The production of wood grain paper is mainly based on coating technology. According to the process and the final product form, it can be divided into two main categories: impregnated paper and printed decorative paper (such as polyboard and decorative board) .
Impregnated paper uses base paper with special functions (such as transparent base paper, plain base paper, and decorative base paper) as raw material, and synthetic resin adhesives (such as phenolic resin, urea-formaldehyde resin, melamine resin, etc.) as impregnation liquid. It is impregnated under certain process conditions, dried to a certain degree, and then firmly bonded to the surface of the substrate by hot pressing. Commonly used equipment includes vertical impregnation machines (simple process, low efficiency, suitable for thin paper) and high-speed horizontal impregnation dryers (can perform multiple impregnations, resulting in thicker coatings).
The printed decorative paper process involves pasting decorative paper printed with wood grain or patterns onto the surface of a wood-based panel substrate, and then coating the surface with a resin coating. Depending on the coating resin, it is mainly divided into polyurethane board (surface coated with unsaturated polyester resin, with a bright and glossy surface) and decorative board (surface coated with amino resin (such as melamine resin), with a matte finish). The advantages of this process include rich surface effects and wear and heat resistance; the disadvantages are shallower resin penetration, thinner film, high requirements for substrate flatness, and a generally less realistic appearance than impregnated paper.
The production of impregnated paper requires the impregnating liquid to have a relatively small molecular weight, low viscosity, and good permeability; the formed paint film needs to be cold-resistant, heat-resistant, water-resistant, chemical-resistant, and wear-resistant; after drying, the paint film should be smooth, full, with suitable gloss, high strength, and good transparency. New processes use materials such as water-based polyurethane resin for coating or as raw materials for the impregnating liquid to improve the product's wear resistance, smoothness, and transparency, and better showcase the underlying texture.
