Water-based adhesives are one of the oldest varieties. In ancient times, people used water-soluble polymers from natural systems such as bone glue and casein as adhesives. It was not until the early 1960s that there was new development in this field. In recent years, during the development and research of adhesives, the implementation of safety and pollution-free practices, especially solvent-free technology, has promoted the development of water-based adhesives.

Water-based adhesives use water as the dispersion medium for polymers. When the polymer is dissolved in water, it is called a water-soluble adhesive. When the polymer is dispersed in water with the help of an emulsifier, it is called a water-emulsion adhesive. The advantages of water-based adhesives include being environmentally friendly, non-toxic, non-flammable, having a high solid content, being applicable with existing application equipment, and being relatively easy to clean the equipment.

What is the reason for the low transparency of the emulsion after drying?

• A low solid content leads to discontinuous film formation.
• The emulsification system is not reasonably designed and should be improved.
• An excessive addition of non-ionic emulsifiers leads to a coarse particle size of the emulsion.
• The influence of impurities. The reaction kettle should be cleaned in a timely manner.
• Improper operation during the seed stage results in a wide molecular weight distribution and a scattered particle size distribution.

Why does the emulsion sometimes have a large amount of micro-foam, and why are there "oil shrinkage holes" on the film after coating?

• Mechanical reasons, reasons related to the composite film, and human operation reasons will not be discussed here.
• The mismatch between the defoamer and the glue system or a small addition amount of the defoamer will both lead to a large amount of micro-foam. The defoamer should have both defoaming and antifoaming functions.
• An excessive amount of defoamer will lead to phenomena such as "oil shrinkage holes", "goldfish eyes", and "volcanic craters". An appropriate addition amount should be determined.
• The mixing of more than two mismatched defoamers or an excessive amount of residual monomers will also lead to oil shrinkage holes.
• n-Octanol can be mixed and used with any other defoamer. It has a rapid defoaming effect and will not lead to oil shrinkage. However, its disadvantage is that it has a relatively strong odor.