WO1991004787A1

WO1991004787A1 - Book deacidification method and apparatus

Info

Publication number: WO1991004787A1
Application number: PCT/US1990/005298
Authority: WO
Inventors: James L. Manganaro; John E. Dabrowski; Anthony J. Dejessa
Original assignee: Fmc Corporation
Priority date: 1989-10-02
Filing date: 1990-09-21
Publication date: 1991-04-18
Also published as: AU6534890A

Abstract

A method of and apparatus for inducing a deacidification chemical compound into the pages of a book by immersing the book in the solution containing the compound with the solvent being subsequently driven off by simultaneously subjecting the book under vaccum and energy in the RF range.

Description

BOOK DEACIDIFICATION METHOD AND APPARATUS This invention relates to methods and apparatu for the preservation of books, manuscripts, documents and other printed records by neutralizing the acidity of the paper on which they are printed.

For over 100 years the processes commonly utilized to manufacture paper have resulted in a product which contains chemicals that form acids. Over time, aci paper turns yellow, becomes brittle and eventually disintegrates. Books, which term is intended hereinafter to also include manuscripts and other printed documents, have been made with such paper. As a consequence, almost all of the libraries in the world are in danger of losing a vast majority of their collections. Certainly, almost all books printed in the past 100 to 150 years will disintegrate unless treated to neutralize the acidity in the paper. The problem has been recognized for some time as evidenced by a recent study "Mass Deacidification for Libraries" by George Martin Cunha, Adjunct Professor of conservation. College of Library and Information Science, University of Kentucky printed in Library Technology Reports, Volume 23, No. 3, May-June 1987, which surveyed all prior methods of mass deacidification. Two elements of the problem are clear. One is the potential detrimental effects of the chemicals employed in the process, such as causing certain types of ink to run, for example. The other problem is the time required to process a book. Whatever chemical process is employed, the time required to perform the deacidification is very important considering the millions of books involved, especially with the disintegration being presently accelerated by acids carried by or produced from air-born pollution, such as vehicle exhausts, that has increased dramatically in the past few decades. Processes for deacidification have required the removal of a moisture and/or a solvent from the books. Since paper has good insulating properties which slows the transfer of heat, drying times in the prior art, which typically rely on vacuum shelf dryers, consumes a major portion of the total process cycle time.

The present invention addresses the time element of the deacidification process and provides a method and apparatus that rapidly removes moisture or solvent and thereby reduces the total cycle time required to deacidify a book load. The present invention also subjects the books being processed to minimal stress, thermal as well as physical, and may be used with either a large quantity of books or with an individual manuscript that may represent a valuable historical artifact, for example. The present invention further processes a book or document uniformly and requires little preconditioning or inspection before being processed. These and other attributes of the present invention, and many of the attendant advantages thereof, will become more readily apparent upon a perusal of the following description and the accc .panying drawing, wherein the sole figure is a schematic representation of the apparatus of the present invention.

Referring now to the drawing, there is shown a schematic representation of an apparatus, indicated generally at 10, according to the present invention. A chamber capable of sustaining a vacuum, such as desiccator 12, is positioned inside of a metal microwave chamber 14. Microwave energy is delivered to the chamber 14 by any conventional means, such as waveguides or ducts. A conduit 16 is connected to the desiccator 12 and communicates with the interior thereof. The conduit 16 extends through appropriate seals in the side wall of the microwave chamber 14 and extends into a trap 18 for condensing and collecting any liquid vapor extracted from the desiccator 12. A conduit 20 connects the trap 18 wit a vacuum pump 22. A valve 24 is teed into the conduit 20 and is adjustable to control the amount of vacuum to whic the desiccator is subjected. A vacuum pressure gage 26 communicating with the conduit 20 provides a means for measuring that vacuum pressure and permits positioning of the valve 24 to achieve the desired vacuum pressure. A liquid pump 28 has its outlet connected to a conduit 30 extending through the chamber 14 and into the desiccator 12. The pump 28 draws a treatment liquid from a closed reservoir 32 through inlet conduit 34. A valve 36 is interposed in the conduit 30 and is positioned to either block the conduit 30 or to permit the pump 28 to flood th desiccator 12 with the treatment liquid. A drain conduit 38, having a valve 40 similar to valve 36 interposed therein, is connected between the desiccator 12 and the reservoir 32. The treatment liquid comprises a deacidification chemical, such as that disclosed in U.S. patent application Serial No. 252,421 filed September 30, 1988, for example, dispersed in an appropriate solvent, such as trichlorr _rifluroethane or hexane.

The process of deacidification starts with packing one or more books B into the desiccator 12. If the interior dimensions of the desiccator 12 permits, the books are preferably slightly open to enhance the drying rate, but the books may be stacked one on top of another or positioned adjacent to each other in an upright closed position. If the books are open, the pages of each will fan out to uniformly fill the space between the covers when vacuum is applied. The desiccator 12 is closed, as are valves 36 and 40, and the pump 22 started to draw a vacuum on the desiccator. The recommended range of vacuu is about 0-30 torr. Vacuum enhances liquid removal, but too high a vacuum will cause condensation of moisture in the conduit 16 and the desiccator 12. Once vacuum has been established on the desiccator 12, microwave energy is introduced to the microwave chamber 14. Microwave energy is at the upper end of the radio frequency or RF range and is between 915 mhz and 2450 mhz. Although any frequency in that range would work, only the extremes are available as a practical matter, because microwave generators are not commercially available except at the 915 mhz and 2450 mhz frequencies. The microwave energy heats the book load, easily pervading each book in the book load, to reduce the residual moisture content in the book load. The application of vacuum by the pump 22 simultaneously with the application of microwave energy affords a very rapid and pervasive removal of the residual moisture. Typically, a book taken from a library shelf will contain 6-7% moisture by weight and is preferably reduced to about 2% plus or minus half a percent to allow for proper deposition of treatment chemical.

In order to avoid damage to the book load, the temperature of the books must be limited to no higher than about 60-65°C. The power evel of the microwave energy and the length of time the power is applied, and, to an extent, the vacuum pressure in the recommended 0-30 torr range, will determine the book temperature. The power level and the length of time the power is applied can be adjusted as a function of the weight of the book load. By standardizing the weight of each book load, the power level and length of time can also be more or less standardized. Fine control of book temperature is obtained by an optical pyrometer or a fiber optic sensor, such as manufactured and marketed by Luxtron. The temperature will provide an indication of moisture loss since the book temperature cannot appreciably exceed the temperature of boiling water at the low pressure in the desiccator until most of the water has been driven off. The loss in weight of the book load during heating will equal the weight of the residual moisture that has been driven off. Thus, load cells under the desiccator will provide a direct measure of moisture loss, as will measurement of the water condensed by and collected in t trap 18.

When the proper moisture level is achieved, t pump 22 is stopped, the valve 36 opened, and the pump 28 started to flood the desiccator 12 with treatment liquid from the reservoir 32. Circulation of the liquid within the desiccator and around the books forming the book load may be achieved by opening valve 40 while the pump 28 is operating. When the books are thoroughly soaked, the pum 28 is stopped and valve 36 closed to interrupt the flow o liquid to the desiccator. Liquid in the desiccator 12 is then drained back to the reservoir through the conduit 38. The valve 40 is closed and the vacuum pump 22 starte to again draw a vacuum on the desiccator 12. Microwave energy is then introduced to the chamber 14 until the solvent is removed. Removal of the solvent is monitored by sensing book temperature, or by ^• eight or volume analysis as described earlier.

While it is generally desirable to exclude fro the microwave field, the presence of metal such as large paper clips, it has been found that some relatively small amounts of metal, such as small clips, metal foil printin and the foil in library security tags, can be tolerated without ill effects. The microwave field strength must b low and uniformly distributed in order to prevent such small amounts of metal from heating excessively and, through conduction, causing localized overheating of the paper in contact with the metal. Inspection of the books for large metal objects as they are initially packed into the desiccator will avoid this problem. The present invention may also be utilized to salvage books that have been soaked or otherwise wetted by water from floods, storms, fire hoses, or broken pipes. In such situations, the potential for permanent damage to the books is far greater and more immediate than that associated with acid paper. Such damage to a book can occur not only from the water itself, e.g. dissolving binding glues, causing ink to run, etc., but also from the attempt to dry it. The significantly lower wet strength of paper and the added weight of the water may result in distortion, wrinkling or other physical damage as the book is handled and dried. In addition,, surface tension of the water resisting separation of adjacent pages may result in torn pages. Yet, if not dried soon after having been wetted, the possibility increases that the book will sustain damage from the growth of molds or fungi. The present invention may be effectively utilized to salvage such books, whether the book is subsequently treated to neutralize acidity or not, although such neutralization may be necessary or desirable even if the book was previously treated since the water itself may reintroduce acids and/or wash n-ot residual buffering che xcals deposited during a prior treatment. Because microwave heating is fast and generated uniformly throughout the book, the excess water is removed quickly and no physical preconditioning, such as opening the book or separating papers, is necessary. By subjecting the book to compressive pressure, i.e., uniformly distributed compressive forces directed perpendicular to the covers of the book, excess water will be squeezed from the book. While some time will be required to permit such water to be extracted from the book, this time will be considerabl less than would be required to remove the same quantity through change of state via heating in a vacuum. With th compressive pressure on the book being maintained or reapplied, the book is simultaneously subjected to vacuum and microwave energy. The microwave energy will heat substantially uniformly, as well as the water, causing th water to boil off at a lower temperature as a result of the vacuum. Maintaining the book under compressive pressure, although this pressure may be less than the pressure applied to squeeze out excess water, while the microwave energy and vacuum are applied will permit the book to dry to the proper residual moisture level without wrinkling the pages of the book. When the moisture level is lowered to about 2%, the previously described process of immersion in treatment solution, and draining the solution and heating with microwave energy under vacuum may be used to deacidify the book.

It will be seen from the foregoing description that the present invention provides a method, and apparatus for practicing that method, which permits a relatively fast deacidification of books, which removes moisture and solvent uniformly without creating wet and dry regions within the books, and which is self-limiting of the temperature rise in the books due to the lowered boiling point of liquids when heated in a vacuum. Wh.ie one embodiment of the method and. apparatus of the present invention has been illustrated and described herein, various changes may be made therein without departing from the spirit of the invention as defined by the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method of introducing a deacidifying chemical compound into the pages of a book comprising the steps of: reducing the residual moisture in said book to a predetermined level; subjecting said book to a vacuum; and simultaneously subjecting said book to microwave energy to drive off said solvent.

2. The method according to claim 1, wherein the reduction of residual moisture is achieved by simultaneously subjecting said book to vacuum and microwave energy.

3. The method according to claim 2, wherein the power level of the microwave energy and length of time the power is applied is related to the weight of said book.

4. A method of introducing a deacidifying chemical compound into the pages of a book comprising the steps of: simultaneously subjecting said book to a vacuum and to microwave energy to reduce the residual moisture in said book to a predetermined level; wetting said book with a solution of said compound in a solvent; and driving off said solvent.

5. The method according to claim 4, wherein said solvent is driven off by simultaneously subjecting said book to a vacuum and microwave energy.

6. The method according to claim 5 wherein the power level of said microwave energy and length of time the power is applied is related to the weight of said book.

7. Apparatus for introducing a deacidification compound dissolved in a solvent into the pages of a book comprising: a vacuum chamber capable of holding said books; means for selectively drawing a vacuum on said chamber means for selectively subjecting said chamber to microwave energy; and means for selectively introducing said solution to and draining said solution from said chamber.

8. A method of drying a book that has been wetted by water from a flood, storm, fire hose or broken pipe, comprising the steps of: subjecting said book to compressive pressure to squeeze excess water therefrom; and simultaneously subjecting said book to a vacuum and to microwave energy until the moisture in said book is approximately 25 by weight.

9. A method of drying a book that has been wetted by water from a flood, storm, fire hose or broken pipe, comprising the steps of: subjecting said book to uniform compressive forces directed perpendicular to the plane of the book's covers; and simultaneously subjecting said book to a vacuum and to microwave energy.

10. A method of treating a book that has been wetted by water from a flood, storm, fire hose or broken pipe, comprising the steps of: pressing said book to extract excess water; simultaneously subjecting said book to a vacuum and to microwave energy until the moisture in same book is approximately 2% by weight, soaking said book in a solution composed of a treatment compound and a solvent; boiling off said solvent by heating with microwave energy under vacuum.

11. Apparatus for treating a water-soaked book comprising: first means for pressing said book to remove excess water as a liquid; a vacuum chamber capable of holding said book; second means for drawing a vacuum on said chamber; third means for flooding said chamber with a solution having a treatment compound in a solvent; fourth means for draining said solution from said chamber; and fifth means for directing microwave energy into said chamber while said second means is actuated both before said third means and after said fourth means have been actuated.