As adhesive users continue to work toward reducing adhesive costs and improving production efficiencies, foaming water-based adhesive is quickly becoming a star player.
Foaming is not a new concept; plywood has been manufactured using this technology for many years. The first attempt to bring foaming to the converting market occurred in the 1980s. This failed due to resistance from adhesive and converting equipment manufacturers. Today’s end users are more informed about the benefits associated with foaming adhesive.
In addition to substantial adhesive cost savings, adhesive end users understand that products manufactured with foaming adhesive have less warp, resulting in another cost savings: less waste. This has presented adhesive manufacturers with puzzling challenges but has left the adhesive end user with the double benefit of cost savings plus better product.
The mixing head incorporates the air into the adhesive, or “foams” the adhesive.
The process of foaming water-based adhesive works as follows: a steady volume of metered air is injected into the adhesive as it is pumped through a mechanical mixer or “foamer.” The mixing head incorporates the air into the adhesive, “foaming” the adhesive.
The foamed adhesive is supplied to the application point and used in the same manner as a non-foamed adhesive.
Types of Foaming Adhesive
The two main types of adhesive foaming systems are high-shear and low-shear. The critical difference is in the design of the mixing head. High-shear mixers are designed with concentric rows of mixing teeth covering a front stator, rear stator and rotor. These mixing heads have slim mixing-head profiles and low residence time. Low-shear mixers have “pins” instead of teeth inside an elongated mixing chamber. To compensate for the lower shear “pins,” the mixing head is elongated for longer residence time.
Foaming brings the following benefits to the end user.
- Better lay flat: less glue means less water
- Better bond: more adhesive at the interface of the substrates
- Better hold out on absorbent substrates
- Improved open times
- Faster setting
- Increased wet tack
- Improved filming characteristics
- Reduced adhesive usage, up to 50%
Foaming was reintroduced to the converting market several years ago, first in single-face laminating and later into both the converting and product assembly markets. The single-face application lent itself very well to foaming due to the need for reduced warp, cost reduction pressures and the large volume of adhesive used.
Foaming is here to stay. The benefits that can be gained by foaming water-based adhesives are significant and will continue to drive the expansion of this technology into more markets and applications. The foaming adhesive manufacturer that recognizes this and can develop a market strategy designed to protect current sales (as well as address new opportunities) will be the company to prosper.