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Water and emulsion adhesives are adhesives which are mainly composed of water. This kind of adhesive is the most widely used adhesive in the history of packaging production. These adhesives are convenient, safe, energy-saving, suitable for various bonding operations, low toxicity or non-toxic, low cost, rich source of raw materials and other advantages.

There are two categories of water adhesives: natural water adhesives and synthetic water adhesives. Natural water-based adhesive is the earliest packaging adhesive, which has occupied most of the market for a long time. However, in recent years, it has been gradually replaced by synthetic adhesive with better performance in many packaging applications. Starch, protein, animal glue, casein glue and natural rubber latex belong to this kind of adhesive.

Polyvinyl alcohol condensation adhesive mainly includes polyvinyl alcohol formaldehyde adhesive, polyvinyl alcohol methyl ethyl acetal adhesive and polyvinyl alcohol butyral adhesive. These adhesives have been used for a long time due to their simple production, wide application and low price. Because of the use of formaldehyde, butyraldehyde and other raw materials in the production of such adhesives, it is impossible to completely react with this kind of aldehydes in the synthesis process, resulting in a certain amount of free aldehydes in the adhesives.

Free aldehydes, on the one hand, can continue to react slowly with the change of temperature over time, thus affecting the storage or use stability of adhesives, and sometimes affecting production and product quality. On the other hand, free aldehydes in the residual adhesives will volatilize in the production technicians or packaging products, so as to the environment and people. The body causes irritation and harm. Therefore, the use of such adhesives has been limited, and people are now making necessary improvements to these adhesives in order to completely eliminate the free aldehydes in the adhesives.