Analysis and treatment of common pouch-making faults(1)
1. Poor heat sealing strength
1.1 Influence of heat sealing material
Different types of heat-sealing materials have different heat-sealing strengths, such as PP, PE, and EVA heat-sealing strengths are inconsistent; products of the same film with different polymerization methods have different heat-sealing strengths; the thickness and uniformity of materials will also affect heat-sealing Strength, different processing methods of the heat seal layer, such as blow molding, cast film, etc., all affect the heat seal strength. If the storage time of the film is too long, the precipitates will increase, and the heat sealing strength will be poor after corona treatment; the hygroscopic material will absorb moisture, the heat cover will delaminate, and the peel strength will decrease.
1.2 Influence of laminated film processing technology
The temperature resistance of the printing ink is poor or the additives in the ink are not suitable. Under the high temperature of pouch making, the printing layer will delaminate and the heat sealing strength will decrease. The heat sealing edge should be designed as no pattern as possible. Adhesive selection is also very important in the composite process. Whether the adhesive ratio, viscosity and other parameters are reasonable or not will affect the sealing strength. In the extrusion compounding or coating process, the processing temperature is high, the degree of surface oxidation of the material is large, and the amount of carboxyl groups is increased, which is not conducive to heat sealing.
1.3 Influence of pouch making process
The edge cooling after heat sealing is not enough; the shaping is not enough, the internal stress cannot be eliminated, the sound strength and appearance should be checked in time, and the cooling water circulation system should be strengthened. The more times of heat sealing, the higher the heat sealing strength. The number of longitudinal heat-sealing depends on the effective length of the longitudinal welding knife and the length of the pouch; the number of transverse heat-sealing is determined by the number of combinations of the machine's transverse heat-sealing devices. Good heat sealing requires at least two times of heat sealing.
