated paper, such as coated paper, calendar paper, matte paper, glass card paper, etc.