1. ***What are the raw materials of modern papermaking?***
A: Modern papermaking utilizes a variety of raw materials, including plant fibers (e.g., wood, bamboo, grass), mineral fibers (e.g., asbestos, glass fiber), other synthetic fibers (e.g., nylon, wire), and polymer materials derived from petroleum cracking. Currently, writing, printing, and packaging papers predominantly rely on plant fibers as the primary raw material.
2. ***What are the types of papermaking plant fiber raw materials?***
A: Plant fiber raw materials for the paper industry can be categorized into two main groups:
- **Wood fiber raw materials**: Fibers directly extracted from trees.
- **Non-wood fiber raw materials**: These include grass fibers, bast fibers, and seed-hair fibers.
3. ***What is the composition and function of common paper additives?***
A: Additives in paper production refer to various auxiliaries incorporated to enhance specific paper properties. These include fillers, binders, dyes, and other chemical additives. Fillers improve paper smoothness and opacity; binders enhance water resistance; dyes increase paper whiteness; and other chemical additives modify paper characteristics for specialized applications.
4. ***What is the role of rubber in paper production?***
A: Paper made from plant fibers contains numerous capillary pores between the fibers and hydrophilic hydroxyl groups within cellulose and hemicellulose, enabling it to absorb water or other liquids. To prevent liquid infiltration, hydrophobic colloidal or film-forming substances, such as rubber materials, are added during the sizing process. This enhances the paper's resistance to liquid penetration and diffusion.
5. ***What are the methods of sizing in the paper industry?***
A: Sizing methods are categorized based on their effects into internal sizing and surface sizing. Internal sizing involves adding hydrophobic substances to the pulp before paper formation, commonly using rosin-based or synthetic rubber materials. Surface sizing applies a thin layer of adhesive material onto the paper surface to enhance its liquid repellency, often utilizing starch, animal glue, or synthetic rubber materials. Surface sizing is primarily applied to offset paper, writing paper, and wrapping paper with liquid-repellent requirements.
6. ***What are the effects of surface sizing on printing paper performance?***
A: ① Increases the water resistance and surface strength of the paper, reducing fiber loss during offset printing;
② Enhances printability by balancing ink absorption-excessive adhesive can slow ink drying and cause smudging, while insufficient adhesive results in dull impressions;
③ Improves erasability by minimizing ink penetration, enhancing the paper's anti-friction properties;
④ Strengthens the paper's mechanical properties, such as tear resistance, fold resistance, and tensile strength;
⑤ Reduces paper curling and deformation.
7. ***What is the role of fillers in paper production?***
A: Fillers are added to impart specific properties to paper, such as whiteness, opacity, and smoothness. They also reduce internal voids, improving ink absorption uniformity. Commonly used insoluble or slightly soluble minerals constitute approximately 10%-25% of printing paper, with variations depending on the type of paper.
8. ***What characteristics should printing paper fillers possess?***
A: Printing paper fillers should exhibit high whiteness, high refractive index, fine particle size, low water solubility, low density, and excellent chemical stability. Additionally, they should be abundant in resources and cost-effective.
9. ***What are the commonly used fillers for printing paper?***
A: The most frequently used inorganic fillers include talc, clay, titanium dioxide, and calcium carbonate. Titanium dioxide is an expensive but high-quality filler, while organic synthetic fillers consist of macromolecular substances.
10. ***What are the effects of fillers on the performance of printed paper?***
A: Adding fillers to printing paper improves its printability by enhancing whiteness, smoothness, opacity, and stiffness. It also improves the paper's affinity, softness, and stability with ink, contributing to better print quality. However, excessive filler addition may weaken paper strength, reduce sizing effectiveness, and cause issues such as powdering, fiber loss, and plate contamination during printing. Using precipitated calcium carbonate (PCC) as a filler minimizes plate wear.