Basic requirements for adhesives for composite packaging

There are many kinds of adhesives, and the adhesives used in packaging (composite), especially food and pharmaceutical compound packaging, must have the following basic properties.

(1) Softness: The reason why the composite packaging material is widely welcomed is that flexibility is very important. Nowadays, plastic-based composite materials are called soft packaging materials. This is in addition to the fact that the substrate itself is flexible and foldable. The adhesive itself must have this property. If the film is hard and brittle, it will lose its significance.

(2) Heat resistance, many foods, pharmaceutical packaging materials, in the manufacturing process to withstand high temperatures (180 °C ~
20 °C) treatment, for example, when heat-sealed into bags, sometimes the hot knife temperature can reach as high as 220 °C to make the composites into bags. In addition, after many food packaging materials are packaged, they must be sterilized by high-temperature sterilization. For example, steamed foods must be retort sterilized at 145°C for 2 minutes or 121°C for 40 minutes, and yoghurt, jam, etc. must also withstand 80-100°C. deal with. This not only requires a variety of substrates to survive the high temperature test, the use of adhesive must be able to stand the test of high temperatures. If the adhesive can only be used at room temperature, but not high temperature, the high temperature treatment, the original composite material to be layered peeling, it is not a composite packaging material. This must be carefully considered when choosing adhesives.

(3) Cold resistance: There are many foods that are packaged and stored at low temperature or frozen. This requires that the packaging material itself can withstand low temperatures. If the adhesive is hardened at a low temperature, brittle, peel, and degumming, that will not work. Sometimes it may require heat and cold resistance at the same time. If you encounter such a package, you must choose the quality of the adhesive.

(4) Good adhesion, because the composite packaging material is made of a variety of different materials, and they are bonded together with an adhesive, so the adhesive has good adhesion to various materials. If you stick to only one of them, you can't stick to another material. Substrates, papers, fabrics, aluminum moorings, and plastics are used in composite packaging materials, and plastics come in various types. Their surface characteristics are different. In the face of so many and complex materials, the adhesive must have the ability to stick to two different materials at the same time.

(5) Anti-media: Food itself is a very complex composition of substances, including water, oil, salt, wine, as well as spicy, spices, and even acetic acid, citric acid, lactic acid, sugar, sulfides, oxides and so on. In the face of these complex components, after being packaged, they are subjected to the tests of high and low temperature treatment and long-term storage. To maintain the integrity of the packaging materials, in addition to the excellent resistance of the substrate itself to the erosion of the media, the stability of the adhesive is also important. Resist the erosion of various media, otherwise it will cause the layered peeling of the composite, losing the packaging effect.

(6) Health performance is better. There are two concepts here, one is no smell odor, and the other is non-toxic. Because food and medicine packaging materials can be protected, the things that are packaged are people's direct entrances, foods or medicines that are eaten almost every day. In order to be responsible for the health and safety of consumers, not only the substrate must be tasteless. It is non-toxic and odorless, and the adhesive used must have the same performance. This is a matter of life and death, and all countries attach great importance to it. In addition to the food hygiene law in China, the hygiene standards for packaging materials have also been formulated, and the hygienic standard for composite packaging materials is GB-9683-88.

The above six points are very important, and we must pay full attention to other aspects, such as: the appearance of the glue, transparency, fluidity, cold resistance (non-freezing), initial tack, sizing operability, etc. also have certain requirements. It's just not that important.

Author / Xu Hongyuan