US2340127A - Process of slitting and coating - Google Patents

Description

Jan. 25, 1944.

I K-. R. KARLSON .PROCESS OF SLITTING AND COATING 2 Sheets-Sheet I Filed May 26; 1941 K. R. KARLSON r nocns s owsuwrme mn comma I I Jan. 25,1944,

Filed May 26) 1941 2 Sheets-Sheet 2 rarzmKa-zs pervious film completely diagrammed'in Fig. 2;

- surfaces. As such material .solvent so asto' leave lar thermoplastic material. The process is iully Patented Jan- 25, 1944 I w UNITED STATES PATENT oFrlc V raocass or 83 12:; mi ooa'rmo Karl n. Karlson, Montcialr,

. Union Bl &

N. 1., assignor to Paper Corporation, New York,

N. Y a corporation oi New Jersey Application May 26, 1941, Serial No. 395,305

It is an object oi this invention to provide a slitting process whereby combined coating and the coating material willnot onlyiorm an impervious film on the surface oi the web oi paper to which it is applied, but will also form an imsealing the edges of the slit strips.

' A further object of this invention is to provide a method of coating and slitting whereby one-entire side of the web is coated with an impervious film, the edges of the web are sealed with a similar film, and a similar film is applied to at least one margin of the reverse side of the web as 1 an integral continuation of the film on the fully coated side.

These and th in the following disclosure when tion with the annexed drawings,in which- Fig. 1 is a schematic diagram oi an apparatus ior carrying out one form of my process;

Fig. 2 is a schematic diagram in which there objects will be fully set forth is added to the disclosure of Fig. 1 supplementary steps for iorminga film over a part of the reverse side of the web;

Fig. 2a illustrates a 'detail of the arrangement Fig. 3 is a schematic diagram of another form of apparatus for carrying out my process in which the sequence oi steps is changed from that of Fig. 1; and

Fig. 4 is a schematic diagram oi still another form of apparatus for carrying out the same steps but in still another sequence.

Throughout this specification the term thermoplastic material" is used to'indicate a material which, under the action oi heat and pressure, will I any combination of act to seal together almost used herein, the term embraces dissolved in a suitable vehicle or such material, in the absence oi'a solvent, brought to a condition oi fiuidity under the inalone. when reference is made the thermoplastic material, it is intended to include not only the coolwing andsolidiflcation of a melted solid, in the absenceoi solvents, but also the driving oi! oi a in solid condition a simiworkable whether the coating material be in cluded within the zclaims. (cum-4) specifically stated otherwise both are to be interms just discussed.

Referring now to Fig. 1' there is a supply roll it oi paper I! which is to be coated and slit into narrow widths. The paper l2 coming from the supply roll Ill passes over a tension roll it and then over a coating roll it rolls in a, vat oi coating material and applies this material to the web I! as it passes over the coating roll it. It will usually be desirable to supply a doctor 22 to clean the applicator roll l8. i

There are available a great many mechanisms for applying a coating of material to a web oipaper and the precise iorm oi apparatus is largely immaterial in this process. It will be undertakenin connec-' I portant in this solution or as a-hot-melt, be mainthat when the several i take any special when the material is applied in solution. 1!, howstood, of course, that, iiv the coating material is applied in solution, probably agitating means will berequired to assure uniformity oi the solution in the vat 20, or, lithe coating be applied as a hot-melt, then, in addition to agitating means,' thermostatically controlled heating means must be provided in the vat 20, and similarly thermostatically controlled heating means should be provided ior the coating roll It and for the applicator roll it.

Fromthe coating roll it the web l2 passes between slitting rolls it, each oi-which is supplied with a cleaning doctor 28. As the web I! passes the slitter rolls 24 it is slit into a number oi narrow widths. A cleaning doctor 28 is also provided for the coating roll IS. The strips leaving the slitters 24 are drawn over a serves slightly to separate the strips. It is improcess that the coating, whether applied as a tained suiiiciently fluid so strips are spread the coating material may flow over each exposed edge to form an integral film over these edges. Since the entire process takes place at high speed, that is irom 800 to 1200 feet per minute, it will not usually be necessary to precautionto maintain fluidity ever, the material is supplied as a hot-melt, it may well be desirable to heat the slitters 2i and the spreader roll I, or even to place a hood over this portion of the apparatus and to supply heated air ior the purpose oi oi the coating. There is no general rule since the various types ofthermoplastic materials have widely varying characteristics and will oi course require specialized-treatment to maintain the 155 requisite fluidity inany particular case. Each.

it. An applicator roll spreader roll 30 which 7 maintaining fluidity however, will come within the basic principle that fluidity must bemaintained.

In some cases it may be desirable to apply to the coated web a smoothing doctor 32 either over the spreader roll 30 or at any rate immediately thereafter in order to insure the deposit of costing material upon the slit edges. I wish to emsigned to effect a coating of the edges. This can be done by wicks, rolls, brushes or sprays acting to supply coating material directly to the slit edges after separation of the strips, or by directing at such points a hot blast to increase fluidity of the coating material adjacent the edges, or by the application to or adjacent to the edges, and by any of the "foregoing means, of additional solvent for the purpose of increasing fluidity of the first applied coating material so as to insure a proper coverage of the raw edges.

From the spreader roll 30 the strips are given a long pass over table rolls 34 and in the course of this pass the coating material solidifies either by cooling, in the case of a hot-melt, or by evaporation of the solvent if the material has been applied in solution. The length of this pass will depend of course on the speed of the web, the quantity of coating material, and the characteristics of the material itself. The length of the pass can be reduced by accelerating the process of solidification, either by chilling, inthe case of a hot-melt, Or by heating and ventilating in the case of solvent evaporation. I have found, however, that in the case of a hot-melt, natural cooling is more desirable, since too rapid cooling may produce minute cracks in the coating and destroy its impervious character, or may tend, in the case of some materials, tomake the coating brittle. It may, indeed, be desirable, in using a hot-melt, to hood 3. portion at least of the cooling pass and provide the hood with warm air so as to slow down the rate of cooling. I

At the end of the solidification stage the strips pass between rolls 30 and are then separated alternately in the vertical plane and are wound up on spaced axes 38. It will be understood, 0! course, that there may be a number of coaxial rolls on each of the axes 30, but-the strips would be alternately brought either to the uppermost or the lowermost plane.

In Fig. 2 the initial coating, slitting and solidification are accomplished in Fig. 1. In Fig. 2 there is a supply roll 50, a

web 52, a tension roll 54, a coating roll 50, an ap-.

plicator roll 58, slitters 00, and a spreader roll 02.

- As the slit strips leave the spreader roll 02,'they go through a solidification stage and are" supported on table rolls 04. At the end of the pass is a second spreader roll 06, from which the strips pass immediately over a second coating roll 00. A series of applicator rolls I0, supplied with coat- I ing material from a vat l2, register each with one edge of each of the strips, as more particularly illustrated in Fig. 2a,. These narrow applicator rolls l0 serve to coat a narrow marginal path oi each of "the strips, and the rolls are so adjusted both as to width and position that they will be certain to merge the film which they apply with precisely as illustrated to be formed into bags and the bags will be used to form extremely impervious packages which may contain either liquids or evacuated solids.

In order to form a simple overlapped seam in the bag, and to have the seam equally as impervious as the web itself, it is necessary to assure an integral unbroken mass of thermoplastic material throughout the interior surface of the bag. It is therefore indispensable that the edges of the paper be sealed since otherwise the raw edge, being exposed to the interior of the bag, would be sutflciently porous to destroy a vacuum, or if the package be filled with a liquid, or even a greasy solid, the raw fibrous edge would act. as a wick and would feed the liquid or grease out of the package and into the-walls of the bag.

- A coating of a marginal strip on the reverse side of the web is desirable but not indispensable since the material could be applied in the course of manufacture of the bags rather than as a step in the original coating and slitting process. Depending, however, upon the type of bag machine and the speed at which operations are conducted,- it will be more or less desirable to supplement the coating and slitting with the additional marginal coating step. No matter how it is applied, however, the material must be present on the reverse side and must merge and integrally join the material coating the exposed edge of the web. since otherwise the material of the web would function, through porosity or capillarity, to destroy the extremely impervious character of the package.

In Fig. 3 the solidification pass and reeling oi the slit strips is identical with what is disclosed in Fig. 1 and discussed in connection therewith. The steps of slitting and coating, however, have been altered. In this figure I show a supply roll which bears against the spreader roll. The strips then are supported on table rolls 4 through a solidification stage, then go between rolls II. and

are separately wound up on spaced axes I It.

In Fig. 4, the solidification pass and the reeling up stages are identical with those of 1 and 3. In Fig. 4 I show a supply roll 200 from which is drawn a web 202. Web 202 between slitters 204 which cut it into a number of narrow strips. These strips then pass over a spreader roll 206 which slightly separatesthem,

andthe separated strips then passover a coating roll 208, against which bears an applicator roll 2l0 fed by asupply roll 2l2 which rolls'in a vat 2 ll of thermoplastic material. A cleaning doctor 209 is provided which bears against the coating roll 208. The separated strips are then drawn over a 'roil 2 and go through a solidification pass supported on table rolls 2| 0. between rolls They then pass 220 and are separately wound up the coated edges of the strips. The strips then go is on spaced axes '222.

It is to be noted in connection with Fig. 3 that the slitting operation is done before any coating material is applied to the web, and it is further to be noted in connection with Fig. 4 that both the slitting and the spreading are accomplished It will, of course, be understood that the arrangements shown in Figs. 1, 3 and 4 may also be used in connection withv the supplementary step illustrated in Fig. 2, and that the precise namm and arrangement of the apparatus is immaterial to the successful carrying out of the process. I

Throughout the following claims, the sequence in which the various steps occur is immaterial unless expressly set forth. A comparison of Figs. 1, 3 and 4 will show that the sequence of steps of slitting a web in strips, separating the strips, and coating the strips is immaterial, and while it is grammatically impossible in the claims to recite the steps except in some sequence, the mere recital of steps in any particular sequence is not intended as a limitation except'where, by the wording of the claims themselves, a particular sequence is specified.

So long as the application of thermoplastic to the paper occurs continuously, no regard need be had for the bag making process. The moment.

however, that discontinuous sections of material are applied to the paper, the operation of the bag machine becomes a controlling factor. There is clearly no mechanical limitation which would prevent the addition to one or both sides of the paper of predetermined'localizecl areas of thermoplasic which could be shaped and placed so as to cooperate in forming the bag bottom. When, however, the web reaches the bag machine, it would be necessary to compensate or otherwise adjust the passage of the web through the machine so as to synchronize the occurrence of the localized areas with the cutoff mechanism of the machine.

In most cases the .bags, as actually sold, will receive ornamental printing which may run to three or more colors, and the recurring printed designs must also be synchronized with the cutoff in the bag machine, and for some purposes it will also be desirable to apply groups of perforations which will assist in forming the bag bottom. The problem may be generalized by stating that either all localized operations, whether the application of thermoplastic, of ornamental printing, Q

or of perforations, must either be done on the bag machine itself by means rigidly synchronized with the cutoif, or they must be done in a single operation with rigid intersynchronization of the several means. The commercial necessities will always dictate the procedpre to be adopted. It is physically possible to add as further steps, to those illustrated herein, the operations of localized application of thermoplastic, of ornamental printing, and of perforating, but it is questionable whether the resultant machine might not be too costly for commercial operations.

What is claimed is:

1. A process of treating paper which comprises: continuously advancing a continuous web of paper; slitting said web into strips and applying to one entire side of said web a thin, superficial coating of thermoplastic material uniformly across the entire paper surface; thereafter separating said strips while maintaining said material in. a suiliciently fluid condition to permit the same to form a thin, superficial film over the slit edges of said strips as said edges are separated, and thereafter solidifying said coating while maintaining said strips separated.

2. A process for treating paper which comprises: continuously advancing a web of paper, applying to one entire side of said web a thin, superficial coating of thermoplastic material uniformly across the entire paper surface, slitting .said web into strips, thereafter separating said strips while maintaining said material in sufficiently fluid condition to permit the same to form a thin,- superficial film over the slit edges of said strips as said edges are separated, thereafter solidifying said coating while maintaining said strips separated, and thereafter applying to one margin of the opposite side of each of said strips a coating of thermoplastic material while regulating the application of such marginal coating so as to insure continuity of the film of coating from the fully coated side around the exposed edge and over the margin of the opposite side of said web.

KARL R; KARL-SON.

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