Ink Jet Deinking Affected by Paper Structural Property, 2010 TAPPI PEERS Conference

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Inkjet digital non impact printing has been expended from personal and office computer to newsprint, display graphics, digital photography, textile and packaging printing with increased market share. The advantages of non-impact digital printing are its speed, improved accuracy, overprint reduction and elimination of storage costs. While the volume increases with digital inkjet printing quickly, it has deinking problem because its submicro size of pigmented inkjet. Even small amount can introduce a serious deinking problem in a paper plant and a sustainable deinking of digital prints is indispensable for our industry. The overall yield of paper recycling on various digital printing technologies do not generally produce the same deinking outcome. Past experiments were conducted to evaluate the efficiency of convention flotation deinking process in detaching those inkjet particles from fiber surface and network. The inkjet printed ONP was flotated to 47 ISO brightness by INGEDE method 11 procedure. It was enhanced to a floated 50 ISO brightness with the additon of Floatsan for better pulping. A patented Electric Field technology12 was used for further improving the floated ISO brightness to 52.5 which is still short of 58 goal for recycling.

To understand the ink-substrate interaction with paper structure property, is very important in the recovered fiber quality in high-grade office, graphics and writing papers. Our work is aimed to provide an understanding of ink-substrate and paper structural relationships and their effects on deinkability. Softwood pulp has been refined at different time intervals. British handsheets were made for the inkjet printing. HP ink jet printer was used to print on many handsheets at different refining time intervals. Microscopic pictures and dirt content histograms at 0, 15 and 30 minutes refining levels showed there is an increased ink adhesion on the fiber surface. 72 hours aging at 140 degree F were performed on printed samples. Fixed amount of aged samples were pulped and floated with a Denver D-12 laboratory flotation cell according INGEDE method 11. Dirt content histogram have been scanned for 0 minute and 30 minutes before and after flotation. The reduction in dirt count is obvious before and after flotation. But the increased refining has attracted ink adhesion before refining and add the difficulty in deinking after refining.