Functional adhesive properties and applications (below)

However, some people will worry about curing too quickly, so that gel phenomenon occurs in the plastic disk on the dry complex machine. In fact, this worry is not necessary. Because the selected functional component is inert at room temperature, only a certain temperature can stimulate its activity, that is, the special functional component will only work when passing through the drying tunnel and in the environment of the curing chamber. To shorten the curing cycle to 24 hours or even shorter compression, thus speeding up the material flow, improve labor productivity and create good economic benefits for customers.
Fifth, high temperature resistant adhesive The so-called durable high temperature, including the long-term high temperature and instantaneous high temperature. The former refers to high-temperature cooking for a certain period of time during heating and pressure sterilization in a food processing process, and the latter is instantaneous high-temperature pressing at the time of bag-making sealing. To meet the requirements of high temperature resistance, that is, in both cases, the adhesive must be able to maintain a good bonding performance and high peel strength, no deformation, no bag breakage. It has been verified by experiments that under the condition that the glue amount reaches 4.5-5 g/m2, the PET and CPP composite film is used for bagging, and the hot and sour food is sealed, and then cooked at a high temperature of 121-125° C. for 30 minutes. In 45 minutes, no deformation or separation occurred.
Sixth, the application of precautions Here to talk about how to determine the complex process conditions in order to allow the adhesive to obtain the best results.
The first is the substrate. Whether it is plastic film or aluminum foil, there is a common requirement that surface conditions. Here are two meanings. First, the surface should be dry and clean, free of dust, free from moisture, and free of oil. Second, the surface tension should be controlled at 38mN/M or more. If it is made of medium and high temperature resistant packaging, the surface tension of the plastic film is preferably raised to 39mN/M or 40mN/M; and the surface cleanliness of the aluminum foil should be Class A, that is, When checked with distilled water, it should all be wetted; the surface tension is above 72mN/M.
Followed by the amount of glue. Different substrates and different final packaging requirements, stay with different amounts of glue. Simple plastic/plastic compound can be less, 2.5-3.0 grams per square meter can be, if the composite material containing aluminum foil, but also to resist erosion of media, 3.5-4.0 grams per square meter. If high-temperature cooking is required, except for the extremely important surface tension, 4.5-5.0 grams per square meter are required.
The third is the control of the residual solvent. The amount of residual solvent not only affects the odor and the hygienic properties of the food, but also has a significant effect on the transparency and peeling force. China's GB9683-88 standard stipulates that the residual solvent must not exceed 10 milligrams per square meter; but it is best to be able to control below 5 milligrams per square meter. Therefore, in the choice of composite process, it must be determined from the factors of solvent type, drying tunnel temperature, start-up speed, blast volume and exhaust air volume.
The fourth is aging conditions. Because the adhesive is a two-component reaction type, proper conditions must be met to allow the main agent in the adhesive to fully react with the curing agent to achieve the best adhesion results. The functional adhesive, which can react chemically with active elements on the surface of the substrate, must have a certain temperature and time.
According to our experience, this reaction is perfect with the increase of the ambient temperature and the extension of time. Such as high temperature cooking glue, at about 50 °C about five days and five nights (120 hours) to complete, but at about 80 °C; then three or four hours on the line. Of course, 80 °C drying room is impossible. In addition, due to the reaction between the curing agent and the main agent; it can also be carried out at room temperature, so some units do not mature into the drying room after being compounded, and it is not necessary to place after a week. The result of this low-temperature maturation is obviously not as good as the result of heat curing, especially for cooking bags. So, hope to pay attention to this.