Stretch film co-extrusion casting

Precautions during processing

LLDPE has high melt viscosity and poor fluidity, and film shrinkage is easy to occur during extrusion cooling, and the film has more crystal points during processing. These problems directly affect the quality of the product. After analysis and testing, the following methods can be adopted to solve them.

(1) Film shrinkage phenomenon.

① Check whether the temperature of the quenching and setting roller is suitable. If the temperature is too low, it will easily increase the shrinkage, and if the temperature is too high, the cooling effect will be poor.

② Check the position, direction and uniformity of the air knife.

③Increase the pressing pressure and the tension of the flattening roller, so that the film is tightly attached to the quenching roller.

(2) Thin film crystal point.

①The temperature of the barrel is too low or too high to be unfavorable. If the temperature is low, the resin cannot be completely plasticized; if the temperature is too high, the melt pressure and shear force are small, which is not good for the plasticization of LLDPE resin, so the appropriate barrel processing temperature is determined according to the resin grade.

②The number of layers and meshes of the French mesh can be appropriately increased to solve the problems of low shear force and poor melting due to low melt pressure

③ The screw speed is low and the shear force is not enough. For shear-sensitive LDPE resin, it is easy to cause poor plasticization, so the screw speed should be increased appropriately.

(3) Processing technology and film self-adhesiveness. The self-adhesiveness of the film directly affects the performance of the product. The problem of poor self-adhesiveness in production can be solved in the following ways.

①In the flat film co-extrusion flow process, the self-adhesiveness and flexibility of the LLDPE stretch film is not dependent on adding a tackifier, but through the quenching of the quenching roller to make the film self-adhesive, so the quenching temperature is extremely critical.

②The thickness of the film also has a certain impact on the viscosity. If the thickness is too large, the self-adhesiveness is not enough and it will cause waste; if the thickness is too small, the film strength is poor, the puncture resistance decreases, and it is difficult to wrap and wrap. Therefore, the film thickness is controlled between 18pm ~ 22pm time is appropriate.

③Increasing the distance between the die head and the cooling roll can also increase the viscosity of the film.

④In order to ensure the viscosity and tightness of the film, properly adjust the contact pressure of winding and the characteristic tension ratio of winding and winding traction.