What factors mainly affect the glossiness of cast-coated paper?

The glossiness of cast-coated paper is primarily influenced by the following factors:

Quality of Base Paper
Air Permeability and Tightness: The base paper should be an excellent conductor of steam, featuring high air permeability, low tightness, and a certain degree of bulk. This is crucial because during the drying process, moisture within the coating needs to evaporate through the back of the base paper. If the base paper has poor air permeability, the steam generated during drying cannot be expelled promptly, potentially causing it to burst through the coating, resulting in pinholes or pits on the coating surface, thereby affecting glossiness.
Surface Strength and Stiffness: The base paper should possess high surface strength and stiffness. This is due to the high usage of adhesives in cast-coated paper coatings, which also renders the coating surface highly strong. If the base paper's surface strength is too low, delamination may occur during the peeling process of the final paper. Additionally, stiffness helps reduce curling during production and storage, thereby maintaining the uniformity and glossiness of the coating.
Basis Weight, Thickness, Evenness, and Smoothness: The base paper's uniformity in basis weight, thickness, evenness, and smoothness is crucial. Any inconsistency in these aspects can lead to reduced coating uniformity, subsequently impacting glossiness.

Coating Formula and Properties
Pigment Influence: The pigments added to the coating significantly impact the film's glossiness. Different pigment types, particle sizes, shapes, and distributions all affect light reflection and scattering on the coating surface, thereby influencing glossiness. For instance, using pigments with small, uniformly distributed particles can help enhance glossiness.
Choice and Dosage of Adhesive: The type and amount of adhesive used also have a notable impact on the glossiness of cast-coated films. Typically, adhesives with low glass transition temperatures, good film-forming properties, plasticity, and glossiness are more suitable for cast-coated paper production. The adhesive dosage must also be appropriate; too much or too little can both affect the coating's glossiness and quality.

Casting Process Control
Drying and Film Formation of the Coating: The degree of coating dryness and film quality directly affect glossiness. If the coating surface dries prematurely or unevenly during the drying process, it may result in cracks or unevenness, reducing glossiness. Therefore, it's essential to control parameters such as drying temperature and air velocity to ensure even and rapid drying, leading to the formation of a high-quality film.
Influence of the Casting Roll: The casting roll presses the coating against the chrome-plated drying cylinder. Its hardness, linear pressure, and surface condition all impact paper quality. Higher linear pressure results in closer adhesion between the coating and the chrome-plated drying cylinder, enhancing paper glossiness. However, excessive linear pressure can cause the coating to rupture or lead to other quality issues.
Drying Cylinder Temperature and Surface Quality: Drying cylinder temperature is another crucial factor affecting glossiness. Excessively high temperatures can cause pits or bubbles on the coating surface, while too low temperatures can affect drying speed and output. Additionally, the drying cylinder's surface should be mirror-polished and regularly maintained to ensure its smoothness and glossiness are transferred to the coating.

Other Factors
Coating Thickness: Coating thickness is also an important factor influencing glossiness. Generally, thicker coatings yield higher glossiness. However, excessively thick coatings can lead to uneven surfaces or other quality issues.
Environmental Factors: Factors such as temperature, humidity, and cleanliness in the production environment can also affect the glossiness of cast-coated paper. For instance, high humidity can cause condensation on the coating surface or other quality issues, while insufficient cleanliness can lead to impurities or defects on the coating surface.

In conclusion, the glossiness of cast-coated paper is influenced by multiple factors, including base paper quality, coating formula and properties, casting process control, and other variables. Comprehensive consideration of these factors and implementation of corresponding control measures during production are necessary to ensure the glossiness of cast-coated paper meets requirements.