The use of high-temperature cooking glue points (2)

In addition to the reason of the glue itself, the production process has a great influence on the properties of the adhesive. The most common one is that the contradiction of the coating amount and the degree of drying affect the peel strength. All suppliers of cooking glues have emphasized that the coating amount of cooking bags must reach 4 grams or more, otherwise the strength after cooking cannot be guaranteed. The figure at the top of the right is a typical curve of the relationship between coating amount and peeling strength of cooking glue.

More than 4 grams of coating amount, but also to ensure complete drying (composite down measurement less than 5 mg), the general small equipment is difficult to do. However, we found that many people use these small devices to cook bags. These factories also learned from the failure experience: more than 4 grams of coating is not as good as about 3 grams. After careful inspection, it was not unreasonable to think that, with more than 4 grams of glue applied, it resulted in poor drying (we often measured the residue of finished product bags for customers, a lot of 20-30 mg). It was not as good as the amount of coating and the drying condition was better. The chance of problems has diminished.

Of course, in order to really increase the strength of cooking bags, we must also work hard to improve the ability of the drying system. Specifically, the air inlet system reduces the amount of circulating air and multiplies fresh air; it increases the amount of exhaust air and keeps the negative pressure of the drying oven. Equipment manufacturers often do not provide exhaust ducts and outdoor exhaust fans for simple composite machines, but they are supported by users themselves. Due to the lack of expertise, the amount of exhaust air is insufficient. What's more, some small copiers are designed with one-sided emphasis on saving energy to please customers. In addition, the use of recycled air was also increased under conditions where the amount of air intake and exhaust was not sufficient. Regardless of safety, although the power was saved, the ability of the drying system was further reduced. Customers who use such equipment can be said to have never produced qualified products, are not flaky in the bags, or have poor mouth opening, and the bags are delaminated from time to time after cooking. The adhesives can not solve the problem if they are changed one by one.

Finally talk about aging. The general trend of the maturation process is a logarithmic relationship between the percentage of hydroxyl and isocyanate reactions and the maturation time. In other words, the reaction proceeds very quickly when the aging proceeds, and as the time goes by, the amount of hydroxyl groups and isocyanate in the adhesive decreases and the reaction rate slows down.

Then, to what extent can the reaction be done in the maturation room? It is impossible and unnecessary to ripen until 100% of the reaction is completed, but some emergency production cooking bags mean that the customer will use it immediately, or it will be ripe to the prescribed time. The peel strength of the bag is not much different, but the temperature resistance and corrosion resistance are not the same. The prescribed time here refers to the continuous maturation time, which cannot be accumulated after intermittent maturation because some areas often have blackouts. Some small plants have only one curing room. In order to take care of other products, the temperature can only be low. From the change of the reaction time in the lower right graph with the aging time, it can be seen that the aging temperature 40Cc is less than the 50CC curve at least one day. Therefore, we require cooking composite membrane aging temperature of 55 °C.

Jiang Zhongqiu Beijing Gaomeng Chemical Co., Ltd.

Source: China Packaging Industry