Literature

Photostabilization of Thermomechanical Pulps by Alkylation and Borohydride Reduction," by Raymond C. Francis et al., Tappi Journal, Dec. 1991, p. 127-133. A known major cause of color reversion is the photo-oxidation of phenolic hydroxyl groups in lignin-rich pulps, but for high-brightness peroxide bleached pulps, yellowing by photo-oxidation of nonphenolic structures appears to be equally important. Both types of color reversion were retarded by borohydride reduction followed by alkylation.

These results agree with the findings in a paper by Lucia Tang, Margaret Troyer and John C. Williams, presented at the 1980 annual conference of the International Institute for Conservation - Canadian Group (IIC-CG): "Evaluation of Sodium Borohydride Treatment in the Stabilization of Experimental Papers." Foldur Kraft and newsprint paper were washed in borohydride solutions of different concentrations, and afterward some of them were washed in dilute calcium hydroxide solutions. This double treatment gave substantial improvement to the strength of the Foldur Kraft, as measured by fold endurance. Brightness retention was also improved. The newsprint was not affected nearly as much.

"The Prevention of Light-Induced Yellowing of Paper: The Inhibition of Reversion by Mercaptans of TMP and CTMP Pulp from Balsam Fir (Abies balsamea) and Black Spruce (Picea mariana)," by C. Daneault, S. Robert & M. Levesque. J. Pulp & Paper Sci. 17 no. 6, Nov. 1991, P. J187-J193. Peroxide bleached thermomechanical pulp (TMP) and unbleached TMP and chemithermomechanical pulp (CTMP) were treated with mercaptans, which both bleached the pulp and prevented color reversion. The larger mercaptan molecules were most effective. Bleached TMP gave the best results. [Mercaptans or, to use the more modern name, thiols, are organic compounds resembling alcohols, but with sulfur where the oxygen ought to be. Many of them smell just terrible. -Ed.]

The same issue of JPPS has a closeup color picture on its cover, showing a recycled paper with dirt specks printed on, to give a "greener" appearance.

"Changes in Physical Properties of Paper Containing High-Yield Pulp by UV Treatments," by Bong-Yong Kim et al. (Dept. of Forest Products, Faculty of Agriculture, Univ. of Tokyo). Japan Tappi, 1989. Mechanical and optical 1properties of paper prepared from mixtures of bleached kraft pulp and an unidentified high-yield pulp or pulps were examined in order to understand the combined influence of UV light and lignin content. [The authors seem to equate lignin content with proportion of high-yield pulp.] Pold endurance decreased drastically after UV treatment, at the same rate regardless of proportion of lignin. This strength loss is attributed to direct depolymerization of cellulose by UV, rather than by the effect on the cellulose of reactive groups from lignin degraded by UV. While high lignin content did not cause faster strength loss, it did have a strong influence on discoloration of UV-treated sheets.

"Characterization of Residual Lignin in Alkaline Pulp of Wheat Straw, by Z. Jiang, D. Tai and Z. Lee. China Pulp Pap. 10 no. 1, 1991, p. 3945 (in Chinese). The abstract in Paper and Board Abstracts 24 no. 10 says that they isolated the lignin by two methods, using selective hydrolysis and cellulosic enzymes. The residual lignin was found not to have any chemical linkages with carbohydrate. They speculate that most residual lignin may be trapped in the cell wall.

"Yellowing of High-Yield Pulp," by K. Fischer. Papier vol. 4,4, no. 10A, Oct. 1990, pp. V11-Vl8 (in German). Yellowing is attributed to the action of oxygen and hydroxyl radicals on light-sensitive groups such as aromatic carbonyls derived from the high-lignin residues in the CTMP studied. It can be reduced by chemical modification of the lignin residues, the use of UV absorbers, or addition of sulphur compounds.

Falmouth Associates has already carried out its multiclient technical audit programs of uncoated woodfree papers and coated papers, but it is offering the six audits (reports) to buyers who were not clients originally, at a pre-publication price ranging from $5300 to $7300 each. Each gives the results of 30 or so tests performed on about 50 grades from each of the following categories:

LWC (light wt coated, usually mechanical pulp papers)
No. 4 Coated (both mechanical content & woodfree)
Premium Coated Grades (Art, No. 1 & No. 2 Qualities)
Text & Cover
Commodity Xerographic
Premium Xerographic & Laser

Tests relevant to permanence that are performed in the audit are: calcium carbonate content, surface pH, tear and fold. In order to make these audits useful for people interested in permanence, one would have to include cold extraction pH, at least for the uncoated papers, lignin content, and any other tests included in the ANSI, ASTM and ISO standards.

Graphic Arts Literature Abstracts (GALA), currently published by the Rochester Institute of Technology (RIT), will be transferred to the Institute of Paper Science and Technology (IPST) as of January 1, 1992. Subscriptions will continue without interruption, and the same subject categories will be used. IPST has published the Abstract Bulletin of the Institute of Paper Science and Technology (ABIPST) for over 60 years, and now it will also be publishing the GABIPST, the Graphic Arts Bulletin of the IPST. For information call 404/8539528.

"Mineral Fillers in Paper," by Ken Beazley. The Paper Conservator 15, 1991, p. 17-27. The author is a senior research scientist with English China Clays International in Cornwall, England. His paper is systematic and didactic, a paper conservator's dream. Sections are headed Introduction, Historical, The reasons for filling, Coating, Bulk fillers, Minor fillers, Ultrafine fillers, Additional pigments present from coated broke/recycled coated paper, Filling and paper permanence, Detection and identification, Concentration or extraction of filler, Analytical techniques available, and Conclusions. An appendix outlines wet chemical analysis techniques used at ECC International for silica, alumina, ferric oxide, titanium, calcium, magnesium, barium, sulphate, potassium, sodium and lithium. 52 references.

The Canadian Financial Post reported August 21 that spokesmen for the Canadian Pulp and Paper Association, in a news conference, had opposed the government's approach to recycling. Forcing papermakers to produce more recycled paper is not the answer, they said; governments should let market demand for recycled products push the industry to produce more. The article, "Paper Firms Urge Against Quotas on Recycling," by John Geddes, continues:

"Last year, the industry recycled waste materials equal to 31% of Canadian consumption of paper and paperboard. By 1995, paper mills will be reprocessing waste amounting to 60% to 65% of Canadian consumption.... "Eighty per cent of our [paper] production is exported. There simply is not enough recyclable waste in Canada to achieve high recycled content levels in each and every one of our products,' Stewart [the CPPA chairman] said. He added that better sorting of different types of paper collected for recycling would make it possible for companies to reprocess more old paper. But he said recycling has its limitations, and called for more incineration of waste paper." (Thanks to David Tremain of Ottawa for sending this clipping in.)