The external fibrillation delaminate the surface layer of the fiber that effect the fiber-fiber bonds as well as improving the retention of fillers, pigments, and colloidal particles in paper making Fardim and Duran Various aspects of the pulp refining on paper characteristics have been studied, but reliable research reports on the impact of refining on paper de-inking is limited.
This study reports the effect of pulp refining on de-inking potential of inkjet printed paper and strength properties of deinked pulp to discover the relation between refining degree and ink to fiber bonding strength. Handsheets were made without adding any filler material. The fiber classification of the unrefined and refined pulps are measured and reported in Table 1. Handsheets from each of the one unrefined and three refined pulps were randomly selected for printing with a HP Photosmart C ink-jet printer, using pigment-based black ink, CBHP To minimize the impact of print intensity, one text was selected for printing on all handsheets, and fresh cartridges were used to avoid the reduction of print intensity.
For ink-jet printing, we used round handsheets, diameter mm, and only one side of the handsheet was printed with about words. To measure the de-inking potential, samples of different HP ink-jet printed handsheets were selected for de-inking. All chemicals were reagent grade supplied by Merck, Dormshtat, Germany. The mixer rotor speed was adjusted at rpm until the pulp suspension was apparently uniform.
Then de-inking chemicals were added to the suspension, and mixing continued for another 10 minutes. The pulp suspension was kept without stirring for 20 minutes to provide sufficient time for chemical reactions. Then the detached ink was washed using a mesh screen under continuous flow of tap water at 30 o C. During the washing process, inks, foam, and contaminants passed through the screen, and the de-inked fibers remained.
Washing was carried out for 2 minutes, and then samples were de-watered and the deinking yield was measured. In pigment based inks, after the initial slushing of the inkjet printed paper, the particles do not agglomerate and cannot be removed efficiently by flotation Nyman and Hakala Therefore, we used flotation chemistry to reach better detachment of the ink particles from the surface of the fibers, and since we anticipated that the detached ink particles were small, we used washing to separate the particles from the fiber slurry.
Four handsheets from each de-inked pulp were randomly selected, and the strength and optical properties were determined according to relevant TAPPI test methods as follow: opacity, T om; brightness, T om; tear strength index, T om; and tensile strength index, T om Four ink-jet printed handsheets from each freeness degree were randomly selected, and printing tests and ink junction strength of these printed handsheets were performed at MAN-ROLAND Laboratory, Germany.http://temp.cmnv.org/how-the-wolves-saved-christmas-the-wolf-cubs.php
Pulp & Paper - Industrial Ink Jet Printing
The printing test methods were the following:. Then, the objects were measured using the appropriate software.
Solid area quality was evaluated using three metrics: optical density, black uniformity, and black mottle. Higher numbers of clusters are indicative of solid areas that appear more uneven and mottled. Text focus was assessed by calculating the sum of the squares of the differences in gray values of any two adjacent pixels horizontal or vertical within a region of interest placed over a block of text. A defined testing method is not available, and since , a computerized method from Image Expert Inc.
Pixel format, pixel pitch, yield points, contrast transfer function narrow vertical, black white vertical line width, letter area, and contact angle of the ink jet nip were analyzed with Design-Expert software by State-Ease. Finally, ink tension was measured using laboratory plasma surface treatment machine Tantec.
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The properties of unrefined and refined pulp fibers are listed in Table 1. Extensive changes were not imparted to the fibers upon refining, and all the properties reported in Table 1 were almost the same. This indicates that the impact of fiber characteristics such as the percentage of the fine is negligible in terms of handsheet properties. Table 1. The yield, roughness, and optical properties of de-inked ink-jet printed handsheets produced using pulps unrefined and refined to different freeness levels are summarized in Table 2.
Table 2. As was anticipated, de-inking eliminated part of the material while separating both ink particles and mainly fines from the pulp suspension. More refining reduced the de-inking yield by 1.
Since identical printing was applied on all handsheets, it can be concluded that more fines were rejected during washing. The maximum yield was reached while de-inking handsheets produced from unbeaten pulp and the lowest yield These redeposited particles cannot be removed without substantial fiber loss ending in lower deinking yield. The maximum brightness value We have used fully bleached market pulp for this study, and the sheets were not heavily printed.
Therefore, the brightness of the deinked pulp is higher than usual deinked pulp. As seen in Table 2, the brighter deinked pulp was generated from the printed sheet produced from either unrefined or refined to mL CSF. At the highest degree of refining, which was required to reach the lower freeness value mL CSF , a smoother surface is produced, which inhibits the penetration of pigment particles into the sheet Li and He and facilitates the separation of the ink particles in deinking process.
The opacity of the de-inked pulp followed the opposite trend compared to brightness. Lowest and highest opacity values were obtained from the pulps with and mL CSF, respectively Table 2. Pulp refining generates fibrillation on the outer surface of the fibers Fig. It has been acknowledged that penetration of ink particles into the fibrillation makes de-inking harder McKinney , and consequently the de-inking will be difficult. However, our study showed that at higher refining degree, the brightness development was better, which is attributed to two factors: 1 detachment of fibrils from the surface of the refined fibers and separation of the generated fines from the fibers; and 2 better felting of the fibers in the paper sheet to produce a smoother surface, which prevents deeper penetration of the inkjet ink pigment particles.
We did not use any filler to avoid the impact of ash content on print quality and deinking, and since the fines content of the different pulps were almost similar, the effect of these variables can be ignored. The results of printability and ink junction strength tests on refined handsheets are summarized in Table 3. Table 3. The pulps were refined to different degrees, and handsheets with different surface roughness were produced. However, the printing characteristics of the handsheets did not vary significantly. It is believed that the surface roughness of the paper will influence the print quality.
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Tensile and tear strength of the paper before unprinted and after de-inking were measured, and results are shown in Fig. Both tensile and tear strength indices of the papers increased upon refining the pulp to different freeness levels. Refining generates external fibrillation, which facilitates more fiber bonding and higher tensile strength. Even though the tear strength of paper usually is reduced due to refining, the possible removal of the fines during sheet forming and better felting and generation of stronger fiber network may improve the tear strength as well.
In any case, it was expected that the tensile strength index of de-inked paper should be lower than unprinted papers. However, the separation and removal of the fines during washing and the swelling effect of NaOH used for deinking improved the tensile strength index of de-inked paper. After meeting Colin I quickly realized he had a great eye for design and handed over the reigns to his incredible aesthetic. Everyone that saw the paper goods for the wedding couldn't help compliment the design and quality. We worked with Colin and he was so helpful with everything!!
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