US2130241A - Method for coating paper - Google Patents

Description

p l938- J. D. MacLAURIN 2,130,241

I I METHOD FOR COATING PAPER Filed June 18, 1934 2 Sheets-Sheet 1 I a w Sept. 13, 1938. J. DVM LAURIN 2,130,241

METHOD FOR COATING PAPER Y Filed June 18, 1934 i 2 Sheets-Sheet 2 avzes $12100! a are)? Patented Sept. 13, 1938 UNITED STATES METHOD FOR COATING PAPER;

James D. MacLaurln,

East Orange, N. J., as-

slgnor to Seaman Paper Company, Chicago, Ill., a corporation of Illinois Application June 18, 1934, Serial No. 731,028

- 1 Claim.

This invention relates to improvements in a method and means for coating paper to render the same suitable for printing purposes, and refers specifically to a method and means for smoothing and uniformly compacting a mobile coating material or materials upon a paper web which has been previously applied to said web in a rough or uneven state.

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

In the drawings, Fig. 1 is a diagrammatic side elevational view of suitable apparatus for carrying out my invention.

Fig. 2 is a diagrammatic plan view of the apparatus of Fig. 1.

Fig. 3 is a diagrammatic side elevational view of the air knife used in spreading and smoothing the coating material or color.

Fig. 4 is a diagrammatic side elevational view of the coating material or color application means.

Referring in detail to the drawings, I indicates a platform or table supported by uprights 2. A

roll 3 of flexible material such as paper or the like may be mounted upon supports 4 and a web 5 may be led therefrom over the upper surface of platform I. It is to be understood that web 5 is intended to represent any type of flexible web and platform I and the operations performed upon said platform, to be hereinafter described, may be utilized in conjunction with a paper mak-- ing machine, in which case web 5 will comprise the newly formed web passing from the paper machine before, after or during passage through the driers.

Web 5 may be carried over platform I in a continuous manner and in so traveling, passes beneath color spray pipe 6. Pipe 6 is provided with a plurality of spaced apertures I from which coating material or color is discharged.

A pump 8 may be mounted upon foundation 9 beneath platform I and may be driven by motor In mounted upon foundation I I. Pipe I2 may be connected to the intake side of pump 8, said pipe being connected at its opposite end to a source of supply of color (not shown). The discharge of pump 8 may be connected to pipe I3 which may be joined by elbow I4 to pipe I5. A shut-off valve I6 and pressure control valve I] may be interposed in pipe I5. The end of pipe I5 may be joined by means of elbow I8 to pipe I9 which may be connected with T 20. One arm of T 20 may be connected to pipe 2| and a pressure gauge 22 may be connected in said latter pipe for measuring the. color pressure. A shut-off valve 23 may be interposed in pipe 2| and may be adapted to control the flow of color in said pipe. The opposite end of pipe 2| may be joined by means of elbow 24 to pipe 25 which may, in turn, connect into one end of spray pipe 6. By this arrangement, color in desired quantities and at suitable pressure may be delivered to pipe 6. The opposite end of spray pipe 6 may be connected by means of pipes 26, 21 and 28 to pipe I2 and is adapted to serve as a means for returning excess color from spray pipe 6 to the intake of pump 8.

An air pipe 29 may be positioned above color spray pipe 6 andmay carry a series of spaced 1 nozzles 30 which may register with apertures I in pipe 6. Pipe 29 is adapted to carry air or other fluid under pressure and nozzles 30 may be so positioned as to cause the streams of air issuing from said nozzles to impinge upon the sprays of color issuing from apertures I. In this manner the color is sprayed upon the upper surface of the web 5 in the form of a finely divided mist, the air streams acting to break up the streams of color into finely divided particles and spreading the same over the entire surface of the web in a manner more or less uniform and regular.

The air or other fluid adapted to be discharged from the pipe 29. may be passed to the system from a source of supply (not shown) through pipe 31, the air or fluid being under superatmospheric pressure. Pipe 3| may be connected by means of T coupling 32 to pipe 33 which in turn may be.connected into a conventional pressure reducer 34 wherein the pressure may be reduced before application, said pressure depending upon various factors including the web speed, color pressure, characteristics of the color and thickness of coating desired. After passing through reducer 34 the air orfluid is passed through pipe 35 which is joined to pipe 36 by means of T 31. Pipe 36 is in turn connected by means of elbow 38 to the pipe 39 which connects into pipe 29, pipe 36 having interconnected therein a control valve 40.

The pressure of the fluid discharged from pipe 29 varies in accordance with the coatings used and the amount of coating material to be applied to the web. I preferably control the coating applied so that all of said coating material remains upon the web and little or none is blown off as will be hereinafter described. When usingbcoating of relatively light consistency, the fluid pressure may be reduced and conversely if the coating material is heavy the fluid pressure is insprayed color and the web is more or less loose,.

the color being susceptible of being readily lifted from the web. Consequently, the function of the air knife is to smooth and evenly spread the color upon the web and compact or incorporate the color into the surface pores of the web so.

that a smooth surface capable of receiving print may be obtained.

The air knife may be constructed in many forms, but for purposes of illustration and description, the air knife will be exemplified by the following construction. The air knife may comprise a cylinder 42 being closed at both ends by caps 43. An elongated slit 44 may be provided in cylinder 42 which may extend throughout a substantial portion of the length of the cylinder. The slit 44 may be defined by flanges 45, creating what may be referred to as a narrow elongated nozzle.

In operation, air or other desired fluid under pressure may be introduced into each end of the cylinder 42 through openings 45 provided in caps 43. The fluid thus introduced will be described through slit 44 and by means of flanges 45 will be directed in the form of an elongated wall of fluid. Flanges 45 may be aimed or directed at the surface of web passing therebeneath, the wall of fluid impinging upon the color upon said web at right angles as shown or at any other desired angle.

Air or fluid under pressure for the air knife 4| may be derived from any desired source of fluid pressure, or, as shown, the fluid may be derived from the same source that supplied pipe 29. In this latter case, a pipe 41 may connect at one end into T 32, the opposite end of said pipe being joined to pipe 48 by means ofelbow 49. Pipe 48, in turn, may be connected to pipe 5|) by means of elbow 5| and a control valve 52 may be interposed in said latter pipe. The end of pipe 50 may be joined by elbow 53 to nipple 54 to the Y-connection 55, each arm of which latter may be connected to flexible conduit 55 which, in turn, connects into openings 46 in caps 43.

It can readily be seen that the fluid pressure applied to air knife 4| may be the same as that at the source to which pipe II is connected, or the same may be reduced by valve 52. If desired, the fluid may be derived from an independent source of pressure. In addition, it is desirable that the pressure of the fluid discharged from slit 44 be uniform throughout thelength of the slit and therefore the volume of cylinder 42 may be relatively great with respect to the area of slit 44.

As has beenv hereinbefore described, when the color is initially applied to web,5 it is applied uniformly on the surface of the web but if permitted to dry in this conditon the surface would not be smooth or even enough for printing or like purposes. Consequently, while the color is still in a mobile state upon the web surface, the fllm of color is subject to the impingement of the wall of air or other fluid discharged from slit 44 at high velocity. The fluid thus discharged smooths the color film and compacts the color upon the web and forces the solid particles of the color into the pores of the web. In addition, a considerable portion of the moisture in the coating or color is evaporated facilitating the drying of the coating. The rapid drying thus obtained permits paper to be coated in conjunction with the fastest running paper making machines, as the coated surface would be sufficiently dry to come in contact with felts or hot driers (not shown) without sticking to either, or damaging the surface of the coating in such contact. In this connection, if desired, the fluid discharged from the air knife may be preheated by passing the same overelectric heating coils (not shown).

In view of the fact that the air or other fluid discharged from the air knife 4| is discharged at relatively high velocity, splashing mayoccur when the wall of fluid impacts with the film upon the web depending upon the degree of mobility of the fllm upon the web. Hence, in order to prevent undue splashing and spatterlng I provide a continuously rotating drum 5'! which is adapted to catch the drops of color splashed from the web. Drum 51 may be mounted upon shaft 58 supported by standards 59 and said shaft may be rotated in the direction shown by the arrow by pulley 60 which may be driven by belt 6|.

A scraper 52 may bear upon the surface of drum 51 and may collect all of the coating material splashed upon the drum. A vacuum pipe 83 having an elongated nozzle 64 may be positioned adjacent scraper 62 and may suck up and remove the coating material accumulated. Pipe 63 may be connected to any suitable source of vacuum (not shown).

The surface of drum 51 may be constructed of brass or copper and is preferably highly polished or, if desired, it may be covered with rubber sheeting. If desired, the vacuum pipe 53 may be eliminated, in which event, the coating material accumulated by scraper 52 may be run off to a scupper (not shown) and from there back to the color supply, thus saving all loss of color as well as preventing dirt and excess color accumulating on the machine.

If desired, other means may be used for catching the splashed color, for instance, a continuously traveling blanket may be disposed adjacent air knife 4| in place of drum 51 and vacuum means similar to pipe 53 may be used to remove the color collected by said blanket in the same manner that pipe 53 collects the color from drum 51.

Web 5 after passing beneath air knife 4|, if desired, may be dried, the resulting sheet even with one application of'coatlng being suitable for certain types of printing. However, said web before described and the parts thereof will be designated by primed numerals referring to corresponding parts of the flrst unit.

Pipe 5 may be connected to the color supply' system by means of pipe 25' which may be joined to pipe 2| by means of elbow 24'. A valve 23' vmay be interposed in pipe 2| and may serve to control the passage of color through said pipe.

The opposite end of pipe 5 may be connected by means of pipe 26' to the color return pipe 21, Pipe 29' may be connected by means of pipe 39', elbow 38' to pipe 36' which latter connects into T 31. A valve 40' may be interposed in pipe 36' and controls the passage of air or other fluid to pipe 29'. The ends of air knife 4| may be connected by means of the flexible conduits 56' to the Y-connection 55' which, in turn, is connected by nipple 54 to pipe 50, a valve 52' being interposed in said nipple whereby air knife 4| may be controlled independently of air knife 4|.

As a feature of my invention, the weight of coating applied to the paper can be closely con-' trolled by varying the web speed, the color pressure, the velocity of the fluid issuing from the air knife, or the consistency or fluidity of the color. Moreover, it is contemplated that substantially all of the color initially applied to the web will remain thereon and will not be removed or blown off by the air knife.

In the case of relatively high web speeds, high fluid velocity from the air knife, high color pressure without correspondingly increased web speed, or variable fluid pressure at the air knife, the color may tend to accumulate upon local portions of the web, usually in front of the air knife. To prevent this non-uniform local accumulation, a vacuum pipe 12 having openings (not shown) facing the web, may be positioned adjacent and transverse with respect to the web immediately in front of the air knife. This vacuum pipe tends to suck up and remove excess color which may accumulate in front of the air knife and consequently a uniform coating is insured. The vacuum pipe 12 may be positioned a distance above the passing web such as to normally not interfere with the color upon the web. However, when an excess of color is built up in front of the air knife, this color must be disposed of and in order to prevent the same being forced oi the web at the sides, the vacuum pipe 12 is provided.

It is to be understood that the coating material may be initially applied to the web in any desired manner, such as, by means of rolls, brushes, stationary or rotating sprays, or by dipping the web in a bath of coating material. In addition, one or both surfaces of the web may be coated and as many coating units as desired may be used in series.

If desired, the first coating unit may apply a relatively cheap coating substance, such as china clay, for instance, while the second coating unit may apply a more expensive coating such as blanc flxe, for instance. In this manner a fine finished paper may be produced at relatively low cost. In most coating systems heretofore used the two color materials are mixed and put on at one time on the coating machine, a larger proportion of expensive coating, say about 75% to 25% of cheap coating is necessary, while, on the other hand, in my process the body of the coated paper'is built up and the pores thereof are filled with a cheap coating and the flnal coating is of a relatively small proportion of expensive material. By this method bulk is gained, a very essential factor in paper coating.

It is to be understood, of course, if two different type color materials are used, a separate pump will be provided for each coating unit. In addition, as many of the same or different coatings may be applied as desired, with corresponding obvious changes in equipment.

My process of coatingis particularly adaptable for use with a paper making machine inasmuch as eflicient coating may be obtained at relatively high web speeds corresponding to those of the usual paper making machines. Moreover, the coating operation may take place while the web is still relatively wet and yet a smooth, uniform coating will be obtained which will not be lifted from the web when the same'is calendered.

If desired, the web may be coated while traveling in a vertical or inclined direction, in which case, however, an excess of coating material is initially deposited since the air knife will blow some of the mobile coating material from the surface of the web.

In view of the fact that the coating as applied by my process sets relatively quickly, the opposite side of the web may be coated in the manner described, the coating of both faces of the web being carried out as a continuous operation without rewinding the web and passing it through the coater a second time for the purpose of coating the opposite side.

By the term compacting as used in the specification and claim, is meant that action of the fluid or air under pressure travelling at high velocity which forces or pounds the coating material into the pores and irregularities characteristic of the surface of paper, and also the action which densities the coating material upon the surface of the paper.

I claim as my invention:

A method of coating paper for printing pur-,

thereon.

JAMES D. MACLAURIN.

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