US3771958A

US3771958A - Gaseous diffusion paper deacidification

Info

Publication number: US3771958A
Application number: US00214217A
Authority: US
Inventors: J Kusterer; R Sproull
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1971-12-30
Filing date: 1971-12-30
Publication date: 1973-11-13
Anticipated expiration: 1990-11-13
Also published as: GB1422385A

Abstract

Paper, for example having a pH of about 5.0 or lower, is rendered resistant to the deterioration that is promoted by acidic conditions in paper by impregnating the paper, for example in the form of a book, with gaseous morpholine.

Description

United States Patent [1 1 Kusterer, Jr. et a1.

[ Nov. 13, 1973 1 GASEOUS DIFFUSION PAPER DEACIDIFICATION [75] Inventors: James E. Kusterer, Jr.; Reavis C.

Sprouli, both of Richmond, Va.

[73] Assignee: Research Corporation, New York,

[22] Filed: Dec. 30, 1971 [21] Appi. No.: 214,217

[52] US. Cl 21/58, 21/7, 21/76,

117/154, 252/401 [51] Int. Cl A611 13/00 [58] Field of Search 21/58, 7, 76;

[56] References Cited UNITED STATES PATENTS 3,472,611 10/1969 Langweli 21/58 2,185,954 1/1940 Ryner 21/58 UX 3,135,627 6/1964 Sadier 117/143 3,419,498 12/1968 Paiumbo et a1 162/160 X Primary Examiner-Morris O. Wolk Assistant Examiner-D. G. Miilman Attorney-John W. Behringer et a1.

[57] ABSTRACT Paper, for example having a pH of about 5.0 or lower, is rendered resistant to the deterioration that is promoted by acidic conditions in paper by impregnating the paper, for example in the form of a book, with gaseous morphoiine.

10 Claims, 2 Drawing Figures PATENIED NM 13 I975 FIG].

F/GZ.

GASEOUS DIFFUSION PAPER DEACIDIFICATION This invention relates to a process for treating paper to render it resistant to the deterioration that is promoted by acidic conditions in paper. More particularly, it concerns such a process wherein the treatment constitutes impregnating the paper with gaseous morpholine.

The recognition of the severe problem of deterioration of documents printed on paper that is or becomes acidic has prompted the development of several different processes for deacidifying such paper so as to halt or slow its deterioration. Prime examples of acidic papers which are susceptible to such deterioration (caused by hydrolysis of acidic ions which impregnate the cellulose during manufacture) are groundwood (as opposed to chemical wood) papers and alum-rosin sized papers, whether made of wood or rags. Some of the deacidification processes which have heretofore been developed are disclosed in "Restoration Methods, by W. J. Barrow, The American Archivist, 6: ll-l54, July 1943; Permanence/Durability of the Book-ll]: Spray Deacidification," published by W. J. Barrow Research Laboratory, 1964; "Vapor Phase Deacidification: A New Preservation Method," by Paul McCarthy, The American Archivist, 32: 333-342, October i969; and U.S. Pat. No. 3,472,611 to Langwell. Each of these processes shares at least one common ob jective: to efi'ect a long lasting elevation of the pH of the paper. If this is accomplished, then the deterioration of the paper that is induced by acidic conditions therein will be substantially alleviated.

The paper deacidification processes heretofore developed, however, often possess significant drawbacks. Some, for example those involving a leaf-by-leaf treatment, while perhaps technically effective, are prohibitively expensive. Others, such as ammoniation, may provide only a short-lived resistance to deterioration. Still other processes may be longer lasting in their intended effect, but have one or more undesirable side effects, such as causing discoloration, e.g., yellowing, of the paper, diminution of the papers fold endurance, cockling of the paper, and leaving the paper with a lingering, unpleasant odor. Still other methods of treatment may require the use of particularly noxious andlor strongly toxic chemicals (e.g., cyclohexylamine), thereby requiring relatively elaborate equipment to conduct the treatment safely. There is, then, an urgent need for effective, safe and relatively inexpensive methods of treating paper so as to render it resistant to acid-catalyzed deterioration. The magnitude of the problem is revealed, for example, in The Case of the Vanishing Records, by David G. Lowe, American Heritage, volume XX, No. 5 (1969), page 34.

The invention will be understood from the following description, made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a view, partly broken away, of an apparatus suited for the practice of the process of the invention; and

FIG. 2 is a horizontal section, taken along line 22 of FIG. 1.

it has now been discovered that paper which is susceptible to acid-catalyzed deterioration can be efi'ectively, safely, and relatively inexpensively deacidified, and thereby made resistant to such deterioration, if it is impregnated with gaseous morpholine. Moreover, it

has been found that such treatment can be effected even with tightly closed books, so well will 7.6, penetrate them, and the resultant deacidification is extremely long lasting, maybe even permanent.

The extent of morpholine impregnation of paper that is to be deacidified by the process of the present invention is preferably sufficient to provide the paper with a pH (measured after the paper has been allowed to stand at room temperature and atmospheric pressure for 24 hours) of at least about 7.6, preferably at least about 8.5. The pH values referred to are those of the resultant aqueous solution when one gram of oneeighth inch square pieces of the treated paper is soaked for 1 hour in ml. of distilled, deionized water at room temperature. As determined by this method, the initial pH value of paper which is susceptible to the deterioration that is alleviated by the present invention is usually about 5.0 or lower, and frequently about 4.3 or lower.

The time period required to complete such an impregnation process will of course vary, depending upon the amount and type of paper being treated, the amount of morpholine employed, the treatment temperature, the pH level desired for the paper, etc. As an example, however, a book having an initial pH of, for instance, about 4.3 can be made to have a pH of 8.3 in as little as 8 hours when immersed in an approximately [00 percent morpholine atmoshpere at room temperature. No harm to the paper has been observed to occur through prolonged treatments, but it is generally unnecessary to continue the treatment for more than about 4 days.

No special treatment temperature is required for the present process; however, preferred operating temperatures are in the range of about 5C. to 128C, most especially about 25C. to C.

The gaseous morpholine used in the present process can, if desired, be in admixture with one or more other gases, such as air, that are non-interfering with the deacidification process. Preferably, though, the morpholine accounts for at least about one-third, and most preferably a major amount, e.g. about to I00 percent, or even 98 to 100 percent, of the volume of the atmosphere surrounding the paper during treatment.

impregnation of the paper with the gaseous morpholine can be effected by simply contacting the aper with morpholine vapors. The vapors may be under atmospheric, sub-atmosphierc or superatmospheric pressure. At room temperature the pressure exerted by a 100 percent morpholine atmosphere is about 7 to 10 mm. Hg, which is entirely adequate to penetrate the paper.

It may be desirable after treating paper according to the present process to pass air over the paper under subatrnospheric pressure so as to permit the escape of any excess morpholine present and thereby lessen the residual morpholine odor of the .paper.

It has been observed that the treatment of this invention can discolor and/or render tacky any book covers that contain pyroxylin. Such covers should therefore preferably either be removed or tightly encased in a protective covering such as polyethylene film prior to treatment of the book.

It has also been observed that paper treated according to the present process retains its high pH slightly better, and therefore better maintains its resistance to deterioration, if it is kept in a dry atmosphere. The

more humid the storage atmosphere, the somewhat poorer will be the pH retention. Nevertheless, the present process is useful even if not followed by storage in a dry atmosphere, as evidenced by the fact that even 6 months storage under I percent relative humidity at 23C. will cause only a modest drop in pH, e.g., from about 8.5 to 7.4 or 7.7.

The invention will be better understood by reference to the following non-limiting examples.

EXAMPLE 1 Four sets of experiments were run using the apparatus shown in FIG. 1 of the attached drawings. Referring now to H6. I, there is shown a rigid, round containment vessel fitted with a lid 11 that is clamped in place during use by clamps l2 and 13. In the bottom of vessel 10 is an open bowl 14 which contains a much smaller, open dish 15. Resting on the top of bowl 14 is a horizontal screen 16 which substantially fills the cross-sectional area of vessel 10. Mounted to the underside of lid 11 is fan blade 17, driven by motor 18. Mounted on top of lid 11 is handle 19. The diameter of vessel 10 is about inches at its base and about inches at its top. The height of the vessel is about 26 inches.

The above apparatus is used in practicing the present process by placing liquid morpholine in dish 15, then putting screen 16 in place on top of bowl 14, and then placing the paper to be treated on top of screen 16. The lid 11 is then clamped into place and fan motor 18 is turned on. The morpholine then vaporizes and mixes with the air in the vessel and impregnates the paper.

In each experiment samples of 100 percent chemical wood paper were treated in the apparatus of FIG. I with gaseous morpholine at room temperature. The paper is composed of 49 percent Puget sulphite pulp, 24 percent bleached soda pulp, and 27 percent Astracel hardwood pulp, is filled with bag clay, and is sized with alumrosin. Control samples of the paper (untreated) were tested for pH, tear resistance, and fold endurance.

The treatment time in the morpholine-containing vessel was shortened with each succeeding set of experiments, as reported hereinafter in Tables I, ll and Ill. After treatment, some of the paper samples were immediately evaluated for pH, fold endurance, and tear resistance, while the remainder were first heat-aged in a dry oven for varying periods at l00C. The pH levels of the treated samples (reported in Table l) were measured after each aging period, and the fold endurance and tear resistance values (reported in Tables ll and III) were obtained after the 12 day aging period. From the fold endurance and tear resistance values were calculated the useful half-lives of the treated and untreated paper at the dry oven accelerated aging temperature, 100C. These too are reported in Tables ll and III.

Fold endurance testing was performed with The Mars sachusetts Institute of Technology Folding Endurance Tester which repeatedly bends a 15 mm. wide strip of the paper to be tested across a line in a 270 arc, under A kilogram tension, until failure. The endurance was recorded as the average number of bends endured per strip, after testing 50 strips. Both machine directional fold endurance (M.D.) and cross directional fold endurance (C.D.) were determined in this manner.

Tear resistance testing was performed with the Elmendorf Tear Tester.

TABLE I pH Length of pll after treatment and aging at 100 C. for the following helore morpholine pH after number of days treattreatment, treatment. Sel. merit hours before aging 2 days 4 days 6 days 8 days 10 days 12 (lays 4.3 8 4 8.4 8.8 7.!) 7.8 7.6 7,5 4. 3 8. 6 8. 4 8.] 7. 7 7. 5 ti. 4 fl. [l 4. 3 8. 7 7 S 7. ll 7. 2 6. l G. 9 ti. 6 4. 3 8. 6 7 7 6. 8 7.0 5. ti 5. H (i. I)

TABLE It Average told endurance after treatment, bends per strip I Average [old endurance before treatment or ag- Length of After treatment, After treatment, Hall-life (days) mg, bends per strip morpholine before aging after 12 days aging at 100 C. treatment, Set MI). 0 D hours M.D. C.D. MD. C.D. M1). (3.1).

397 88 9B 347 El 62 36 4. 6 l0. 7 397 88 48 360 B1 21 3 7 397 88 24 418 98 24 26 3 6. 4 397 88 8 352 91 11 i7 2. 4 4. 6 397 88 None 397 88 1D 12 2. 3 4

Aged but not treated with morpholine.

TABLE III Average tear resistance alter treatment, grams tear Average tear resistance before treatment. or aging, Length of Alter treatment, After treatment, Hall-lilo (days) grams tear morpholine before aging alter 1'2 days aging at I00" (7. treatment, e hot v1.1) C D hours MI). (3.1). MI). (Ll). MA). (3.1).

5'2. 0 57. z 96 56. 2 60. 1 41. l 43. 8 3D. 2 52. [l 57. .2 4B 53. 2 B2. 0 33. 7 40. 0 2t). 4 21 52.1) 57. 2. 24 53. U 65. 0 39. J 48.1) 27 27 52.0 57. .2 it 54.1 50.8 34. 38.5 18.7 17.3 52.1) 57. 2 Nom- '5.!. ll 57. Z '17.!) 2}. 4 8 7 J. 3

Aged but not treated with morpholine.

The test data in Table 1 illustrate quite clearly the long-lasting quality of the deacidification that is effected by the process of the present invention.

The test data in Tables I1 and ill demonstrate that the deacidification treatment of the present invention provides resistance to strength loss and a much longer useful life than that to be expected for the untreated paper. Thus, for example, the paper that had been treated with morpholine for 96 hours (i.e., that of set 1), had a fold endurance half-life at 100C. of 4.6 days in the machine direction and 10.7 days in the cross direction, whereas the untreated paper had a half-life under those conditions of only 2.3 days M.D. and 4 days C.D. Similarly, the tear resistance half-life at 100C. of the paper that was treated with morpholine for 96 hours was about 30 hours in both directions, while the untreated papers half-life was only about 9 hours in both directions.

EXAMPLE [I Four more sets of experiments were run, but using a different apparatus than that depicted in FIG. 1 of the attached drawings. The essential difference was that the apparatus used for this set of experiments was airthis example was considerably greater, due to the removal of air by the vacuum pump. To prevent morpholine from contacting and possibly harming the pump, a condenser was placed in the line between the treatment chamber and the vacuum pump.

in this apparatus and manner, then, samples of the same type of chemical wood paper used in Example 1 were treated with gaseous morpholine, and untreated control samples were tested for tear resistance as well as pH.

Again the treatment time was shortened with each succeeding set of experiments, as reported hereinafter in Tables 1V, V, and V1. After treatment, some of the paper samples were immediately evaluated for pH, folding endurance, and tear resistance, while the remainder were first heat-aged in a dry oven for varying periods at 100C. The pH levels of the treated samples (reported in Table IV) were measured after each aging period, and the fold endurance and tear resistance values were obtained after the 12 day aging period. From the folding endurance and tear resistance values there was calculated for each sample the half-lives (both M.D. and CD.) after the 12 day accelerated aging process. These percentages are reported in Tables V & V1.

TABLE IV 1V" 4.3 96 9.1 8.9 8.8 8.7 8.5 8.5 8.5 2V" 4.3 48 9.1 8. 5 8.8 8.3 8. 4 8.5 8. 4 3V 4.3 24 8.9 8.5 8. l 8.4 8.4 8.3 8. .2 4V 4.3 8 9.0 8. 5 8. 5 8.3 7. 4 7.8 8. 0

"V=Treated in vacuum chamber.

TABLE V Average 101d endurance Average told endurance after treatment, bends per strip before treatment or ag- Length of After treatment After treatment, Half-life (days) ing, bends per strip morpholine before aging after 12 days aging at 100 C.

res ment Set MJ) C.D. hours M.D. C.D. M.D. C.D. M.D. (1.1).

397 88 96 136 19 16 4. 5 1(1 397 88 48 143 44 20 16 4. 7 $1 397 88 24 171 49 2B 20 5 10. 3 397 88 B 154 54 23 Z] 4. 3 R. 7 397 88 None 397 '88 10 12 2. 3 4

Aged but not treated with morpholine. "V=Ireated in vacuum chamber.

TABLE VI Average tear resistance after treatment, grams tear Average tear resistance before treatment or Length of After treatment, After treatment, Half-life (days) aging, grams tear morpholine before aging alter 12 days aging at 100 C. treatment, W Set M.D C.D. hours M.D. O.D. M.D. C.D. M.D. CD

52. 0 57. 2 96 56. 8 64. 0 37. 9 43. 6 23. 4 27 52. 0 57. 2 48 56. 0 60. 4 41. 8 47. 2 33. 7 35 52. 0 57. 2 24 53. 3 60. l) 40. l 47. 0 3'2 34. 3 52. 0 57. 2 8 54. 7 62. 5 40. 8 47. 4 25. 7 28 Control 52. 0 57. 2 None '52. 0 '57. 2 '17. El 21. 4 8. 7 9. 3

'Aged but not treated with morpholine. =Treated in vaceum chamber.

tight and attached to a vacuum pump. in each of the present experiments, then, the impregnation chamber was placed under a partial vacuum, measuring about 30 inches of mercury. Thus, as compared to the experiments of Example 1, the morpholine concentration in the gaseous atmosphere around the paper treated in The test data in Table IV again illustrate quite clearly the long-lasting quality of the deacidification that is effected by the process of the present'lnvention. Also, the values indicate that higher pH values are obtained by using a more concentrated morpholine atmosphere in treating the paper than that used in Example I.

It was also noted, but not reported in Table N, that a decrease in the pH of the treated paper is generally effected by extensive handling of the paper, as, for example, in testing it for tear resistance. This pH depression is generally slight, however. In the case of the samples reported on in Table IV, for instance, the pH of the paper after aging and testing was usually at least 8.0 and was always at least 7.5.

The test data reported in Tables V and V] again show quite clearly that the morpholine treatment of the present invention enables the paper to withstand much better the accelerated aging process, insofar as the papers tear resistance and folding endurance properties are concerned, than if the paper were not so treated.

As indicated above, the process of this invention is applicable to any paper that is subject to deterioration due to acidic conditions in the paper. Thus, the paper can be manufactured from, for instance, sisal, jute, flax, wood, cotton, or any combination of the foregoing. Other experiments have been run, for instance, with a paper composed of 50 percent cotton linter and 50 percent chemical wood furnish which had a pH of about 4.7. impregnation with gaseous morpholine raised that pH to about 8.6, and the paper retained its basicity and physical properties as in the case of the 100 percent chemical wood paper.

We claim:

1. A process for treating paper to render it resistant to the deterioration that is promoted by acidic conditions in paper, which process comprises impregnating the paper with a gaseous atmosphere consisting essentially of morpholine, the said morpholine being present in at least about one-third the volume of the said gaseous atmosphere.

2. The process of claim 1 wherein the paper is in the form of a book.

3. The process of claim 1 wherein the morpholine accounts for about 90 to 100 volume percent of the atmosphere surrounding the paper during the impregnation.

4. The process of claim 3 wherein the paper is in the form of a book.

5. The process of claim 1 wherein the amount of morpholine impregnated into the paper is sufficient to provide the paper with a pH (measured after the paper has been allowed to stand at room temperature and atmospheric pressure for 24 hours) of at least about 7.6, as determined by soaking one gram of one-eighth inch squares of the paper for one hour in ml. of distilled, deionized water at room temperature and then measuring the pH of the resultant aqueous solution.

6. The process of claim 5 wherein the paper is in the form of a book.

7. The process of claim 5 wherein the paper prior to treatment has a pH of about 5.0 or lower.

8. The process of claim 7 wherein the paper is in the form of a book.

9. A process of treating a book made of paper having a pH of about 5.0 or lower so as to render the paper resistant to the deterioration that is promoted by acidic conditions, which process comprises impregnating the book with a gaseous atmosphere consisting essentially of morpholine, the said morpholine being present in at least about one-third the volume of said gaseous atmosphere, at about 25 to C. in an amount sufficient to raise the pH of the paper to at least about 8.5, said pH values being as determined by soaking one gram of one-eighth inch squares of the paper for one hour in 70 ml. of distilled, deionized water at room temperature and then measuring the pH of the resultant aqueous solution.

10. The process of claim 9 wherein the morpholine accounts for about to volume percent of the atmosphere surrounding the book during the impregnatlon.

t I i U UNIT D STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,77 ,95 Dated November 3, 973

InVentOI-(S) James E. Kusterer, Jr., and Reavis C. Sproull It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 2, "7.6, should read --the morpholine--:

'line 46, "aper" should read --paper--;

line +8, "sub-atmosphierc should read --subatmospheric--. Columns 3 and 4, Table III. fifth column, "53.0" should read --5 I.O--. Columns 5 and 6, Table IV should have column headings so as to read as follows:

new

'pH Before I length 0! pH After Treatment, pH After Treatment and Aging 100 C}. for the Set Treatment Morphollne Before Aging fiollowlng number of days Treatment 2 days 4 days 6 days 8 days 10 days 12 days 1 V" 4.3 hours 9.1 8.9 8.8 8.7 8.5 8.5 8.5

a v 4.3 48 hours 7 9.1 8.5 8.8 8.3 8.4 8.5 Y 8.4

a v 4.3 24 hours 8.9 8.5 8.1 8.4 8.4 8.3 8.2

4 V" 4.3 8 hours 9.0 8.6 8.5 8.3 "7.4 7.8 8.0

Treated invacuum chamber Signed and sealed this 2nd day of April 1971;.

(SEAL) Attest:

EDWARD M.FIETCHER,JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-l050 (IO-69) USCOMM-DC 60376-P69 U.S. GOVERNMENT PRINTING OFFICE I989 O'366-8J4.

Patent No. 3577 895 Dated November 35 973 In e t James E. Kusterer, Jr., and Reavis C. Sproull It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2,1 line 2, "7.6, should read --the morpholine-:

"line '46, "aper" should read --p-aper--;

line 48, "sub-atmosphierc" should read --subatmospheric--. Columns 3 and 4, .Table III. fifth column, "53.0" should 7 read --5 +.0- I Columns 5 and 6, Table IV should have column headings so 1 as to read as follows:

pH Before Length of pH After Treatment, pH Mme; "Treatment 'and Aging 100 C. for the Set Treatment Morphollne Before Aging iollowing number of days Treatment 2 days 4 days 6 days 8 bye 10 days 12 days 1v" 4.3 95mm 9.1 8.9 8.8 8.7 8.5 I 8.5 8.5

1v 4.3 48 hour! 8.1 v 8.5 8.8 8.3 8.4 8.5 8.4 3 4,3 24 hours 8.9 8.5 8.1 8.4 8.4 8.3 8.2

4V" 4.3 Shouts 9.0 I 8.6 I 8.5 8.3 "7.4 7.8 8.0

" .ITIGIIBG in vacuum: 'chamber Signed and sealed this 2nd day of April 1978.:

(SEAL) Attest: I

EDWARD M.FIETCHER,JR. c. MARSHALL DANN Attest'ing Officer Commissioner of Patents U.S. GOVERNMENT PRINTING OFFICE l9, 0-30-834.

FORM Po-1o5o (10-69) USCOMWDC x Patent No.

Inventor(s) Dated November 13, 1973 James E. Kusterer, Jr., and Reavis C. Sproull It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 2, "7.6, should read --the morpholine--:

line 46, "aper" should read --paper-; line 48, "sub-atmosphierc" should read --subatmospheric".

Columns 3 and 4, Table III, fifth column, "53.0" should read 54.0".

Columns 5 and 6, Table IV should have column headings so as to read as follows:

Table IV pH Before length 0! pH After Treatment, pH After Treatment and Aging 100' C. to; the Set Treatment Morpholme Beflore Aging following number of days Treatment 2 dayl 4 days 6 days 8 days 10 days 12 days IV" 4.3 96hourl 9.1 8.9 8.8 8.7 8.5 8.5 8.5

i V" 4.3 48 houtl 9.1 8.5 8.8 8.3 8.4 8.5 8.4

3 V" 4.3 24 hour! 8.9 8.5 8.1 8.4 8.4 8.3 8.2

4V" 4.3 Bhourl 9.0 8.6 8.5 8.3 7.4 7.8 8.0

" I Tuned in vacuum chamber Signed and sealed this 2nd (SEAL) Attest:

EDWARD M.FIETCHER,JR. Attesting Officer II PO-IDSO (10-69) day of April 1971+.

USCOMM'DC 5376-P59 1! [1.5. GOVIHNIENT HIIIIIIIG OIIICE llll 0-588-314.

Claims

2. The process of claim 1 wherein the paper is in the form of a book.
3. The process of claim 1 wherein the morpholine accounts for about 90 to 100 volume percent of the atmosphere surrounding the paper during the impregnation.
4. The process of claim 3 wherein the paper is in the form of a book.
5. The process of claim 1 wherein the amount of morpholine impregnated into the paper is sufficient to provide the paper with a pH (measured after the paper has been allowed to stand at room temperature and atmospheric pressure for 24 hours) of at least about 7.6, as determined by soaking one gram of one-eighth inch squares of the paper for one hour in 70 ml. of distilled, deionized water at room temperature and then measuring the pH of the resultant aqueous solution.
6. The process of claim 5 wherein the paper is in the form of a book.
7. The process of claim 5 wherein the paper prior to treatment has a pH of about 5.0 or lower.
8. The process of claim 7 wherein the paper is in the form of a book.
9. A process of treating a book made of paper having a pH of about 5.0 or lower so as to render the paper resistant to the deterioration that is promoted by acidic conditions, which process comprises impregnating the book with a gaseous atmosphere consisting essentially of morpholine, the said morpholine being present in at least about one-third the volume of said gaseous atmosphere, at about 25* to 75*C. in an amount sufficient to raise the pH of the paper to at least about 8.5, said pH values being as determined by soaking one gram of one-eighth inch squares of the paper for one hour in 70 ml. of distilled, deionized water at room temperature and then measuring the pH of the resultant aqueous solution.
10. The process of claim 9 wherein the morpholine accounts for about 90 to 100 volume percent of the atmosphere surrounding the book during the impregnation.