US2286942A - Method of manufacturing paper and/or board - Google Patents

Description

June 16, 1942. A. TUTEN METHOD OF MANUFACTURING PAPER AND/0R BOARD Filed July 11, 1939 m NZ WW m7 W A been known in Europe for many years.

Patented June I 16, 1942 UNITED METHOD MANUFACTURING I APER AND/OR BOARD Alvin Tuten, Georgetown, S. 0., assignor, by mesne assignments, to International Paper Company, New York, N. Y., a corporation of New York Application July 11, 1939, Serial No. 283,755

1 Claim.

' that it will take readily and evenly glue or other adhesive used in making the corrugated board and that the other surface will possess character-. istics as to permit a smooth and even application of printing inks.

Board of the type above described has been i made on the so-called multicylinder board machine where individual webs ofmatrial possessing the desired characteristics are first formed For example, in the manufacture and thereafter united in the usual manner well known to those skilled in the art. However, due

to the inherent characteristics of this form of paper or board machine, it can be run only at comparatively slow speeds and the resultant product, although possessing the desired surface characteristics, has a decided tendency to split along the lines where the individual webs have been joined during the paper or board making process. In fact by a mere visual examination of a cylinder board it is possible to determine the linesof demarcation between the individual webs.

Use of amultiple headbox system in conjunction with a Fourdrinier paper machine is not new. In fact the so-called Diana machine has Reference is also made to United States Patents Nos. 2,018,382; 2,098,733; and Reissue Letters Patent 20,667 taken out in the nameof John W. Sale. Undoubtedly other patents disclosing a multiple headbox system for the manufacture of paper or board on a Fourdrinier machine are known to the art. The above mentioned inventor, John W.

Sale, has explored in a preliminary waythe problem of manufacturing multi-ply paper or board method of operating a multiple headbox system for the manufacture of paper or board. Briefly, g, that invention relates specifically to a process wherein stock flowing from the primary headbox is formed into a sheet and dehydrated sufliciently to permit operation of a dandy roll in advance of the secondary headbox. The dandy roll not only functions in a conventional manner, but serves particularly to iron out both inequalities of caliper and uneven spots in the primary sheet and thus to present to the stock flowing from the secondary headbox a substantially uniform surface with the elimination of high spots. This effectually prevents localized showing through of parts of the base sheet which, possessing characteristics differing in many cases from the characteristics of the secondary stock, would otherwise be definitely detrimental to the printing qualities of the final board.

An object of my present invention which constitutes an improvement over my earlier application is to define definite optimum basic operating conditions for the regulation of the action of the primary headbox relative to that of the secondary headbox.

A further object of this invention is to provide a method and means for the accurate control of the action of the primary headbox relative to that of the secondary headbox based on easily observable data.

A still further and more specific object of this invention is to define optimum operating conditions for the primary and secondary headbox relative to the speed of the fourdrinier wire and to provide a method of controlling these operations based on easily observable data.

These and other objects will be made clear as the detailed description ceeds.

In the'drawing I have represented schematically a paper or board machine of the fourdrinier type showing a fourdrinier wire having mounted thereover a secondary headbox embodying the principles of my invention together with the conventional form of primary headbox.

Papermaking has been, and probably for many years will be, one of the most empirical of all major industries due to the fact that the manufacturing process from the woodpile to the freight car involves not only a tremendous number of variables, but many variables which are beyond control. In the manufacture of board, particularly, the manufacturing units are very large, operate at great speeds, and the system at any given moment frequently contains as much as e of the invention protons of board making material between the beaters or mixing tanks and the reel receiving the finished paper. Accordingly, when a change in the character of the material being supplied to the paper machine becomes apparent due to a falling ofi of some desired characteristic of the finished goods, operating changes must be made to correct the condition and the changes may have to be dispensed with very shortly after they are put into effect. As used hereafter the term optimum condition has reference to a condition of operation which produces the best results most of the time. Temporary contingencies may arise which will necessitate temporary adjustments of one or more factors to points radically difierent from optimum conditions, but such departures are strictly temporary and the optimum condition will be reverted to as soon as the effect of whatever disturbing factor may have arisen has subsided.

The pointwhich must constantly be kept in mind in discussing the operating of a Fourdrinier machine is that the Fourdrinier machine is essentially a continuous process machine whereas the manufacture of pulp is essentially a batch process. Variations in pulp may occur between the several batches which will be delivered seriatim to the Fourdrim'er machine and these variations must be compensated for, first,

by the treatment of the pulp between the diffusersand the Fourdrinier machine, e. g., beating and/or jordaning, etc., and second, by adjustment of the operating characteristics of the Fourdrinier machine itself.

Whatever characteristics the finished product is to. have are substantially fixed by the time the sheet leaves the press rolls and goes to the dryer. The present press and drying rolls are capable of relatively few adjustments which have any appreciable effect on the quality of the sheet and therefore the major adjustments in ,the Fourdrinier machine to meet varying conditions must be made at the wet end.

Fundamentally the headbox of a paper machine is operated at a pressure suificient to give the stock emerging from the headbox a velocity approximating the lineal speed of the Fourdrinier wire. This velocity is strictly a function of the static pressure on the stock adjacent the slice opening whether the box be of the gravity velocity of emergence of the stock should be proportional to the square root of the static head expressed in feet .of water. Naturally, the efiect of baflies and flow eveners in the headbox is to reduce the actual velocity of emergence of the stock below the velocity theoretically obtainable byvirtue of any particular head. The quantity of stock emerging is a function of both the velocity and the degree of opening of the slice.

The paper or board machine, particularly as' used in the Fourdrinier board industry, is apt to be of a width approximating 200" and the extent of the slice opening usually varies across the width of the machine to take care of local variations caused by eddy currents. As a result, adjustment of the slice opening is a rather delicate operation and not one to be resorted to for any quick change. If, for example, due to a change in the character of the'pulp coming to the machine the headbox consistency were to increase eriously the number of cubic feet per minute of stock emerging 'from the headbox would have to be reduced in order to maintain constant the basis weight of the sheet being quently the quantity of stock emerging.

What has thus far been described is standard papermaking practice and applies equally" to multiple headbox operation and to single headbox operation. I have discovered, however, that for the multiple headbox operation certain operating characteristics, if maintained as closely as possible within the limits hereinafter set forth, will yield the best results in producing a uniformly desirable finished product. These characteristics are as follows:

1. The velocity of emergence of stock from both the primary headbox and the secondary headbox should be less than the lineal speed of v the wire.

emergence bearing a ratio to the speed of the wire not less than 0.900 nor greater than 1,100;

Obviously, if the velocity of emergence of stock from the primary box has a ratio to the wire speed of 0.900, the velocity of emergence of stock from the secondary box must have the ratio of not less than unity relative to the velocity of emergence of stock from the primary box. Contype or of the pressure type. Theoretically the versely, if the velocity of emergence of stock from the primary box relative to the wire speed has the ratio of 1.100, the velocity of emergence of stock from the secondary headbox must have a ratio to the velocity f emergence of stock from the primary headbox of not more than unity, although it might well be less than unity down to 0.900.

So far as the above numerical ratios are con cerned, the velocities referred to are the theoretical velocities of emergence computed as equal to the square root of 2GH in which G is the acceleration of gravity and H is the static head efiective on the slice measured in feet of water.-

isfactory technique for making such a determination which in any event would have to represent an average across a slice opening of 200" in length. Accordingly, for the purpose of regulation the most satisfactory measurement from the standpoint of easy and accurate determination is the static head measured directly in inches in the case of a gravity head or in pounds per square inch translated into feet of head in the case of the so-called pressure type headboxes. I accordinglypropose to regulate the ratios above discussed by regulating the effective heads in the primary and secondary headboxes.

1 effective heads of the headboxes.

feet on the theoretical velocity,

The heads, of course, vary with the square of the velocity and the numerical ratios above set forth.

Because of the practical difliculty of obtaining accurate measurement of the actual velocity of emergence, I find it sim ler to control the velocitiesof emergence of stock by controlling the The desired ratio between the head in the secondary headbox and that in the primary headbox correspond to the velocity ratios above set forth and would place the range of head ratios between 0.810

corresponding to a velocity ratio of 0.900, and

1.210 corresponding to a velocity ratio of 1.100.

The slice openings H's of the secondaryheadbox and H? of the primary headbox are indicated because under a few conditions of operation these openings might be of suflicient extent to modify the effective head. ,In running extremely heavy basis weights at very low wire speeds the effective head may be reduced to as little as measuredfrom the bottom of the headbox while the slice opening may amount to as much as 2". ities are determined by measuring the effective head from the center of the slice opening instead-of from the bottom of the box, and in such height of the slice opening relative to the effec:

tive head is so small that half of the slice opening is ineffective to produce any substantial ef- Referring now to the drawing in which like numerals indicate like parts, I have shown a paper and/0r board making machine of the Fourdrinier type in order to illustratethe above described process. The'paper or board machine, well known in the art, comprises a breast, roll l0, a couch roll I2, conventional table rolls l4 and suction boxes Hi. The paper making screen or wire I8 is trained at one end around the breast roll I0 and at the other end around the couch .roll l2 which is usually of the suction type. Conventional guide and-tensioning rolls are also provided as is also well known in the art. Positioned over and closely adjacent to the breast roll I0 is the primary headbox containing a flow evener 22 which serves to assist in controlling the evenness of flow of the stock emerging from the slice of the headbox, the height of which is shown by the arrows H'P. The table rolls H are rotatably mounted and not only sup- I port the paper making screen or wire, but serve also to assist in withdrawing water from the paper and/or board making stock through the" screen or wire so as to leave the fibres of the stock in a felted mass in web form; The first set of suction boxes are positioned ahead of'the dandy roll 28 and serve to withdraw sufficient water from the forming web of stock so that the latter may be properly conditioned to be worked In such case theoretical velocdepending upon the length of the wire and the the last group of suction boxes. Sumcient suction is used so that by the time the .stock from the secondary headbox and the base sheet reach the dandy roll 30, the top surface of the composite sheet is in such condition that it may be subjected to the action of a dandy roll without damage thereto and without breaking the sheet. In other words there is substantially no pond present on the top surface of either the base heet or the top surface of the secondary stock gmwhen. each is subjected to the action of the dandy rolls.

As will be appreciated by those skilled in the art the dandy roll should operate ona web of fibrous material while it is as wet as possible.

The web, however, must be sufliciently formed and must be sufficiently dry so as to prevent the'fibres thereof from being picked up by the dandy roll which consists usually merely of a hollow member having a wire mesh operating 30 surface. It is universally recognized in the paper making art that a dandy roll cannot operate successfully if the web on which it operates is still in a pended condition,that is, the'upper surface of the web cannot be in such watery con- 5 dition that the fibres are floating in the water of the paper or board making furnish. As I have disclosed and; claimed in my copending application Serial No. 252,725, filed January 25, 1939, for Board manufacture, I have found that 40 it is possible sufliciently to dehydrate the base sheet so that the pond which would normally exist at the point in the wire where the dandy .-roll 28 is located has disappeared. f v In operating the multiple headbox system previously described in accordance with the process which I have developed, it .will be appreciated that I can accurately control the amounts of stock deposited by the primary and secondary headbox,. and can assure a close control ofthe formation of the base sheet and the top layer without resorting to make-shift arrangements. By maintaining a ratio of the respective heads to each other and to the speed of the wire, vI canprovide at all times an accurate control of the manufacture of ply board or paper having the surface characteristics required by the box and container making industry.

My invention also contemplates, in connection with the process above described, the use of varip1e,- use the same variations of stock disclosed by me inthe aforesaid copending application.

The process lends itself not only to a complete and accurate control of the board making process, but also to the formation of a paper and/or board using all kinds of combinations of fibrous stbcks, the particular combination used and the order of deposition depending upon the types of paper and/or board desired.

It will be appreciated that the invention may be modified considerably without departing in any way from the spirit of th invention or the scope of the appended claim which "is to be broadly construed.

' sheet, is immediately subjected to the action of' ous types of stock depending upon the characteristics ofth board required. I can, for exam- I claim:

A method of making an interfelted cellulosic fibrous web on a Fourdrinier machine having a traveling wire, a primary headbox and a secondary headbox each adapted to discharge stock in the direction of travel of the wire; which comprises laying down stock from said primary headbox on the moving fourdrinier wire, dehydrating said stock to form a base sheet to such a point as substantially to eliminate all floating fibers on the upper surface of said base sheet on the wire, then laying down a secondary celluiosic fibrous stock from said secondary headbox on top of said base sheet, drawing the fibers of the secondary stock into interlocking engagement with the stock forming the base sheet to form a composite interfelted sheet, regulating the static head effective on the primary and secondary headboxes to maintain a velocity of emergence of the stock from the primary headbox which is less than the lineal speed of the wire but which shall not have a ratio to the wire speed of less than 0.900 and to maintain a velocity of emergence of the stock from the secondary headbox which is less than'the velocity of emergence of the stock from the primary headbox except where the emergence of the stock from the primary headbox is at its lower limit of 0.900 and in such case to maintain a ratio of velocity of emergence of stock from the secondary headbox to velocity of emergence of stock from the primary headbox of 1.00 and without permitting the ratio of the velocity of emergence of the stock from the secondary headbox to the speed of the wire to drop below 0.900

ALVIN TUTEN.

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