Pulp and Paper Canada

Features Innovation Technology
PAPER STANDARDS: The new Canadian permanent paper standard (CAN/CSGB-9.70-2000): development process and its implications

In January 1992, concerns about the permanence, or lasting qualities, of paper made under acidic conditions led the Federal Government of Canada to decide to print publications that are to be retained...


July 1, 2001
By Pulp & Paper Canada

Topics

In January 1992, concerns about the permanence, or lasting qualities, of paper made under acidic conditions led the Federal Government of Canada to decide to print publications that are to be retained on alkaline-based “permanent” paper. This was a landmark decision because it recognized the importance and role of long-term access to government information, that great strides had been made in the understanding of paper degradation, and finally that manufacturers had begun to alter production methods to produce paper of much improved permanence. Along with this decision, the government directed the National Archives of Canada, the National Library of Canada and the Canadian Conservation Institute to participate in the development of a Canadian standard for permanent paper. Such a standard, supported by both paper user and paper manufacturer communities, would ensure access to commercial papers which would be permanent.

Definition and debate

Permanent paper has been defined in many standards: the ANSI standard [1] and ASTM standard in the USA [2], the DIN standard in Germany [3] and the international ISO standard [4]. These standards have many similarities. All specify that permanent papers should be alkaline and contain at least 2% calcium carbonate to act as an alkaline reserve. However, some of these standards also demand that the lignin content of the paper must not exceed 1%. This has been the centre of the debate for the last decade. On one side, librarians and archivists wanted a restriction of lignin content due to their strong belief that the presence of lignin causes poor permanence. They observed that many papers made from mechanical pulps under acidic conditions in the 1930s have poor permanence. On the other side, the paper producers felt that the restriction of lignin content and paper composition is not necessary, and would exclude some papers that had already been deemed permanent. Some published research results indeed show that alkaline lignin-containing paper is quite stable during natural and accelerated aging. In addition, they argued that recent trends and technical developments in the paper industry are making it very difficult to use strictly composition-based specifications.

Advertisment

Two main concerns emerged from this debate on paper composition or lignin content. The first concern is the effect of air pollutants on the permanence of lignin-containing papers. The second one is the chemical stability of these lignin-containing papers. Paper users and paper producers agreed that these two concerns should be addressed before a Canadian standard for permanent paper was established.

Permanent paper

research project

In 1994, under the auspices of the Canadian General Standards Board (CGSB) a research program was established and financial support obtained from both industry and government: i.e. the user community and the paper producers. This research program was unique because the research was managed and carried out jointly by two separate organizations: Paprican, and the Ottawa-based government laboratory representing the user community, the Canadian Conservation Institute (CCI). The CCI forms part of the Department of Canadian Heritage. The research work began in 1994 and was completed in 1997. The main findings from this co-operative project [5] included:

Acidity, rather than fibre composition, is the most significant factor affecting the stability of both lignin-containing and lignin-free papers in accelerated aging tests.

The mechanical and chemical properties of alkaline lignin-containing papers are equally stable.

The addition of calcium carbonate as a buffering compound significantly improves the stability of both alkaline lignin-containing and lignin-free papers exposed to air pollutants.

The optical properties of alkaline lignin-containing papers are less stable than those of alkaline lignin-free papers.

These results were well accepted by both paper users and paper producers in Canada.

New Canadian

permanent paper standard

In 1998, following the completion of the Canadian Co-operative Research Program, the CGSB asked its Sub-committee on the Permanence of Papers to develop a permanent paper standard. The sub-committee completed its work in early 2000, and in September 2000, CAN/CGSB-9.70-2000 Permanence of Paper for Records, Books and Other Documents was approved as a National Standard of Canada by the Standards Council of Canada.

The Canadian standard requires permanent papers to have an alkaline reserve, a pH value in the range of 7.0 to 10.0, and the strength and performance properties as required by end-use. A key difference to the existing ISO and ANSI/NISO standards is in specifying a much broader range of paper grades and by not limiting the lignin content or the types of fibres that may be used. The standard recognizes that for most paper applications, the physical integrity of paper is the main requirement; thus the use of lignin-containing fibres should not be an issue. However, to help assure maximum optical permanence, where required (e.g. artwork), the standard currently recommends restricting the lignin content to 1% to provide both mechanical and optical permanence. It should be pointed out that CAN/CGSB-9.70-2000 suggests that this requirement be reviewed once reliable test methods to predict colour stability are available.

This Canadian permanent paper standard has gone a long way towards creating a less restrictive standard without compromising the paper permanence requirements. The use of permanent papers as specified in this standard will help to ensure that books and documents remain accessible and usable for centuries.

Important opportunities

The acceptance by paper users of the new research results on lignin and permanence, along with the new Canadian permanent paper standard, can lead to the revision of other existing permanent papers standards, to include alkaline lignin-containing papers. This will create product development opportunities for paper producers. For example, fine papers containing high-yield pulps (e.g., BCTMP) or recycled fibres can be classified as permanent paper, as long as they are made under alkaline conditions and the end-use performance targets are met. With the removal of the lignin restriction in permanent papers, an increased use of high-yield pulp in traditional wood-free paper grades is expected. On the other hand, alkaline papers with 100% mechanical pulp furnish can also be classified as permanent in terms of their mechanical properties.

Future

The release of the Canadian Permanent Paper Standard is a significant step because of its acceptance of lignin-containing pulps in papers with mechanical permanence. However, the current standard is probably just a transition, aiming ultimately towards a performance-based standard, i.e., there should be no specifications on paper composition and any paper that can pass a standard aging performance test can be classified as permanent. The current standard clearly mentioned that it would be open to review and amendment, based on relevant research results. ASTM’s current work on developing aging performance tests will hopefully help develop such standards.P&PC

Literature

1. ANSI/NISO Standard Z39.48-1992, Permanence of Paper for Printed Library Materials, American National Standards Institute, American National Standard for Information Science.

2. ASTM Standard D3290-00, Standard Specification for Bond and Ledger Papers for Permanent Records, American Society for Testing Materials, 2000.

3. ISO Standard 9706:1994(E), Information and Documentation – Paper for Documents – Requirements for Permanence, International Organisation for Standardisation, 1994.

4. DIN 6438, Paper and Board, Useful Life Classes, Deutsches Institut fr Normung e.V., 1992. 5. Zou, X., N. Gurnagul, S. Deschtelets, P. Bgin, J. Iraci, D. Grattan, E. Kaminska, and D. Woods, Canadian Co-operative Permanent Paper Research Project: The Impact of Lignin on Paper Permanence, Final Report, Pulp and Paper Research Institute of Canada and Canadian Conservation Institute, January
1998.

Xuejun Zou, Norayr Gurnagul, Paprican, Pointe-Claire, QC.