Vacuum bags will inevitably be in the process of production in small white spots and small bubbles, in general, we will be less than 1 mm diameter and uniform distributed small spot called & other;
White spot & throughout;
, whereas larger diameter can clearly see the two thin film layers are called & other
Bubbles & throughout;
The reasons for this are mostly results from two layers of thin film is not tight closely joint.
Packaging manufacturers to ensure the quality of vacuum packing bag and the defective rate will be effective control on the gluing quantity, amount of glue to appear too much or too little spots, bubble.
Here are other reasons for analysis: a liquidity problem, glue due to the dry compound roll version is used by net-like structure, composite glue after coating roll is transferred to the substrate is also a dense mesh point distribution, resulting in the plastic film on the site after a small clearance, composite glue is required to have good liquidity, pressure under the action of the machine, glue uniformly smooth, avoid to produce white spot, air bubble phenomenon.
Second, solvent residue problem dry compound process, solvent residue control mainly depends on the substrate after coating, into the heating stage, under the action of temperature and wind, solvent evaporation in the glue.
Vacuum packaging the gluing quantity generally to 3.
More than 5 g/m2, thickness of glue is close to 3.
Due to large vacuum packaging coating thickness, if the temperature of the composite equipment, convulsions can not meet the requirements, or glue less volatile solvent, glue in evaporation of solvent in the oven can't be effectively to agglomerate.
The coating substrate into the compound roll and rolling base adhesive, the second solvent will be left in the middle of the two layers membrane;
Into the drying chamber aging, in between the two layers membrane under the action of temperature, solvent volatilization, gaps between the two layers of film, composite membrane in white patches, bubble after curing.
Therefore, must be regular inspection of composite equipment temperature control and ventilation air volume, first of all, to strengthen the detection of solvent residue before production, and in the choice of raw materials, should choose solvent volatile better adhesive glue.
Three or composite roller, roller defect problem even if we on the gluing quantity and volatile control in a reasonable scope, or there will be a white spot or bubbles appear, we first observed the regularity of air bubbles, if is every certain period, and the shape is similar, this is often the glue roller on defective or with foreign body, partial pressure of false, form a regular bubbles.
To prevent the occurrence of such problems, in response to compound equipment parts before production to check and prevent has the foreign bodies such as tape, glue stick on the roller.
Four, composite roller pressure is insufficient, composite heat roller temperature is not hot roller heating under the action of temperature is the purpose of the melt adhesive, increasing the flow, the uniform distribution, the pressure discharge air, make the two membrane evenly and closely fit.
General composite equipment of the composite coating base material is clingy hot roller, heat from the sub passed to the underlying material, and in the second paper base material between the guide roller is equipped with heating roller, but in the actual production due to the rolling base material belongs to the second drawing materials, general preheating roll has no use.
When the temperature decrease, while the composite heat roller temperature is not low, but because of vacuum packing bag with sub thick, hot pressing process with short time can't make the substrate temperature rising rapidly.
Two membrane while hot cold, liquidity, in the middle of the adhesives produced white spot, increased the possibility of air bubbles.
And composite roller pressure slants small, can cause melting to dry solid adhesives, flow force decreases, and adhesive on the base of insufficient flowing property, increase the likelihood of white spot, bubbles appear.
When produce vacuum bags should be aimed at the climate change, timely adjust the temperature of the composite roller, and to ensure that the compound pressure.
Five, the composite roll and the Angle between the base material is not suitable for coating substrate after baking oven into composite department and compound roll a certain Angle, Angle is too big, easy cause buckling even bubbles.
In addition, the base material rotates at high speed, can produce a lot of static electricity, the surface air layer is very thick, the air layer before entering the compound roll will be squeezed out of the very few, easily through a pressing point into the composite membrane, the small bubbles formed in the composite membrane.
Carefully adjust the Angle, change the Angle, as far as possible according to tangent into the composite roller.
In addition, avoid by all means for the composite bonding points, so that will have a lot of air is entrained into the composite membrane.
The vacuum packaging