Recycling of the waste paper and the handsheets forming.

Bolanca Mirkovic, Ivana ; Majnaric, Igor ; Bolanca, Zdenka 等

Abstract: The results of the image analysis of handsheet obtained by different formers are presened in this paper. Handsheets are formed from the fibers obtained from the recycling process of prints produced in digital technique based on electrophotography with liquid and solid toner. The investigation results can be applied in the production of the recycled papers, and in the design of graphic products taking into consideration the postulates of the sustainable development.

Key words: digital printing, recycling, handsfeet formers, image analysis

1. INTRODUCTION

The paper making procedure is inevitably required to measure the various changing parameters of process control (Holik, 2006). Control with regard to drainage, retention and formation of sheets is important in terms of productivity and quality of final products (Swerin & Mahler, 1996).

Drainage property in wet-end stage means the degrees of dewatering of paper stock. If the drainage of wet-end part is not good, insufficient dewatering may cause the problem regarding the reduction of paper making productivity. It can be also a reason of poor physical properties of paper (Switzer et al. 2004).

When the retention is low it results in the accumulation of fines and contaminants in white water. Except that the bed formation as a result of increased consistency can be expected.

Unsuitably flocculation can influence the paper formation and time lowering properties of paper like printability, opacity and strength (Huber et al., 2004).

The investigation results of the application of well known handsheet former Rapid Kothen Sheet Machine and laboratory sheet former on optical characteristics of sheets made from the recycled fibers obtained from the digital technique based on electrophotography are presented in this paper. In the scientific sense the work is a contribution in the area of equipment like handsheet former and the mechanism of the waste paper recycling. The investigation results can be applied in the production of the recycled papers, in formulation of new printing materials and in the design of graphic products taking into consideration the postulates of the sustainable development.

2. EXPERIMENTAL

The prints for analysis made on machine Xerox DocuColor 5000 (powder tone is the two components one and consists of polymer, pigment, and the carrier of iron oxide) and digital offset machine Turbo Stream HP Indigo (ElectroInk contains about 5% monomer pigment paste, about 94% volatile mineral oil and about 1% agens for increasing electric conductivity).

To see the influence of the indirect electrophotographic printing on the effectiveness of the flotation of prints and the quality of the secondary raw material, one series of prints was made by varying the voltage of the offset cylinder (series 1).

For prints recycling the method of alkaline chemical deinking flotation was used, which was described in details in the previous work (Bolanca Mirkovic, 2009). Four series of sample were made in relation to the time of the disintegration process (10 min- marked by 10, 20 min-marked by 20, 30 min-marked by 30, and 40 min-marked by 40). Two flotations were done in these processes.

The handsheets before and after flotation were made using the Frank Rapid Kothen Sheet Machine (marked by A), and the laboratory sheet former (Pulp and Paper Institute, Ljubljana; Slovenia) (marked by B). Standard ISO 5269-2 was used for sheet formation.

The Rapid Kothen Sheet former machine is built for fully automatic and manual formatting (Fig. 1.-A). After preparing the pulp sample, the process is started and water is pumped into the stock container. The suspension is agitated with compressed air, and then is allowed for the turbulence to cease. After dewatering the sheet is finished and automatic drying process begins.

[FIGURE 1 OMITTED]

Handsheet former presented in Fig 1 has screen size of 210 x 297 mm (Pulp and Paper Institute, Ljubljana). The former is filled with water and the suspension is evenly spread on the screen. For suspension homogenization the part with holes is used. After that the water is let out of the machine and the formed handsheet remains on the screen. The sheet is detached from the screen by means of a roller and paper of great absorbency, passing the roller carefully in one direction. The sheet is detached from the screen and dried in the air.

Residual specks which include, toner particles number and area were assessed with image analysis software Spec*Scan, Apogee System. This system is utilizing scanner to digitize image. Threshold value (100), white level (75) and black level (65) were chosen after comparing computer images to handsheet.

3. RESULTS AND DISCUSSION

Tab. 1. presents the results of the image analysis of handsheets obtained by formers presented in Fig 1. The prints with different disintegration times were used for recycling.

[FIGURE 2 OMITTED]

The investigation results show that in the frame of the described experimental conditions, in great majority of the cases the dirt content on the sheets formed with Rapid Rapid Kothen Sheet former mashine is somewhat greater in regard to the other former. The aberration range from 0,02 to 4.2 %. By increasing the disintegration time from 10 to 40 min the flotation effectiveness increased. When the Rapid Kothen Sheet former mashine was used for sheet formation, for 79,5% lesser speck number was found after flotation on handsheet, while using the other sheet former this number was smaller, it was smaller for 77,5%.

From the presented dirt content histogram it is visible that in five dirt spot sizes for handsheet former A and B, the number of specks is equal.

The results show that the second flotation does not influence so much the effectiveness flotation as it was found out in the case of time disintegration increase from 10 to 40 min (Tab. 2).

The calculated effectiveness of the second flotation in regard to the first one is 28,7%. The difference in results in regard to the sheet formation by using the different formers is within the limits of the earlied presented results.

The difference in speck count and area between the screen and felt side is determined. Greater speck count and area of about 8% was notice on the felt side of handsheet. Greater differences in regard to the used handsheet formers when there are specks which did not belong to the size classes between 1,00 - 1,5 [mm.sup.2] and >= 5 [mm.sup.2] were not found out. Greater differences can appear when sheets are prepared from the fibers after recycling of prints made by indirect electrophotography in combination with some substrates (series 1).

4. CONCLUSION

By the described investigations the characteristics of different machines for sheet formation on the example of the recycling of digital prints based on electrophotrography made with solid and liquid toner are compared. By image analysis, no significant aberrations in characteristics of handsheet produced by the recycled fibers by using different formers were found.

The obtained results point at the need for further investigation including the experimental design and creation of the statistic models.

5. REFERENCES

Bolanca Mirkovic, I.; Majnaric, I.; Bolanca Z. & Grgasovic, A., (2009). Recycling of waste paper with different density of liquid toner, Proceedings of the 20th International DAAAM Symposium, November 2009 Vienna, ISBN 1013-982 Katalinic, B. (Ed.), pp. 075-077, Published by International Vienna, Vienna

Holik, H.; (Ed.) (2006). Handbook of Paper and Board, Wiley-VCH Verlag, 978-3-527-30997-9, Weinhein

Huber, P.; Pieere, C.; Bermond, C. & Carre, B. (2004). Comparing the Fiber Flocculation Behavior of Several Wetend Retention Systems, Tappi Journal, 19, 4, 19-24, ISSN-0734-1415

Staib, R. R., (1991).Evaluating paper sizes using a Turbulent-pulse Sheet Former, Tappi Journal, 7, 12, 102-111, ISSN-0734-1415

Swerin, A. & Maller. A., (1996). Formation, retention and dranage of a fine paper stock, Nordic Pulp and Paper Research Journal, 12, 1, 35-42, ISSN 02832631

Switzer L. H., Klingenberg, D., J., & Scott, C., T., (2004). Handsheet formation and mechanical testing via fiber-level simulations, Nordic Pulp and Paper Research Journal, 19, 4, 434-439, ISSN 0283263

Tab. 1. Specks count and area on handsheet formed from fibers
after disintegration (marked by D) and after flotation (marked
by F) by using the earlier mentioned formers

Samp. Total Count Count
 count >0,04 <0,04
 specks [mm.sup.2] [mm.sup.2]

10AD 718 83 635
10BD 705 76 629
10AF 342 75 267
10BF 340 66 274
20AD 729 67 662
20BD 741 63 678
20AF 121 23 98
20BF 127 18 109
30AD 781 65 716
30BD 794 58 736
30AF 123 27 96
30BF 90 20 70
40AD 815 64 751
40BD 835 54 781
40AF 77 12 65
40BF 69 18 51

Samp. Area Area Area
 [mm.sup.2] >0,04 <004
 [mm.sup.2] [mm.sup.2]

10AD 14.71 9.04 5.67
10BD 14.70 9.29 5.41
10AF 11.69 8.50 2.90
10BF 10.90 8.00 2.91
20AD 11.95 6.48 5.47
20BD 10.20 4.75 5.46
20AF 3.80 2.85 0.95
20BF 3.50 2.36 1.14
30AD 12.73 6.74 6.00
30BD 12.20 6.14 6.06
30AF 3.26 2.33 0.93
30BF 2.58 1.80 0.78
40AD 11.72 5.23 6.49
40BD 11.32 4.48 6.84
40AF 2.77 2.26 0.51
40BF 2.76 2.41 0.36

Tab. 2. Specks count and area on handsheet formed from fibers
after the first and the second flotation by using the former A
with the screen of A4 size

 Total Count Count
Samp. Count >0,04 <0,04
 speck [mm.sup.2] [mm.sup.2]

BF1 331 56 275
BF2 315 51 264

 Total Area Area
Samp. area >0,04 <0,04
 [mm.sup.2] [mm.sup.2] [mm.sup.2]

BF1 10,889 8,133 2,756
BF2 8.201 5,597 2.604