Environmentally Aware Printing – Dealing with the stickies problem – Part 2 – 1st March 2010

A number of factors, both chemical and physical, influence the solid. Colloidal content in the system. Increasing agitation during pulping will increase the colloidal particle concentration and reduce solid particle size, thus making effective screening more difficult. A similar situation may occur when pH is raised during the de-inking process.

Low attrition systems, utilising a much lower shear pulpling stage, will obviously favour products which can be effectively removed by screening. This type of system is commonly employed in the more modern European mills and is increasingly accompanied by a closed loop water recirculation system. These are becoming more prevalent as a result of tighter restrictions on disposal of contaminated water. Within the recirculation system problems with dispersed particle concentration may develop over a period of time causing saturation, agglomeration and possible formation of secondary stickies. In these cases, efficient screening of adhesive particles is preferred.

Stickies can potentially cause problems both at the wet end and dry of the paper machines where they may build up on forming fabrics, the press section, calendars, blades and drying cylinders. This leads to recued efficiency, web breaks and regular cleaning necessitating costly downtime.

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 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 – Dealing with the stickies problem – Part 1
• Environmentally Aware Printing – Definition of recyclability of Adhesives
• Environmentally Aware Printing – Inks | Adhesives | Bookbinding adhesives
• Environmentally Aware Printing – Adjusting to alcohol free printing
• Environmentally Aware Printing – Alcohol free benefits

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 short run, long run and wide format colour printing. Based in Crewe, Cheshire, in the North West of England – delivering to customers across the UK and Ireland.

Also see our other websites The Printing House, Print Buying Direct, Prospectus printing, Golf Club Centenary Books

Environmentally Aware Printing

Dealing with the stickies problem – Part 1

Consumers and therefore the industry will not accept lowering of finished product standards and at the same time there is a clearly identified need to increase the waste/ virgin stock usage ratio. This means that dealing with contraries satisfactorily in recycling will become an increasingly important issue. As concentrations increase, control and removal efficiency of contraries must be improved in order to take advantage of the commercial opportunities presented.
The typical repulping mill will contain a vast array of contraries in the system and, certainly in the newer mills, an associated complex system of methods either to remove or minimise the effects of these impurities. It is fair to say that in many mills permanently high background levels of contraries exist, but these are known and controllable. This perhaps highlights the impact of non-adhesive entities such as pigments, fillers, plastic films etc. adhesives, however, in the form of ‘stickies’, still constitute the major problem in most mills.

Traditionally, the term stickies has been applied to permanently tacky pressure sensitive adhesives but has latterly encompassed all adhesives types which are considered reactivatible at elevated temperatures. In some cases the intrinsic tack of the adhesive may be non-existent or acceptably low, but complexed with components of other coatings and/ or chemical paper additives, the adhesives components may be chemically activated. Common constituents of adhesives and therefore stickies are ethylene vinyl acetate (EVA), polyvinyl acetate (PVA), acrylic and styrene containing polymers. Deposits will often contain rosin or rosin-based tackifying resins but it is not always clear whether it originates from the adhesives or waste paper fibres themselves.

If the stickie particles remain in the solid form during processing they are comparatively easy to deal with using the sophisticated screening systems of modern mills. However, if the particle is soluble or colloidal in nature, it becomes more difficult to handle.

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 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 – Definition of recyclability of Adhesives
• Environmentally Aware Printing – Inks | Adhesives | Bookbinding adhesives
• Environmentally Aware Printing – Adjusting to alcohol free printing
• Environmentally Aware Printing – Alcohol free benefits
• Environmentally Aware Printing – Alcohol in fount solvents

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 short run, long run and wide format colour printing. Based in Crewe, Cheshire, in the North West of England – delivering to customers across the UK and Ireland.

Also see our other websites The Printing House, Print Buying Direct, Prospectus printing, Golf Club Centenary Books

Environmentally Aware Printing – Definition of recyclability of Adhesives – 16th February 2010

For an adhesive to be truly recyclable is must either be:
(i)    Re-used completely – this requires the adhesive to be totally separated from fibres, re-formed and used again in a secondary application. Or
(ii)    Fully incorporated into the finished product- this implies that all the adhesives must travel through the mill system to give 100% retention on the fibres in finished paper.

A combination of (i) and (ii) may also be acceptable.

Currently as a result of technological limitations, the term recyclable is applied to adhesives which are dispersed or soluble in alkali or water or indeed, filterable in the pulping process.

In both cases adhesives must be removed from the system and disposed of. With dispersed or soluble adhesives, build-up and removal from the backwater system is the main problem, involving costly water treatment programmes. In the case of adhesives which are screened out during the process, screen rejects, usually attached to fibre, must be disposed of either in landfill sites or by incineration.

Whilst these approaches cannot be considered to produce a totally recyclable adhesive, they are certainly a step forward from the traditional problems with soft, tacky adhesives in mill systems. These approaches, one can say, allow the finished products to be recycled more effectively.

Other variables which must be considered when trying to produce a totally recyclability are mill systems and test methods. The wide range of different mills inevitably employs slightly different systems which can affect the ability to recycle certain materials with regards to handling contraries. Process variables such as pulping shear forces/ speeds, temperature, consistencies, pH, dispersion/ screening capabilities, de-inking processes and cleaner efficiency can have a major impact on the quality of the finished product and recycling efficiency in the mills. The bottom line here is that an adhesive which is acceptable to one mill may cause problems at other mills. This will become evident in subsequent sections.

Due to the complexity and variability of different mill systems, it is difficult to imagine how a standard test in the laboratory can be developed and validated. Many recyclability tests exist utilising both laboratory and small scale pilot plant equipment, but none really truly reflect the adhesives’ ability to be recycled since they cannot accurately simulate the whole mill treatment system. Tappi UM 666 is most widely quoted as an adhesive recycling test nevertheless this is still only a simplistic, laboratory scale test which can only be used as an initial guide or screening process. Currently, the only true test of a product’s recyclability is to run a full scale mill trial.

Development of a suitable standard test method is a project which industry research organisations, recycling mills and adhesive manufacturers must investigate if significant technical and economic advances are anticipated.

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 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 – Inks | Adhesives | Bookbinding adhesives
• Environmentally Aware Printing – Adjusting to alcohol free printing
• Environmentally Aware Printing – Alcohol free benefits
• Environmentally Aware Printing – Alcohol in fount solvents
• Environmentally Aware Printing – Citrus-based washes

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 short run, long run and wide format colour printing. Based in Crewe, Cheshire, in the North West of England – delivering to customers across the UK and Ireland.

Also see our other websites The Printing House, Print Buying Direct, Prospectus printing, Golf Club Centenary Books