US2216143A - Process of coating paper - Google Patents

Description

\ Odi 1, 1940. w. F. THIELE r-:r AL

' PRocEss oF coATING PAPER Filed May 11, 19:56 2 Sheng-sheet 1 2 Sheertvs-Sheet 2 W. F. THIELE ET Al..-`

PROCESS QF COATING PAPER Filed May 11, 1936 Oct. 1`, 1940.

lo to the trade as tissues.

y Patented Oct. l, 1940 UNITED STATES PATENT OFFICE PROCESS oF COATING PAPER Application May 11, 1936, Serial No. 79,043

4 Claims.

This invention relates to an improved paper coating method and apparatus. and refers speciflcally to a method of coating relatively thin or tissue paper made on a so-called Yankee paper machine, the coating operation comprising one of a plurality of continuous steps in the manufacture of the paper.

Yankee paper machines are primarily designed for producing light weight papers known Such machines have but one dryer, which is in the form of a drum, usually ten or twelve feet in diameter, short forming wires, a limited number of presses and a limited drying capacity. Cooperating top and bottom felts are employed for Itransferring the paper web from the Fourdrinier wire to the dryer.

Heretofore, great diiliculty has been experienced in producing opaque papers of light weight on Yankee paper machines. D ue to the short- 20 ness of the forming wire and the thinness of the sheet of paper usually made on this type of machine little success has been had in obtaining a desired degree of opacity of the paper web by loading the paper with materials such as clay, titanium oxide, zinc oxide, satin white, and like materials. The addition of clay or similar opacity producing material to the web as it is formed on the wire of the machine causes the top pick-up felt to become iilled very quickly with the material so added making it necessary to shut down the paper machine and wash lthe top felt at frequent intervals. y

Our invention contemplates the application of Y a relativelythick paste-like materiahcomprlsing one or more minerals and one or more adhesives, or a combination of them, tothe web of paper after it has been transferred to the dryer of the paper machine by the top pick-up felt, the coating materials being .squeezed into the depressions 40 of the adjacent. side of the web of paper which would normallybe rough, thereby producing the opacityl desired. However, although our linvention is capable ofapplying relatively thick or heavy materials to `the paper, which coating 45 processes heretofore proposed have been ,unable to use, it is to be understood that we do not wish to be limited to -this specific type of material since our process is capable of use with thinner or more liquid coating or other web surface modif ying materials. y

f 'I'he utility, objects and Aadvantages of 'our invention will be more apparent from the accompanying drawings and following detail descrip- '65 tion.'

In the drawings:

Fig. 1 is a fragmentary diagrammatic side elevational view of suitable apparatus for carrying out our process.

- Fig. 2 is a detail side elevational view of the coating mechanism per se.

Referring in detail to the drawings, I indicates a portion of the frame of a paper machine of the Yankee type, which may be supported by a plurality of columns 2 one only of which is shown in the drawings. 'I'he frame I supports oppositely positioned bearings 3, one of which is shown, and in which a shaft 4 isjournalled, said shaft carrying drying drum 5.

In the Yankee type of paper machine, which is particularly adaptable for making light weight or tissue paper, but one drying drum is used which, however, is of relatively large diameter, in the neighborhood of or ,12 feet. A canopy or hood 6 encompasses a large portion of the periphery of the drum 5, said hood comprising a conduit 1 for discharging air, usually hot air, into contact withthe paper web carried upon the surface of the drum. The drum 5, of course, is usually `heated by means of steam which is carried in the interior thereof. l

The paper web is formed upon a relatively short forming wire (not shown) and upon being stripped therefrom is carried between two felts 8 and 9, being the upper and lower felts respectively. The felts, of course, assist in the 'removal of moisture from the web of paper by capillary attraction. this rr oval being facilitated by passing the felts and interposed web between one 'or more' presses IIIcomprising osculating rolls II. After passagethrough the last press I0, theweb is stripped from the lower felt S'which returns to the wet end of the machine over guide roll I2, said web being carried upon the upper felt 8 over a couch roll I3 which osculates with drum 5. -At the point of osculaton between couch roll I3 and4 drum 5, the web is stripped from the felt -8 and transferred directly to the heated external surface of the drum, while felt 8, returns tothe wet end of the machine. During passage of the web over the drum 5 the surface in contact therewith becomes smooth and iinished, while the other surface of the web is subjected to the contact of the hot air delivered from the conduit 1, the web-of paper being relatively thin is substantially dry when it is stripped from the drum and passed around roll'. I4, the web being design nated I5. After passagearound the roll Il the web may be cut into sheets, or reeled as a continuous web.

Paper made in the manner and upon a machine, as has been hereinbefore described, is very thin and consequently tendsto be translucent. If the attempt is made to fill the paper with clay or the like during formation of the web to render the same more opaque, difficulty is encountered in that the upper felt is quickly filled and necessitates shutting'down the machine towash the felt. This,-manifestly. is very objectionable from the standpoint of economy and also because the speed of production of the paper web is materially reduced.

Our invention contemplates the coating of the paper web I5 after it has been transferred to the dryer drum, that is, after the web has left the hereinbefore described. A frame I8v is supported by means, of straps I1 from the main frame I, as

, may be seen in Fig. l. Mounted on frame I6 are a plurality of transversely extending rolls I8, I9, 28 and 2I which are disposed, during normal operation, in serially contiguous relationship. Roll I8 engages and extends transversely across the path of travel of the paper web I5, during the initial portion of its movement around the dryer 5. Said roll is slightly shorter in length than the width of the web or the width of the drum 5, so that the coating material applied by roll I8, does not come in contact with the outer surfaceof the dryer drum 5. Roll I8 is journailed in oppositely disposed bearings 22. which are in turn carried by blocks 23. Frame I8 on each side of the machine comprises members 24, and 26, members 24 being spaced from members-25 and 26, to form ways for the blocks 23 which are slidably positioned between the members 24 and 25. A channel 21 is secured at the end of frame I6 to members 24 and 25 and serves as a spacing means for said members.

. rIn carrying out 'our process, roll I8 is disposed in contact with the Web'I5 upon drum 5 immediately adjacent the point where said web has been stripped from the upper felt 8. Aswill be hereinafter more fully described, roll I8 is adapted to carry a film of coating material or other modifying' material upon its surface which is transferred to the surface of the web of paper. A capstan screw 28 is threaded in the web of channel 21, the head of said screw, during normal operation, serves as a stop against which block 23 abuts, and thereby controls the degree of proximity of the surface of the roli I8 to the web I5, upon the dryer drum surface. It can readily be seen that L inasmuch as roll I8 is' shorter than the width of web I5, there is no danger of depositing coating material on the highly finished surface of the drum which may be destructive to said surface.

`v'.Sh'aft 29 carries roll I9 and is journalled in opr'fp'ositely disposed bearings (not shown) which are I6. Consequently, roll I9 is movable toward and away from roll I8. A capstan screw 32 is threadedly positioned in block 23 and the head thereof provides a stop against which the block 38 may abut to limit the degree of proximity of roll I9 to roll I8. A screw 33 is threadedly positioned in block 38, the shank of said screw passing freely through an aperture 34 provided in block 23 and serves to control the degree of separation of blocks 23 and 38 and hence rolls I8 and I9.

A worm pinion (not shown) is mounted upon the shaft 29 and is adapted to mesh with a worm wheel (not shown) mounted upon shaft 35v within housing 36. Eccentric mechanisms 31 are associated with shaft 35, said eccentric mechanisms being ultimately anchored to blocld 38. This mechanismis of conventional type, having heretofore been widely used and comprises no part, per se, of our present invention. The purpose of the mechanism is to oscillate roll'38 axially simultaneous with its rotation.

Roll 20 is journalled in opposite bearings 38 carried by blocks 39 which are slidably disposed in ways comprising members 24 and 26. A capstan screw 48 is threadedly secured to block 38 and its head is adapted to .provide a stop against which the block 39 abuts to control the degree of proximity of rolls I9 and 28. A screw 4I is also threadedly engaged in block 38, the shank of which passes freely through aperture 42i provided in block 39 whereby the mammum separation or spacing of blocks 38 and 39 and hence rolls I9 and 28 may be adjustably controlled.

Roll 2| is journalled in opposite bearings 43 carried by blocks 44 which are slidably disposed in the ways comprising members 24 and 28. A capstan screw 45 is threadedly secured to .block 39 and its head is adapted to serve as a stop against which the blocks 44 abut to control the degree of proximity of rolls 28 and 2I. A bolt 46 having a head 41 and nut 48 is loosely positioned through apertures 49 and 58 provided in blocks 39 and 44, respectively and serves to adjustably control the spacing of blocks 39 and 44 and hence rolls 28 and 2 I.

, A cylinder 5I (Fig. 1) is mounted at the end of frame I and carriesa piston (not shown) the piston rod 5I a projecting from the cylinder and being connected to block 44. 'Ille purpose of the cylinder-piston mechanism is to slidably move blocks 23, 38, 39 and 44 to the right or left along member 24, 25 and'26. It can readily be seen that ghen fluid under pressure, preferably air, is intro uced into cylinder 5I on one lside of the piston, rod. 5Ia will tend to move said blocks along the axis of the rod. If, for instance, the piston rod moves to the right, asviewed in Fig. 2, block 44 will move to the right thereby separating rolls 28 and 2I until the head 41 and nut 48 abut blocks 39 and 44 respectively. Blocks 39 and 44 will then move in unison, drawing roll 28 away from roll I9 until the head of screw Ul'icontacts block 39. B}ock 38 will then move in uni'- son with blocks 39 and 44 thereby moving roll I9 awayfrom roll I8 until the head of screw 33 contacts block 23, at which time block 23 will be moved with the remaining blocks thereby separating roll I8 from the web I5 on the drum 5. Of course, when the rolls are thus separated,'the device is rendered inoperative as a coating agency.

A roll 52 is carried by shaft 53 which in turn is journalled at its ends in bearings 54 slidably mounted in standards 55, which aremounted on the opposite blocks 38 and consequently are stationary with respect to the axial motion of the mentioned the coating material that we have found suitable for carrying out our invention is in the form of a relatively thickpaste-like material, and for rendering the thin web of paper opaque we employ a compound and one or more adhesives, or a combination thereof. It is to be understood that this invention is not to be lim ited to the use of minerals such as clay, calcium' carbonate, titanium oxide, zinc oxide and satin White and adhesives'such as casein, starch, glue and the like, for rendering the paper opaque, because manifestly this-invention may be used for applying any usable substance for modifying the .surface of the web of paper. coating materials have only been used in dilute solutions. now found it possible to employ paste-like coating material wherein the consistency thereof is at least 10% solids, and may be as high as 60%. The surface of the paper thuscoated for rendering it opaque also acquires an excellent finish which renders it particularly suitable for printing thereon.

Roll I3, may be driven by means of belts, gears, motors or directly from the dryer drum 5, so that the peripheral speed of said roll and the drum are the same, and roll I9, may also be driven in `a manner similar to roll I8. Roll 2|] is preferably driven by means covering a wide variable range of speeds. While roll 2I` is preferably driven by a separate motor having a speed range from 1 R. P. M. to a peripheral speed equal to the peripheral speed of rolls I8 and I9, the purposes of which willrhereinafter appear. Roll 52 may be driven from the same power source as roll I9,

since their peripheral surfaces desirably travel at the same rate of speed.

In operation, the screws 28, 32, 33, 40, 4I, 45 and bolt 46 are first adjusted so that the adjacent rolls maybe separated at desired amounts. The coating material is then deposited in the upwardly open trough formed by the rolls 20 and 2l and dams 51, and the web of paper I5, started through the machine in the usual manner. Then the rolls I8, I9, 2U, 2| and 52 are brought up to the desired speeds, at which time compressed air is admitted to the 4cylinder 5I, which through the connections above described, pushes the rolls to the left, with respect to thev position indicated in the drawings, for disposing. the rolls in a desired relation to each other, and with the roll I8 engaging the web of paper I5, trained around the dryer drum 5, It will now be clear that as rolls 2li and 2l rotate a quantity of vcoatingmaterial in the form of a film will adhere to the surface vof roll 20, which is transferred to the surface of roll I9, and which in turn transfers the film of coating material to the roll I8 for applying it to the outer surfaceof theweb of paper which is trained around lthe dryer 5. The yroll 52, positioned above the roll I9, which rotates and reciprocates, causes the coating material to be uniformlyand smoothly distributed over the surface of roll I9,

from which it is picked up by roll I8 for applying Heretofore By virtue Vof ourinvention We havel it to the web of paper. The roll'i8, is preferably positioned relatively to the paper web so that the coating material-V is squeezed into the depressions of the adjacent surface of the paper web, producing the opaque effect desired. By virtue of the character of coating material that may be employed and the novel arrangement of appa ratus for applying it, the' coating operation becomes one of a series of 'continuous steps for producing coated paper and We are able to obtain excellent results, wherein the finished web of paper is uniformly opaque, and is free fromskips, ridges and the usual defects. It will be manifest, however, that the coating material selected may be for purposes other than for rendering the paper opaque, and we do not Wish to be understood as limiting our invention to the specific use herein disclosed, which is merely illustrative of this invention.

We claim as our invention:

1. A method of producing coated paper having a uniformly smooth surface'coated to render the same substantially opaque and to form a coated surface thereon suitable for the reception of printing which comprises, forming a fibrous web as a continuous operation; removing a portion of the'water from the Web by mechanical pressure, passing the web into heat exchange contact with a heated rotating surface, transferring 'a mobile c oating material of relatively high solids content from a rotating surface to said web while the same is still wet substantially simultaneously with the initial generation of vapor in the ,web and before an appreciable amount of moisture has been driven from the web by heat,.and carrying said coated web around said heated rotating surface to dry said web and coating in the form that it was originally applied to the web to a predetermined moisture content. l

2. A method of producing relatively thin paper having a uniformly smooth surface coated to' render the paper substantially opaque which comprises, forming a relatively thin fibrous web as a continuous operation, removing a portion of the Water from the web by mechanical pressure, passing the web into heat exchange contact with a heated rotating surface, and transferring a mopaper making machine relatively thin paper having a uniformly smooth surface coated to render the paper substantially opaque which comprises,

forming av relatively thin fibrous web. as a con-- tinuousvoperation, removing a portion of the water from the web by mechanical pressure, passing the web into heat exchange contact with a heated rotating surface, and transferring a mo-A bile coating material of relatively high solids content from a rotating surface to said web while the same is still wet substantially simultaneously with the'initial generation of vapor in the web and ,before an appreciable amount of moisture has been driven from the web by heat, said coating upon the web being undisturbed after its initial application to the web.`

4. A method of producing relatively thin paper having a uniformly smooth surface coated with a mineral coating material to render the paper substantially opaque which comprises, forming a relatively thin fibrous webas a continuous operation, removing a portion of the Water from the web by mechanical pressure, passing the web into, heat exchange contact with a heated rotating surface, transferring a mobile coating material containing from 10% to 60% solids from a rotating surface to said web while the same is still relatively wet substantially simultaneously with the initial generation of vapor in the web and before an appreciable amount of moisture has been driven 'from the web by heat, and strippingl said web with the coating applied thereto from said heated rotating surface in substantially the form that the web was applied to said 5 surface.

HOWARD BREWS'IER RICHMOND.

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