US1950351A - Paper manufacture - Google Patents

Description

A March 6, 1934. J. DA. CLARK ET AL 1,950,351

PAPER MANUFACTURE Filed Aug. '7. 1931 2 Sheets-Sheet 1 March 6, 1934. J. DA. CLARK El AL PAPER MANUFACTURE Filed Aug. 7. 1931 2 Sheets-Sheet 2 gwwntw )a/rru/J 0M 9* 3517 M W I Patented Mar. 6, 1934 UNITED STATES PAPER MANUFACTURE James dA. Clark and John E. Graves, Chillioothe, Ohio, assignors to The Mead Corporation, Dayton, Ohio, a corporation of Ohio Application August I, 1931, SerialNo. 555,757

.20 Claim.

such a method in the formation of a paper sheet which produces paper free from. two-sidedness". Still another object is to provide as a superior product a paper formed with controlled body and surface characteristics, of adequate strength.

Another object of the invention is to provide 16 apparatus for carrying out this method and producing such a product, which is simple in con-- structicn and efi'ective in operation.

Other objects and advantages of the invention will be apparent from the description thereof set out below and from the accompanying drawings and from the claims.

Reference is made to a patent of William Edison Bair, Jr., No. 1,875,208, issued August 30, 1932, upon an application filed March 9, 1931, the invention hereof having to do with the practicing of the invention of the said application of Bair.

In the drawings, in which like characters of reference designate like parts throughout- Fig. 1 is a view, largely diagrammatic, of a Fourdrinier machine having the invention hereof embodied therein;

Fig. 2 is an enlarged view of a part of the mechanism shown in Fig. 1;

Fig. 3 is a view of a modified form of slotted D 1 Figs. 4 and 5 show other forms of slotted pipes; and

Fig. 6 shows a modified arrangement for feedmg the filler suspension to the slotted pipe.

As is well known in the manufacture of paper it is the general practice to bring the paper forming stock onto a forming wire,such as the traveling wire of a Fourdrinier machine-, through which the water may pass leaving a web or sheet of matted fibers upon the wire. The stock constituency varies according to the operating circumstances and the end product desired, and comprises pulp made from the properly separated fibers of wood, or the like suspended in general practice, particularly where paper of a better grade is to be made,-such for example as is used for book or magazine printing--, to admix with the fibrous suspension a considerable proportion of finely divided clay or other filler,

water, with admixed filler, size, etc. It is a very size or other constituents; the materials and the proportions thereof used varying somewhat according to the character of sheet desired. While the stock is on the forming wire some of the water escapes through the wire, thefibers re- 00 maining to form the web or sheet of paper which is subsequently removed from the wire and subjected to additional treatment, such as pressing, drying, calendering, coating, and the like.

Withparticuiar reference to a Fourdrinier maas chine, which type is illustrated in the drawings for purposes of description, as the stock is flowed onto the wire there is quite a rush of water through the wire during the first few feet of travel of the stock upon the wire, and some of the finely divided filler and other finely divided constituents, and some of the finer fibers, tend to fiow away with the water through the forming wire. A large part of so much of the water of the stock as ultimately escapes through the forming wire before the formed web is removed therefrom, escapes before the suction boxes are reached, partly under the action of gravity and partly due to the action of the table rolls. The remainder of the water which is removed before 39 the forming web is taken from the wire is removed during the remaining distance of travel of the wire, particularly while it is passing over the suction boxes and while it ispassing over,a suction couch roll, if such is used. As the stock flows 5:; onto the wire the greater portion of the fibers are stopped by the wire and matted thereon forming a filtering matv or web through which the remainder of the water passes or is drawn to escape through the wire side. The table rolls as they to revolve carry around a film of the escaping water which tends to further wash out filler and other finer materials. Also at the suction boxes the suction tends to withdraw some of the filler, etc. with the removed water; and the same thing is 5 true at the suction couch roll. A paper sheet as heretofore so formed ordinarily has different surface characteristics on its opposite sides. The wire side difiers from the opposite or upper side both in texture and appearance; this condition of different surface characteristics being lmown in the industry as two-sidedness. In the formation of the sheet, with all of the water being drawn downwardly or through the sheet in one direction to escape through the wire, there results a nonhomogeneous distribution of the filler, and of the fiber also, within the sheet. As a result the fibers of the upper side are generally finer than those on the wire side giving different textures and appearances. to the opposite sides. Also the relative n I quantity of retained filler, etc. decreases from the top side to the wire side, which may have substantially no retained filler. This lack of homogeneity, and the exaggerating of it which attends in progressing degree upon the use of increased quantities of filler, is'universally recognized in the become too marked the sheet has no marketability and utility,-or, at least, its marketability and commercial value are seriously decreased, even if not destroyed. This is especially true with book paper, such as is used for magazines and the like.

'It has heretofore been ordinarily considered commercially impracticable to provide as much as 25% of filler on the dry weight of the fiber, in the finished sheet, and still secure paper suitably usable on the score of two-sidedness. Even with 20% of filler it has been very difficult to maintain .the wire side and the opposite side of sufficiently similar surface characteristics. However, from a practical point of view additional quantities of filler are very desirable, for it may be generally said that the printing qualities of a sheet of paper improve as the quantity of filler carried at the surface increases. Also, as the filler is probably the cheapest ingredient going into the stock, from a commercial point of view it is desirable to minimize the amount of pulp,-using so much fibrous material as is necessary for giving sufficient strength to the desired paper web, with added inclusion of filler to add body, opacity and printing'quality. The present invention permits of forming a sheet of paper under such conditions as to produce new surface characteristics with the wire side approximately the top side characteristics. This permits of forming a sheet having a quantity of filler equal to or even greatly increased over those quantities heretofore considered practicable, but with the sheet still quite free from the objectionable two-sidedness heretofore experienced. I

For purposes of description, and as setting out a form of mechanism which will operate in a very satisfactory manner for the carrying on of the method of this invention and the producing of the new paper product, a conventional form of Fourdrinier paper making machine is illustrated in the drawings, largely in diagrammatic form. In the drawings the numeral. 10 designates generally the frame of the wire section of the paper making machine, which frame carries the usual ,forming wirell supported by a breast roll 13, .and a couch roll 14 preferably of the suction couch type. Any suitable stock supplying inlet or means may be utilized, such means being shown diagrammatically and designated by the numeral 15. The numeral 16 designates the dandy roll just beyond which are located the suction boxes 17. Located between the suction couch roll 14 and the suction boxes 17 is the wire guide roll 20.

In accordance with the present invention additional forming material is applied to the wire side of the paper, after it has arrived at a sufficiently definite stage of formation. When filler suspension is applied under such conditions of dryness of the web that the liquid of the forming material suspension is readily absorbed by the wire side of the sheet it will carry the filler,

etc. into the interstices,-into the body of the sheet-, where it will be deposited and retained, some being also retained in and on the fibers at.

the slotted pipe 25.

the surface of the web. In the type of machine shown in the drawings this definite or initial stage of formation is ordinarilyreached during the passage of the forming sheet or web over the suction boxes, and the condition is indicated by the web losing the liquid appearance which it has up to that stage. When the forming paper web moves up to theregular suction box zone it gives the appearance of a pool or sheet of water suspension, but as the wire moves along the watery sheen or glitter disappears as more water is removed, until the sheet as it assumes its initial definite form has the appearance of a damp or moderately wet sheet of paper. This change usually occurs as the web passes over the suction box zone, but whatever the precise moment of its occurrence it is an easily recognized change. In actual commercial use of the invention it was found that as the initially formed sheet moved away from the last suction box it contained from 14 to 19% of solids-or 81 to 86% of, water. At this stage the sheet, as stated, is sufiiciently definite in form and has sufficient water absorption capacity to permit of practicing the present inventlon. Actual commercial practices also show that the above described change in the sheet probably takes place when suilicient water has been removed to leave approximately 90% of water and 10% of solids in the forming web.

When the invention is practiced with the apparatus shown a slotted pipe 25 is positioned beyond the regular suction box zone so that added forming material may pass up through the wire onto the wire side of the web, as a result of which additional filler content will be embodied into the web in a proportion from the surface inwardly. The depth to which the filler penetrates and its distribution may of course vary somewhat; but it penetrates in decreasing quantity to a considerable distance and without abrupt change or line of cleavage, as would be the case with a layer of coating material applied merely to the sheet surface. By properly proportioning the constituents of the additive material, as to filler, etc. the surface characteristics may be caused to more or less closely approach the characteristics of the other side of the web, as to actual texture, susceptibility to printing, apparent surface characteristics, etc. In addition to deeply penetrating the sheet, the filler is also deposited and held on the surface fibers so as to whiten the wire side and give that side the same appearance as the other side. The effect in this respect is as if the wire, side had been whitewashed to bring it up to the same appearance of whiteness as the other side. In actual commercial operations the appearance of the wire side of paper formed according to this invention so closely approaches in characteristics the upper side that there is no ,evidence of objectionable two-sidedness.

Causing the filler suspension to pass up through the wire and onto the wire side of the web may result in somewhat weakening the finished sheet, but by the addition of suitable amounts of size or bonding agent, this tendency to weakening of the web is avoided and the finished sheet will have as great strength as if it had been formed in the heretofore usual way.

As shown in the drawings a constant head box 30 is positioned to supply the filler suspension to This constant head box is provided with a separating wall 31, dividing the box into two compartments, with the wall 31 serving as a constant level weir. The filler suspension is introduced into the head box, and to one side of the weir 31 through the pipe 32, and into the compartment 33, from which a pipe 34 leads to the slotted pipe 25. The filler suspension is supplied somewhat in excess of that required the excess overflowing the weir 31 into .the compartment 35, and discharging through the pipe 36 to suitable container weirs it may be recirculated. A pump 37, of suitable character, may be positioned within the pipe 32 causing feeding of the filler suspension to the head box. By means of this construction the level of the suspension in the compartment 33 is maintained constant and the material in the pipe 25 is thus fed through the slot 40, under constant head. This head can be proportioned according to the operating conditions, but in actual practice upon a machine operating about three hundred and fifty feet a minute, in the making of book paper, a head of from six to twelve inches of water has been found satisfactory. The slot 40, in the pipe 25, is of uniform width and extends across the width of the forming wire, and under constant head a substantially uniform application of the suspension to the forming web is secured. Very satisfactory results have been obtained using a slot approximately inch wide.

As shown in Fig. 2 of the drawings the slot is positioned to one side of a vertical plane passing through the axis of the pipe, and on the breast roll side of such plane, so that the slot opens against the direction of the oncoming wire. With the arrangement as shown, and the pipe so positioned as to slightly raise the wire from its normal path of travel, and with the wire completely overlying the entire width of the slot, the suspension material may be fed up through the wire, under suitable heads such as those indicated, so that there is no overflow, all of the filler suspension going onto the wire, and through the wire onto the web.

As the wire passes over the slot 40 it picks up the suspension material which is thus brought into contact through the wire with the wire side of the web and is incorporated therein. The paper at this point having lost a considerable portion of the original water content, as stated above, is absorbent and readily receives the water and entrained suspended material so that a firm and homogeneous mixture and bonding of the new material into the forming sheet, in an amount decreasing inwardly, is secured. As stated above, the web after it leaves the regular suction box zone, and thus as it moves up to the slotted pipe 25, contains from 14 to 19% solids and 86 to 81% water. This particular moisture content is not thought essential, but very satisfactory results are secured with this ratio.

Positioned beyond the slotted pipe is a vacuum or suction box 45, which may be of usual construction, and which serves to remove from the paper web, as it passes over the vacuum box 45; some of the water absorbed by the web as it passes over the slotted pipe. This vacuum box 45 should preferably be provided with slots, which are so arranged as to present an uninterrupted opening all the way across the web, the suction exerted being thus uniformly exerted upon the wetted sheet, to cause a uniform withdrawal of water, and filler or suspension material, therefrom. Very satisfactory results are secured when the vacuum in this box 45 is maintained above 12 inches of mercury, but this is not essential. This uniform suction upon the sheet is advantageous and tends to prevent an irregular appearance to the finished sheet, which otherwise sometimes occurs where the suction after the added suspension material is applied, is not uniformly distributed. The suction pump connected with suction box 45 is preferably arranged so that it discharges the withdrawn liquid into the mixing box in Fig. 6 into which is fed at the same. time a proportionate amount of new filler and other desired ingredients to maintain the proportions of filler size and water which are desired to be supplied to the slotted pipe. Preferably the makeup materials are added in concentrated form, to reduce the amount of water which will be withdrawn at the suction box, and a quite concentrated form may be secured by boiling together a carbonate filler, such as referred to herein, and

starch. Also the suction box is positioned adja cent the slotted pipe.

After passing the suction box 45 the web passes over the couch roll 14,. which may be of the usual suction couch character, and is then passed onto the felt 50, which passes it through the several sets of presses, of which one set is shown and designated by the numeral 51.

through the several sets of presses in the usual Q manner the paper will then be passed on through the other parts of the machine where it can receive the usual, or suitable modified, treatment as may be needed to produce the desired final product.

As a usual characteristic of paper machine Wires slight ridges or waves run lengthwise of the wire. In order to make suitable contact between the wire and slotted pipe, all the way across the slot, the pipe has to be raised sufiiciently hard against the wire to cause this contact. In the form of slotted pipe or box shown in Fig. 3 the securing of this condition is facilitated by providing the slot along its edges with raised ribs or beads 60. In the form of box shown this rib is formed by attaching to the surface of the box in a suitable way, for example by brazing, half round brass strips. The form of circular slotted pipe shown in Fig. 4 is also provided with similar beads or ribs 60' which in each case may be plated with suitable resisting metal such as chromium. As desired the rib may be dispensed with, and the top wall of the box or slotted pipe inclined upwardly, as shown in Fig. 5, in which event suitably close contact of the wire with the edges of the slot will be secured.

In Fig. 6 is shown a somewhat modified construction in which the slotted pipe 25' is connected with the head box 30 by means of a plurality of pipes, instead of by one larger pipe as shown in Fig. 1. If especially accurate control of the feeding of the filler suspension to the slotted pipe, with correspondingly acuratefeeding of the suspension through the slot, is desired, the additional pipes 70, 71 and '72 may be used which lead from the compartment 33 of the head box, each of these pipes being provided with a control valve 75 by means of which the supply of filler suspension to the slotted pipe or box 25' may be secured. By a proper regulation of these valves the desired feeding of the filler suspension through the slot of the pipe, to secure the desired surface characteristics, may be readily effected. In the form of construction shown in Fig. 6 the overflow pipe 36' discharges into a mixing tank 80, having a suitable mixer, shown as a rotary shaft 81 with the mixing vanes thereon, whereby the filler suspension may be kept agitated and of uniform consistency. The supply pipe 32', with the pump 3'7 therein opens into this mixing tank. Circulation of the After passing 1 the proper rate is thus secured, a suitable valve 82 being provided to regulate the rate of supply of the filler suspension to the compartment 33. Additional make up material, to replenish the circulating supply of filler suspension, added to the traveling paper web, may be added in any desired way, either in patches, or from a source of continuous supply.

In the forming of paper sheets the stock originally supplied must contain a considerably greater quantity of filler, etc., than will appear in the ultimate product. In actual operations it has been found that to secure a finished sheet having 25% filler, about of filler, on the fiber content, should be added to the stock. But without the practicing of this invention such proportion of filler in the finished product would give evident and marked two-sidedness. In the practicing of this invention the percentage of filler contained in the stock has been increased to about of which about 27% remains in the finished sheet. Satisfactory results, with substantial elimination of two-sidedness, has been secured where the material within the trough 30 consists of a suspension of a carbonate, or other similarly acting filler in water, containing 22 pounds of carbonate filler and 3 /2 pounds of size, such as boiled starch, in 40 gallons of water. With such suspension the web will receive and retain of the additive material. an amount of filler which represents from 1 to 2% of the total weight of the finished sheet. That is, with a sheet being formed from the stock above specified which would give approximately 27% of filler in the finished sheet, by adding the suspension material as described an additional 1 to 2% of filler will be included with the elimination of two-sidedness. It has been found that the amount of suspension material withdrawn at the suction box varies with variations in suction and inthe effective area through which the motion is effective. By controlling the concentration of solids in the suspension such variable conditions may be compensated for to producepaper of uniform or desired characteristics. In operation satisfactory results have. been obtained with a suspension of 1 pounds of solid per gallon of water, with a substantial increased opening and suction. The resulting sheet will be satisfactorily improved as to'its two-sidedness, even if the size is omitted, but the strength of the sheet and the bonding of the added filler to the sheet will be materially improved if the size is added. It has been found in actual operation in the manufacture of high grade book paper, utilizing the addition of filler suspension to the forming web in the manner disclosed in this application, and also in the copending application of William Edison Bair, Jr. above referred to, that the final sheet will suffer a decrease in strength of approximately 10% if the size is omitted and that the surface particles of filler will not be as well bonded to the sheet; but by the addition of suitable size for example as specified above, this decrease and lessening of the bonding will be prevented and the finished sheet will have characteristics as to strength and bonding equal to those of a sheet formed out of the same pulp stock, etc., in the heretofore regular manner, and will in addition have the desirable characteristics as to freedom from two-sidedness, etc.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In the manufacture of paper the method which comprises bringing the paper forming stock onto a forming wire, and removing water therefrom to effect an initial definite formation of the web, then bringing a suspension of additive material into absorbing contact with the wire side of said sheet, and thereafter subjecting the sheet with the additive material to a controlled-suction.

2. In the manufacture of paper the method which comprises bringing the paper forming stock onto a forming wire, and removing water therefrom to effect an initial definite formation ofthe web, then bringing a suspension of additive material into absorbing contact with the wire side of said sheet, and thereafter subjecting the sheet with the additive material to a controlled vacuum of the order of twelve inches of mercury.

3. Apparatus for manufacturing paper comprising a forming wire, means for supporting said wire, means for introducing onto the wire paper forming stock including fibrous material, filler and the like, means for adding additional forming material to the wire side of the sheet after the loss of sufiicient water from the forming sheet to effect an initial definite formation of the web,

and means effective to subject the formed sheet with the added material to a predetermined vacuum.

4. Apparatus for manufacturing paper com prising a forming wire, means for supporting said wire, means for introducing onto the wire paper forming stock including fibrous material, filler and the like, means for adding additional forming material to the wire side of the sheet within the suction box zone and after the loss of sufficient water from the forming sheet to effect an initial definite formation of the web, and means effective to subject the formed sheet with the added material to a predetermined vacuum.

5. Apparatus for manufacturing paper comprising a forming wire, means for supporting said wire, means for introducing onto the wire paper forming stock including fibrous material, filler and the like, means for adding additional forming material to the wire side of the sheet within the suction box zone in advance of a suction box and after the loss of sufficient water from the forming sheet to effect an initial definite formation of the web, and means effective to subject the formed sheet with the added material to a predetermined vacuum after it has passed the last suction box. I

6. Apparatus for manufacturing paper comprising a forming wire, means for supporting said wire including a breast roll and a suction couch roll, means for introducing onto the wire paper forming stock including fibrous material, filler and the like, means for adding additional forming material to the wire side of the sheet within the suction box zone in advance of a suction box and after the loss of sufficient water from the forming sheet to effect an initial definite formation of the web, and means effective to subject the formed sheet with the added material to a predetermined vacuum at the suction couch.

7. Apparatus for manufacturing paper com prising a paper forming part having a. forming wire, means for introducing onto the wire paper forming stock which includes fibrous material filler and the like, a suction box for removing water from the stock on the wire, a slotted pipe extending transversely of the wire and in contact with the under side thereof, the slot within said pipe lying within the zone of the pipe in contact with the wire, a head box, means for maintaining in said head box a predetermined depth of additive material containing filler and the like in sus containing filler and pension, a pipe connecting said maintained quan tity of additive material to said slotted pipe whereby the material within said head box is fed under a predetermined head to the wire side of the forming paper web through the slot, and suction means effective through the wire upon the forming web beyond the slotted pipe.

8. In the manufacture of paper the method which comprises bringing a paper forming stock onto a forming wire and removing water therefrom to effect an initial definite formation of the web, and then bringing a suspension of additive material containing filler and size under controlled pressure into absorbing contact with the wire side of the sheet while in its initially formed condition.

9. In the manufacture of paper the method which comprises bringing a paper forming stock onto a forming wire and removing water therefrom to effect an initial definite formation of the web, and then bringing a suspension of additive material under controlled pressure into absorbing contact with the wire side of said sheet while in its initially formed condition, said suspension size in the proportions of approximately twenty-two pounds of carbonate filler and three and one-half pounds of size in forty gallons of Water.

10. In the manufacturing of paper the method which comprises bringing a paper forming stock onto a forming wire and removing water therefrom to effect an initial definite formation of the web, and then bringing a suspension of additive material under controlled pressure into absorbing contact with the wire side of said sheet while in its initially formed condition, said suspension containing filler and size in the proportions of approximately from fifteen to twenty-five pounds of carbonate filler and two to four pounds of size in forty gallons of water.

11. In the manufacturing of paper the method which comprises bringing a paper forming stock onto a forming wire and removing water therefrom to effect an initial definite formation of the web, and then bringing a suspension of additive material under controlled pressure into absorbing contact with the wire side of said sheet while in its initially formed condition, said suspension containing filler and size in the proportions of approximately from fifteen to seventy-five pounds of carbonate filler and two to eight pounds of size in forty gallons of water.

12. A method of manufacturing paper which comprises introducing a paper forming stock onto a forming wire, removing suspension water therefrom to effect formation of a web of paper, then applying a suspension of mineral matter and adhesive to the wire side surface of the formed web paper, and thereafter subjecting the web with its added material to controlled suction to remove a part of the material applied.

- 13. A method of manufacturing paper which comprises introducing a paper forming stock onto a forming wire, removing water therefrom to effect formation of a web of paper, then bringing a suspension containing finely divided mineral material into contact with the wire side of the web, and applying a controlled pressure to said additive mineral material suspension while in contact with said web to incorporate said material int; the surface stratum of the wire side of the we 14. A method of manufacturing paper which comprises introducing a paper forming stock onto a forming wire, removing water therefrom to effect formation of a web of paper, then bringing a suspension containing finely divided mineral material into contact with the wire side of the web, and applying a controlled incorporating pressure to said mineral ma.erial suspension while in contact with said web and thereafter removing from said web part of the suspension thus applied to leave a predetermined amount of the mineral material within the surface stratum of the web.

15. In the manufacture of paper having a filled surface the process which comprises forming a web of paper and removing water therefrom, then applying a suspension of filler material and adhesive of controlled composition to the wire side surface of the Web of paper under controlled incorporating pressure and thereafter removing from said web part of the suspension thus applied to leave a predetermined amount of the filling material incorporated within the surface stratum of the web.

16. The method of manufacturing paper which comprises introducing a paper forming stock onto a forming wire, removing suspension water therefrom to effect formation of the web of paper, applying a suspension of filler and adhesive under conditions of controlled pressure and extent of contact with the web to effect controlled incorporating-of said filler in the surface stratum of the web and thereafter removing part of the suspension thus applied to leave a predetermined amount of the filling material within the surface stratum of the web.

17. In the manufacture of filled paper the process which comprises forming a web of paper and removing water from said formed web to effect partial drying of the web, applying a suspension of filler and adhesive to the wire side surface of the web to incorporate an excess of said applied suspension in the surface stratum of the web, and then removing the excess of suspension to leave in and upon the surface of the web an amount of filler material of the order of 1 lb. per ream on the dry weight of the finished paper.

18. In the manufacture of filled paper the process which comprises forming a web of paper and removing water from said formed web to effect partial drying of the web, applying a suspension of filler and adhesive to the wire side surface of the web to incorporate an excess of said applied suspension in the surface stratum of the web, and then removing the excess of suspension to leave in and upon the surface of the web an amount of filler material of the order of 1 lb. per ream on the dry weight of the finished paper, the said mineral filler material comprising calcium carbonate.

19. Apparatus for manufacturing paper comprising a forming wire, means for supporting said wire, means for introducing paper forming stock onto the wire with resultant drainage therethrough to effect the formation of the paper web, means for applying a suspension of filler and adhesive under conditions of controlled pressure and extent of contact with the surface of the web to cause incorporation of said suspension material into and upon the surface stratum of the web, and means for removing the surface of suspension material thus applied to leave a preafter removing from said web part of the suspension thus applied to leave a predetermined amount of the filling material within the surface stratum of the web, said amount being of the order of 1 to 2% of filler on the dry weight of the finished sheet of paper.

JAMES dA. CLARK.

JOHN E. GRAVES.

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