The sizing machine in a paper - making machine is a device used to apply sizing agents to the surface of paper or paperboard,
which aims to enhance the resistance of paper and paperboard to the penetration and diffusion of aqueous solutions, as well as improve their smoothness,
hydrophobicity, and printing adaptability.
There are different types of sizing machines. For example, the film - transfer sizing machine is a pre - metering - roll - type sizing equipment.
The sizing liquid is pre - metered onto the sizing roll through a metering component to form a uniform sizing film.
When the paper web passes through the nip of the sizing roll, the sizing film is transferred from the sizing roll to the paper web to complete the sizing process.
Due to the pre - metering, the sizing film is thin and uniform.
When the paper web passes through the nip, it is subjected to less impact from the sizing liquid, and the amount of sizing liquid that penetrates into the paper web is limited,
resulting in less re - wetting, less decrease in paper web strength, and being beneficial for reducing breaks at the sizing press and improving the operation of the paper - making machine. It can be applied within a wide speed range of 50 - 2000 m/min.
Moreover, depending on the different hardness of the roll covering, it can be used for surface sizing, pigment coating, and can also perform different operations on both sides of the paper (such as coating on one side and sizing on the other).
Another example is the size - press coater, which is configured on the paper - making machine to perform surface sizing on the paper web.
It has the same meaning as sizing - press coating, and its mechanical structure is basically the same as that of the dewatering - press component, consisting of a rubber - covered roll and a chrome - plated roll.
There are three arrangements: horizontal, inclined, and vertical. Generally, it is installed at the rear of the drying section of the paper - making machine, where the moisture content of the paper web is basically close to the air - dried state. It is used in paper - making machines for producing high - grade cultural paper, high - grade printing paper, kraft paper, etc.
