Wikipedia

Wood-free paper

(Redirected from Tree-free paper)

Wood-free paper, tree-free paper, or fine paper is paper created from bleached, chemically-separated paper pulp, as to minimize lignin contents (the "wood" in question).[1] It is not as susceptible to yellowing as paper containing mechanical pulp.[2][3][4]

A sheet of wood-free paper

Overview

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Lignin

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Lignin is a natural complex polymer containing aromatic compounds that provide much of a plant's strength. In its natural form, it gives rigidity and resilience to the plant's structure, but its presence causes paper to weaken and turn yellow as it ages and eventually disintegrate. The reason for this is that as the paper ages, lignin releases acid which degrades the paper.[5] Lignocellulose from the xylem of shrubs and cambium from the inner bark of trees are made up of lignin, hemicellulose and cellulose, relevant to papermaking.[6]

Pulp

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Paper pulp consists of cellulosic materials that have been broken down chemically and physically and filtered and mixed in water to reform into a web: creating pulp by breaking down the materials chemically is called chemical pulping, while creating pulp by breaking them down mechanically is called mechanical pulping.[6][7]

In the chemical pulping of lignocellulose - plants with lignin content - chemicals separate the wood fibers. The chemicals lower the lignin content because chemical action solubilizes and degrades components of wood fibers, especially hemicelluloses and lignin. Chemical pulping yields single unbroken fibers that produce strong quality papers because the lignin that interferes with hydrogen bonding of wood fibers has been removed. Chemical pulps are used to create wood free paper that is of high quality and lasts long, such as is used in arts and archiving.[6] Chemical pulping processes take place at high pressures and temperatures under aqueous alkaline, neutral or acidic conditions, with the goal of totally removing the lignin and preserving the carbohydrates. Normally, about 90% of the lignin is removed.[7]

Mechanical pulping, in contrast, converts raw lignocellulose into pulp without separating the lignin from the cellulose.[7] No chemicals other than water or steam are used. The yield is about 90% to 98%. High yields result from the fact that lignin is retained. Mechanical pulps are characterized by low cost, high stiffness, high bulk, and high yield.  Mechanical pulp has low strength because the lignin interferes with hydrogen bonding between wood fibers. The lignin also makes the pulp turn yellow when exposed to light and air. Mechanical pulps are used in the production of non-permanent papers such as newsprint and magazine paper. Mechanical pulps made up 20% to 25% of the world production and this is increasing because of the high yield of the process and increasing competition for fiber resources. Advances in technology have also made mechanical pulp increasingly desirable.[clarification needed][6]

Categories

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Woodfree uncoated paper

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Woodfree uncoated paper (WFU), uncoated woodfree paper (UWF) or uncoated fine papers is the paper industry technical term for base wood-free paper.[8] Both softwood and hardwood chemical pulps are used and a minor part of mechanical pulp might be added (often of aspen or poplar). These paper grades are calendered.[9] The properties are good strength, high brightness and good archival characteristics.[10] They provide less glare than woodfree coated paper (WFC) as there is no coating involved.[11]

Offset paper

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Offset paper is a type of woodfree uncoated paper primarily designed for offset printing. It can range from 60 gsm (grammage, or grams per square meter), to over 200 gsm. Lighter weights can compose brochures and flyers, while heavier weights are used for packaging and other durable applications.[12] SC (supercalendered) offset paper has an ISO brightness of > 67% and a surface strength is optimized for offset printing.[13]

Composition

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Wood-free paper is made from a variety of raw materials, including

  • Tissue pulp: This is the most common type of wood-free paper. It is made from wood pulp that has been treated with chemicals to remove the lignin.[14][15][16][17]
  • Balsa pulp: This is a type of wood pulp that is made from balsa trees. It is very strong and lightweight, making it ideal for use in envelopes and other lightweight applications.[18][19]
  • Coniferous pulp: This is a type of wood pulp that is made from coniferous trees, such as pine and fir. It is strong and durable, making it ideal for use in writing and printing papers.[20][21][22][23]
  • Non-wood pulp: This is a type of pulp that is made from non-wood materials, such as cotton, hemp, kenaf, linen, and bamboo. It is often used in high-quality papers, such as those used for art and photography.[20][22][24]

Wood-free paper has a number of advantages over paper that contains mechanical pulp:

  • Wood-free paper is more resistant to yellowing because lignin, the main cause of paper yellowing, has been removed from the pulp.[21][25][26]
  • It is stronger because the cellulose fibers in wood-free paper are longer and more uniform than the fibers in mechanical pulp.[14]
  • It is more durable because it is less likely to tear or crease.[14]
  • It is smoother because its surface is more refined than that of paper containing mechanical pulp.[14]

Wood-free paper is used in a variety of applications:

  • Writing and printing papers: Wood-free paper is the most common type of paper used for writing and printing.[27] It is available in a variety of weights and finishes.[21]
  • Envelopes: Wood-free paper is the most common type of paper used for envelopes.[28][29] It is available in a variety of colors and finishes.
  • Art and photography papers: Wood-free paper is the most common type of paper used for art and photography.[27]
  • Other applications: Wood-free paper is also used in a variety of other applications, such as packaging, labels, and currency[20][30]

See also

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References

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  1. ↑ He, Zhibin; Hui, Lanfeng; Liu, Zhong; Ni, Yonghao; Zhou, Yajun (1 April 2010). "Impact of High-Yield Pulp Substitution on the Brightness Stability of Uncoated Wood-Free Paper". TAPPI Journal. 9 (3): 15–20. doi:10.32964/tj9.3.15. ISSN 0734-1415.
  2. ↑ Bajpai, Pratima (2015), "The Control of Microbiological Problems∗∗Some excerpts taken from Bajpai P (2012). Biotechnology for Pulp and Paper Processing with kind permission from Springer Science1Business Media.", Pulp and Paper Industry, Elsevier: 103–195, doi:10.1016/b978-0-12-803409-5.00008-2, ISBN 9780128034095, PMC 7158184, S2CID 89782614{{citation}}: CS1 maint: work parameter with ISBN (link)
  3. ↑ "Print lingo explained: Woodfree paper". Warners Midlands Plc. 10 May 2016. Archived from the original on 10 December 2022. Retrieved 10 December 2022.
  4. ↑ Papers, Peters (12 March 2020). "Know your paper terms: Wood-free paper". Peters Papers. Retrieved 10 December 2022.
  5. ↑ "The Coniferous - Leading Paper Trading Company". theconiferous.com. Retrieved 19 October 2023.
  6. 1 2 3 4 Biermann, C. J. (1996). Handbook of pulping and papermaking. Elsevier.
  7. 1 2 3 J.C. Roberts, The Chemistry of Paper, 1st edn., Cambridge, 1996
  8. ↑ "The paper made without using mechanical pulp". Archived from the original on 5 April 2015. Retrieved 26 September 2025.
  9. ↑ Tillmann, Otmar (20 January 2006). Paper and Board Grades and Their Properties. 6.9.4.2.1 & 6.9.4.2.2.
  10. ↑ Paulapuro, Hannu (2000). "1". Paper and Board grades. Papermaking Science and Technology. Vol. 18. Finland: Fapet Oy. pp. 35–37. ISBN 952-5216-18-7.
  11. ↑ "Quality Wood Free Coated Paper Suppliers". PG Paper. Retrieved 18 April 2026.
  12. ↑ "Offset Paper: Types, Weights & How to Pick the Right One". Mail Processing Associates. Retrieved 18 April 2026.
  13. ↑ Tillmann, Otmar (20 January 2006). "Handbook of Paper and Board". 11.2.1.1.2.
  14. 1 2 3 4 Manninen, Marjo; Kajanto, Isko; Happonen, Juha; Paltakari, Jouni (1 August 2011). "The effect of microfibrillated cellulose addition on drying shrinkage and dimensional stability of wood-free paper". Nordic Pulp & Paper Research Journal. 26 (3): 297–305. doi:10.3183/npprj-2011-26-03-p297-305. ISSN 2000-0669. S2CID 137540823.
  15. ↑ Kemppainen, K.; Siika-aho, M.; Pattathil, S.; Giovando, S.; Kruus, K. (January 2014). "Spruce bark as an industrial source of condensed tannins and non-cellulosic sugars". Industrial Crops and Products. 52: 158–168. Bibcode:2014IndCP..52..158K. doi:10.1016/j.indcrop.2013.10.009. ISSN 0926-6690.
  16. ↑ Kumar, Varun; Pathak, Puneet; Bhardwaj, Nishi Kant (February 2020). "Waste paper: An underutilized but promising source for nanocellulose mining". Waste Management. 102: 281–303. Bibcode:2020WaMan.102..281K. doi:10.1016/j.wasman.2019.10.041. ISSN 0956-053X. PMID 31704510. S2CID 207965485.
  17. ↑ Bajpai, P. (5 April 1999). "Application of Enzymes in the Pulp and Paper Industry". Biotechnology Progress. 15 (2): 147–157. Bibcode:1999BioPr..15..147B. doi:10.1021/bp990013k. ISSN 8756-7938. PMID 10194388. S2CID 26080240.
  18. ↑ Wong, C.H.; Nicholas, J.; Holt, G.D. (1 April 2003). "Using multivariate techniques for developing contractor classification models". Engineering, Construction and Architectural Management. 10 (2): 99–116. doi:10.1108/09699980310466587. ISSN 0969-9988.
  19. ↑ American Institute of Timber Construction (16 July 2012). Timber Construction Manual. Wiley. doi:10.1002/9781118279687. ISBN 978-0-470-54509-6.
  20. 1 2 3 Windrich, E. (1 January 1998). "Book Reviews : Adebayo Adedeji (ed.), South Africa and Africa: Within or Apart'? (London: Zed Books and Cape town: SADRI Books, 1996), xiii, 258 pp. Cloth $55.00, paper $19.95". Journal of Asian and African Studies. 33 (3): 278–279. doi:10.1177/002190969803300306. ISSN 0021-9096. S2CID 220925623.
  21. 1 2 3 Bajpai, Pratima (2015), "The Control of Microbiological Problems∗∗Some excerpts taken from Bajpai P (2012). Biotechnology for Pulp and Paper Processing with kind permission from Springer Science1Business Media.", Pulp and Paper Industry, Elsevier: 103–195, doi:10.1016/b978-0-12-803409-5.00008-2, ISBN 978-0-12-803409-5, PMC 7158184, S2CID 89782614{{citation}}: CS1 maint: work parameter with ISBN (link)
  22. 1 2 "BASF sells Intertech & Pira to the Smithers group". Focus on Pigments. 2010 (12): 6–7. December 2010. doi:10.1016/s0969-6210(10)70272-1. ISSN 0969-6210.
  23. ↑ Hakkila, Pentti (1989), "Utilization of Residual Forest Biomass", Springer Series in Wood Science, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 352–477, doi:10.1007/978-3-642-74072-5_8, ISBN 978-3-642-74074-9, retrieved 12 October 2023 {{citation}}: Missing or empty |title= (help)
  24. ↑ Coppola, Floriana; Fiorillo, Flavia; Modelli, Alberto; Montanari, Matteo; Vandini, Mariangela (April 2018). "Effects of γ-ray treatment on paper". Polymer Degradation and Stability. 150: 25–30. doi:10.1016/j.polymdegradstab.2018.02.004. ISSN 0141-3910.
  25. ↑ Wu, Zonghua; Tanaka, Hiroo (April 1998). "Permanence of wood-free paper I: Paper-making additives in naturally degraded wood-free papers". Journal of Wood Science. 44 (2): 111–115. Bibcode:1998JWSci..44..111W. doi:10.1007/bf00526255. ISSN 1435-0211. S2CID 95493027.
  26. ↑ BUKOVSKÝ, VLADIMÍR (1997). "Yellowing of Newspaper after Deacidification with Methyl Magnesium Carbonate". Restaurator. 18 (1). doi:10.1515/rest.1997.18.1.25. ISSN 0034-5806. S2CID 96841775.
  27. 1 2 Tillmann, Otmar (20 January 2006). "Paper and Board Grades and Their Properties". Handbook of Paper and Board. pp. 446–466. doi:10.1002/3527608257.ch11. ISBN 9783527309979.
  28. ↑ Velebil, J.; Malaťák, J.; Bradna, J. (31 December 2016). "Mass yield of biochar from hydrothermal carbonization of sucrose". Research in Agricultural Engineering. 62 (4): 179–184. doi:10.17221/73/2015-rae. ISSN 1212-9151.
  29. ↑ Hsieh, Yung-Cheng (1997). An investigation of the factors affecting dot gain on sheet-fed offset lithography presses (Thesis). Iowa State University. doi:10.31274/rtd-180813-10494.
  30. ↑ Hoekstra, Arjen Y. (2015), "The water footprint of industry", Assessing and Measuring Environmental Impact and Sustainability, Elsevier, pp. 221–254, doi:10.1016/b978-0-12-799968-5.00007-5, ISBN 9780127999685, retrieved 12 October 2023{{citation}}: CS1 maint: work parameter with ISBN (link)
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