US2024248A - Paper treating means - Google Patents

Description

. 17,1935. H. R. RAFTON l PAPER T REATING MEANS Filed Nov. 1"; 1932 gmc/nto@ A/AeoLo P PAF TON PAPER TREAT ING MEANS AFiled Nov. 1, 1932 2 "sheets-shea 2 (c5/7g 4 amante/a #Aso/.023km Patented Dec. 17, 1935 UNITED STATES PAPER TREATING S Harold Robert Rafton, Andover, Mass., assignor to Raffold Process Corporation, a. corporation of Massachusetts Application November 1, 1932, Serial No.l 640,714

A3 Claims. (Cl. 91--55) My invention relates to means for treating a paper web.

The principal object of my invention is to provide means for treating a paper web with an agent dissolved or emulsified in a liquid.

An important object of my invention is to provide means for treating a paper web with an agent dissolved in or emulsied with an organic solvent and to provide means for recovering the solvent.

A further object of my invention is to provide means for applying sizing to a paper web by means of a solution of sizing agent in an organic solvent and recovering the solvent for reuse.

A further object of my invention is to provide means for sizing paper filled with alkaline ller by means of sizing agent dissolved in or emulsied with solvent and recovering said solvent.

Other objects and advantages of my invention will become apparent during the course of the following description.

In my copending application, Serial No. 487,- 377, filed October 8th, 1930, I have described a method for sizing paper filled with alkaline ller by the application of thermoplastic material in liquid association to a paper web containing alkaline ller. When this liquid association of the thermoplastic material comprises a solution Y of said material in an organic solvent, it becomes necessary, as explained in my copending application referred to, to evaporate the said solvent after application of the'solution to the paper web, and it is in the interest of economy to recover the same. When the solvent is miscible with water the solution may be applied either to the wet or to the substantially dry web, but where the solution is substantially immiscible y with water, it is preferable, as described in the said copending application, to apply the solution to thesubstantially dry web. t

As stated in my copending application, the solution of thermoplastic materialmay be applied to the web either.directly on thepaper ma-l chine oras a separate process subsequent thereto. In either case the solvent may be removed from the paper web either by the application of heater reduced pressure or both. While the evaporation of the solvent under reduced pressure is a satisfactory method, heaty ordinarily being supplied to the web in quantity atleast suicient to equal the latent heat o evaporation of the solvent, such method requires for its functioning an apparatus o considerable size, which may appropriately comprise a vacuum chamber, suitably reinforced structurally, in combinati@ 4impart treatment to the paper web other than with a system for maintaining vacuum such as a pump, and associated with solvent recovery mechanism. Not only is such an apparatus very expensive, but the power requirement thereof is necessarily substantial.

However, as 'indicated in my copending application, the solvent may be evaporated by heat without using reduced pressure, and of course under such conditions it is also desirable to recover the solvent. l It is an object of the present 10 invention to provide, suitable equipment for carrying out the process of applying thermoplastic material in solution in a solvent, or emulsied with a solvent, to a paper web containing alkaline ller andf-of evaporating said sol- 15 vent byy the means of heat alone without the use of vacuum apparatus, and of recovering said solvent. It will of course be understood that such equipment may be employed for sizing' paper webs other than those containing alkaline filler, and also for applying either Ato alkaline iilled paper webs or other paper webs, agents `Vdissolved in solvents, .or emulsii'led with solvents, such as organic solventsv which agents may be used to that of sizing, such treatment comprising for example the imparting to the paper of waterproofness, greaseproofness, electrical resistance," strength, pliability and the like. vIt also will be understoodthat such equipment may be employed for' applying to the paper web nonthermoplastic "agents, whether for sizing purposes or otherwise, when/,inlassociation with an organic solvent, such as in solution or emulsion. In this connection cross reference is hereby made to my copending application Serial No. 609,555, filed May 5, 1932.

The equipment disclosed herein has the advantage over vacuum equipment of being relatively more simple, of requiring less power, of

rbeing much less expensive, and of being veasier vtooperate and more economical to maintain.

Expressed in simple terms, my invention com prises the `combination of means for guiding a continuously advancing paper web,means for applying to'the web a solution or emulsion of an agent in a solvent, means for supplying the heat' required to evaporate said solvent substantially at atmospheric pressure, and recovery,` means for said solvent, thel system being maintained with a minimum and/or desired content of air. With the above referred to means may be combined means foil utilizing said solvent for the-solution of a further quantity of said agent to be eventually suppliedto thesolution applying means. 55

More particularly, one suitable illustrative .example of my invention comprises a casing which serves to `enclose the guiding, solution applying, and heating means. From this casing leads a duct in which may be suitably placed the solvent recovery means, which conveniently may comprise cold or chilled surfaces on which the solvent may be condensed, and in addition if ,desired other solvent recovery means, such as active absorbent material e. g, silica gel| or the like. Means connected to the duct is provided for leading therefrom the condensed solvent, which may be used for dissolving further quantities of the agent to be applied to the web, and then returned cyclically to the solution applying means. provided with means for creating a moderate eduction current in said duct, such means being suitably a fan, blower or the like. The object of this eduction current is to lead away from the casing the evolved vapors of the solvent, together with such quantities of air or other gas as may be associated therewith. It is considered an equivalent structure if the duct be connected to independent solvent recovery means, since in such case the wall or walls enclosing' the recovery means are in eiect a continuation of the duct.

It is desirable that the casing be made in such a manner as to be substantially air tight except at the points where the paper web enters and leaves. Thispermits the withdrawal of the solvent vapor by the fan with minimum dilution of the vapors with air, and `thus much smaller volumes 'are required to be handled by the fan than if free leakage of air were permitted. This is also of great advantage in that it enables a much simpler and easier recovery of the solvent to be eiected,`and also in the case where in- 'I'he duct is also and-these strips serve to effect reasonably airtigh seals for the rolls. Y If desired, similar sealing means may be provided for the ends of the rolls.

It will be noted that the web inlet and outlet means referred to permits a web to be passed through the casing Without bringing in or taking out with it substantial amounts of air or gaseous iiuids. However, it is a feature of my invention that it is not necessary to form absolutely airtight joints at, the inlet and outlet ends of the casing as it is not desired to maintain any sub-. Astantial degree of negative pressurev within the casing (which would tend to draw in air), the pressure in the casing being maintained at substantially atmospheric pressure or just sufiiciently l5 below such pressure to prevent any passage of gas or vapor from within the casing into the air of the room in which the casing is installed. Under such conditions, except for adventitious leaks which should be avoided, substantially the 2O only air introduced into the casing is that contained in the entering web itself, unless it be desired to admit extra air or other gas as indicated above. 1

The solution applying means may be of any 25 convenient form, one of which is shown in Figure 1 and comprises ay trough I5 for containing the solution I6, together with a guide roll I1 at the inlet end or' the trough for leading the web into the solution, a second guide roll I8 disposed in 30 the solution, and a pair of rolls I9 disposed at the exit side of the trough. The rolls I9 act as squeeze rolls, thus serving to remove the excess.

flammable solvents are used, the composition of the vapor air mixture in the casing can be controlled within safe limits. However, there may be' provided an inlet controlled by a suitable valve or gate to admit regulated amounts of air, which may be heated ifdeslred, or other diluent gas, such as steam for example.

In the drawings I have shown several embodiments of the invention. In this showing, Figure 1 is a diagrammatic view of one form of apparatus,

Figure 2 is afragmentary diagrammatic-.view showing a modified form of means for feeding a paper web from the casing,

Figure 3 is a similar view showing a modified form of solution applying means,

Figure 4 is a similar view of a further modified form of solution applying means,

Figure 5 kis a modied form of the apparatus wherein the condensing means is arranged in' the heater casing,

Figure 6 is a similar view showing the use of a single heating roll for an eduction duct arranged above the heating means, and,

Figure 7 is a similar view showing a modied form of the apparatus wherein a different form of heating means is employed.

Referring to Figure l, the numeral I0 designates a casing having openings at its ends in which are arranged pairs of rolls II and I2 respectively. The paper web I3 is fed into the casing between the rolls I I and passes from the outlet end of the casing between the rolls I2. One or both of the rolls of each pair, if desired, may be covered with resilient material. The outer surfaces of the rolls of both pair may contact with suitable sealing devices Such as strips of flexible material I4, which may be formed of felt or similar material,

solution applied to the web, and preferably being capable of regulation. In addition, it will be apparent that ther rolls I9 serve as guide rolls for the web. l

From the rolls I9, the web is led vover or exposed to means of any desired type for supplying heat, and in Figure 1 the heating means is illustrated as comprising rolls 20, 2l and 22. The number of heating rolls employed will depend largely upon the nature of the solvent, and the apparatus 'is not limited to any particular number or arrangement of heating rolls. With the arrangement illustrated in Figure 1, the `web passes upwardly over .the roll 20, downwardly around the roll 2 I, and thence upwardly around the roll 22, and after passing from the roll 22, the web may pass around a guide roll 23' preferably ar- 50 ranged in the plane of the line of contact between the rolls I2 to feed the paper web between such rolls. Y

The heat supplied by the heating means employed serves to evaporate the solvent from the web, and such heating means may be heated by any suitable meansvsuch as a hot liquid, steam, electricity or Athe like. The amount of heat required to be applied to these rolls depends upon the amount of heat required to evaporate the solvent at the speed at which the'machine is operated, and also depends upon whether it is desirable to heat the web above the point at whichthe solvent will be evaporated, such as if it be desired to flux the agent applied to the web and such i-luxing takes place at a ltemperature higher than that required for the mere evaporation of the solvent. For this purpose, one or more'of the heating rollsV may operate at a higher temperature than the others, if desired.

It will be noted that, in combination, the web inlet and outlet rolls, the rolls of the solution applying device, and the heating rolls may comprise the web guiding means, but it will be apdesirableto have the eduction means near the Cil bottom of the casing, while on the other hand,

the eduction duct may be placed higher if the vapor ofl the solvent isv of low specific gravity. In Figure l, the eduction duct is shown as being connected to the bottom of the casing adjacent the outlet end thereof and is indicated by the numeral 23. This duct communicates with the casing through a suitable opening 24 and suitable solvent recovery means is placed within the duct 23. In the present instance the recovery means is illustrated as comprising a cooling coil 25 through which passes a suitable cold fluid.

The size of the coil 25 and the. temperature of the uid passing therethrough are regulated so as to substantially completely condense the solvent. In certain cases, it is desirable to provide additional recovery means which may comprise a silica gel absorbing unit 25 communicating with the duct 23 near the bottomthereof, but such unit is not always necessary. A fan 21 is connected to the unit 26 to draw air therefrom and exhaust it to the atmosphere. Such fan, of course, will affect the pressure in the casing III and provides almoderate eduction current in the duct 23. Inasmuch as the solvent recovery system should be adjusted so as to recover substantially all of the solvent, the Vdischarge duct of the fan may be suitably vented to the open air.

Preferably directly beneath the coil 25 the duct 23 is provided with a draw-off conduit 28 which preferably leads through ,a liquid seal 29 to a container 30 which may provide intermediate storage means for the recovered solvent. It will be apparent that vapors condensed bythe coil 2.5 flow into the container 30 through the pipe 28. A valved draw-off pipe 3I is provided for the container 30 to provide for the removal of water from the bottom thereof. If the solvent used has a higher specific gravity than water this pipe is placed near the top of the side of container 30 instead.

A valved outlet` pipe leads from, the container 30 to a solution make-up tank 33 to deliver the condensed solvent thereto. A hopper 34 containing the desired treating agent may be arranged above the tank 33 and may have its outlet spout controlled by a suitable valve or gate 35. The opening of this gate permits the agent to flow downwardly in suitable quantities into the tank 33 through a normally closed inlet spout 35 in the top thereof. A Solution of suitable strength thus may be maintained inthe tank 33. As will be apparent, a solution of the appropriatey strength may be produced continuously instead of intermittently, if desired, by continuously feeding agent and solvent in proper proportions into tank 33, by means of suitable known devices.

Suitable means may be provided yfor feeding the solution in the tank 33 to a supply tank 31. As shown, a pump 38 has its inlet side connected to the bottom of the tank 33 through `a valved conduit 39, and a second conduit 49 is connected from the outlet side of the pump 38 to the top of the tank 31. An .overflow pipe 4I has its upper end arranged in the solution applying trough I5 and its lower end communicating with the tank 31 to prevent the accumulation of solution inthe,

trough I5 above a predetermined level, as will be apparent.

A valved conduit 42 communicates between the bottom of the tank 31 and a supply pump 43. The outlet side of the pump 43 is connected to the trough I5 by a supply conduit 44 and accordingly it will be apparent that a suitable supply of the solution I6 is maintained in the solution applying trough. Y 1

Several variations of the apparatus may be employed under certain conditions. For example, instead of but preferably in addition to, providing rolls as at the point of exit of the web from the casing, a narrow nozzle-like duct 45 may surround the outgoing web for some little distance from the tank, as shown in Figure 2. Such nozzle may communicate with the casing through suitable small ducts 45, and the object of such construction is to introduce a small amount of air into the casing, such air passing over the already dried web coming out of the casing-in order to remove by the counter-current action of the air any last trace of solvent which still may remain in or near the web. The small amount of air` thus introduced into the casing may be finally exhausted through the fan 21 into the open air, as previously indicated. A similar arrangement may be used at the point of inlet of the web if desired, or a mere slit in the casing may serve in certain cases as va substitute for the inlet and/or exit rolls. Likewise the apparatus is not limited to any particular type of' solution applying means, such as the immersion type previously described, but may be of any other suitable type for example such as that illustrated in Figure 3. In such modified type, a roll 41 may revolve while partially immersed in the solutionI 48, and contact with one side of the paper web. It will be apparent, of course. that applying rolls may contact with both sides of the web, if desired. It also will be apparent that the' solution applying means may be of the spray type shown in Figure 4 wherein an apertured pipe 49 is adapted to spray the solution against the paper web, as indicated at 50.

Another suitable and somewhat more compact arrangement of the apparatus is shown in fragmentary form in Figure 5. In this arrangement, the web passes around heat rolls 5I and thence around a guide roll 52 to be fed from the casing between rolls 53, similar to the rolls I2 previously described. Instead of the solvent recovery means y previously referred to, however, a cooling coil 54 may be placed directly within the casing itself and the condensed solvent passes from the bottom of the casing through a conduit 55 disposed beneathv the coil 54. A silica gel unit 56 also may be employed in connection with this form of apparatus,

transfer of air or V'solvent vapor in or.out of theV casing in which case the eduction fan and outlet may be dispensed with. However, it is diiiicult in most cases to maintain this exact equilibrium, and while I may operate my invention at pressure slightly superatmospheric, I do not prefer to. So in order to provide for occasional slight excess of t pressure developed within the casing,'it is desir- CII ' a fan be not connected therewith.

It will be understood that although in any of the several modified forms of my apparatus i1- lustrated there may be maintained a-slight negative pressure within the casing by means of the fan, for example, one disposed in the eduction duct from the casing, it is not intended that this negative pressure should be present in any substantial degree. yIn certain cases it may amount\` to from a fraction of an inch to an inch or thereabouts of water, or somewhat more if desired, and would not be such as substantially to .lower the boiling point of the solvent employed or as to require any substantial reinforcement of the casing against any inward pressure of the atmosphere. `As will be apparent, this is entirely different from a vacuum system in which a heavily reinforced structure must be employed with substantially air-tight seals, together with vacuum pumps and associated apparatus for exhausting the vacuum chamber.

4A simplified form of my invention is illustrated in Figure 6 and is adapted for use under certain conditions such as where only one heating roll is employed, and the solvent vapors are\of light specific gravity. In this form of the invention,

, immersed in the solution. The paper web passes 62, and thence around a heating roll 63 arranged in a vertically extending portion 64 of the casing. 'Ihe roll 63 may be arranged adjacent the outlet' opening of the casing, and the latter may be provided with a sealing strip 65 cooperating with the roll 63,` and similar in construction to the strips I4 previously described. A similar strip 66 cooperates witha guide roll 61 around which the paper web passes after leaving the heating roll 63. 'I'he upwardly extending portion 64 of the casing is provided with an eduction duct 68 with which is associated the vapor condensingl and collecting means previously described.

In the form of the invention illustrated in Figure 7, a casing 69 is employed having an eduction duct 10 similar tozthe duct 68 just described. The paperweb passes into and out of the casing be-v tween suitable pairs Vof rolls 1I vand 12, similar to the pairs of rolls I I and I2 previously described. In this form of apparatus the solution applying means ,maybe in the form of a spray pipe 13 apertured to spray the 'solution ,upon one side of the paper web as at 14, and itwill be apparent that both sides of the web may be treated if desired. `Instead-of the heating rolls described in connection with the other forms of apparatus, the apparatus shown in Figure '1 may be provided with a iiat electrically heated plate 15 connected to a suitable source of v.current through the wires 16. The web may pass over the heating plate in contact therewith, but preferably passes over the plateslightly spaced therefrom.

Another variation of the apparatus is to prol vide in the casing of any of the forms of the apparatus described a partition between the solution applying means and the heating means and provided with a slot or pair of rolls through which the web may pass. The object of such variation is to maintain the solution applying means in a relatively cool enclosure. A further extension 5 of the same idea is to'provide an independent casing for the heating and solvent recovery means, and to apply the solution -to the web outside this casing. The solution applying means then may be'suitably enclosed inan independent casing conveniently vconnected to the eduction duct of the main casing or the solution applying means may be conveniently used without requiring enclosure in a casing, or requiring at most only a hood to provide suitable ventilation, if the solu- @tion be kept cool so as to minimize evaporation.

In all of the casings described, suitable substantially air-tight manholes and/or hand holes (not shown) may be provided, as will be apparent.

The solvent recovery tank may be itted lwith a draw-oil conduit in order that any Water which may condense out with the solvent may be with.- drawn from the system, and such a conduit has been illustrated in Figure 1 in the form of the pipe 3|. This is especially useful if steam be introduced into the casing such as in the case of a wet web and/or inammable solvent being used, the use in the casing of an inert gas such as steam minimizing danger of ignition of the solvent vapor, and at the same time preventing large excess gas volumes in the system by its mutual condensation with the solvent. It also `will be apparent that any of the systems may be provided at one or more points with a safety or control device or devices for the regulation of the pressure within the system. I

In certain cases it may be desired to evaporate the solvent from the web with heating means comprising hot gas such as air, instead of, or in conjunction with, heated rolls. In such case heated air, for example,.may be admitted into the casing through a suitable induction duct and thus be contacted with the paper web to evaporate the solvent therein, whereupon the solvent laden air will pass out and be subjected to the l solvent recovery means. The air may be reheated and cyclicly returned to the casing if desired.

scription that my apparatus may be made a part of the paper machine proper, being situated suitably just after the driers and before the calenders, in the case where water immiscible solvent is used (the solution being thus applied to the substantially dry web), or it may be employed as a mechanism independent of the paper machine, treating the web as a separate process. Where water miscible solvent is used, of course, the'web U5 may be wet when treated and in this case more drying capacity, e. g. drying rolls, should be provided, in the casing, as well as more condensing capacity in the solvent recovery means. Also where water miscible solvent is used and water 7U contacts with it, appropriate means must be provided for removing such waterin whole or in part from the solvent before reintroducing it into the system to s erve to dissolve further agent.

Where in the'claims I speak of material dis- 75 solved in a volatile solvent, I mean this expression to include the case where material is emulsied i-n or with a volatile solvent; and where I speak of solution I mean to include the case where an emulsion exists, as well as the case Where a true solution exists. y

While I have described in detail certain illustrative examples of my' invention, it will be understood that I do not intend to be limited in any way by such examples, as my invention may be practiced with widely lvarying forms and constructural changes, all within the scope of my invention, as set out in the subjoined claims.

I claim: y

l. Apparatus of the character described comprising a casing having restricted communication with the atmosphere whereby the interior of the Vcasing remains substantially at atmospheric pressure, said casing having means for continuously feeding a paper web therethrough, means in said casing for applying to the web a solution of a material dissolved in a volatile solvent, heating means for the paper web after said solution has been applied thereto by said applying means, an eduction duct communicating with said casing, means for recovering solvent evaporated from the web, a conduit having its inlet arranged to receive gaseous Iluids which have passed said recovery means without having been recovered thereby, said conduit having its outlet end connected to the atmosphere, means operative for producing an eduction current through said c'onduit, a recovery container connected to said duct to receive recovered solvent therefrom, a solution container connected with the recovery container and having means for supplying additional material thereto, and means for transferring solution from said solution container to said'solution applying means.

2. Apparatus of the character described comprising a casinghaving restricted communication with the atmosphere wherebythe interior of the casing remains substantially at atmospheric pressure, said casing having means for continuously feeding a paper web therethrough, means in said casing for applying to the web a, solution of a material dissolved in a volatile solvent, heating connected with the recovery container .and having means for supplying additional material thereto, a supply container, means for trans- 15 ferring solution from said solution container to said supply container, and means for transferring solution from said supply container to said solution applying means.

3. Apparatus of the character described com- 20 prising a casing having restricted communication with the atmosphere whereby the interior of the 'casing remains substantially at atmospheric pressure, said casing having means for` continuously feeding a. .paperweb therethrough, 25 means in said casing for applying to the web a solution of a material dissolved in a volatile'solvent, heating means for the paper web after said solution has been applied thereto by said applying means, an eduction duct communicating with 30 said casing, means for recovering solvent evaporated from the web, a conduit having its inlet arranged to receive gaseous iluids which have passed said recovery means without having been recovered thereby, said conduit having its outlet 86 end connected to the atmosphere, means opera- V tive for producing aneduction current through said conduit, a body of absorbent material arranged in said conduit, a recovery container connected to said duct to receive recovered solvent 40 therefrom, a solution container connected with the recovery container and having means for supplying additional material thereto, and' means for transferring solution from said solution .container to said solution applying means.

, HAROLD ROBERT RAF'ION.

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