What are the functions and characteristics of extrusion coating technology using a coating machine?

Extruded coating by a coating machine is a multifunctional coating technology that applies a molten web of synthetic resin onto a substrate material. It is used for the economic application of various plastics, especially polyethylene, cardboard, corrugated fiberboard, paper, aluminum foil, cellulose, non-woven fabric or plastic film. What are the functions and characteristics of extrusion coating technology using a coating machine?

The function of extrusion coating technology of coating machine

1. Paint:

The actual process of extrusion coating involves directly extruding resin from a slit die at a temperature of up to 320 ℃ onto a moving web, which can then be passed through a roller gap composed of rubber covered pressure rollers and chrome plated cooling rollers in a coating machine. The latter cools the molten film back to a solid state and imparts the required smoothness to the plastic surface. The speed at which paper is extruded from the mold is usually much faster than that of resin, and the resulting coating thickness is proportional to the speed ratio and slit gap.

2. Laminated:

Extrusion lamination is a similar process, with the difference being that the extruded hot melt resin serves as the bonding medium for the second material web.

3. Co extrusion:

Co extrusion is also a similar method, but two or more extruders are connected to a single die, where separately extruded melts are put together and finally extruded into multiple layers of film.

Coating machine is a production equipment mainly used for surface coating processes of films, paper, etc. It brings convenience to people's coating production. Its winding and unwinding are equipped with a full speed automatic film connecting mechanism for use and operation, and the tension closed-loop automatically controls the operation of the coating equipment. Therefore, the operation is simple and fast during use, but the machine is essential for wear and tear during use.

The transmission parts of the coating machine are severely worn during operation, one is the dryer shaft head wear, and the other is the paper roll bearing chamber wear. When solving this problem, methods such as welding, thermal spraying, and electric brush plating are generally used for repair. If the machine is severely worn, it is best to take it to a regular shop for repair! In addition, when using machines in daily life, it is necessary to follow the correct operation and do a good job in the daily maintenance of the machine, so as to reduce the wear and tear of the machine and extend its service life!

The coating machine is used for the coating production of BOPP sealing adhesive tape. Coat the rolled substrate with a specific functional adhesive, coating, or ink, and dry it before winding. It uses a dedicated high-speed coating head, which can effectively reduce the occurrence of bubbles. The unwinding and unwinding of the coating machine are equipped with full speed automatic film connection arrangement and tension closed-loop automatic control.

Characteristics of coating extrusion technology using coating machines

The monotonicity of the slurry after coating by the coating machine is composed of the following two heat and mass transfer processes

1. The evaporation and vaporization process of the surface liquid

The wet coating undergoes heat exchange with monotonic hot air, absorbing the heat of monotonic air. The liquid on the surface of the coating continuously evaporates into steam and enters the air, which is then carried away by the monotonic air. When the liquid content of the wet coating is relatively high (above the critical moisture content), the speed of surface vaporization depends on the following factors: A surface air activity speed; B monotonic humidity of air; The temperature of monotonic air. When the moisture content of the coating reaches the critical moisture content, the vaporization rate on the surface depends on the loosening speed of the liquid inside the coating.

2. The process of internal liquid loosening occurs because the vaporization on the surface of the coating reduces the concentration of the liquid on the surface of the coating, causing the liquid inside the coating to continuously loosen towards the surface.

(1) The coating applied during the transition stage enters the monotonic box, and the surface of the film gradually decreases in temperature due to the evaporation and heat absorption of solvents or water, resulting in a leveling process.

(2) The deceleration monotonic stage is characterized by:

A、 Monotonic speed is controlled by internal loose speed

B、 Monotonic speed decrease

C、 The temperature of the coating increases monotonically for a long time

(3) Constant speed monotonic stage, characterized by:

A、 The coating surface has satisfactory moisture or solvent,

B、 The monotonic speed is controlled by external conditions - gasification speed.

C、 Monotonic speed stability

D、 Most of the water or solvents vaporize at this stage.

E、 The surface temperature of the coating is equal to the wet bulb temperature of monotonic air