Nano chemistry and the power of "Z" give printers an edge.

Advances in silica nanoparticle systems, working in concert with proprietary surface chemistries for sizing and coating--notably zirconium crosslinkers--are helping papermakers boost performance for printers. The results include a smoother sheet, better ink control, and prevention of carbonate release onto printing blankets. Craig White, surface applications specialist with Eka, Marietta, Georgia, USA stresses the importance of synergy between wet-end silica nanoparticle systems to improve formation, and surface sizing and crosslinkers like ammonium and potassium zirconium carbonates (AZC and PZC)) to enhance the surface.

Explained White, "Printers are increasingly aware that their paper suppliers have the means to improve sheet performance. Our role as developers of complementary nano-products can be a vital asset to the competitiveness of our customers."

White believes that the metered size press will continue to produce innovations, such as the application of proprietary multi-functional surface coating systems. Said White, "Printers can run ten color presses more effectively because of new chemical technology that combines sizing and zirconium crosslinkers, building upon a strong silica nanoparticle foundation in the base sheet."

What Eka refers to as their Multi-Print[TM] system includes the use of starch, zirconium crosslinkers and surface size polymers in a size press solution, where the system works by immobilizing the starch and surface size at the surface of the sheet. According to Lee Sampson, marketing manager, North America with Eka, "Zirconium crosslinkers are designed to react with starch, surface size and fibers of the sheet. This permits the size press solution to remain closer to the surface and not work its way as deeply into the sheet, where it has little value. Multi-Print may also allow the use of lower grade starch without sacrificing print quality, and the constant clean up of carbonate dust on the blankets."

SNAPPY PRINTING

White notes that nanochemistry can contribute directly to producing a stronger sheet through increased starch retention. Because the paper is stronger, that means a printer can use high tack ink, which gives images the "snap" they are looking for.

According to one North American coated paper producer, helping printers notch up print quality and run smoothly matches with their commitment to maximizing coating performance. He suggests that AZC is the most efficient crosslinker available for many coating formulations, because it imparts a degree of wet pick resistance that you would not otherwise have. Moisture absorption risk is a common problem for 6 to 8 to 10 color jobs, where the pick up often a concern by the 4th unit.

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This production manager pointed out that the demand for shades, tones, and accents in printing, topped off with a polycoating or UV-cured coatings at ever increasing speeds, means that coating strength must be better than ever. As for their continued development efforts and their success with printers, he believes that "no comments from printing customers is often the best sign of success, especially when the issue is surface strength." He said that quality coating builds upon a well-formed sheet, and pointed to their long history with silica nanoparticle retention/drainage systems at the wet end to achieve this objective.

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Another papermaker also emphasizes the importance of a uniform base sheet, made possible with advanced nano-chemistry. In his words, "many North American coated sheets are single pass, so you don't have an opportunity to cover anything up. Even two passes on each side requires a very high quality base sheet."

The technology is now gaining ground in China, where two papermakers have applied the technology to produce better paper for book grades, also utilizing lower cost tapioca starch without any negative impact. Recently, zirconium has gained acceptance in Brazil, where it will be applied to improve the base sheet for a paper producer, also be used at the off-line coater.

For papermakers seeking to increase recycled content, or utilize lower grades of recycled paper, AZC has also shown to be beneficial for the reduction of stickies and white pitch deposits. Typical deposition control feedpoints include coated or recycled broke and the headbox.

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THE NANO RUNWAY

In the words of Greg Bengtson, director of marketing, North America for Eka, "Most gains begin with better sheet formation through nanoflocculation, combined with the use of more dilution water in the headbox, or more refining."

As he sees it, "Higher speeds are much easier to reach, resulting from increased dewatering on the table and in the press and dryer sections In terms of equipment, nothing more is required than the traditional polymer make-down units. The new advanced nanoparticle systems are very simple to apply to the machine--simply by pumping the chemicals from a tote."

He added, "Building on a better base sheet, utilizing advanced surface sizing and crosslinking technologies, the papermaker has a broader palette of options to meet the needs of marketing departments, and to improve the bottom line. The key is to choose a step-by-step strategy, and design compatible chemistries around it."

COMPLEMENT TO PAPER MACHINE ADVANCES

Any advances in equipment for paper machines will only be complemented by the nanoparticle systems. Modern high-speed machines, such as gap formers, allow the papermaker to make more tons with improved sheet quality. These machines also benefit from advanced retention control due to their high shear tendencies. In a similar way, broader application of the metered size press is allowing surface sizing and crosslinking formulations to become routine.

WHAT YOU WILL LEARN

* How advances in silica nanoparticle systems are helping papermakers boost performance for printers.

* How nanochemistry can contribute directly to producing a stronger sheet through increased starch retention.

* Mill applications where zirconium crosslinkers are being used today.

ADDITIONAL RESOURCES

* "Nanoparticulars on Colloidal Retention," by D.S. Carr, PIRA, Wet End Chemistry Conference, Boston, October 2005.

* "The Role of Zirconium Insolubilizers in Coatings & Sizing," by Lee Sampson, ABTCP, Sao Paulo, October 2004.

* "Nanotechnology Supports Grade Evolution," by Martin Koepenick, Pulp & Paper Canada, January 2003.

RELATED ARTICLE: Z POWER

The potential benefits to be gained from nanotechnology include the use of unusual materials, such as zirconium, for applications from medical breakthroughs to paper coating. Current implants for the human body, such as heart valves, are made from titanium and stainless steel alloys. These metal alloys may wear out during the lifetime of a recipient. By contrast, nanocrystalline zirconium oxide (zirconia) is a hard, bio-corrosion resistant and biocompatible alternative.

In a similar way, as our understanding of papermaking grows on the nano level, the application of zirconium-based compounds already offer high performance gains in surface treatments and coatings. The crosslinking benefits offer notable gains in the coated sheet, including a reduction in linting and dusting, and improved ink jet printability.

Experience in the use of zirconium compounds to improve the efficiency of various starch modifications and several synthetic surface sizes indicates that improved surface size efficiency may be obtained to improve paper quality, machine runnability, and overall costs. Cost benefits include the ability to increase internal CaCO3 content, the ability to obtain good results with low cost starch derivatives, improved "clean up" times during printing, and the ability to use a wider range of SMA resins.

Web rub results with Eka AZC.

                       Coating Additives
                       Product Benefits
Products                  Features                  Benefits

Eka AZC 5800M          Inorganic Molecule           No VOCs
Recommended Dosage:    Fast Cure Rate               Less picking on
4-8% on dry binder                                    machine, less
                                                      binder migration
                       Insolubilizes/               Only product that
                         Crosslinks Latex             completely
                                                      insolublizes
                                                      latex. Reduce
                                                      milking and print
                                                      blanket
                                                      contamination.
                       Insolubilizes/               Insolubilizes
                         Crosslinks Starch            starch quickly and
                                                      keeps the starch
                                                      on the surface of
                                                      the sheet.
                       Insolubilizes/               Gives higher cure
                         Crosslinks Protein and       on machine and at
                         all other natural binders    the reel. Improves
                                                      water resistance.
Eka PZC 5000           Potassium Based              No Ammonia odor
Recommended Dosage:    Other features same as
4-8% on dry binder       AZCOTE
Eka RC 5550            High Potency product         Can replace most
Recommended Dosage:                                   glyoxal based
5-10% on dry binder                                   crosslinkers using
                                                      lower dosages
                       Best Starch Insolubilizer    Gives best overall
                                                      starch
                                                      insolubilization.
                       Glyoxal Based                No formaldehyde
Eka RC 5650            Lower Potency version        Lower cost product
Recommended Dosage:      of 5550
5-10% on dry binder
Eka LC G50             Small particle size range    More stable, less
0.7%-1.5%                                             sediment
(dry on pigment)       Uses a proprietary           No NPE's
                         surfactant
                       Low grit                     Less chance to cause
                                                      machine scratches
                       Low amounts of free lime     Fewer interactions
                                                      with coating color
                                                      components. No
                                                      viscosity
                                                      increases.
Eka LC G60             Non-ionic                    No viscosity
0.75%-1.5%                                            increases when
dry on pigment                                        added to a coating
                                                      formulation
                       Polyethylene Lubricant         No sediment,
                                                      Reduce coefficient
                                                      of friction, gives
                                                      release properties