The basic manufacturing process of composite packaging bags is: printing, compounding, slitting, and bag making four steps, of which the two processes of compounding and bag making are the most suitable assembly methods.
Printing color checking
In the design process, in addition to choosing the wrong adhesive during the process, no matter how good the lamination process is, it will also lead to poor adhesion, low adhesion in post-processing, lamination, leakage, and broken cysts. rust.
There are many reasons to be considered in the selection of adhesives for daily chemical software packaging. Generally speaking, the following conditions should be met as a composite adhesive:
- No harmful extracts appear after packaging the liquid;
- Applicable food storage temperature requirements;
- Good weather resistance, no yellowing and foaming, no pulverization and delamination;
- Resistant to oils, fragrances, vinegar and alcohol;
- Does not corrode printing pattern ink, and has high affinity to ink.
Lamination is an important process in the production and processing of flexible packaging. Its common faults mainly include: generation of air bubbles, low lamination fastness, wrinkling and curling of finished products, stretching or shrinking of lamination products, etc. This section will focus on analyzing the causes of wrinkling and edge curling and their elimination methods.
This phenomenon accounts for a considerable proportion of dry composite faults, and the occurrence of this fault directly affects the quality of the finished bag.
composite white point
White spots due to poor ink coverage: For composite white inks, when the ink absorbs ethyl ester but does not volatilize enough to cause white spots, the method of improving the drying capacity can be used; if there are still white spots, the general solution is to increase the coverage of white ink Force, such as checking the fineness of white ink, because the ink coverage rate is strong if the grinding fineness is good.
Bubble phenomenon in compounding
1. The wetting of the film is poor, the concentration of the glue and the amount of coating should be increased, the surface of MST and KPT is not easy to wet, and it is easy to produce air bubbles, especially in winter. The air bubbles on the ink can be removed by increasing the amount of glue.
2. If the ink surface is uneven and foamy, the composite temperature and composite pressure of the composite film should be increased.
3. The amount of glue coating on the ink surface is small, the pressing time of the compound roller should be increased and the smooth roller should be used, the film should be fully preheated, the compound speed should be reduced, the glue with good wettability should be selected, and the ink should be selected correctly.
Poor peel strength
Poor peel strength means that due to incomplete curing, or too little glue, or the mismatch between the ink and the adhesive used, etc., although the curing has been completed, the bonding strength between the two layers of composite film is not enough. reduce the peeling force.
Pay attention to the proper storage of the glue, the longest is not more than 1 year (the tin can is sealed); prevent foreign matter from entering the glue, especially water, alcohol, etc. will easily cause the glue to fail, and the double-component type must be prepared immediately; use. It can also appropriately increase the amount of glue applied; increase the drying temperature and air volume, and reduce the compounding speed. Perform secondary treatment on the surface of the film to increase the surface tension; reduce the use of additives on the composite surface of the film. These methods can help us to improve the problem of poor composite peel strength.
Poor heat seal
The manifestations and causes of poor heat sealing of composite bags are basically as follows:
1. Poor heat seal strength. The main reason for this phenomenon is that the adhesive is not fully cured or the heat sealing temperature is too low. This problem can be improved by optimizing the curing process or increasing the temperature of the sealing knife appropriately.
2. Delamination and curling of the heat cover. The main reason for this phenomenon is that the adhesive is not cured. Adjusting the curing time or adjusting the curing agent content can improve this problem.
3. The opening is not good/the opening of the inner film is poor. The reason for this phenomenon is that there is too little anti-blocking agent, too much binder (modifier), and sticky or greasy film surface. This problem can be improved by increasing the amount of blocking agent, adjusting the amount of modifier, and avoiding secondary pollution on the surface of the film.