Spring 2008 Newsletter   Ink Jet Paper Performance	John Penniman
Stock Heterogeneity We have shown that the microparticulate process creates a structure that can cost-effectively improve retention, drainage and formation. (1)  This is important in order to simultaneously achieve a stable, efficient papermaking process with good runnability that yields a consistently high quality product. Properly executed, the microparticulate process employs an anionic nanoparticle of around 400m2 /gram and is a straightforward exercise in nanotechnology.  In that sense, it is extremely sensitive to thoroughness of mixing, with the objective of obtaining homogeneity of stock and chemicals down to molecular dimensions. We follow the lead of 6 Sigma in measuring standard deviation of a key parameter as a measure of thoroughness of mixing, or homogeneity, with the following typical results:         Venue                                        Zeta Potential Standard Deviation             Laboratory                                0.2mV         Old, slow machine                   0.2-0.5mV         High speed tissue                   1.6mV            “        “     alkaline paper        2.9mV with 6-10 wet end breaks/day The highest zeta potential standard deviation we encountered was 4-5mV, accompanied by unacceptably poor runnability, on a multiple head-box, re-cycle, coated board machine.  High standard deviations can be created by:  common white water systems, multiple head boxes, coated broke, recycle product and anionic pigment dispersions; resulting in degradation of both runnability and product quality. Homogeneous Nanoflocculation A high level of homogeneity, accompanied by low zeta potential standard deviation, can easily be accomplished by adding the requisite amount of anionic nanoparticle to the anionic stock, mixing thoroughly, then adding sufficient cationic component to precisely neutralize the anionic charge, with thorough mixing.  The result is nanoflocculation, high retention and drainage, excellent formation, high strength and excellent uniformity.  (2) Macroflocculation Van der Waals Force states that the attraction between small particles increases inversely to the 6th power of the distance separating them.  Therefore, maximizing the benefits of papermaking nanotechnology turns on minimizing the distance between particles.  Our laboratory has been successful in utilizing a low surface tension catalyst to achieve cost-efficiency increases of 1 to 2 orders of magnitude in chemical usage. The industry generally, however, has not mixed thoroughly, has refrained from charge-neutralization and relied on high molecular weight, low charge density retention aids to macroflocculate the anionic nanoparticle.  Heterogeneity of macroflocculation is therefore generally achieved by all manufacturers of P&W papers.  While either quality would be sufficient to question use of the paper as an ideal printing substrate, the combination is disqualifying.  The performance of P&W papers is not appropriate to their intended purpose.       ColorLok© The ColorLok©  Technology represents a paper performance standard associated with several digital printer manufacturers and cooperating paper producers.  Testing of printed samples to attain certain performance standards is done by an independent print applications laboratory.  It entails use of a special paper coating that enables faster drying, (less smearing), jetter blacks, brighter colors and crisper definition. ColorLok©  Technology is used to surface treat a sheet substrate for ink jet printing.  As described in US Patent 6,207,258, it is a coating composition, typically containing the salt of a divalent metal and cationic starch in which an internal size, such as AKD, is dispersed.  The coating is primarily intended to fix a pigmented ink jet on a treated surface. One of the cooperating paper producers is developing a filler-fiber composite technology, intended to enable higher filler levels.  The concept appears to be poorly conceived, in the sense that one of the major tenets of nanoscience is that performance improves as a function of decreasing the size of particulates. Use of filler-fiber also increases complexity and cost. Discussion It is within the state-of-the-art of modern nanotechnology to process the functional chemicals of the ColorLok© Technology integrally with the wet end papermaking process.  The chemical usage economy of homogeneous nanoflocculation is so great that a properly executed system will consume even less chemical than ColorLok© Technology currently requires, and completely eliminate the coating process.  We can simultaneously achieve nanoflocculation, homogeneity of structure and substantivity to ink jet pigments together with an unprecedented high level of quality and performance. John Penniman www.papermaking-chemistry.com Bibliography (1) “Optimizing Microparticulate Process Efficiency”, Tappi Proceedings, 1993 Papermakers Conference, J. Penniman et al.   (2)  “Maximizing van der Waals Force in Papermaking” www.papermaking-chemistry.com/waal.htm