Environmentally Aware Printing – Types of Adhesives (continued)
Wednesday, March 10th, 2010Environmentally Aware Printing – Types of Adhesives (continued) – 11th March 2010
d) Reactive hot melts adhesives
Undoubtedly one of the most likely technologies to have an impact in the replacement of solvent-based products and recyclability in general is that of reactive hot melt adhesives.
Conventional hot melts are made of relatively low molecular weight thermoplastic materials, to ensure melting and application at moderate temperatures. This leads to obvious limitations with heat resistance and strength which can be exploited in the high temperature, high shear repulping process giving rise to small average particle size.
To overcome this, moisture-curing polyurethane hot melts have been developed utilising a cross-linking reaction which raises heat resistance and strength to previously unattainable levels whilst maintaining flexibility and low temperature adhesion. This unusual blend of properties makes this type of product ideal for recycling purposes since the high cohesive strength and excellent flexibility allows the product to remain intact rather than deforming/ breaking down under heat and shear to be forced through screens or shattering as a hard, highly cohesive conventional hot melt might.
Laboratory work on these products suggests that the adhesive does indeed remain as a discrete film and is filtered out completely in the process. These laboratory results have been borne out in typical recycling mills where complete spines of directories/ books have been removed at the first coarse screening stage, with no trace of the adhesive further down the line.
This approach is gaining in mills from a safety viewpoint since there is little or no chance of adhesive contamination in the papermaking process. The technique obviously still involves disposal of the rejected adhesive, probably in landfill, but the amount compared with conventional hot melts is halved.
To be continued…
Peter Harrison is Joint Managing Director of The Printing House Ltd, and Print Buying Direct of Crewe, Cheshire, UK.
NEW: We now sell Large Poster Printing and Banner printing online (A1 Posters, A0 Posters etc) and Banner Stands
Also – checkout our new online print prices Print Buying Direct are UK market Leaders in Leaflet Printing | Brochure Printing. For more free articles on Printing and Graphic Design see our Online Printing | Print Buying Direct Website. For more information on printing and graphic design please see some of our recent blog articles;
- Environmentally Aware Printing – Types of Adhesives (continued)
- Environmentally Aware Printing – Types of Adhesives (continued)
- Environmentally Aware Printing – Types of Adhesives – part 3
- Environmentally Aware Printing – Types of adhesives – part 2
- Environmentally Aware Printing – Types of adhesives – part 1
Print Buying Direct is the online division and a Trading Name of The Printing House Ltd. One of the UK’s leading quality printing companies for graphic design, short run, long run and large format colour printing. Based in Crewe, Cheshire (Cheshire Printers), in the North West of England – delivering to customers across the UK and Ireland.
NEW Product Alert – we now sell Exhibition Stands, Pop Up display stands and A Boards
See our other websites The Printing House, Print Buying Direct, Prospectus printing, Golf Club Centenary Books, Online printing, Printers in Oxford
See Our Latest Press Release about our Web to Print Solution. See us on the RED TIE Web to Print site