US1921369A - Method of coating paper - Google Patents

Description

Aug. 8, 1933. P. J. MASSEY METHOD OF COATING PAPER Filed NOV. 4, 1931 3,Sheets-Sheet 1 jzforneg- Aug. 8, 1933. P. J. MASSEY METHOD OF COATING PAPER Filed Nov. 4, 1931 3 Sheets-Sheet 2 J' yen for:

Aug. 8, 1933. P. J. MASSEY METHOD OF COATING PAPER Filed Nov. 4, 1951 3 Sheets-Sheet 3 Patented Aug. 8, 1933 STATES METHOD OF COATING PAPER.

Peter J. Massey, River Forest, Ill.

Application November 4, 1931. Serial No. 572,895

7 Claims.

This invention relates to improvements in a process of manufacturing coated paper upon a paper making machine and refers specifically to a process wherein the paper may be formed,

coated and dried in one continuous operation.

One of the objects of my invention resides in a method of forming paper on any one of the various types of paper making machines, coating the web of paper as it leaves the forming portion of the machine and as soon as it possesses tensile strength sufiicient to be passed through the coater, and drying the coated web, all as a continuous, uninterrupted process of making coated paper.

Among the advantages of my invention may be mentioned: a saving of space and equipment; more rapid production of coated paper; the production of a coated paper having superior surface qualities; the elimination of waste due to shrink- I age and tear; and the effecting of a saving of space, equipment and time due to the flexibility of operation.

Other objects and advantages of my invention will be apparent from the accompanying drawings and following detail description.

In the drawings, Fig. l is a diagrammatic, side elevational view of a paper making machine having a Fourdrinier wet end, press rolls and driers, in conjunctionwith which my invention may be carried out.

Fig. 2 is a diagrammatic, fragmentary side elevational view of a modified arrangement of the apparatus shown in Fig. 1, the coating operation taking place between the first and second presses.

Fig. 3 is a diagrammatic, fragmentary side elevational view similar to that shown in Fig. 2, illustrating the coating device between the second and third presses.

Fig. 4 is a view similar to Figs. 2 and 3 illustrating the coater between the presses and the drier.

Fig. 5 is a diagrammatic, side elevational view illustrating my invention as practiced upon a cylinder machine.

Fig. 6 is a diagrammatic, side elevational view showing my invention as applied to a combination machine.

Fig. 7 is a diagrammatic, side elevational view illustrating my invention as practiced upon a Harper machine.

Fig. 8 is a transverse, sectional view through one of the fountains utilized with my coating device, illustrating means for circulating the color. v

Referring in detail to the drawings, 1 indicates the Fourdrinier part or wet end of a paper making machine, 2 indicates a coating unit, 3 the presses and 4, the driers, calender and reel.

The Fourdrinier part or Wet end 1 may comprise a flow or head box 5 from which the pulp or stock may be conducted over an oil cloth or rubber apron to a wire screen 6, which may be driven by the couch roll '7 and may be supported by the breast roll 8, table rolls 9 and wire rolls 10. Deckle straps 11 may be provided to keep the stock from running off the edges of the wire. During the passage of the stock from the head box 5 upon the wire 6, much of the water drains through the wire at the table rolls 9. More of the water may be removed from the stock when the wire 6 e passes over suction boxes 12 and the fibers may be laid down by the dandy roll 13 and couch roll 14.

In the usual method of manufacturing paper the wet web 15 which leaves the couch rolls 7 and 14 passes directly through the press unit 3, drying unit 4, and is subsequently calendered and reeled. In one aspect of my invention I contemplate coating the web 15 immediately upon its passage from the couch rolls '7 and 14 and previous to its passage to the press drier 4.

In carrying out my invention the web 15 may be passed through a coating device 2 which may be of the type shown and described in my copending application, Serial No. 450,614. Briefly described, the coating unit may comprise fountains 16, distributing rolls 17 and coating rolls 18. The fountains 16 may contain the coating solution or suspension. By suitable mechanism such as described in my co-pending application above referred to, the color maybe transferred from the fountain 16 over the surfaces of the various distributing rolls 17 and to the peripheral surfaces of the coating rolls 18. When the color is deposited upon the coating rolls 18 the same may be formed in a smooth film of uniform thickness, the film may be transferred by each of said coating rolls to the upper and lower faces of the moving web 15.

As stated in the aforesaid application and as will be apparent from the description of the coating mechanism contained herein, the purpose of the invention is primarily to obtain what is known as coated paper which is suitable for printing purposes as contra-distinguished from mere water 1 5 proofing processes. In this art, as it is commercially practiced, paper webs, which previously have been formed, are subjected to an aqueous solution of coating material and after the same has been applied to the web suitable brushing, 110

scraping or smoothing devices are employed to work it and distribute it upon the web. The high water content of the coated solution, however, has a tendency to streak the web and the mechanical action to which the aqueous coating solution is subjected after it has been placed upon the web had the tendency to injure the web. Moreover, considerable drying must take place after the coating solution has been applied and because of the dry condition of the web, there is a tendency for the coating material to peel, as hereinbclow pointed out in detail.

To overcome these disadvantages my coating apparatus is designed to mechanically work the coating solution to smooth and. to substantially dehydrate it so that when it is applied by the rollers 18 it takes the form of a preformed plastic film with no subsequent treatment being necessary. It readily adheres to the web because the web is in a wet condition and obviates the re- 7 treatment steps pointed out on pages 10 and 11 hereof.

The web 15 referred to as coated web 19 may then pass to the press unit 3 which may comprise a plurality of press rolls 20, 21 and 22 through which the web 19 may pass-in series. If desired the web 19 may pass through the presses 20, 21 and 22 in company with felts 23 and 24. However, felts 23 and 24 may be eliminated inasmuch as they are not essential to the carrying out of my invention.

It is to be understood, of course, that I do not wish to be limited to the use of three presses inasmuch as any number of presses may be utilized depending 'upon the type of paper to be manufactured.

After leaving the press unit 3 the coated web 19 may be carried to the drying unit 4 which may comprise a plurality of drying rolls 25 of the usual construction. When the web 19 has been suitably dried the same may be carried to a calender 26 or a battery of calenders from whence the web may be reeled as shown at 2'7 in Fig. 1.

If desired, the coating unit 2 may be interposed in the press unit 3, for instance, as shown in Fig. 2, the coater 2 may be positioned between the first and second presses 20 and 21 respectively in which case the percentage of moisture of the web 15 will obviously be lower than the moisture content of the web leaving the couch rolls '7 and 14 shown in Fig. 1. The coated web 19 may be passed from the coater 2 to the second and third presses 21 and 22, or to the remaining presses if more than three are used. Said web may then be carried to the drier 4 and may subsequently be calendered and reeled.

It may be found desirable to eliminate a greater percentage of moisture from the web 15 before the coating is applied, in which case the coater 2 may be positioned between the second and third presses 21 and 22 respectively as shown in Fig. 3 or the web may pass entirely through the press unit 3 comprising all of the presses 20, 21 and 22 in which case the coater 2 will be positioned between the press unit 3 and the drying unit 4.

It is to be understood, of course, that any number of presses may be utilized and also that the coating step may take place before, after or intermediate the pressing operation as illustrated in Figs. 1 to 4 inclusive.

My invention may also be used in conjunction with other types of paper making machines,'for instance, as shown in Fig. 5, my invention may be practiced in connection with a cylinder machine. The cylinder machine may comprise the usual cylinder molds 28 which may be adapted to rotate within suitable vats, not shown, containing a pulp solution or the stock. It is to be understood, of I course, that any number of cylinder molds 28 may be used depending upon the type and thickness of the paper to be made. A felt 29 may pass between each of the cylinder molds 28 and the couch rolls 30 at which period a layer'of papermay be deposited upon the lower face of the felt or upon the lower face of the web previously deposited by a preceding mold. The felt 29 carrying the deposited layer or layers of stock from the molds 28 upon its lower surface may pass around strain roll 31 and be carried through the first squeeze rolls 32 at which point the upper felt 33 comes into contact with the web of paper carried upon the surface of the felt 29. In this manner, the web is carried between the two felts and a relatively small quantity of moisture is expelled from said web in its passage through the squeeze rolls 32. The felts 29 and '33 with the web carried therebetween may pass through a plurality of squeeze rolls and may be carried to a baby press unit 34 which may comprise a plurality of baby press rolls 35, the number of which is dependent upon the type of paper to be made. In the last baby press roll the upper felt 33 may return to the wet end of the machine over felt.

rolls 36. It is the usual practice to return the upper felt at this point but, if desired, said felt may be carried forwardly to the first press 37 and may return from said press to the wet end of the machine. It is to be understood, of course, that any of the variations in operation of the cylinder machine are contemplated in my invention.

Upon passing through the first press 37 in company with the lower felt 29, a quantity of moisture contained in the web may be expelled. After passingv through the press 3'7 the web is removed from the lower felt and said felt is returned over felt rolls 38 to the first cylinder mold. The web 39 may then pass through the second press 40 and may be carried to the next succeeding press 41 at each of which presses more moisture is removed. Upon leaving the third press 41. the web may be passed through the coater 42 which may be similar in construction and operation to the coating unit 2 shown in Figs. 1 to 4 inclusive. In this manner one or both sides of the web 39 may be coated. The coated web 43 may then be passed to the drying unit 44 which may comprise a plurality of the usual type drier rolls 5. It can readily be seen that inasmuch as the web at this period contains a considerable amount of moisture and also that the coating applied to the surface or surfaces of the web possesses a relatively high moisture content, the drying of both the web and the coating thereon may take place simultaneously in the drying unit 44, and consequently uniform drying will result and no unbalanced stresses will be set up within the web. The web 43 may then be carried from the drying unit 44 to one or more calenders 45 which may suitably compact the surfaces of the web. From the calenders the web may be carried to the winder 46 where the paper may 'be reeled upon suitable drums.

It is to be understood, of course, that the coating step of my process may take place before the web 29 has passed to the first press 37. In this event the lower felt 29 will be returned to the first cylinder mold 28 previous to the passage of the web through the coating device. It is also to be understood that the coating unit 42 may be interposed between any one of the presses 87, 40 or 41, or may be interposed between the last of said presses and the drier 44. I

My invention may-also be utilized in conjunction with a combination machine which may 6 comprise the usual Fourdrinier wire 47 supported bybreast roll 48, table rolls 49, couch rolls 50 and wire rolls 51. The pulp from the head or flow box may be conducted to the wire '47 at the breast roll 48 and said pulp while in more or less liquid condition, may be prevented from flowing over the sides of the wire by the deckle straps 52 which may be of the usual construction.

As the wire 47 carrying the wet paper web passes between the couch rolls 50, said web may be picked up by the felt 53 which is also carried between the couch rolls 50. A cylinder mold 54 may be adapted to rotate within a vat, notshown, which may contain a quantity of pulp. The pulp which adheres to the surface of the cylinder mold 54 may be transferred to'felt 55 which passes between the cylinder mold 54 and a couch roll 56. The felt 55 carrying the web received from the cylinder mold 54 may be brought into contact with the felt 53 carrying the web taken from the Fourdrinier wire 47 at 57. At this period the web from Fourdrinier wire and the web from the cylinder mold are maintained in contact between the upper felt 53 and lower felt 55. While in this state the upper and lower felts with the composite web interposed therebetween is passed through the first press 58 which removes a quantity of moisture from said web and tends to compact the two webs into a unitary strip of fibrous material 59.

After passing between the press rolls 58 the composite web may be removed from both the upper and lower felts 53 and 55 respectively and may be passed between the coating rolls of the coating device 60 which may be similar in construction and operation to the coating devices 2 and 42. In this manner a coating may be applied to one or both sides of the web 59. The coated web 61 may then be passed through a desired number of presses 62 and 63 from whence said web may be carried to smoothing rolls 64 and dried in the drying unit 65. The dried web may then be passed through the calender 66 and may subsequently be reeled upon the drum 67 as a completely manufactured coated paper.

It is to be understood, of course, that the web 59 may be coated previous to its passage through the presses 58, 62 and 63 or after its passage through said presses, or at any intermediate position between any of the presses. It is also to be understood that any number of presses may be utilized in conjunction with this process and also, if desired, the felt which accompanies the web through the presses may be eliminated.

In the use of my invention in conjunction with the Fourdrinier machine, the cylinder machine or the combination machine, the coated web may be passed through the driers 4, 45 or respectively with or without an accompanying felt.

In Fig. 7 my invention is shown in its application to a Harper machine. Said machine comprises the usual Fourdrinier wire 68 which may be carried over breast roll 69, couch roll 70 and wire rolls 71. The pulp or stock may be conducted from the head or flow box, not shown, to the wire 68 during its passage over the breast roll 69. The stock may be prevented from running oif the edges of the wire 68 by means of deckle straps 72 which may be of theusual construction.

Inasmuch as this type of machine is ordinarily used for relatively thin papers such as tissue paper or the like, automatic means is provided for removing the web from the Fourdrin ier wire. Said means may comprise a felt 73 which may pass the couch rolls 70 at which point the web of fibrous material carried by the wire 68 is transferred to the surface of the felt 73. Said web may be carried in company with felt 73 over the rolls 74 and may pass between press rolls 75. The felt 73 passes over the lower press roll 75 and returns to the couch roll 70. A second felt 76 also passes between the press rolls 75 and the arrangement is such that the web 77 passing between the press roll 75 is positioned between the felt 73 and felt 76. Consequently when the felt 73 returns to the couch roll 70 the web 77 is picked from said felt by the upper felt 76 by which means it is carried to the baby drier 78. At this period the felt 76 separates from the web 77 and said web may be carried directly through the rolls 79 of the coating device 80. The coating unit 80 is similar to the units 60, 42 and 2 utilized in connection with the combination, cylinder and Fourdrinier machines respectively hereinbefore described. After web 77 passes between the rolls 79 a uniform coating is applied to one or both faces of the web and said coated web 81 is passed over a plurality of driers 82. It is to be understood, of course, that my invention is not to be limited in its use in conjunction with a Harper machine to the particular arrangement shown, inasmuch as it may be utilized with various modified constructions of said machine.

It can readily be seen that my invention broadly contemplates the method of manufacture of coated paper upon any type paper making machine as a continuous, uninterrupted process of forming or felting, coating and drying the paper.

It is also apparent that the process contemplates coating the paper while the web possesses a relatively high percentage of moisture inasmuch as said coating step may take place before drying of the web by evaporation takes place. In addition, the web may be coated before any appreciable amountof the moisture in the web is pressed or squeezed out inasmuch as the coating step may take place before the web passes through the presses. Since the web passing from the presses 'of a Fourdrinier machine for instance, usually contains substantially 65% moisture, and inasmuch as the coating step may take place before the web enters the presses, the web may have a water content of 90%, more or less, when coated.

Whether the coating step is performed before, intermediate or after pressing, of course, may be determined by any one skilled in the art, depending upon the type of paper made and the charac teristics of the coating desired.

By utilizing my invention in the manufacture of coated paper, a coated paper may be produced at the paper mill; subsequent handling of the paper, such as has been heretofore found necessary where the paper was first formed, pressed, dried, calendered and reeled and subsequently coated, dried, recalendered and reeled, is eliminated; losses fromecontraction and expansion and tearing are eliminated since the paper may be coated when the moisture content thereof is relatively high and, hence, the paper may be dried uniformly since the drying step simultaneously expresses or expels the moisture normally contained in the wet web incident to its formation, and the moisture imparted to the web in the coating stage. In addition, a saving of time, space and equipment is obtained inasmuch as the loop driers brdinarily used to dry the coated paper are eliminated since the moisture normally contained in the web and the coating is dried simultaneously upon the usual roll or drum driers.

A better quality coated paper may be made by my process since the fibres of the paper will not be weakened by excessive heating as is the case where the paper to be coated is first formed, pressed and dried and then coated and redried. It can'- readily be seen that in the coating process heretofore practiced only the surface or surfaces of the paper would be moistened. Hence, when the coating is dried, the interior of the paper web being already dry, would be baked and the fibres weakened. If baking and the consequent weakening of the fibres is to be avoided, slow drying of the coated dry paper must take place which necessitates either slow production and decreased capacity or abnormally large, expensive drying equipment. By the use of my process the web being thoroughly wet throughout its thickness is dried simultaneously with the wet coating and, hence, a stronger paper will result.

Further, inasmuch as the paper contains a relatively high percentage of moisture the coating when applied will be firmly bonded and compacted upon the wet fibres and when said web and coating dries, the coating film and web will be bonded together as a unitary structure. In coating the paper after it has been dried, as practiced by the prior art, during the coating stage only the outer surfaces of the web will be moistened and this imperfectly and non-uniformly and, hence, difiiculty has been experienced in properly uniting the coating to the paper. This results in defects in the coated paper which manifest themselves in various ways, for instance, the coating when dry being imperfectly bonded to the fibres of the web will peel or crack, a condition which cannot possibly exist in the product made by my process. In addition, inasmuch as the coating imperfectly and non-uniformly moistens the surface fibres of the dried paper when drying takes place, the paper will contract nonuniformly and, hence, unbalanced stresses will be set up in the web which tend to weaken the paper and tend to crack the coating. Further, since the bond of the wet coating upon the relatively dry surfaces of the Web is very weak, extreme care must be exercised in the subsequent drying of the paper since the coating may easily be rubbed from the surface of the paper While wet. In utilizing my invention the bonding of the coating and the surface fibres of the web is sufiiciently strong to permit the coated web to be passed directly to the heating surfaces of the drying rolls of the paper making machine.

When utilizing my invention, speed of production need not be sacrificed inasmuch as the coating step maytake place at a speed equal to or higher than that of the paper making machines now in use. In other words a coated paper may be made at the same speed that ordinary uncoated paper has heretofore been produced at.

Referring particularly to Fig. 8, a detailed, transverse sectional view of a fountain which may be utilized in conjunction with the coating devices 2, 42, 60 and is shown. Said fountain may comprise a vat 83 which may be adapted to contain a coating material 84 in aqueous suspension or solution, the material preferably used being mineral substances such as calcium sulphate, barium sulphate, aluminum hydrate, magnesium carbonate, satin white, clay or the like. To prevent precipitation of the soluble material within the coating solution of suspension I may cause continuous circulation to take place through the fountain. The aqueous suspension or solution may be introduced into the fountain through the pipe 85. An aperture 86 may be provided in the lower portion of the fountain and may be adapted to be closed by valve 87 which may be mounted upon the lower portion of the stem 88. A float 89 may be mounted upon the upper end of the stem 19 and may be adapted to lower or raisethe valve 87, thereby closing or opening the port 86 when the level of the liquid coating solution or suspension 84 within the fountain lowers or raises. It can readily be seen that by this construction circulation of the material within the fountain may be controlled merely by controlling the passage of the material through the pipe 85. A pipe 90 may connect into the lower portion of the vat 83 at the port 86and may be adapted to conduct the material from the vat 83 when the valve 87 is in its raised position to a pump or supply reservoir, not shown, from which it may be recirculated through the pipe 85 and re-introduced into the vat '73.

It is to be understood, of course, that I do not wish to be limited to this particular means of recirculating or agitating the liquid 84 within the vat 83 inasmuch as numerous arrangements may suggest themselves to any one skilled in the art for accomplishing the same purpose, namely, to prevent precipitation of the soluble materials within the suspension or solution 84.

A roller 91 may be mounted upon shaft 92 which, in turn, may be journalled on the ends of the vat 83, the arrangement being such that the lower portion of the roll contacts the solution or suspension 84. A doctor blade 93 may be mounted upon support 94 which, in turn, may be positioned upon the upper portion of the vat 83, said blade being adapted to regulate the thickness of the film of coating material 84 carried upon the periphery of the roller 91. The blade 93 may be moved toward or away from the surface of the roller 91 by means of set screws 95 which may be threadedly positioned in the support 94. By this arrangement the thickness of the film carried by the roller 91 may be accurately controlled.

1 As has been fully described in my co-pending application, Serial Number 450,614, the film carried by the roller 91 may be transferred to a series of distributing rollers which, in turn deposit a film upon the coating rolls.

By the term forming as used in the specification and claims is meant the production of a fibrous web on any paper making machine before said web is passed to the driers. In other words, the forming operation may include felting on the Fourdrinier wire, or on the cylinder molds or both and may or may not include the pressing operation.

I claim as my invention:

1. A continuous method of producing a uniformly coated fibrous web of paper suitable for printing purposes which comprises thefollowing successive steps; forming a continuous wet fibrous web, bringing said web into contact with a moving surface carrying a uniformly distributed film of coating material, and transferring said material as a pre-Worked, plastic, substantially dehydrated and continuous film to said web and dryin said coated web.

2. A continuousprogressive method of producing a uniformly coated fibrous sheet of paper suitable for printing purposes, which comprises the following steps; forming a continuous wet fibrous web, removing a portion of the moisture from said web, bringing said web into contact with a moving surface carrying a uniformly distributed film of coating material, and transferring said material as a pre-worked plastic and substantially dehydrated continuous film to said web and drying said coated web.

3. A continuous progressive method of producing a uniformly coated fibrous sheet of paper suitable for printing purposes which comprises the following steps; forming a continuous wet fibrous web, removing a portion of the moisture from said web, bringing said web into contact with a moving surface carrying a uniformly distributed film of coating material which has previously been reduced to a proper plastic consistency, and transferring said film to said web as it is applied thereto.

4. A continuous progressive method of producing a uniformly coated fibrous sheet of paper which comprises the following steps; forming a continuous wet fibrous web, partially drying said web, bringing said web into contact with a moving surface carrying a uniformly distributed film of coating material which has previously been reduced to proper consistency, uniformly spreading and compacting the same upon the surface of the web and drying said coated web.

5. A continuous progressive method of producing a uniformly coated fibrous sheet of paper suitpre-formed film to said web and drying said coated web.

6. A continuous progressive method of. producing a uniformly coated fibrous sheet of paper suitable for printing purposes which comprises the following steps; forming a continuous wet fibrous web, simultaneously bringing both surfaces of said relatively wet web into contact with rotating surfaces carrying pre-formed plastic and substantially dehydrated films in which the coating material is uniformly distributed and which are of uniform thickness, simultaneously transferring said films to opposite surfaces of said web and drying said coated web.

7. The herein described method of producing coated paper suitable for printing-.purposes, the steps which comprise forming a continuous fibrous web and continuously advancing the same, subjecting an aqueous coating mixture to mechanical working action whereby to substantially dehydrate it and to form a final film structure of uniform thickness, transferring the film to the advancing web and compressing the same thereon as it is transferred and continuously drying the thus advancing web with the film of coating material thus applied whereby to form coated paper suitable for printing purposes.

PETER J. MASSEY.

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