Pay attention to the following 3 points when making boiled packaging bags
① Under the condition of ensuring the appearance of the sealing, set a slightly higher heat sealing temperature to avoid the unstable heat sealing quality caused by the thickness deviation of the composite film.
② During normal production, the edge sealing should ensure three effective heat sealing times. When restarting after shutdown, it may appear that the parts that have been hot-pressed once or twice have been cooled when the machine is turned on again (the first hot-pressing can only play a role in preheating), and the actual effective number of heat-sealing is only two. Therefore, it is also necessary to set a higher heat-sealing temperature (the heat-sealing is good after two heat-pressing) to avoid a small number of poor sealing phenomena when the machine is turned on after the machine is shut down.
③Most boiled pouches are packaged in liquid, which requires high drop resistance performance. Avoid undercutting of the heat-sealed edges when making the bag, especially the edge of the heat-sealing knife should not be too sharp, and should be chamfered or polished appropriately. .
1. The representativeness of sampling
① When the first sample is confirmed, the quantity of one continuous sampling should cover the length of all sealing knives, so as to effectively avoid the phenomenon of partial sealing failure and missed inspection.
②Sampling is to take samples after the debugging is normal, adjust the heat sealing temperature, pressure, machine speed, and reconfirm after replacing the film roll.
2. The validity of the method of heat-sealing strength testing and judging
①The correct method is to cut the heat-sealing side of the bag into a narrow strip of 20-30mm and then tear it in the direction perpendicular to the sealing line. You cannot use bamboo sheets to lean against it.
②The inside of the sealing edge should not be torn apart with a width of more than 2mm. Otherwise, the strength is qualified during the machine test, but the heat-sealing layers are not completely integrated, resulting in a greater reduction in the sealing strength during boiling and the phenomenon of poaching broken bags. When the bag is separated from the interface of the two inner layers of PE on the sealing edge after boiling, it is a problem that the heat sealing edge is not strong.
3. Key points of boiling test
(1) Sampling method
① After the test machine of the boiled packaging bag is normal, the inspector shall randomly draw a number of sample bags in each row in the test machine bag (the number of samples shall cover the length of the longitudinal sealing knife), encapsulate in water, and carry out the boiling test.
②When sampling bags with more than one out of two, use a marker to clearly mark the out of the bag and the left and right directions in order to accurately determine the position of the sealing knife where the heat sealing is not strong.
③When the normal production process conditions have changed significantly, such as machine speed, temperature adjustment, etc., it must be re-sampled for boiling test.
④After each shift, samples should be re-sampled for boiling performance test.
⑤Isolate and deal with the unqualified products found in the process in time.
(2) Test conditions
①Put 1/3 to 1/2 volume of water in the packaging bag, and try to exhaust air when sealing. If too much air is enclosed, it is easy to cause misjudgment. When boiling test, add a cover to slightly increase the pressure in the bag.
②The boiling time is subject to the customer's use conditions, or according to relevant testing standards.
(3) Test qualification standard
①There is no overall or partial wrinkling or delamination on the bag surface; the peel strength is tested after boiling.
②The printing ink has no discoloration or bleeding;
③There is no leaking bag breaking phenomenon; there is no obvious edge running phenomenon at the sealing edge (the running edge width is controlled within 2mm)