Are water-based adhesives really water-based?

Text/Polymer

Due to growing attention to environmental issues, water-based adhesives are increasingly used in plastic packaging, mainly in books, packaging, tape, paper lamination, flooring and construction, footwear, automotive interiors and exterior decoration and others

1. What is water based glue

Water-based adhesive is an environmentally friendly adhesive made from natural polymers or synthetic polymers using water as a solvent or dispersant instead of toxic organic solvents that pollute environment. amount is relatively small.

Table 1-1 Classification of water-based adhesives

2. Characteristics of water-based adhesives and film formation mechanism

2.1 Water-based adhesive characteristics

The advantages of water-based adhesives are high solid content, high initial viscosity and low toxicity; low solvent content, high composite strength and no need for curing; sticky monomer is easily polymerized, and polymer is obtained. Emulsion polymerization can have not only a large molecular weight, but also a lower viscosity.

Disadvantages are products for single use, large restrictions on use, slow drying speed, resistance to boiling, ease of freezing at temperatures below freezing, and difficulties in transport and storage in winter.

2.2 Film formation mechanism

Water-based adhesives are high molecular weight polymers with high shear strength and initial peel strength. The adhesive microparticles in water are evenly dispersed in water. After being heated by desiccant, water evaporates slowly, and polymer microsphere particles slowly collect to form a film that forms a film on surface, creating a bonding effect.

Third, use of water-based adhesives in flexible packaging

At beginning, single-component water-based adhesives could only be used for consumer goods, and composite products were mainly two-layer roll films, and product structure was relatively simple. For example: BOPP//VMCPP, BOPP//CPP, BOPP//LDPE, etc.

Figure 3-1 Trend of two-component and functional water-based adhesives from 2010 to 2018

[1] Zhang Lirun. Application and innovation of water-based adhesives in field of plastic flexible packaging [J]. Plastic Packaging, 2020, 30(02):16-21+33.

In recent years, market sales of water-based two-component adhesives and water-based functional adhesives have been growing very rapidly. Two-component water-based adhesives and water-based functional adhesives introduce cross-linking groups through addition of hardeners or special cross-linking agents, which improve properties of adhesive after film formation and constantly expand field of application. can produce not only ordinary plastic flexible packaging, but also boiled and steamed products. All indications are superior to solvent-free adhesives and comparable to solvent-based composite adhesives, further expanding scope of water-based adhesives and further expanding market for use.

Fourth, direction of innovation and development of water-based adhesive enterprises

The direction modified water-based acrylic adhesive has low temperature resistance, which is only suitable for plastic flexible packaging field, and it cannot be used in many packaging fields; direction of water-based polyurethane adhesive is relatively high in cost. Enterprises can use these two directions as direction of enterprise innovation and development.

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