Summary of coating methods of paper coating machine

1. Air knife coating
This coating type is the most widely used and has wide adaptability. It is blown by a high-pressure fan (air pressure 15~60kpa) and enters the air knife body. It is composed of two stainless steel lips on the upper and lower sides of the air knife. The gap is 0.4~1.2mm and the nozzle is sprayed to form a knife-like air flow. It blows at a certain angle (usually 40 °~45 °) to the paper web, blowing off excessive paint, and blowing the surface coating of the paper evenly.
The coating amount depends on the distance between the air knife and the paper web (generally 2~8mm), the angle, the air pressure of the air knife, the paper transport speed and the coating viscosity. Generally, the vehicle speed can reach 100-400m/min, the coating volume is 10-20g/m2, the coating viscosity is 50-400mpa. a, and the solid content is 30-50%.
Its advantages: strong adaptability to the base paper, no matter the quantitative fluctuation of the base paper or the uneven surface, it can make the coating uniform, smooth and easy to operate; Large amount of coating is beneficial to improve the coating surface quality; Adapt to different requirements of coating viscosity. Due to the limited air flow energy of the air knife, it is only suitable for producing coatings with low solid content and low viscosity. In addition, the high-pressure air of the air knife needs to be purified.
This type of coating head is applicable to the production of coated printing art paper, coated paperboard, carbonless carbon paper, photographic paper, art paper, etc.
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2. Dip coating
The impregnation coating process is to make the base paper impregnate and absorb latex, resin, oil and other chemical agents, so that the paper can obtain special performance requirements such as waterproof, fireproof, wear-resistant, reinforcement, moisture-proof and insulation.
The impregnating agents used for impregnating cloth mainly include synthetic resin, synthetic latex, polystyrene latex, oil, paraffin, etc. The base paper used for impregnating Xu cloth can be plant fiber paper, inorganic fiber paper, synthetic fiber or synthetic paper. However, no matter what kind of paper, the following requirements must be met: ① The base paper has sufficient wet strength to prevent paper breaking or cracking during impregnation, so it generally uses more long-fiber wood pulp. ② The base paper has good absorbency. Therefore, the base paper is not sized; And the degree of beating, pressing and polishing is low.
Due to the difference of all impregnating agents, the properties and uses after processing are different.
1) Resin impregnant
Such impregnating agents include phenolic resin, melamine formaldehyde resin, formaldehyde resin, etc. After impregnation, the paper has waterproof, oil-proof, wear-resistant, insulation and other properties. This kind of paper can be used as decorative paper, laminated composite paper, electrical insulation paper, laundry label paper, etc. After impregnation with melamine, the paper can have a thin layer of transparent resin on the surface, which has corrosion resistance and waterproof properties; Phenolic resin has good insulation.
2) Latex impregnant
Such impregnating agents include styrene-butadiene latex, neoprene latex and acrylic latex. After impregnation, the internal strength of the paper is improved, and the abrasion resistance of the paper is improved. For example, special paper for securities, wood veneer binding paper and packaging and decoration paper.
3) Oil and paraffin impregnant
Such impregnating agents include dry oil (linseed oil, tung oil, etc.) and paraffin. After oil impregnation, it has good water resistance, moisture resistance, high strength and transparency. After paraffin impregnation, it has water resistance and opacity, and is mainly used for oil-proof, water-resistant and moisture-proof packaging paper.