Patent Publication Number: US-2004056235-A1

Title: Active substance and device for the deacidification of printed matter

Description:
[0001] The present invention relates to an active substance according to the preamble of claim 1 and a device according to claim 6.  
       [0002] Since the invention of mechanical wood pulp in 1844, all printed matter worldwide has undergone decomposition caused by inherent overacidification. In order to save the cultural wealth stored in billions of documents, numerous experiments have been carried out to deacidify the paper matter.  
       [0003] These experiments can be divided into three groups:  
       [0004] 1. Wet treatment  
       [0005] 2. Gas treatment  
       [0006] 3. Dry treatment with alkaline powder  
       [0007] Wet treatment using solutions such as peroxide, etc. has proved to be the most dangerous method of treating valuable documents; the pages become distorted or curl, and in some cases the ink even dissolves and runs. The use of gases such as morpholine vapours, etc. requires the use of a costly vacuum chamber and also increases the cycle time for the treatment. Dry treatment with alkaline powdered substances has often failed owing to the non-uniform application of the powder and the effectiveness of the substance.  
       [0008] A process for the deacidification of printed matter and a substance according to the preamble of claim 1 are known from U.S. Pat. No. 5,433,827. In this process, the pages of books are brought into contact with paper coated with a highly concentrated deacidifying substance and mechanically compressed for several days at a high level of humidity—over 75%, preferably 97% relative humidity. Alkali carbonates and alkaline-earth carbonates and their mixtures are used as the deacidifying substance. An alternative proposal is to dust with calcium or magnesium carbonate the pages to be deacidified. The processes are based on ionic migration of the deacidifying substance and are therefore largely dependent on pressure and humidity. The processes described are also very labour-intensive and take from one day to several weeks to carry out.  
       [0009] Therefore, the primary object of the invention is to provide a fast reacting active substance for the deacidification of printed matter, in particular also bound books. The quality of the paper should be of secondary importance, i.e. the active substance should be as universally usable as possible. It must not damage or alter the printed matter. The active substance must be applied uniformly over the entire surface of the paper and produce the same pH value from the first to the last page of a book.  
       [0010] A device according to the preamble of claim 6 is known (DE-A1-44 36 635) in which books are held by the spine in a vertically arranged holder and circular-section jets laden with active substances move and blow through the individual pages from the bottom upwards. This results in heavy mechanical loading of the pages, which are also not leafed through in a defined manner, i.e. the diffuse circular-section jets do not uniformly charge the pages with active substance. The device is not suitable for individual pages or plates because the non-uniform application of the active substance has a particularly negative effect.  
       [0011] Accordingly, an improved device is to be provided which is fitted with a receiver and is also able to deacidify bound books, catalogues, brochures, etc. without mechanically impairing or damaging them.  
       [0012] This object is achieved by an active substance having the features of claim 1; the device is characterised in claim 6.  
       [0013] The active substance according to claim 1 is distinguished by good adhesion to the surface of the paper and, owing to the residual moisture still present therein, is three-dimensionally distributed over the paper.  
       [0014] Preferred embodiments are described in dependent claims.  
       [0015] The mixture described in claim 2 gives a resulting pH of 9.0 to 9.5, i.e. an alkaline excess is established on the paper, thereby neutralising any further progressing acidification.  
       [0016] The mixture according to claim 3 has proved successful in selectively setting a pH of 8.2 to 8.5 and is used for less stressed documents.  
       [0017] Alternatively, a mixture according to claim 4 is used, the resulting pH of which is adjustable in a range from 7.2 to 7.5.  
       [0018] The addition of polystyrene balls according to claim 5 increases the flowability and thus the conveyability of the active substance.  
       [0019] Placing the printed matter in a device according to claim 6 has proved particularly successful, the device leafing through the printed matter and uniformly charging it with active substance by means of a staggered row of flat jets. In the case of bound books, these are inserted into the supporting parts with the spines facing downwards and are gently treated by the device. By means of suitable holding arrangements, however, unbound or non-stitched leaves can also be treated.  
       [0020] Preferably, the receiver for the printed matter is accommodated in a case closable by a hinged cover according to claim 7, thereby avoiding emissions.  
       [0021] A device according to claim 8 is advantageous from the point of view of promoting flow.  
       [0022] The supplemented embodiment according to claim 9 is kinematically advantageous, i.e. it only requires a simple drive.  
       [0023] The arrangement of the air diffuser directly above the supporting parts is particularly advantageous; cf. claim 10.  
       [0024] By the use of a fan according to claim 11, the active substance is circulated and thereby used repeatedly.  
       [0025] By the incorporation of a secondary flow with a filter, the device can be emptied of powder and thus opened without problems; see claim 12.  
       [0026] A dehumidifying chamber according to claim 13, which is inserted into a further secondary flow and by means of which the moistness of the applied powder is kept relatively constant, has proved successful. The moisture drawn out of the books during treatment is thereby absorbed.  
       [0027] The recirculation of the secondary flow into the main flow according to claim 14 allows particularly simple control of the humidity inside the device.  
       [0028] Feeding the secondary flow in at the powder inlet according to claim 15 is advantageous because in this way the powder is first acted upon by dry air and conveyed before it comes into contact with the moister air of the main flow.  
       [0029] In larger installations, a thermal dehumidifying and heating system appears advantageous because it permits virtually continuous operation; cf. claim 16. 
     
    
    
     [0030] Embodiments of the invention will be further described in the following with reference to drawings, in which like reference numerals are used for like functional components:  
     [0031]FIG. 1 shows a receiver for printed matter which can be fanned out;  
     [0032]FIG. 2 shows a plan view of side parts of the receiver according to FIG. 1;  
     [0033]FIG. 3 shows a section through the side parts according to FIG. 2;  
     [0034]FIG. 4 shows an overall view of a device for deacidification, with open hinged cover;  
     [0035]FIG. 5 shows enlarged details from FIG. 4, with books and files placed in the device;  
     [0036]FIG. 6 shows parts of the device according to FIG. 5 in their operating position, demonstrating the leafing-through of the printed matter;  
     [0037]FIG. 7 shows an enlarged view of the air supply arrangement according to FIGS.  4  to  6 ;  
     [0038]FIG. 8 shows a part sectional view of the air supply arrangement according to FIG. 7;  
     [0039]FIG. 9 shows a plan view of the air supply arrangement according to FIG. 8 rotated through 90°;  
     [0040]FIG. 10 shows the view according to FIG. 4 with the receiver removed;  
     [0041]FIG. 11 shows the device according to FIGS. 4 and 10 viewed from behind and with the hinged cover closed;  
     [0042]FIG. 12 shows the device with the hinged cover closed and viewed from the front;  
     [0043]FIG. 13 shows a simplified pneumatic diagram of the overall installation, and  
     [0044]FIG. 14 shows an extended, simplified pneumatic diagram. 
    
    
     [0045]FIG. 1 shows a receiver  1  in the form of a stand for printed matter, in particular books, brochures and the like. The stand has supporting parts  2 ′ and  2  on the left and right-hand side respectively. These supporting parts comprise a plurality of openings  3  allowing the passage of air. Smaller books  5  are placed on a simple pedestal  4  so that their ends lie at the same height as other printed matter  6 ′, in this case a brochure.  
     [0046] The supporting parts  2 ,  2 ′ are provided at their ends with covers  7  and are fixed to mounting and transporting strips  8 . The sectional view according to FIG. 3 shows the section A-A from FIG. 2. It can be seen from this how the flow S inside the supporting parts  2 ,  2 ′ forms a channel flow and draws the book covers outwards and opens the book.  
     [0047] The device according to FIG. 4 substantially comprises a closable case  10  provided with closing parts  13 ′ and receiving the stand  1 . The hinged cover of the case  10  is designated by  11  and, on its front side, comprises a viewing window  12 , closing parts  13  and handles  14 . A box-type air diffuser  15  with an outflow plate  16  for its part provided with air outlets  17  is displaceably fixed in the hinged cover  11 . A sealed guide rod  18 , which here projects beyond the end of the air diffuser  15 , is provided for the longitudinal displacement of the air diffuser  15 .  
     [0048] A low-pressure fan  19   a  is mounted below the case  10  and, via a large-volume suction tube  20  and an air-inlet tube  21  of the same type, sucks the air from the interior of the case  10  and supplies it again via the air diffuser  15  and the air outlets  17 . A cooling unit  22  is additionally arranged outside the case  10  and is connected thereto via tubes  23 .  
     [0049] In FIG. 5, the hinged cover  11  (not shown) is open and the position of the air diffuser  15  is shown accordingly. Here, the parallel, staggered air outlets  17  can be seen in plan view. The grid width of a row of parallel air outlets  17  in a staggered arrangement one behind the other is designated by R.  
     [0050] In FIG. 6, the hinged cover  11  is closed and the installation is in operation, during which the air diffuser  15  is moved back and forth at a constant rate by the amount R—cf. FIG. 5—characterised by +v and −v. The pages of the printed matter  5 ,  6 ,  6 ′ are leafed through individually by the flow S and charged with active substance.  
     [0051]FIG. 7 shows, as a further detail, the guide rod  18  with its slide bush  27 , which is additionally protected from soiling by the active substance by means of an expansion bellows (not shown).  
     [0052] The sectional view in FIG. 8 corresponds to the section B-B indicated in FIG. 7 and shows more precisely the box-type structure of the air diffuser  15 . The latter is fixed to the hinged cover  11  via a suspension/guide  28  and is closed by the outflow plate  16  provided with the air outlets  17 .  
     [0053]FIG. 9 shows the direction of movement v of the box  15  and also, on the right-hand side, the flexible air-inlet tube  21  with its connecting piece  21 ′.  
     [0054] In FIG. 10, the same details can be seen as in FIG. 4, only in this case the receiver  1  has been removed to reveal supporting brackets  24 ,  24 ′ and cooling fins/deflectors  25  and heating fins  26  with deflectors.  
     [0055] As shown in FIG. 11, the rear of the device has a hot-water reservoir  35  and a cooling-fluid reservoir  36  provided with corresponding connections  35 ′ and  36 ′ and connected to the tubes  23  shown in FIG. 10. The low-pressure fan  19   a  with its drive, being an electric motor  30 , and a screw conveyor  32  mounted on a carrier plate  31  and provided with a powder inlet  32 ′ can also be seen here. A geared motor  33 , which provides the linear drive of the air diffuser  15 , is arranged thereabove—cf. FIGS. 6 and 7. Upper hinges  34  for opening the hinged cover  11  can also be seen.  
     [0056] The device is shown in the operational state in FIG. 12, the closing parts  13  hermetically sealing the box-type interior. The pressure connection  37  to the case  10  can also be seen here.  
     [0057] The schematic diagram in FIG. 13 again shows the case  10  with its reciprocating air diffuser  15  and the accommodated stand  1 . A main flow H, accelerated by a low-pressure fan  19   a , sucks air from the bottom of the case  10  and feeds it back into the latter via the air diffuser  15 . The powder inlet  32 ′ of the rotating screw conveyer  32 , which is charged with the active substance designated by K, opens into the main flow H.  
     [0058] On completion of a treatment process, the fan  19   a  is switched off and a further low-pressure fan  19   b  in a secondary flow N 0  is switched on, which extracts the powdered active substance K from the air stream via a filter  38  and feeds it into a collecting container  40  via an outlet  39 . The purified secondary flow is designated by N 0 ′.  
     [0059] The installation in FIG. 14, which has been extended in relation to. FIG. 13, comprises, in addition to FIG. 13, a three-way valve  41  which divides the main flow H into a main flow H′ and a secondary flow N 1 . The secondary flow N 1  is fed via a further filter  38 ′ with outlet  39 ′ and collecting container  40 ′ to a dehumidifying chamber  43  comprising a carrier sieve  44 , spherical air diffusers  45  arranged below the sieve  44  and dehumidifying material  46  arranged above the sieve  44 . The collecting chamber  47  thereabove comprises a filter  48  having a sieve inlet  49  and supplies a dehumidified secondary flow N 1 ′ to a mixing nozzle  50  formed as a two-component ejector. The nozzle  50  feeds the active substance K into the air diffuser  15  by means of the dehumidified secondary flow N 1 ′.  
     [0060] The three-way valve  41  is centrally connected to an adjusting member  42  permitting continuously variable division of the main flow H′ and the secondary flow N 1 .  
     [0061] The active substances K can be inexpensively and very simply prepared by repeatedly grinding the components together and then drying them.  
     [0062] Mixture 1  
     [0063] 90% KHCO 3  with 10% K 2 CO 3 , adjusted to a residual moisture content of 10% to 15% by weight, imparts a pH of 9.0 to 9.5 to the treated paper after average treatment time.  
     [0064] Mixture 2  
     [0065] 99% KHCO 3  with 1% K 2 CO 3 , adjusted to a residual moisture content of approximately 10% by weight, imparts a pH of 8.2 to 8.5 to the treated paper.  
     [0066] Mixture 3  
     [0067] 99.9% KHCO 3  with 0.1% K 2 CO 3 , adjusted to a residual moisture content of approximately 10% by weight, imparts a pH of 7.2 to 7.5 to the treated paper.  
     [0068] It has been shown that the residual moisture in the mixtures increases very rapidly when stored for a few days at room temperature, in particular in the case of mixture 1.  
     [0069] To improve the flowability or conveyability of the active substance in the installation, it is advisable to mix in an electrostatically active substance, for example in the form of polystyrene balls with a diameter of less than 2 mm.  
     [0070] For preparation of the components, the following has proved successful:  
     [0071] rough mixing of the main components KHCO 3  and K 2 CO 3    
     [0072] addition of optional further components, for example potassium hydrogen phosphate or ammonium thiocyanate  
     [0073] grinding of the mixture in a standard pinned-disc mill in at least two passes  
     [0074] light drying of the mixture in a circulating-air drying cupboard at a maximum of 50° C. for 12 h in a layer thickness of 5 mm  
     [0075] packing in air-tight and moisture-tight material.  
     [0076] Process  
     [0077] The printed matter  5 ,  6  and  6 ′ to be treated is inserted into the stand  1  with the spine facing downwards and placed and sealed in the case  10 . During a period of 15 to 30 minutes, the main flow H is fed through the low-pressure fan  19   a  via the air diffusor  15  and the printed matter is dried as necessary at room temperature or a slightly higher temperature until it loses approximately 0.5% to 2% of its intrinsic weight. During this process, the printed matter—usually books—is completely leafed through while the air diffuser  15  moves back and forth in a linear, saw-toothed manner, covering the distance R; cf. FIG. 7.  
     [0078] Active substance K—selected according to the pH to be obtained—is now fed into the main flow H via the screw conveyor  32 . The mass of active substance K required is dependent on the mass of printed matter and amounts to approximately 5% of the mass of the latter. Homogeneous distribution of the active substance on the paper is ensured by the turbulent air circulation in the case  10 . After a treatment period of 10 to 15 minutes, excess material is removed from the printed matter by switching off the main flow H and switching on the secondary flow N 0  and the printed matter can be removed substantially dust-free.  
     [0079] The active substance K can be used repeatedly and must be restored to its predetermined mass before each treatment. By renewed grinding and drying, the active substance can also be recirculated and the desired moisture content can be re-established.  
     [0080] In certain instances, it can be advantageous to remoisten, i.e. recondition the printed matter after treatment with the active substance K. The easiest way of doing this is in a cross-flow container which is fitted with an ultrasonic atomiser and generates a moist air stream.  
     [0081] Quality Features  
     [0082] The treatment is distinguished by complete deacidification of the printed matter and applies a detectable alkaline reserve thereto. The deposition of this reserve amounts on average to 0.5% of the weight of the paper. There is no reaction with the paper matrix or the type and printing, i.e. there are no thermal effects and no variation in print quality to be observed. There are no toxicologically harmful deposits and no unpleasant odours imparted to the printed matter. There is no discoloration and no permanent dusty deposits, not even on high-gloss printed pages. The spine of the book remains mechanically sound, irrespective of the type of binding. Treatment quality does not depend on the number of pages; this has been verified with books from 30 to 1000 pages. The size of the printed matter is also unimportant with respect to treatment quality and/or type.  
     Analysis of Printed Matter Comprising Different Weights of Paper  
     [0083]                                                   Open   Open   Coated   Coated       Quality   paper   paper   paper   paper       criterion   50 g/m 2     80 g/m 2     80 g/m 2     120 g/m 2                    Complete   achieved   achieved   achieved   achieved       deacidication       Deposited   up to 2%   up to 1.2%   0.4% to   0.3% to       alkaline reserve   CaCO 3     CaCO 3     0.6% CaCO 3     0.4% CaCO 3         No detectable   achieved   achieved   achieved   achieved       reaction with       paper and print       No toxi-   achieved   achieved   achieved   achieved       cologically       harmful       deposits       No unpleasant   achieved   achieved   achieved   achieved       odours       No discoloration   achieved   achieved   achieved   achieved       No dusty   achieved   achieved   achieved   achieved       deposits       (permanent)       No effect on   achieved   achieved   achieved   achieved       bindings                    
     [0084] Processing Capacity  
     [0085] Using the previously described testing installation, the following treatment times were measured:  
                                           Duration [minutes]   Duration [minutes]           Treatment programme   Treatment programme       Process parameter   Standard   Short                  Loading    3′    3′       Drying   30′   15′       Charging   15′   10′       Dust-removal    5′    5′       Unloading    3′    3′       Purifying    3′    3′       Total duration = cadence   59′   39′                  
 
     [0086] On the basis of an installation availability of 19 days per month and a load per batch of 20 kg of books, between 35 t and 58 t of books can be permanently deacidified per year depending on the programme selected.  
     [0087] The use of a chemical dehumidifying chamber  43  is particularly economical in smaller installations. In this case, it is sufficient to feed the secondary flow N 1  from an oil-free compressor (residual moisture content RH 15% at 25° C.) into a 30 cm high drying chamber with a 300 cm 2  base and filled with silica gel 3 cm to 5 cm in height. The resulting moisture level in the secondary flow N 1 ′ is 3% RH. In larger installations, the secondary flow N 1  is preferably branched off from the main flow H and also chemically dehumidified; cf. FIG. 14.  
     [0088] In large installations, it is advisable to provide a separate cooling unit with air circulation provided by a cyclone separator so that the necessary dehumidification and optional subsequent heating can be carried out outside the case  10 , without the danger of corrosion and icing.  
     [0089] Naturally, in the sense of a kinematic reversal, it is also possible for the receiver for the printed matter to be moved and the flat jets to be employed in a stationary manner.  
     [0090] Further components can also be added to the active substance; for example these can be substances with strongly hygroscopic properties and a suitable pH, such as potassium hydrogen phosphate and ammonium thiocyanate. This type of mixture appears to improve the deposition of the alkaline reserve, in particular in the case of highly coated high-gloss papers.  
     [0091] The subject of the invention is distinguished by a high level of economy. Both the active substance and the installation are very cost-effective to provide and maintain.  
     [0092] For large-scale applications—in large libraries, etc.—the subject of the invention can be set up for a high operational capacity through the agency of “industrial handling” and be substantially automated.  
     [0093] The installation can be transported easily and can be used in situ, for example in archives and libraries, so that unnecessary and, in addition, risky transportation of valuable printed matter does not have to take place.