IL23953A - Method for drying of moisture-setting inks - Google Patents

Description

·»β·» «·zs— ·»s—ssi·»s·"X««·»··s>»—"««*a "·β = ="* Method for drying of moisture-setting inks INTERNATIONAL BUSINESS MACHINES CORPORATION Ci22967 23953/2 This invention relates to the drying of moisture-setting inks, and more particularly to a pressure dampening system for drying moisture-setting printing inks* An object of the invention is to provide a new and improved method for increasing the drying rate of moisture-setting inks* Another object is the provision of a new and improved method for adequately drying heavy ink films with an Increase in productive capaolty.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawing wherein: Fig. 1 is a sohematic front view of a portion of a rotary card makin press including a printing station. and an ink drying pressure dampening station according to the invention; Fig. 2 is a schematic view of the printing station and a partial edge view of a freshly printed portion of the web; and .

Fig. 3 is a schematic view of the ink drying station and a partial edge view of the web^ after emergence from this station.

The rotary card manufacturing machine of which a portion is illustrated in Fig. 1 is described more com- pletely in U. S. Patent No. -2, 181, 935 to F. M. Carroll dated = December 5, 1939. The machine operates on a continuous web of fibrous cardstock material to print record forms thereon which are subsequently cut apart into unit card lengths, each with a printed form. The unit record form manufactured in this manner is the familiar tabulating card or punched card used in business and data processing machines. Only so much of the rotary card manufacturing machine is illustrated here as is essential to an understanding of the invention.

A web 11 of fibrous cardstock material pre- cut to the desired width unrolls from a supply roll not here shown.

After passing between feed or idler rolls 13, 13', the web 11 travels vertically upwardly between print rolls 15, 15' forming a portion of the print station 17. The web 11 at this point is printed on both sides since the print station 17 includes a mirror image set of rolls on either side, the rolls on one side being identified by the primed numeral of the corresponding roll on the other side. Upon leaving the print station, the web 11 continues on upwardly between pressure dampening rolls 19, 19' forming a portion of the ink drying station 21 according to the invention. The web 11 with substantially dry ink on both sides then passes between cut-off rolls 23, 23' at the cut-off station 25. The rolls 23, 23' contain mating cutters 27, 27 ' which engage the web 11 between card lengths to sever the web into unit lengths and form the cards 29. The individual cards pass upwardly between fluted rolls not here shown and are clipped to the periphery of a rotary carrier wheel 31 for carrying the cards to the other side before being released for stacking in a finished pile.

The type of printing performed at the print station 17, be it letterpress or offset, including dry offset, is immaterial to the invention. Offset printing is here illustrated and is performed for instance by a pair of inking rolls 33 which apply ink to an offset roll 34, this roll in turn being in engagement with the print roll 15 for transferring the impression to the web 11. In general it can be said that a suitable moisture setting ink is used. Upon leaving the print station 17, the ink on the printed web is in a wet condition.

The ink drying station 21 includes, in addition to the pressure roll 19 previously mentioned (only one side will be described), a dampening roll 35, a metering roll 37, and a spray applicator 39. The dampening roll 35 is covered with a soft moisture retaining material 41 such as molleton, soft rubber, a knitted sleeve or .the like. Moisture is conveyed from a supply reservoir not here 1 shown through a pipe 42 to the spray applicator 39 whose stream 2 impinges directly on the moisture retaining cover 41 at the nip. 3 The metering roll 37 has a hard hydrophilic surface and is mounted 4 · for adjustment to and from- the center of the dampening roll 35 to regulate the amount of moisture retained by the cover 41. The . 6 surface of the pressure roll 19 is in contact with the' cover 41 of • 7 the dampening roll and is coated with a thin film of moisture there- 8 from. The surface of the roll 19 is hydrophilic in order that the ■ 9 film of moisture thereon "is spread evenly over its entire surface ' without the formation of droplets. 11 ' The effect of passing the printed web 11 12 between the dampened pressure rolls 19, 19' can be seen by 13 comparing Figs. 2 and 3. wherein a typical cross section of the 14 thickness of the cardstock is illustrated. On a microscopic scale the surface of the web 11 can be likened to a series of hills and 16 dales. Upon leaving the print station 17, after passing between the 17 print rolls 15, 15', ink 43 in wet condition is deposited on the 18 surfaces of the cardstock on or near the fiber peaks. Upon leaving 19 the ink drying station 21 after passing between the pressure rolls • 20 19, 19', it is seen that the ink is pressed and distributed into the 21 '■ inter- fiber voids by the high nip pressure of the engaging rolls. 22 Thus there is -now less tendency for the ink to smear and setoff, i. e. 23 transfer to an adjacent surface as for instance when stacking the 24 cards. In addition, there is moisture transfer to the ink of a portion • 25 . of the film of moisture on the pressure rolls 19, 19', and drying of 26 the. moisture setting ink is initiated by this transfer of moisture.

Since the pressure rolls have a uniformly hydrophilic surface, this moistened surface constitutes a barrier assuring prompt release of the ink from the pressure roll at the nip exit. The operation of the pressure dampening system in drying moisture-setting inks is a combination of these three effects: high nip pressure, moisture transfer, and ink release.

The dampening solution is normally aqueous since most moisture setting inks are dried by water. The dampening solution may contain other ingredients according to the type of pressure rolls used and the particular moisture setting ink. Typically the dampening, solution is slightly acetic in character in order to continuously re-etch or rejuvenate the. pressure rolls. Since most commercial moisture setting printing inks contain alkaline components, with a neutral solution these alkaline components of the ink would tend to make the surfaces of the rolls less hydrophilic. As an example, let it be assumed that the pressure rolls are either magnesium rolls or steel rolls plated with chrome. The printing ink is a moisture setting type having alkaline components, such as commercially available black. A dampening solution having a pH of about 5. 5 has the following constituents: 6 quarts distilled water 2 quarts methanol 3 ounces phosphoric acid in dilute form 2 ounces gum arabic The. methanol reduces surface tension and also serves as wetting a ent, as does the um arabic- The dilute hos horic acid is a H 1 controller. 2 In the event that a pre- etched pressure roll 3 is used, such as a magnesium pre- etched roll, the dampening 4 solution may be neutral. The following is an example of a neutral ' 5 dampening solution: distilled water and a 1% solution of glycol '6 ether sold under the name Turgitol N. P. X. To this at times a 7 defoamer may be added. This particular dampening solution is 8 used for instance with a tinting ink where better results are obtained 9 using glycol ether due to some ingredient in the ink which makes it bleed (i. e. blur) when the pH is too low. It is seen that the ingre- 1 dients of the dampening solution can be varied according to the 2 particular problem and conditions at hand. 3 The advantages of the invention are best 4 appreciated by comparing it with the commonly used existing method 5 of precipitating moisture setting inks by projecting saturated steam 6 ' through nozzles or orifices in the direction of the printed web. In 7 this method, condensation of steam on the surface of the web 8 furnishes water to initiate the precipitation- drying process. The 9 present pressure dampening system for drying moisture setting inks 0 provides better contact of the moisture with the newly printed ink. 1 · This is because moisture is supplied under roll pressure, which 2 contributes to improved permeation of moisture and the ink film and 3 an increased rate of absorption of the ink solvent into the paper fibers. 4 - When, saturated steam is used, the amount of moisture actually . available for ink precipitation is governed by the quantity of steam 6 . that, can be condensed on the surface of the ink film. The rate of 1 . condensation drops continuously as more steam is added because 2 of a corresponding rise in the dew point of the ink film. The 3 improved moisture contact provided by the pressure dampening · , · 4 .system is particularly effective in . drying heavy ink films. . With saturated steam, a skin of initially precipitated ink forms a barrier 6 which tends to restrict further penetration of moisture into the 7 underlying strata of the ink film. Substantial amounts of ink vehicle 8 will thus remain in the ink. Precipitation being a reversible 9 process, these quantities of vehicle can re-dissolve the dried sur- ' face layer of ink such that the ink is once again in the wet stage 11 and capable of transferring as set-off and smear marks. . With 12 . pressure dampening drying, sufficient moisture is applied directly 13 to heavy ink films to effect their drying. 14 Another advantage of the invention is the independence from boundary layer effects. Since moisture is 16 transferred in the liquid form, the pressure dampening system is 17 not handicapped by boundary layer effects along the surface of a 18 rapidly moving web. When using saturated steam, the access of 19 steam to the web proper is limited by the boundary layer of air set up at high web speeds. Pressure roll dampening functions indepen- 21 dently of boundary layer effects along the web. Thus the drying 22 rate of moisture-setting ink films on a web in a high 'speed printing 23 press is increased, and this is particularly advantageous with 24 heavier ink films.

. In summary it can be said that the invention 26 increases the drying rate of moisture setting inks by the application of high roll pressure directly onto the ink film. Transfer and accumulation of ink on the pressure rolls is effectively prevented by providing a protective coating of dampening fluid to the surface .of the pressure rolls. The surfaces of the pressure rolls can be kept hydrophilic by continuously re-etching the pressure rolls by special techniques to a degree permitting application of a uniform . moisture layer without the formation of droplets. Moisture can be supplied to these pressure rolls by means of a dampening unit designed to permit control and regulation of the flow rate of damp-· ening fluid to meet the particular requirements of the ink film to be dried. The pH of the dampening fluid can be controlled to . effect continuous re-etching of the pressure rolls. Drying of both thin and heavy films of most commercial printing ink is possible, using this method and apparatus, at speeds at least up to 1, 000 feet per minute.

Other ways of dampening the pressure rolls 19, 19' can be employed. For instance, moisture can be applied by a wick urged against the pressure roll by a leaf spring. A litho- style dampening system may be employed comprising a fountain roll revolving in dampening solution, a molleton covered ductor roll, a hard vibrator roller, and a molleton covered roll in contact with the pressure roll. A third variation is an endless belt running in contact with the pressure roll and about a fountain roll.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein .without departing from the spirit and scope of the invention.

, What is claimed is: -10 23943/3 ^ 1

Claims (1)

1. CLAIMS A method drying of moisture Betting inks applied in a printing to a fibrous web the fibrous leaving the printing is passed between a pair of pressure rolls whereby an aqueous Solution containing a solvent for the ink is applied to the surface of at least one of the pressure A method according to Claim wherein the aqueous solution containing a solvent for the ink is applied uniformly to the rolls by means of at least one dampening the dampenin roll being covered with a and A method according to Claim wherein the aqueous solution containing a solvent for the is applied to the dampening rolls A the aqueous solution containing a solvent for the ink is applied to the dampening rolls by means of a A method fo o moisture setting inks applied in a printing process to a fibrous web substantially as hereinbefore by way of example and with reference the accompanying insufficientOCRQuality