Metallic Catalysts in the Oxidative Degradation of Paper - Advances in

3 Metallic Catalysts in the Oxidative

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Degradation of Paper J. C . W I L L I A M S , C. S. F O W L E R , M . S. L Y O N , and T. L. M E R R I L L Preservation Research and Testing Office, Library of Congress, Washington, D . C . 20540

Impermanent acid papers can ordinarily be stabilized using alkaline earth carbonates. However, paper which contains transition metal catalysts, compounds of copper, cobalt, or iron can still fail by oxidative degradation. Paper was treated with copper acetate at various pH levels, given accelerated aging, and the degradation was followed by the change in folding endurance. There was more drop in folding endurance in the humid than in the dry oven. Dryoven aging has little predictive value for oxidative degradation.

T ) a p e r , which was invented i n China around the beginning of the Christian era, lasts well when properly made and properly stored. A specimen of what once was considered the oldest paper i n the world was found i n 1942 i n the ruins of a watchtower i n Tsakhortei, south of the Bayan Bogdo mountains i n the modern Ninghsia area. This fragment, discovered b y Professors L a o K a n and Shih Chang-ju of the Academia Sinica, is a crumpled ball of coarse, heavy paper on which are written about two dozen decipherable characters. T h e frag ment is believed to have been buried accidentally around A.D. 109 when the military post was abandoned during an attack b y the western Hsi-ch'iang tribe. In Professor Lao's opinion, the paper, made of vegetable fibers, was produced about the time of Ts'ai L u n ( J ) . A more recent discovery at a tomb at Pa-ch'iao i n Sian, a modern city i n Shensi province, yielded paper specimens that may be older than those found at Tsakhortei. Scraps of thin, yellowish paper found there in M a y 1957 are believed to belong to the western H a n dynasty, 202B.C-A.D.

9(1).

I n the early papermaking process, a wet mass of short cellulose fiber was pounded and worked until, on stirring into water, the fibers gave a 37 Williams; Preservation of Paper and Textiles of Historic and Artistic Value Advances in Chemistry; American Chemical Society: Washington, DC, 1978.

38

PRESERVATION OF P A P E R A N D TEXTILES


smooth dispersion. The sheet was formed by filtration on a flat screen. O n drying, the fibers bonded together as a result of the beating. Simple as papermaking thus appears, the invention seems to have been made only once, i n China, and all papermakers derive their art from the orient. The Chinese managed to keep papermaking a secret for several centuries. However, the knowledge was finally spread by the fortunes of war. Papermaking was introduced to the city of Samarkand i n A.D. 751. According to an old Arabic manuscript, "Routes of Travel and Kingdoms," two papermakers were among the prisoners taken by the governor of Samarkand on a raid of Chinese territory. The two captives offered to exchange the knowledge of their craft for their freedom. Samarkand, with its abundant stock of flax and hemp and a ready supply of water from irrigation canals, was naturally suited to papermaking. The craft developed quickly and "Paper of Samarkand" soon became an important article of commerce. A second factory was started i n Baghdad i n A.D. 795 when Harun al-Rashid brought Chinese papermakers to the capital city (2). More than a thousand years passed between the invention of paper and its introduction into Spain by the Moors. After learning the trade at Samarkand, the Arabs monopolized papermaking i n the West for five centuries. Not until Spain was captured by the Moors did papermaking spread to Europe. The Arab conquerors of the Iberian peninsula wasted no time in establishing local mills for the production of paper and by the middle of the twelfth century, papermaking was an industry i n the Spanish cities of Xativa (or Jativa) and Toledo. A n early reference to papermills in Spain is found i n the writings of traveler A b u 'Abdallah Muhammad al-Idrisi. Describing Xativa in A.D. 1150, he wrote: "Schatiba is a charm ing town with castles whose beauty and strength have become proverbial. Paper is there prepared as nowhere else i n the civilized universe and is sent both East and West (3). The papermaking process which the Europeans learned from the Arabs made excellent, long-lasting paper. Here are directions written i n A . D . 1025: According to ibn Badis, the flax is soaked in quicklime, rubbed with the hands, and spread out i n the sun to dry. It is then returned to fresh quicklime. This is repeated a number of times. Then it is washed free of the quicklime many times, pounded in a mortar, washed, and intro duced into molds of the proper measure. Care is exerted so that the thickness of the paper is regular. It is then left to dry. It is treated with rice water or bran water. Starch is also used for this purpose. It also helps to glaze the surface of the paper (4). W h i l e the papermakers stayed with these fundamentals, they made excellent paper. The old books i n the libraries of Europe are still, generally, i n good condition. However, as the demand for paper grew, changes were made i n the process, which, while they increased produc-

Williams; Preservation of Paper and Textiles of Historic and Artistic Value Advances in Chemistry; American Chemical Society: Washington, DC, 1978.

3.

W I L L I A M S ET AL.

Metal Catalysts in Oxidative Degradation

tion, proved unfortunate from the standpoint of the permanence of the paper and of the records kept thereon.


"Improvements" in the Papermaking Process The Chinese and Arabs worked the cellulose fibers b y beating the moist fibrous mass or pounding it i n a mortar and pestle. The resulting "fibrillation" gave the necessary fiber-to-fiber bond i n the sheet. Euro peans exchanged the mortar and pestle for iron shod stampers driven by water power. In 1700, the Hollander beater came into use. The "Hollander" moved the stock i n a circular path with a wheel on which iron bars were set. These bars worked the fibers against a stationary, iron-bed plate. The fibers were fibrillated as desired. They were also bruised, fractured, and disintegrated. The iron beating tackle wore away, introducing iron into the paper where, functioning as an oxidation cata lyst, it caused yellowing and foxing. Scheele's discovery of chlorine i n 1774 led to its use to bleach stock. This often brought the degree of oxidation of the stock too high with disastrous consequences to the M e of the paper. As demand for paper continued to increase, the supply of rags could not meet the requirements. The papermaker was forced to turn to wood for the necessary fiber. Chemical methods for separating cellulose from the lignin i n wood were developed. These rather severe treatments often brought the degree of polymerization of the cellulose too low for permanence. The paper machine came into use around 1830. Before, paper had been sized i n a separate operation with gelatine or glue. N o w a new size was introduced, rosin and alum, which could be added to the beaten stock. The paper then came from the machine i n the sized condition. The amount of alum required for sizing left the paper acid. This was the final blow to permanence. A c i d paper does not last well; it quickly turns brown and brittle. The life of paper which under good conditions could be 2000 years now was reduced to around 75 years. Consumer Reaction The new, poor-quality papers brought forth many well-deserved adverse comments. These continue to the present day. Murray (5) wrote i n 1824, "I have i n my possession a large copy of the Bible, printed at Oxford, 1816, (never used) crumbling Hterally into dust." I n 1825 Thomas Hansard (6) spoke of "whole piles of quired stock, meaning books unbound . . . crumbling to dust i n the warehouses of booksellers." In 1856 Herring (7) n o t e d , " . . . It was not at all an uncommon occurrence for a parcel of paper to become so completely perished from the circum stances of its not having been thoroughly washed after bleaching that


39


40

PRESERVATION OF PAPER AND TEXTILES

an entire ream, composed of 480 sheets, might be as readily snapped asunder as a piece of rotten wood." There were many people who believed that the problems arose from abandoning rag as the source of the fiber. I n 1891 Johnson (8) wrote: "Centuries hence, some bibliographer w i l l construct an ingenious theory to explain why no books were printed between 1870 and 19—, the date at which we accomplish the destruction of the forests and begin again on cotton." Kingery (9) spoke for all librarians in 1960 when he stated that half of the books i n the N . Y . Public Library needed repair. " A casual exami nation of the current intake indicates that about 25% of it w i l l require attention with nine years. Ten percent should have immediate attention . . . we are well along towards spending half as much each year on keeping our collection as we are i n adding to it . . . disregarding what we spend on binding." Suggestions began to be made on methods of holding brittle paper and its message together. Martens (10) i n 1911 advocated treating decayed papers and parchments with a cellulose acetate solution. L y d e n berg (11) i n 1915 described a method of protecting paper with rice paste and Japanese tissue. H e calculated that to bind an ordinary daily paper i n this way would cost $420 a year. B y now a multitude of methods of preserving information are available—lamination of paper or encap sulation, microforms, magnetic tape, etc. E a c h new method brings i n new unknowns in regard to its own permanence, and many would not be necessary or desirable if paper were made correctly. Finding the Trouble Scientific investigations were launched to discover what had gone wrong with paper. In 1912 Hjelmsatter (12) exposed a number of papers to sunlight from June to August and measured the loss in properties. In all the papers, including some tub-sized, hand-made papers, the exposure to light produced a profound deterioration i n the resistance to folding. The size disappeared i n all cases, and the rosin-sized samples were badly discolored. F r o m tests i n which papers were steeped in solutions of aluminum sulfate, potassium sulfate, and aluminum acetate and then exposed to light, Hjelmsatter concluded that the deterioration was brought about by the presence of aluminum sulfate. Kohler and H a l l (13) reached a similar conclusion i n 1925 that the acidity produced by the use of aluminum sulfate was the root of the problem. Their research brought together techniques which have become standard. Chemical degradation of paper is speeded by raising the temperature; Kohler and H a l l accelerated the aging of paper by exposing


3.


WILLIAMS E T A L .

1

— i

i

41

i

10


UJ o z
—. —.

69

—

6.5

68

—

6.5

65

—

6.7

—

66

— — —

64 62 58

Na CO 2

— — 70 — 68 — — 65

Sy

73

28

7.0

— —

—

H.O. 0

4

—

6

—

4

—

0

8 4 10

50 ppm Copper 68 67 — 62 — 55 55 —

7.3 — — 6.8 — 7.0 — — 6.3

7.0 6.6 — 6.2 — 6.2 6.0 —

— — 2 — 0 — — 8


14

0 4 — 10 — 8 18 —

PRESERVATION O F PAPER AND TEXTILES


30-

^20-

Q

1.0-

100

200

300 400 500 HOURS IN OVEN

600

700

800

Figure 4. For test in humid over at 90° C and 50% r.h. A, control; W, 50 ppm copper and 0.1 % Na CO . 2

s

30

Q _l O

20 CD O

_1

100

200


600

700

800

Figure 4A. For test in dry oven at 100°C. A, control; '•, 50 ppm copper and 0.1% Na CO . 2

s



W I L L I A M S ET AL.


100

200

300 400 500 600 HOURS IN OVEN

700

800

Figure 5. For test in humid oven at 90°C and 50% r.h. A, control; M, 50 ppm copper and 1.0% Na CO . 2

s

Q _l O

§2X>

ID

100

200


600

700

800

Figure 5A. For test in dry oven at 100°C. A, control; •, 50 ppm copper and 1.0% Na CO . 2

s


56


Table V .

Foldur K r a f t — 1 % N a C 0 2

3

Fold


Hours in Oven 0 69 78 120 189 189 380 645 645

Dry oven (100°C)

Humid oven (90 C, 50% r.h.) D.O. H.O. D.O. H.O. D.O. H.O.

1444 ± — 1147 ± 142 — — 1369 ± 349 — — 752 ± 136

B r i g h t n e s s

166 900 ± 189 — 613 ± 160 551 ± 241 — 158 ± 4 2 31 ± 16 —

— 42 — — 41 — — 43

72

48 — 48 48 — 43 38 —

p

— 9.4 — — 8.6 — — 7.8

H

9.9

m e q / k g

7.3 — 7.0 6.9 — 6.8 7.1 —

273 — 32 152 — — 0 — 0 128 — — 4.0 — 0 84 —

Foldur Kraft—1% Na CO , 50 ppm Copper 2

0 24 74 84 144 144 336 600 600

1317 — 143 ± 63 — 41 ± 24 1215 ± 283 — — 25 ± 26 1164 ± 149 — — 3± 3 — 0.6 ± 0.5 474 ± 6 3 —

— — 38 38 40

s

71

37 36

— 30 — 23 19

—

— — 9.1 — 9.3 — — 7.6

9.8

7.6 7.0

— — 6.7

6.6 6.6

—

273 34 0

— — 146 —8 — 108 — — 104 — 40 —

slow oxidation taking place. Brightness has been lost. I n the humid oven, more acid was produced and the p H dropped sharply. T h e coppercontaining sample fell off badly i n folding endurance as well as i n bright ness. This appears to be the free radical effect. The experiment illustrates that the dry oven gives much less information than the humid oven. In the experiment (Figures 6 and 6A and Table V I ) the copper catalyst was added to the paper before the alkaline salt. Paper was sprayed on both sides with dilute copper acetate solution until the wet weight indicated 50 p p m copper and then it was air dried. One set of paper dipped i n magnesium bicarbonate solution (9 g / L magnesium carbonate). One set was given the Barrow two-step treatment—immer sion i n lime followed by immersion i n calcium bicarbonate. Accelerated aging was carried out i n the dry and humid ovens. I n the humid oven, the copper-magnesium treated-paper regression line is close to that of the paper alkalized with magnesium carbonate. T h e calcium carbonatetreated paper is not so well protected. This bears out the findings from the oxygen-alkaline pulping process that magnesium is a more effective



WILLIAMS ET AL.

3.0

Q _l O


"20

i.o

240

480

720

HOURS IN HUMID OVEN

Figure 6. Calcium and magnesium carbonates compared as stabilizers in coppertreated paper. O, 50 ppm copper-magnesium carbonate; •, 50 ppm copper-2-step calcium carbonate; A, control-magnesium carbonate; X, control at pH 4.8.

240 480 HOURS IN DRY OVEN

Figure 6A. Oxidative degradation effects shown in the humid oven (see Figure 6) disappear in the dry oven. O, 50 ppm coppermagnesium carbonate; •, 50 ppm copper2-step calcium carbonate; A, control-magnesium carbonate; X, control at pH 4.9.


58


Table VI.

Foldur Kraft—50 ppm Copper, Magnesium Bicarbonate Fold (V kg) 2


Hours m Oven 0 168 336 504 696

Dry oven (100°C) 1394 ± 1024 ± 1221 ± 1077 ±

Humid oven (90 C, 50% r.h.) D.O. H.O. D.O. H.O. D.O. H.O. B r i g h t n e s s

1668 ± 334 186 1176 ± 187 254 775 ± 129 288 634 ± 187 177 479 ± 125

72.8 68.8 63.5 67.3 59.5 67.4 57.4 66.8 57.7

p

8.9 8.5 8.6 8.8

H

m

8.7

9.0 8.5 8.3 8.3

e

q

142 110 82 100

/

k

140

g

116 96 — 100

Foldur Kraft—SO ppm Copper, Barrow Two-Step Calcium Treatment 0 168 408 744

1665 ± 229 1229 ± 168 664 ± 144 1145 ± 198 240 ± 135 1061 ± 150 34 ± 24

73.5 70.4 62.8 69.6 59.3 68.6 55.5

8.8 8.8 9.3

8.5

8.6 8.8 8.2

366 388 378 384 342 382 347

stabilizer than calcium carbonate. Note that a l l points fall on the same line i n the dry-oven aging as shown i n Figure 6A. The effect of K I is shown i n Fiugre 7 and Table V I I . A commercial paper bulked w i t h plastic microspheres was analyzed using atomic Table VII.

Paper Bulked with Plastic Microspheres

Fold (V kg) 2

Hours Humidoven in Dry oven (90°C, Oven (100°C) 50% r.h.) D.O. H.O. B r i g h t n e s s

p

H

m

e

q

/

k

g

y

0 144 312 888

1535 929 137

1602

1012 652 11

76.0 69.6 66.0 64.8 60.4 50.7 48.7

D.O. H.O. 8.6 8.5 8.2

8.7

D.O. H.O.

9.0 8.5 8.3

496 494 462

—

328 — 474 452 330 460

408

474 454 304

Paper Dipped in 1% KI 0 72 96 144 288 864 1440

1642

—

1434 981 430 87

1836

—

1189 1607 1537 1270 906

68.8 — 65.7 64.8 60.4 63.6 57.9 60.5 43.4 53.2 39.8 47.2

9.7

—

8.5 8.6 8.4 8.3

8.8

8.7 8.8 8.9 8.7 8.7


478

— 448 472 296 264 260

3.

WILLIAMS ET AL.



3.0

3 2.0 o U_

CD O

1.0

0

480

960 HOURS IN OVEN

1440

Figure 7. Potassium iodide represses humid oven oxidation in microsphere bulked paper. O, Kl-humid; •, control-humid; X, Kl-dry; A, control-dry. absorption by L . Tang of this laboratory and found to contain 16 p p m copper, 341 p p m iron, and 0.7 p p m cobalt. The paper was given accelerated aging i n the dry and humid ovens as received and after being immersed i n 1% K I . The results are shown i n the graph and tables. The bulked paper, as shown i n the figure, gave a highly improved regression line for humid-oven aging after the iodide treatment. Trier (34) described one bulked paper as being loaded w i t h micro spheres of a copolymer of vinylidene chloride and acrylonitrile. Such polymers are known to split off hydrochloric acid. W h i l e this may have occurred i n oven aging, the p H of the sample d i d not drop below 7 so acid degradation does not seem to have been involved. O n the other hand, the paper d i d degrade rapidly i n the humid oven, and this was very well corrected by the K I treatment. F r o m the evidence i n the litera ture peroxides and, through the catalysts, free radicals appear to be at work, which the K I corrected. This is an application that recalls its use i n oxygen-alkaline pulping and i n the prevention of the peroxide defects i n microfilm.


59

60

PRESERVATION OF PAPER AND TEXTILES

Conclusions


• The presence of transition metal compounds as oxidation catalysts can cause rapid degradation of calcium carbonate-alkalized papers under humid conditions. Magnesium carbonate offers better protection than calcium carbonate. • T A P P I method T-453-ts-63, which uses only the dry oven, gives a satisfactory estimate of the stability of acid paper but has no value i n predicting oxidative degradation or the life of a paper containing the oxidation catalysts. T h e humid oven w i l l find both acid degradation and oxidative degradation. • D r y storage of paper w i l l not protect against acid but w i l l mini mize the effect of oxidation catalysts and oxidation. • Temperature and humid conditions of storage, and the presence of oxidation catalysts i n the paper, as well as the p H and alkaline reserve, must be taken into account i n applying the Arrhenius relation to predict the life of paper. Literature Cited 1. "Papermaking, Art and Craft," p. 9, Library of Congress, Washington, D . C . , 1968. 2. Ibid., p. 16. 3. Ibid., p. 18. 4. Levey, M . , Trans. Am. Philos. Soc., New Ser. (1962) 52, Pt. 4, 10. 5. Murray, J., "Observations and Experiments on the Bad Composition of Modern Paper," Whittaker, London, 1824. 6. Hansard, T. C., "Typographia," Baldwin, Craddock and Joy, London, 1825. 7. Herring, R., "Paper and Papermaking, Ancient and Modern," 2nd ed. 81, p. 97, Longman, Brown, Green and Longmans, London, 1856. 8. Johnson, R., Library J. (1891) 16, 241. 9. Kingery, R. E., "Permanent/Durable Book Paper," p. 15, Virginia State Library #16, Richmond, 1960. 10. Martens, A . , Mitt. Materialprufungsanst.. Tech. Hochsch. Darmstadt (1911) 29, 57-60; J. Soc. Chem. Ind. (1911) 30, 414. 11. Lydenberg, H. M., Library Journal (1915) 40, 240-242. 12. Herzberg, W., Papierfabrikant (1914) 42, No. 17, 478; J. Soc. Chem. Ind., 33, 545. 13. Kohler, S., Hall, G., Pap. Ind. (1925) 7, 1059-1063; Hall, G., Pap. Trade J. (1926), April 8, Technical Section, 185-191. 14. Jarrell, T. D . , Hankins, J. M., Veitch, F. P., Tech. Bull. No. 334, U.S. De partment of Agriculture, Washington, D.C., Sept. 1932 as adapted by Williams, J. C., Bull. Am. Group,I.I.C.(1971) 12, 16-32. 15. Schierholtz, O., U.S. Patent 2,033,452, 1936. 16. Clapp, V. W., Scholarly Publishing (1971) Jan., 107-124. 17. Thomas, J. J., "Deterioration and Preservation of Library Materials," Winger, H . W . , Smith, R. D . , Eds., pp. 99-107, University of Chicago Press 1970 18. Hanson, F. S., Pap. Ind. Pap. World (1939) Feb., 1157-1164. 19. Barrow, W . J., "The Manufacture and Testing of Durable Book Papers," Church, R. W., Ed., p. 25, Virginia State Library, Richmond, 1960.



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61

20. Cowling, E. B., "Cellulose as a Chemical and Energy Resource," Wilke, C. R., E d . , pp. 164-168, Interscience, John Wiley & Sons, 1975. 21. Battista, O. A., Ind. Eng. Chem. (1962) 54, No. 9, 20-29. 22. Golova, D . P., Nosova, N. I., Russ. Chem. Rev. (1973) 42 (4) 327-338. 23. Ericcson, B., Lindgren, B. O., Theander, O., Sven. Papperstidn. (1971) 74, 757-765. 24. Klienert, T. N., Marraccini, L . M., Sven. Papperstidn. (1963) 66, 189-195. 25. Robert, A . , Traynard, P., Martin-Borret, O., U.S. Patent 3,384,533. 26. Noreus, S. E. O., Samuelson, H. O., U.S. Patent 3,652,386. 27. Minor, J. L . , Sanyer, N . , J. Polym. Sci., Part C (1971) 36, 73-84. 28. McCamy, C. S., Pope, C. I., Nat. Bur. Stand. Tech. Note, #261 (1965). 29. Henn, R. W., Mack, B. D., Photogr. Sci. Eng. (1969) 13, 276. 30. Borchardt, L . C., Butler, J. P., Anal. Chem. (1957) 414-419. 31. Praskiewicz, R. W., Subt, S. S. Y., Government Printing Office, Washing ton, D . C., private communication, 1976. 32. Gilbert, A . F., Pavlovova, E., Rapson, W . H., Tappi (1973) 56, No. 6, 95-99. 33. Manoucheri, M., Samuelson, O., Sven. Papperstidn. (1973) 76, 486-492. 34. Trier, G., Tappi (1972) 55, 769-771. RECEIVED March 24,

1977.


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