No Need To Sacrifice Strength

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No Need To Sacrifice Strength

December 08, 2015 - 10:57
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BEDFORD, MASSACHUSETTS, Dec. 1, 2015 (PPI Magazine) -Increase machine efficiency and lower production costs of recycled packaging grades by adding GCC fillers

The recycled packaging industry has grown steadily since the mid-2000s due to growing demand for boxes and other containers for shipping, carrying, and/or storing finished products (non-durable and durable goods). A recent market analysis1showed North American recycled packaging mills produced 21 million tons per year with an annual growth of 3.3% since 2009.

The recycled fiber packaging market is defined as any grades in the packaging market which uses close to 100% OCC. This includes boxboard, boxboard C1S, corrugating medium, liner, bag/sack, wrapping paper, chipboard, tube stock, and gypsum liner.

Due to rising fiber and energy costs, Omya initiated a project to investigate different approaches and pigments to help packaging mills achieve even higher levels of process and product excellence through improved runnability, higher machine efficiency and improved product quality while also reducing their energy footprint.

This article will review the current recycled packaging market on a regional level perspective and report on an extensive pilot plant machine trial conducted at Western Michigan University in 2013.

 

Market size and evaluation

Zhao1claims that the world recovery rate is fast approaching the cost-effective limit of 80%. This indicates minimal future growth in the availability of fiber (OCC) for the North America recycled board market. While OCC exports to Asian markets have been sluggish since 2012 (reflected in North American OCC prices, Fig. 1), the need for more recycled fibers is real, due to the forecasted new machine start-ups, especially in Asia. Increasing recovery rates on a regional basis will be more challenging, and should result in lower quality OCC to the mix. Lower quality means a lower yield i.e. more throw-aways and ultimately, pulp cost at the headbox will increase.

A North American market analysis based on FisherSolve Database2indicates a production increase of nearly 3.5 million tons to 21 million tons/yr compared with 2009, Fig. 1. This is an astonishing 20% growth.

This growth is driven by two paper machine conversions (Atlantic Packaging, Whitby, ON and SP Fibers Technologies, Dublin, GA), two equipment rebuilds (Propasa, San Nicolas de Los Garza, Mexico and RockTenn, Uncasville, CT), and two new machines (Unipak – Grupak Hildalgo, Mexico [2015] and Norampac - GreenPac, Niagara Falls, NY [2014]). By the end of 2015, there should be two more new machines producing recycled packaging grades: at Pratt in Valparaiso, IN (360,000 tons/yr) and IP in Valliant, OK (160,000 tons/yr) for a total of 520,000 new tons.

Over the next two years, forecasted demand is predicted to grow at a similar rate of up to 3% per year (2015-2016)3. This increased demand will require an additional 1,200,000 tons of OCC fiber, which will further stress an already tight supply market, raising the question of whether mills will be able to find a suitable and reliable OCC fiber supply. Mills may be forced to look at other fiber sources such as white fibers (SOW, ONP, OMG, etc.) or even new species (bamboo, straw, hemp, etc.). These factors raise the obvious question of: “What about using more filler in place of fiber?”

 

Literature

Little has been published promoting the use of fillers in the recycled packaging industry, the exception being filler use in the recycled coated board sector. A summary of these insights follows.

In 1999, Xu4mentioned the successful use of PCC in the recycled container board industry as a fiber substitution with filler loadings up to 5%. The paper showed that the use of a PEO/PFR (polyethylene oxide/phenol formaldehyde resin) combination was best to retain fillers and fines based on an OCC-based sheet.

In 2009, Song et al.5introduced a new process for the linerboard industry by blending a filler (clay or PCC) and raw corn starch produced either on-site or off-site. This combination could be sold as a dry or wet product depending on the transportation cost (logistic cost) of these compounds. The authors showed good success in trialing this new concept in many mills. In 2010, a similar but more complex approach was proposed by Laleg6. He showed that by co-blending raw starch, a polymeric component (i.e. coagulant), a latex (i.e. SB), and a filler (PCC), strength loss could be minimized for any paper or paperboard product.

In a recent conversation with a PM superintendent7, it was mentioned that the mill tried to use filler clay for a short trial and concluded that up to 4% clay could be added to the base sheet while maintaining an acceptable level of strength.

Omya believes that the uncoated/coated board market needs new ideas and new ways to reduce costs while preserving strength.

Currently, calcium carbonate fillers are being used at increasing levels in the coated boxboard industry. Most mills apply calcium carbonate in the coating, but increasingly, calcium carbonate is being added in the top and bottom plies to improve coverage, increase optical properties (brightness/opacity), and reduce overall furnish costs through the use of cheaper recycled white fibers.

 

Pilot machine trial work

In 2013, Omya conducted a pilot paper machine trial at the Western Michigan University (WMU) pilot facility. The purpose of the trial was to understand the impact of GCC supplied in both a dry and slurried (pre-dispersed) state in a 100% cleaned OCC furnish from a southern US mill. The OCC was repulped to a freeness of 330 ml CSF and stored in tile tanks at 1.8% consistency. No further refining and/or cleaning was done.

The Design of Experiment (DOE) was to use three GCC products at two dosage levels (4% and 8%). The characteristics of these GCC products are shown in Table 1.

The additives included a small amount of AKD (5.3 lb/ton) to give a stable Cobb test around 30 seconds and a wet-end cationic starch (waxy maize) being used at 5 and 15 lb/ton. No other retention aid was used.

The target basis weight board was a 36-lb sheet (172 g/m2). Twenty-two pilot machine conditions were run over a 3-day period.

For simplicity, the results of only the 4% filler conditions will be discussed. At the 8% loading level a minor loss of sheet strength was observed. During the trial no attempt was made to optimize the strength properties. For this reason, the results of the higher filler loadings were not included in this article.

 

Machine operation

The pilot machine ran without any major issues. The First Pass Retention (FPR) and the First Pass Ash Retention (FPAR) ranged from 80 to 95% and 60 to 80% respectively, depending on the conditions. The headbox consistency was 0.56% ± 0.09%.

The machine speed without filler was 33 ft/min. With the addition of filler, the machine speed was increased to 37 ft/min. The steam pressure differential between the mainline and after dryer was 2.0 psi without filler and 3.0 to 4.0 psi with filler. These two parameters clearly show the tremendous potential in adding GCC fillers in board/paper board manufacturing. This is explained by drainage improvement on machine (higher couch consistency) thereby reducing the amount of energy spent to dry the sheet.

 

Board properties

The Western Michigan University tested burst index, tensile index in MD and CD, STFI in MD and CD, TABER stiffness in MD and CD, slide angle, ISO brightness, and Sheffield roughness. Ash analysis was performed in Omya’s Lab in Cincinnati, OH.

All results were normalized to 4% fresh GCC loading. The Omyaboard 140* referenced in Fig. 2 is a blend of Omyaboard 140 and wet-end starch to improve the flocculation and retention of the GCC.

A summary of the board testing results are shown in Fig. 2 and 3. The wet-end starch dosage was 5 lb/ton for blank and 15 lb/ton for all GCC conditions.

Figure 2 details results using Omyaboard 140 (pre-dispersed GCC) and pre-flocculated Omyaboard 140* versus blank. Figure 3 shows results using Omyaboard 350 (pre-dispersed GCC) and Omyaboard 500 (dry GCC) versus blank.

While the type of GCC used in this study varied from 1.5 to 5 microns, we can confirm that when GCC (either as a pre-floc or separate feedpoints) was added with a small additional amount of starch, most physical parameters were preserved. For example: burst index, tensile index in both directions, stiffness, and STFI in both directions were near target levels with 4% GCC fillers in the base sheet.

One very important aspect in converting liner to boxes is the coefficient of friction or slide angle. As indicated in both of the following figures the addition of GCC improves the slide angle up to 20% with only 4% filler loading.

The Sheffield roughness is reduced (-5%) by the addition of GCC. This gives a smoother sheet hence improves printability for customers wanting to print directly on board. While the brightness is not shown in these graphs, the board testing showed an increase of one ISO point for every 2% GCC filler increase.

 

Conclusion

In summary, these experiments demonstrated that it is feasible to add 4% GCC to the furnish as a filler, especially in conjunction with the use of typically available strength agents. The inclusion of GCC in the furnish can help paperboard producers lower production costs without sacrificing strength.

In addition to providing fiber substitution, the GCC filler also serves as a drainage aid providing higher levels of solids off the couch, which translates to higher solids in the press section. As a rule of thumb, 1% higher solids out of the press section can yield up to a 4% increase in machine speed and/or board production.

Major benefits to a recycled packaging mill using GCC fillers are:

  • Increased drainage leading to higher solids off the couch or vats
  • Significant speed increases leading to higher productivity
  • Energy/steam savings
  • Minimal loss in strength properties
  • Higher COF without using an expensive mineral solution such as silica
  • Improved board printability
  • Higher brightness
  • Better coverage in multi-ply and white top applications (potential to reduce higher priced white fiber).

 

Acknowledgement

The author would like to express deepest gratitude to Omya’s personnel for their support especially to Mike Strutz, Joel Landesman, Steve Stueck, and Tim Bradley. Also, a special thanks to Ingredion, especially Connie Klaisner and Joe Kramer for their unwavering support (pre-lab work and product).


Louis R. Morimanno, Technical Innovation Manager, Omya Inc., Cincinnati, OH

REFERENCES

[1] ZHAO, H., RISI - Sixteenth Biennial – International Containerboard Conference, Chicago, IL, Nov 5-7, 2014.

[2] Fisher International, FisherSolve Database, Query done in May 2015

[3] WAGHORNE, K., RISI - Sixteenth Biennial – International Containerboard Conference, Chicago, IL, Nov 5-7, 2014.

[4] XU, Y. and DENG, Y., Retention of Precipitated Calcium Carbonate in Old Corrugated Container Furnishes, TAPPI Journal, Vol.82, No. 8, pp 121-126.

[5] SONG, D. et al., Filler Engineering for Energy Savings and Improved Paper Properties, PaperConN 2009, St-Louis, MO

[6] LALEG, M., Patent US2010/0078138, Unruptured, Ionic, Swollen Starch for Use in Papermaking, April 2010.

[7] Private conversation with the PM superintendent of an uncoated recycled board mill on the US East Coast, October 2014.PPI