The production process of cultural paper mainly consists of two core stages: pulping and papermaking. While the specific processes vary depending on the type of cultural paper (such as coated paper, woodfree paper, and newsprint), the overall process is similar.
Pulping Process
Pulping is the process of separating plant fiber raw materials (such as wood, bamboo, straw, and waste paper) into fibers suitable for papermaking. It mainly includes the following methods:
Chemical Pulping: Using chemical solutions (such as the sulfate process) to cook the raw materials removes impurities such as lignin, retaining pure fibers. This method produces pulp with high strength and light color, suitable for high-quality cultural papers such as woodfree paper and offset printing paper.
Mechanical Pulping: Using a wood grinder to directly grind wood segments into fibers. This method has a high yield but the fibers are shorter, and the paper is prone to yellowing. It is mostly used for newsprint and other paper types where durability requirements are not high.
Semi-chemical/chemimechanical pulp: Combining chemical pretreatment and mechanical refining, balancing yield and quality, it is commonly used in mid-range cultural paper products such as molded paper.
Recycled pulp: Made from waste paper through deinking, washing, and screening processes, it is environmentally friendly and energy-saving, and widely used in the production of various cultural papers.
Papermaking Process
Papermaking is the process of uniformly dispersing pulp in water and then producing finished paper through steps such as forming, dewatering, pressing, drying, coating, and calendering. The main process is as follows:
Pulp Mixing and Preparation: Pulps from different sources are mixed in proportion, and fillers (such as calcium carbonate and titanium dioxide), sizing agents (to improve water resistance), dyes, and other additives are added to meet the performance requirements of specific paper types.
Paper Forming (Forming): After dilution, the pulp is fed into the wire section of the paper machine, where water is filtered through a high-speed wire screen, and fibers are uniformly deposited to form a wet paper sheet. This is a crucial step determining the uniformity and smoothness of the paper.
Pressing and Dewatering: The wet paper sheet passes through multiple pressure rollers to further squeeze out moisture, improving the paper's dryness and strength.
Drying: The paper sheet enters the drying cylinder, where steam heating evaporates the moisture to the standard moisture content (usually below 6%), ensuring paper stability and printability.
Surface Treatment (Depending on Paper Type)
Coating: Used for coated paper, lightweight coated paper, etc., this involves coating the paper surface with kaolin, latex, or other coatings to improve gloss, smoothness, and print clarity. Based on the coating amount, it can be classified as super, premium, or regular coated paper.
Calendar: The paper is pressed using hot and cold rollers to improve surface gloss and smoothness. Commonly used for woodfree paper, offset paper, etc.
Rolling and Slitting: The finished paper is rolled into large rolls, then slit into sheets or smaller rolls according to market demand, and packaged for shipment.
