Gluing

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Sizing is a process in paper production and has nothing to do with gluing in everyday life. It is used to improve important paper properties and has its origins in very old Chinese knowledge from the 3rd century. A distinction is made between surface sizing (thin glue application on the upper side of the paper web, the paper sheet) and engine sizing (addition of glue before sheet formation in the fiber mass). The sizing is used specifically to the sizing effect, the surface sizing in addition, the increase in the surface strength ( judder - and Radierfestigkeit , reduces the tendency to form dust and improves the writability ).

purpose

A papermaker understands by sizing or sizing the partial hydrophobization of paper in order to make it writable or printable with aqueous or solvent-based printing inks . The term is derived from the fact that animal glue was previously used for this purpose. Instead of the term gluing, the term impregnation can be used accordingly. In the English language is used correctly sizing instead of glueing what the most important feature of the sizing, namely the hydrophilic reduction and thus the Saugfähigkeitsbegrenzung is derived.

Without glue, writing inks would run on the paper

Water-based and low- viscosity writing materials such as ink or Indian ink run on unsized paper, for example kitchen paper or toilet paper , and the high capillary values ​​of the paper prevent clean writing. On the one hand, sizing reduces the internal surface tension of the paper fleece and thus the capillarity; on the other hand , the sizing also seals the fiber-to-fiber bonding points and thus significantly increases the tear resistance of the paper.

Contrary to what is often assumed, the papermaker's glue is not an adhesive in the usual understanding and therefore has a different effect on many questions of paper properties. During sizing, the hydrophobic resin particles are fixed to the surfaces of the fibers, but free resin particles also remain (free glue). For example, free glue in the vat reduces the binding capacity of the fibers by occupying the binding fibril ends and thus preventing them from becoming linked during drying. Tear length and burst strength decrease with increasing use of glue.

The so-called Cobb value is used as a measure of comparable water absorption . This value indicates how many grams of water can be absorbed by one square meter of paper under standardized conditions.

Paper with a weight of around 80 g / m 2 (as much as normal copy paper weighs ) absorbs around 100-120 g / m 2 of water when unsized . After it has been glued, the water absorption is only about 20-25 g / m 2 . Too little water absorption should also be avoided because otherwise the ink / printing ink will not be absorbed quickly enough and can smear. The effect of over-gluing can then be perceived as the writing material dripping off the surface of the paper.

Methods of sizing paper

In the early East Asian and Arabic papers, natural starch and various vegetable mucilages were used as sizing agents (vegetable sizing). Later, when the knowledge of papermaking came to Europe, animal glue or hide glue was used - hence the name. Both animal glue ( gelatin solution ) and starch solution can only be used sensibly as surface sizing , since their inherent retention is too low for use in the mass . The paper glued with it is very well protected against environmental influences and writing materials, but it is not erasable . Until after 1810 the papers were drawn individually through hot animal glue and their quality was improved by surface sizing .

Since around 1806 previously modified tree resins ( saponified by boiling with lye ) , predominantly rosin , have been used in bulk , but the glues usually contain numerous other substances, such as animal or vegetable glue and synthetic resin additives. However, the new resin soaps had one disadvantage: they did not adhere to the cellulose fibers. In order to achieve adhesion, by previously etching the cellulose fibers with alum , potassium aluminum sulfate, reaches a fixation. Alum helped the papermakers keep the resin soaps on the paper; But alum has one fatal property for paper: it is acidic . The so-called acid precipitation of the saponified resins in the paper machine or vat took place first through the aluminum ions of the potassium alum and later through that of the cheaper aluminum sulfate . This corresponded to the traditional experience of papermakers with alum.

Since in both cases an excess of free aluminum ions must be used to prevent free glue compared to the reactive colloidal glue substances, a slightly acidic paper product is created - the acidic or acidic paper. When exposed to atmospheric moisture , this forms sulfuric acid , which damages the paper from the inside out ( catalytically caused cellulose degradation). The paper turns from light yellow to dark brown, is brittle and cracks, at edges and corners, disintegrates the book, it comes to the paper disintegration .

Wood pulp ages faster than pulp. When wood pulp and acid resin sizing come together, a paper cannot be resistant to aging. The hydrolysis of the alum content remaining in the paper - regardless of whether it is cellulose paper or wood pulp paper - partially produced sulfuric acid, which led to acidification and accelerated degradation of the papers of the 19th and 20th centuries. However, it must be said that old rag papers sized animal were also treated with alum. Lime milk was also added to the animal glue for clarification, followed by alum solution.

The most modern and paper-friendly process is the synthetic sizing that is currently in use . Polymers with a hydrophobic effect (for example copolymers of styrene and acrylic acid esters or maleic acid ), alkylated ketene dimers (AKD sizing) or alkenylsuccinic anhydrides (ASA sizing) are primarily used . In the surface sizing , starch, starch derivatives (ethers, are ester ), animal glue, casein , paraffin , wax , Celluloseester ( methyl cellulose , sodium carboxymethyl ). Sizing agents are also used, such as alginates , manno - galactans ( glucomannans ).

Depending on the amount of glue added, a distinction is made:

  • unsized papers
  • Quarter gluing
  • Half-gluing
  • Three-quarter gluing
  • Full gluing

literature

  • Hans-H. Hofer and Josef Weigel: Possibilities of paper sizing. In: H. Bansa (Ed.): Journal for Libraries and Bibliography. Durability of Paper: Lectures at the 4th International Graphic Restorers' Day 1979. Special h. 31, Klostermann, 1980, ISBN 3-465-01448-0 , pp. 82–90, online (PDF; 356 kB), at iada-home.org, accessed on October 25, 2016.
  • Günter Engelhardt, Klaus Granich, Klaus Ritter: The glueing of paper. Fachbuchverlag, Leipzig 1972, DNB 730155331 .
  • Kurt Hess: The chemistry of cellulose and its companions. Academic Publishing Company, Leipzig 1928, OCLC 313883984 .
  • Andreas Pingel Keuth: Paper production: From cellulose to filter bags, writing paper, .. In: Chemistry in our time . 2005, 39 (6), pp. 403-409, doi : 10.1002 / ciuz.200500234 .
  • Mass sizing (PDF; 595 kB), on gruberscript.net, accessed on October 21, 2016.
  • Use of starch in paper and their metering devices. (PDF; 1.02 MB), from gernsbacher-meister.de, accessed on October 24, 2016.

Individual evidence

  1. ^ Joseph Needham : Science and Civilization in China: Vol. 5 Chemistry and chemical technology , Cambridge University Press, 1985, ISBN 0-521-08690-6 , p. 73.
  2. ^ Wolfgang Schlieder: paper. Traditions of an ancient craft. Fachbuchverlag, Leipzig 1985, ISBN 978-3-343-00346-4 , p. 10.
  3. ^ Carl Zerbe: Mineral oils and related products: 2nd edition, 2nd part, Springer, 1969, ISBN 978-3-642-87510-6 , p. 696.
  4. ↑ Erich Siebel, Rudolph Korn, Friedrich Burgstaller: Handbook of materials testing. 2nd edition, 4th volume, Springer, 1953, ISBN 978-3-662-21990-4 , p. 68.
  5. ↑ Cf. Moritz Friedrich Illig : Instructions on how to glue paper in bulk in a safe, simple and inexpensive way. As a contribution to the art of papermaking. Research Center for Paper History, Mainz 1959, DNB 452205972 , reprint of the original edition from 1807.
  6. ↑ Otto Lange: Chemisch Technical Regulations: 2nd volume, 3rd edition, Springer, 1923, ISBN 978-3-662-31454-8 , pp. 161-176.
  7. ↑ Werner Griebenow: Signs of aging in paper - mainly from a chemical point of view. In: Restauro. Journal of art techniques, restoration and museum issues. Vol. 97, no. 5, 329–335, Online (DOC; 1.8 MB) at viks.sk, accessed on October 26, 2016, No. 6, 409-415, 1991, ISSN  0933-4017 .
  8. ↑ Irene Brückle: The Role of Alum in Historical Papermaking. In: The Abbey Newsletter. Volume 17, Number 4, Sep 1993, pp. 53-57, online at cool.conservation-us.org, accessed October 26, 2016.
  9. ↑ Thomas Krause, Werner Franke (Ed.): Testing of paper, cardboard, cellulose and wood pulp. Volume 1, Springer, 1991, ISBN 978-3-642-48379-0 , pp. 87 ff.