US3321359A

US3321359A - Continuous starch cooking method for calender stack sizing of paper and apparatus therefor

Info

Publication number: US3321359A
Application number: US219502A
Authority: US
Inventors: Shaughnessy William James
Original assignee: Tate and Lyle Ingredients Americas LLC
Current assignee: Primary Products Ingredients Americas LLC
Priority date: 1962-08-27
Filing date: 1962-08-27
Publication date: 1967-05-23
Anticipated expiration: 1984-05-23

Description

May 23, 1967 w. J. SHAUGHNESSY 3,321,359

CONTINUOUS STARCH COOKING METHOD FOR CALENDER STACK SIZING OF PAPER AND APPARATUS THEREFOR Filed Aug. 27, 1962 2 Sheets-Sheet 1 QQ @Q Y S 5 E N w m m H m S QQQ M m mm m w A [IV I. bkw

max *QQ 65:53 122.6 255 325.2328 mm 523 6528 0255 Q% oz 52; @2535 Ar] :umfiw SEE o 0968 Q mm IN V EN TOR.

May 23, 6 w. J. SHAUGHNESSY 3,321,359

CONTINUOUS STARCH COOKING METHOD FOR CALENDER STACK SIZING OF PAPER AND APPARATUS THEREFOR I Filed Aug. 27, 1962 2 Sheets-Sheet 2 a v m &

INVENTOR. WILLIAM J. SHAUGHNESSY H mm 9% on a 3,321,359 CONTINUOUS STARCI-I COOKING METHOD FOR CALENDER STACK SIZHQG OF PAIER AND AP- PARATUS THEREFOR William James Shaughnessy, Albany, N.Y., assignor to A. E. Staley Manufacturing Company, Decatur, 111., a corporation of Delaware Filed Aug. 27, 1962, Ser. No. 219,502 6 Claims. (Cl. 162-175) This invention relates to improvements in surface sizing heavy paper and paperboard with starch at the calender stack of a paper machine. More particularly, the invention relates to certain improvements and innovations in the preparation of cooked or pasted starch and the manner of holding and feeding the same to the size boxes of the calender stacks of paper machines (either Fourdrinier or cylinder machines). The invention provides a number of unexpected improvements and results certain of which show up in the product (ie the heavy paper or paperboard) and others of which show up in the calender stack operation.

In the manufacture of paper there are two broad classifications of sizing operations, i.e. internal sizing and surface sizing. As the name implies, internal sizing refers to the introduction of sizing materials on the interior of the paper. Often, the name is used jointly with loading as internal sizing and loading. This form of sizing is accomplished by introducing the sizing or loading materials into the web at some point prior to or during web formation. Thus, the sizing and loading materials may be introduced into the furnish, into the white water line, or into the head box.

On the other hand, surface sizing as this name implies, refers to application of the sizing materials to the surface of the sheet after it has been dried. There are several methods or techniques of surface sizing one of the main ones being known as calender stack sizing. This particular technique or method of sizing is well known in the paper manufacture art and is described, for example, in Pulp and Paper, by Casey, Second edition (1960), pages lll9 and 1120, volume II.

Heretofore, in carrying out the calender stack sizing operation, it has been the practice to first cook or paste a large batch of starch, sufficient to last for one or more shifts. For example, the starting slurry may contain two pounds of starch per gallon with a typical batch containing 200 to 1000 gallons of the concentrated slurry. The cooked, concentrated starch paste is then transferred to a holding tank where it is diluted to a concentration of say 53-16% and retained at or near its boiling point until used. The hot starch is recirculated from this holding tank or tanks to the size boxes of the calender stack. Depending upon the particular installation and the manner in which it is being operated, there may be one or several so-called size boxes associated with the calender stack or stacks. These boxes are maintained full of the cooked starch paste by circulating suflicient quantity thereof so as to keep some of the starch paste running over a level control weir. Each of the size boxes has an elongated flexible lip by which the starch may be applied to the associated calender roll.

The foregoing conventional system and technique for calender stack starch sizing has a number of recognized disadvantages and drawbacks which have been :long tolerated in the paper industry for lack of anything better. The more important of these shortcomings may *be summarized as follows:

(1) Uniformity and control of the sizing application are diiiicult to achieve and maintain, with some variations being normally unavoidable.

(2) A low degree of responsiveness to both undesired ited States latent changes that occur in operation and desired changes. Thus, if it is desired to compensate for an undesired variation, or bring about a desired variation, in the amount of the surface sizing, this can be achieved only after a considerable lapse of time.

(3) A considerable amount of reject paper is produced when the calender stack size operation is out of adjustment.

(4) Considerably more starch is used than is necessary.

(5) There is considerable danger to personnel working in the presence of large quantities of boiling starch.

(6) It is difficult or impractical to incorporate other sizing or coating materials with the starch such as titanium dioxide.

The foregoing difiiculties and disadvantages have been either completely or substantially eliminated by the present invention. Briefly stated, the present invention involves the following steps:

1) Preparing and maintaining a relatively large body of concentrated unpasted or uncooked starch slurry (erg. to 500 gallons containing 2 to 3.5 pounds of starch per gallon at ordinary room temperature).

(2) Continuously blending a stream of water with a stream of the concentrated starch slurry in predetermined proportions to produce a stream of relatively dilute unpasted or uncooked starch (e.g. one containing 516% starch solids).

(3) Continuously pasting the stream of dilute starch slurry with a jet of steam in a highly uniform immediate manner.

(4) Introducing the resulting stream of hot cooked or pasted starch without quenching or chilling into a relatively small body of cooked or pasted starch maintained at an elevated temperature of at least about F. (eg. 20 gallons at F).

(5) Feeding, with suitable recirculation, the size boxes of the calender stack with cooked or pasted starch from the relatively small body of the starch.

It has been found that practicing the present invention in calender stack sizing operations atfords the following unexpected results and advantages:

(1) Higher Vanceometer tests (resistance to oil or ink, see Casey, Pulp & Paper, 2nd edition (1960), page 1791, vol. III) can be obtained with a given solids content in the cooked starch or, alternatively, the same Vanceometer test can be obtained with lower solids content of cooked starch.

(2) Much faster changes and adjustments can be made in the starch solids content thereby providing rapid means of correcting or varying Vanceometer tests while at the same time minimizing production of reject paper and the throwing away of starch when going from fiat ink to gloss ink orders.

(3) Reduced requirement of optical brightener or increased brightness with an equal amount of bn'ghtener.

(4) Curl problems are eliminated or greatly reduced.

(5) Provides a convenient manner for application of titanium dioxide and similar materials at the calender stack.

(6) Eliminates variations in solids content due to recirculation build up.

(7) Provides higher Vanceometer to solids ratios; that is, more efiicient usage of the cooked starch.

(8) The danger of having large quantities of boiling For a more complete understanding of the nature and scope of the invention, reference may now be had to the following detailed description thereof taken in connection with the accompanying drawings wherein:

FIG. 1 is a diagrammatic view of an integrated system for producing a continuous stream of cooked or pasted starch having the properties required in practicing the present invention; and

FIG. 2 is a diagrammatic view of an integrated system which takes the stream of continuously pasted starch produced in the system of FIG. 1 and utilizes the cooked and pasted starch to feed the size boxes of a calender stack in accordance with the principles of this invention.

Referring to FIG. 1, the system for preparing and continuously cooking or pasting starch shown therein is based on the disclosure contained in Etheridge Patent No. 2,980,576, dated Apr. 18, 1961. In fact, the particular system shown in FIG. 1 is a composite of the system shown in FIGS. 1 and 8 of that patent.

The starch slurry mixing and holding tank 5 on the right of FIG. 1 may have a capacity ranging between 300 to 1,000 gallons although the actual size is not critical. Water is introduced into the tank 5 through the water inlet nipple 6 which is connected with a water supply line 7 equipped with a trip type water meter-valve 8 having an operating handle 10. The meter-valve 8 will be set so as to automatically deliver a predetermined quantity of water each time it is tripped. For example, to make up a starch slurry containing 3.0 pounds of starch per gallon, the meter-valve 8 will be set to deliver 30 gallons of water each time a lOO-pound bag of starch is emptied into the tank 5. The meter-valve 8 may be set to run or feed in each increment of water in approximately the time required for the starch to disperse, e.g. one and a half minutes. In this way, the contents of the tank 5 are maintained uniform even during starch and water additions.

The contents in the tank 5 are quickly and uniformly mixed and agitated by means of a portable agitator 11 which may be of the type referred to in the art a a Lightning Mixer. This mounts on the side of the tank 5 and is equipped with two or more agitator plates 12. It will be seen that the lower agitator plate 12 is located adjacent the water inlet. Preferably, the starch slurry will be withdrawn from the tank 5 at a location remote from the inlet 6 so that the withdrawn slurry will have the greatest uniformity. Thus, the outlet strainer 13 is disposed diametrically opposite the water inlet 6 and connects with a nipple 14 which projects through the wall of the tank 5. Nipple 14 connects with a slurry line 15 equipped with a valve 16 which leads to the inlet connection of a slurry pump 17 that may be driven by an electric motor 18 by means of a belt 19. In order that the starch slurry may be drained from the tank 5 from time-to-time as desired, an outlet or drain nipple 20 is provided in the bottom of the tank which connects with a line 21 having valves 2222 and connects with a T 23 in line 15. Preferably, line 21 is also provided with T 24 intermediate the valves 22 so that the contents of the tank 5 may be discharged to a drain line 25 having a valve 26.

The discharge connection of the pump 17 is connected with a concentrated slurry line 201 which connects with a T 203. The T 203 is connected by a line 204 to a diluting and pasting control panel so that concentrated starch slurry may be introduced into this unit through the line 204. The remaining connection of T 203 is connected with a return line 202. Line 202 connects with a T in the short line 32 interconnecting T 31 with a pressure relief valve 33. The discharge port of the pressure relief valve 33 is connected with line 34 which constitutes a return line to the tank 5.

In operation, after the tank 5 has been loaded to the point where slurry can be withdrawn through strainer 13, the pump 17 serves to recirculate the slurry through the looped circuit including the

branches

201 and 202 so that starch is prevented from settling out and plugging up the delivery lines. In the meantime, the requirements of the diluting and pasting control panel unit 30 are supplied through the line 204 as needed. In the event an excess pressure builds up in the delivery and circulating system this is relieved by starch slurry discharging through the relief valve 33 and into the return line 34 to the tank 5.

The construction and operation of the diluting and pasting control panel unit 30 are shown and described in detail in Etheridge Patent 2,980,576 in connection with FIGS. 2-5, inclusive, of the patent drawings to which reference is hereby made. In addition to being supplied with concentrated starch slurry through line 204, the unit 30 is supplied with diluting water through line 37 and steam through line 35, both of which are suitably equipped with shut-off valves. The panel unit 30 operates to blend and dilute the incoming stream of concentrated starch slurry from line 204 with a stream of water from line 37, in any desired ratio or proportion in an automatic manner. In other words, these two streams will be automatically combined in a desired predetermined ratio regardless of the rate of flow volume. After the dilution and blending has been accomplished, the diluted stream of uncooked and unpasted starch is automatically cooked or pasted to the desired degree and then discharged from the unit through line 40. The manner in which the starch in the diluted stream is automatically cooked or pasted is of considerable importance in the present invention. It is cooked or pasted in an immediate manner which is substantially instantaneous. Furthermore, the cooking or pasting is such that each granule of starch receives and undergoes the same treatment. Practically all of the starch cells are well dispersed due to the diluted condition of the uncooked and unpasted starch slurry. Since all of the starch cells and granules are individually reached and acted upon by a high velocity jet of steam to the same extent, it is possible to paste or cook the starch to a very selective degree and with very high uniformity as described in detail in Etheridge Patent 2,805,966, dated Sept. 10, 1957, to which reference is hereby made.

The cooked and pasted starch slurry from the diluting and pasting control unit 30 is delivered directly and without cooling or quenching through line 40 into one of two

small holding tanks

50 and 51 as shown in FIG. 2. While one of these tanks will sufiice, it is usually desirable to provide two for purposes of flexibility of operation, e.g. in the event that it is desired to blend in an additional material into one of the holding tanks which is to go to certain of the size boxes. Typically, the capacity of the holding

tanks

50 and 51 may range from 10 to 50 gallons and in operation they will ordinarily contain from about 10 to 20 gallons of the cooked and pasted starch slurry. (The capacity expressed in gallons is actually dependent upon paper machine demand. The gallons shown above would be typical for small machines in the North. Larger Southern machines may need capacities up to five or ten times those indicated.)

The

tanks

50 and 51 are interconnected by means of a communicating line 42 leading therebetween provided with a transfer pump 49. Desirably this is a reversible type pump of known type so that the contents may be transferred either way between the

tanks

50 and 51.

Three size boxes 43, 44 and 45 of conventional known type are adapted to bring the cooked or pasted starch slurry into contact with the rolls of a calender stack represented in FIGURE 2. by

rolls

81, 82, and 83. The calender stack or stacks are of the type generally found on a Fourdrinier or cylinder paper machine. Each of the small hold tank and 51 is provided with a circulating pump 52 and 53, respectively, so that the contents of the

tanks

50 and 51 may be withdrawn at desired rates and delivered through

lines

54 and 55, respectively, to the calender stacks (represented by

rolls

81, 82, and 83) where suitable connections are made to the size boxes 43, 44, and 45. Thus, line 54 leads to a three-way valve 56, a second connection of which is connected with line 57 and the third connection of which is connected a line 58. Line 58 connects with the inlet to the size box 45 while lines 60 and 61 serve to connect the line 57 with the inlets of size boxes 44 and 43, respectively.

The delivery line 55 from tank 51 connects with a threeway valve 62, a second connection of which is connected with as line 63 leading to the inlet of size box 45. The third connection of valve 62 is connection with line 64 which leads to the inlet size box 43. There is T 65 in line 64 from which is connected line 66 leading to the inlet of size box 44.

As mentioned above the size box as 43, 44 and 45 are of the type which are maintained in the full condition during operation with a certain desired volume of the hot, starch dilute cooked starch overflowing the level control opening or weir into an outlet connection from which the unused paste that is the paste not used in the calender sizing operation (represented by calender stack rolls 81, 82, and 83) is continuously withdrawn and returned to tanks 50 and/ or 51. The return lines from the size boxes 43, 44 and 45 are indicated as

lines

67, 68 and 70 respectively. Line 67 connects at a T 71 with line 68 which in turn connects with one connection of a three Way valve 72, a second connection of the valve 72 being connected with line 73 which discharges into tank 51 while the third connection of valve 72 is connected with line 74 which discharges into tank 50. The return line 70 from size box 45 connects with one of the connections of a three way valve 75 the second connection of which is connected by a line 76 to the tank 51 while the third connection is connected by line 77 to the tank 56.

It will be apparent that by suitable operation of the valving that hot, dilute starch slurry may be fed from either or both of the

tanks

50 or 51 to all three of the size boxes 43, 44 and 45. On the other hand, various feeding combinations may be readily set up so that size box 45, for example, is receiving starch only from the tank 50 while size boxes 43 and 44 are receiving starch slurry from tank 51. These and other obvious feeding arrangements provide the desired degree of flexibility in operation.

It will be apparent that the overall system described in FIGS. 1 and 2 lends itself to a considerable degree of automation. For example, the

hold tanks

50 and 51 may be provided with level control apparatus of known type whereby the transfer pump 52 will automatically be operated to maintain the supply of starch slurry in tank 51 at the desired level and to maintain the supply of starch slurry in tank 50 at the desired level by automatically controlling the operation of the diluting and pasting control panel unit 30. However, the particular manner in which the system or various parts thereof are operated does not form a part of the present invention and the control of the system could be completely manual if desired.

The following example will serve further to illustrate the nature of the invention and the advantages thereof.

EXAMPLE The integrated system shown in FIGS. 1 and 2 combined can be used to surface size 2.4 point paperboard with an application of /2 pound of starch per 1000 square feet. Initially, the tank 5 is loaded with the starch (e.g. hydroxyethyl starch ether) and any other ingredients to be used in the sizing formulation. In order to build up in the tank 5 a slurry containing 3.0 pounds of this starch per gallon of water with the starch being dumped in from 100 1b. bags, the meter valve is set to deliver 30 gallons of water each time it is tripped.

After the contents in the tank have been built up to a level above the outlet strainer 13, the diluting and pasting control panel 30 is placed into operation, and the pump 17 is turned on to circulate the starch slurry through the recirculation loop. As described in Etheridge Patent 6 2,980,576, this panel 30 is started up with the water and steam streams or connections turned on. When it is desired to cook or paste the starch, then the necessary valves are opened so that the concentrated starch slurry is being delivered to the unit 30 through the connection 204.

The setting of the controls for the unit 30 are such that the water and concentrated starch slurry streams are automatically blended in such proportions that the resulting stream contains about 14% of the starch by weight on a dry substance basis. The steam is set so that the pasted stream of dilute starch discharges from the unit 30 at a temperature of approximately 205 F. The diluted hot pasted or cooked starch slurry is discharged at between 5 and 10 gallons as required per minute. The hot pasted starch slurry is delivered through the line 40 into the hold tank 50 and after this tank has been filled to level above the pipe connection 42 the pump 49 is started so as to deliver or transfer some of the hot pasted starch to the tank 51. Both of these tanks are filled approximately half full before the circulating pumps 52 and 53 are started. Thereafter, the flow of starch through the line 40 is set so as to maintain the operating levels within the

tanks

50 and 51. The temperature of the starch within the tanks 59 and 51 is maintained at or near the boiling point of 212 F. The three-way valve 56 is set so as to deliver the hot starch slurry only to size boxes 43 and 44 While the other three-Way valve 62 is set so as to deliver hot pasted starch from tank 51 only to the size box 45. The three-way valve 72 will be set so that overflow from the size boxes 43 and 44 is returned to hold tank 50 while three-Way valve is set so that return from the size box 45 is discharged to hold tank 51.

The sizing operation is followed by making Vanceometer tests and basis weight determinations on specimens of the web and suitable adjustments are made so as to either increase or decrease the amount of sizing starch that is deposited on the paperboard web at the size boxes. If a Vanceometer test is too low in any instance then it can be raised quickly by delivering a higher concentration of cooked starch to the appropriate size box or size boxes. Alternately, if a Vanceometer test is too high, then it can be quickly lowered by reducing the concentration of the hot pasted starch.

Since the quantities of hot pasted starch retained in the

hold tanks

50 and 51 are relatively small, are being continuously circulated, and are receiving additional fresh hot pasted starch through line 40, there is little or no change that occurs in the strength of this sizing material during the calender starch sizing operation.

The invention has been tested under actual production conditions in three different paper mills in comparison with the batch equipment which these mills had been utilizing for some periods of time each. The results of these tests are set forth as follows:

Mill Test N0. 1

This particular paper mill had been calender stack sizing with a starch hydroxyethyl ether of commercial variety using a batch starch preparation system. Problems were encountered when high Vanceometer tests were required for gloss ink printing. Some grades required 60-second Vanceometer readings of or better. The batch method used involved cooking up the starch at three pounds per gallon in a 300 gallon tank. The cooked starch is pumped to a second 300 gallon tank in which it is diluted to a concentration of 14-16% and kept near the boiling point by an open steam line discharging into the tank. The hot diluted starch is pumped to size boxes or water boxes and recirculated back into the hot tank. In operation, if a Vanceometer test is too low, then more concentrated cooked starch is pumped to the dilution tank to raise the concentration of the starch going to the calender stack. On the other hand, if a Vanceometer test is too high, more water is added at the dilution tank to decrease the concentration of the starch going to the calender stack. The temperature of the starch in the dilution tank is maintained at the boiling point so that the temperature of the starch at the calender stack is maintained at l85-195 F. This prevents the starch from thickening, which otherwise might cause the sheet or web to pick and even cause a break in stack.

With calender stack sizing being carried out in this manner a number of problems were encountered the more important of which were:

(1) Difficulty was encountered in maintaining a steady Vanceometer test.

(2) Often it was difficult to reach the desired Vanceometer tests quickly when starting on a gloss iink order, and substantial quantities of the board had to be rejected because of low Vanceometer readings.

(3) The large quantity of boiling starch in the dilution tank represented a safety hazard to personnel in the vicinity.

A system substantially as that shown in FIGS. 1 and 2 was installed on a temporary basis at this mill and run on several different days for hourly periods alternating with the regular system described above. During each hourly operation of the regular batch installation and the experimental system, temperatures and concentrations in terms of percent solids as measured at the size boxes were recorded at to minute intervals. 'At the same time samples of the board were taken and tested for Vanceometer readings. The Vanceometer readings were divided by the solids for each time interval to obtain a Vanceometer to solids ratio or index. During two production runs, each of several hours duration, it was discovered that the average Vanceometer to solids ratios obtained when operating with continuously cooked starch from the experimental installation of the present invention, were 6.7 and 6.8, while the corresponding ratios obtained when operating with the regular batch cooked starch were 5.8 and 5.9, respectively. Thus, the difference in the ratios for the two runs between the continuously cooked starch and the batch cooked starch was the same, i.e. 0.9. This represents an increase of 15.4% Vanceometer index when using cooked starch in accordance with this invention instead of the batch cooked starch. The significance of this increase is that higher Vanceometer tests can be obtained at given solids by using the continuous cooked starch system of the present invention. Conversely, for any desired or given Vanceometer tests, less starch would be required when using the continuous system of the present invention. In fact, calculations show that the savings in starch that can be effected in this manner can easily run in the order of 7%, which mean several thousands of dollars a year saving for a single paper machine.

During the comparative trial runs it was also demonstrated that desired Vanceometer readings could be obtained much faster when using the experimental continuously cooked starch than when the batch cooked starch was used, thereby providing for less rejected paper While achieving correct Vanceometer readings. The small holding tanks near the machine containing only about 15 gallons of hot boiling starch each in comparison to the large batches of typically 250 gallons of batch cooked starch represents a virtual elimination of this hazard to personnel.

Mill Test N0. 2

This mill Was experiencing difiiculty in obtaining consistent Vanceometer test results. The continuous starchpreparation-and-cooking system was installed in accordance with FIGS. 1 and 2 and used to size paperboard with a modified starch which was a hydroxyethyl ether. In this test the batch cooked starch was also prepared in a cooker tank and then pumped to a holding tank located in the basement under the paper machine. The holding tank had a closed steam coil which was used to keep the starch hot so that it would not cool below a desired operating temperature of 150 F. at the calender stack. Vanceometer tests were made at the same time solids were recorded with a hand refractometer at the calender stack. These determinations were made for both the batch cooked and for the continuously cooked operations. During one of the trials titanium dioxide was added to the continuously cooked starch in one of the small hold tanks. Comparisons were made between the conventional batch system at this mill and the experimental system which was installed in accordance with the present invention. It was found that with the experimental system and the continuously prepared and cooked starch, a much more consistent Vanceometer test could be maintained. On grades of paperboard where high Vanceometer tests were needed they easily and quickly reached with the continuousLv cooked starch, whereas they were reached only with difiiculty and after substantial periods using batch cooked starch. In this particular mill test an interesting phenomenon was observed when running with the batch cooked starch. If the diluted cooked starch was started off at say 6% solids, then the concentration would build up to 12% solids after 4 to 5 hours. This occurred as the starch was recycled from the calender stack to the holding tank having the closed heating coil. Since a substantial evaporation occurs in the stack this means that each time a quantity of cooked starch made a complete cycle from the stack to the tank and back, it released considerable moisture to the atmosphere. Since there was no place in the system for this moisture to be replaced, the starch solution continued to increase in solids with time. Ultimately this had to be compensated for either by dumping the remainder of the starch batch, or by diluting it and making readjustments to get the right setting again for the desired V anceometer readings. In this mill test it was also noted that the amount of optical brightener could be reduced for any given brightness during times when the continuously cooked starch was used. In fact, during one run it was found that the amount of optical brightener could be reduced 50%. The run that was made using titanium dioxide with the continuously cooked starch system produced a very bright and smooth system. The titanium dioxide was well dispersed from the high sheer developed in the continuous cookers in the diluting and pasting control panels.

Mill Test N0. 3

This mill was having great difficulty in obtaining and maintaining high Vanceometer tests on gloss ink orders. The mill was using a 3% ethylated starch and alginate gum in combination in a formulation containing 50 pounds of starch, 10 pounds of the alginate gum and 88 gallons of Water. Great difi'lculty had been encountered in making 16 point board requiring a Vanceometer of -90 for 60 seconds. Only one size box on the calender stack was being run because of the very bad curl problem that was encountered when putting a double application on the top side of the sheet. The experimental system in accordance with FIGS. 1 and 2 was installed so that it could operate on test runs alternately with the regular batch system. A slurry of a less expensive 2% ethylated starch was made up at gal. of water and 300 lb. of starch. It was found that a flatter sheet (less curl) could be produced with the experimental system when sufficient starch was applied to one side of the sheet at a solids content sufiicient to produce the desired Vanceometer test while another application of starch was made to the opposite side of the sheet to eliminate curl.

A clay coating test was set up using a formulation containing 90 gallons of water, 600 pounds of clay, and pounds of a commercially available oxidized, cross-linked starch. This formulation was prepared and cooked in the experimental equipment, being cooked in the panel unit at 210 F. and applied at the calender stack at 200 F. At first only one size box or water box was used and the coating was applied at 27% solids. Later two size 9 boxes were used and the solids increased to 30%, then to 36%, then to 44% and finally to 50%.

Several results of a series of comparative tests were ascertained. For one thing, it was found that with the experimental system the use of the relatively expensive alginate gum could be dispensed with while desired Vanceometer values were readily obtained, thereby reducing the cost of the sizing material itself by about half. A less expensive starch product could also be used. During one of the tests with the experimental equipment the Vanceometer test readings suddenly dropped due to a disturbance at the wet end of the machine. However, by manipulating the experimental system the starch solids were boosted almost instantly to solids simply by controlling the automatic panel unit and the Vanceometer tests were back to normal in just a very few minutes. If this had happened when the system was being operated with batch equipment and batch cooked starch it would have taken at least a half hour and required dumping starch already made up and loss of considerable off-test paper.

Contrary to the teachings of Etherid-ge Patents 2,805,- 966 and 2,980,576 it was found to be unnecessary as well as undesirable :to cool or quench the continuously cooked or pasted starch before use in the calender sizing operation.

What is claimed as new is:

1. In the manufacture of heavy papers and paperboard the improvement in introducing cooked starch in a calender stack sizing operation, which starch is applied to paper or paperboard which comprises, preparing and maintaining a body of concentrated uncooked starch slurry, continuously blending a stream of water with a stream of said concentrated starch slurry to produce a stream of dilute uncooked starch slurry, continuously pasting said stream of dilute starch slurry with a jet of steam in -a uniform immediate manner continuously, introducing the resulting stream of hot cooked starch without quenching into a body of cooked starch having a temperature of at least about 180 F. said body of cooked starch being substantially smaller than said body of uncooked starch, and feeding size boxes of a calender stack with the cooked starch from said body of cooked starch for use in said calender stack sizing operation.

2. The improvement called for in claim 1 wherein an inorganic paper coating material is blended in with said body of concentrated uncooked starch.

3. The improvement called for in claim 1 wherein said body of concentrated starch contains at least about 250 gallons and said body of cooked starch contains less than about gallons.

4. In the manufacture of heavy papers and paperboard the improvement in preparing and introducing cooked starch in a calender stack sizing operation in which starch is applied to paper or paperboard which comprises, preparing and maintaining a body of concentrated uncooked starch slurry containing at least about 2 pounds of starch per gallon, continuously blending a stream of water with a stream of said concentrated starch slurry to produce a resultant stream having a solids content not exceeding about 16% by weight, continuously pasting said stream of diluted starch slurry with a jet of steam in a uniform immediate manner, introducing the resulting stream of hot cooked starch without retention and without quenching at temperature of at least about F. into a body of cooked starch said body of cooked starch being substantially smaller than said body of uncooked starch and continuously feeding and recirculating said cooked starch to at least one size box of a calender stack for use in said calender stack sizing operation.

5. The improvement called for in claim 4 wherein said hot cooked starch is delivered without retention and without quenching into a plurality of bodies of said cooked starch being continuously recirculated to supply a plurality of size boxes of a calender stack.

6. Apparatus for supplying cooked starch to a calender stack of a paper machine for use in a calender stack sizing operation which comprises in combination: a vessel equipped with agitator means and water supply means for forming and maintaining a body of concentrated starch slurry; a means for withdrawing and feeding said starch slurry from said vessel to a continuously operated, automatically controlled starch diluting and cooking means, said diluting and cooking means having connected thereto Water inlet means for first diluting said concentrated starch slurry, steam inlet means for then cooking said diluted starch slurry, and means for discharging said cooked starch slurry from said diluting and cooking means into at least one cooked starch holding tank; conduit means for interconnecting said holding tank With at least one size box of a calender stack; and pumping means connected to said conduit means for continuously supplying said size box with said cooked starch for use in said sizing operation.

References Cited by the Examiner UNITED STATES PATENTS 1,685,917 10/1928 Hans --1621 35X 2,980,576 4/ 19 61 Etheridge 1621'7 5 S. LEON BASHORE, Primary Examiner. D. H. SYLVESTER, Assistant Examiner,

Claims

1. IN THE MANUFACTURE OF HEAVY PAPERS AND PAPERBOARD THE IMPROVEMENT IN INTRODUCING COOKED STARCH IN A CALENDER STACK SIZING OPERATION, WHICH STARCH IS APPLIED TO PAPER OR PAPERBOARD WHICH COMPRISES, PREPARING AND MAINTAINING A BODY OF CONCENTRATED UNCOOKED STARCH SLURRY, CONTINUOUSLY BLENDING A STREAM OF WATER WITH A STREAM OF SAID CONCENTRATED STARCH SLURRY TO PRODUCE A STREAM OF DILUTE UNCOOKED STARCH SLURRY, CONTINUOUSLY PASTING SAID STREAM OF DILUTE STARCH SLURRY WITH A JET OF STEAM IN A UNIFORM IMMEDIATE MANNER CONTINUOUSLY, INTRODUCING THE RESULTING STREAM OF HOT COOKED STARCH WITHOUT QUENCHING INTO A BODY OF COOKED STARCH HAVING A TEMPERATURE OF AT LEAST ABOUT 180%F. SAID BODY OF COOKED STARCH BEING SUBSTANTIALLY SMALLER THAN SAID BODY OF UNCOOKED STARCH, AND FEEDING SIZE BOXES OF A CALENDER STACK WITH THE COOKED STARCH FROM SAID BODY OF COOKED STARCH FOR USE IN SAID CALENDER STACK SIZING OPERATION.

6. APPARATUS FOR SUPPLYING COOKED STARCH TO A CALENDER STACK OF A PAPER MACHINE FOR USE IN A CALENDER STACK SIZING OPERATION WHICH COMPRISES IN COMBINATION: A VESSEL EQUIPPED WITH AGITATOR MEANS AND WATER SUPPLY MEANS FOR FORMING AND MAINTAINING A BODY OF CONCENTRATED STARCH SLURRY; A MEANS FOR WITHDRAWING FEEDING SAID STARCH SLURRY FROM SAID VESSEL TO A CONTINUOUSLY OPERATED, AUTOMATICALLY CONTROLLED STARCH DILUTING AND COOKING MEANS, SAID DILUTING AND COOKING MEANS HAVING CONNECTED THERETO WATER INLET MEANS FOR FIRST DILUTING SAID CONCENTRATED STARCH SLURRY, STEAM INLET MEANS FOR THEN COOKING SAID DILUTED STARCH SLURRY, AND MEANS FOR DISCHARGING SAID COOKED STARCH SLURRY FROM SAID DILUTING AND COOKING MEANS INTO AT LEAST ONE COOKED STARCH HOLDING TANK; CONDUIT MEANS FOR INTERCONNECTING SAID HOLDING TANK WITH AT LEAST ONE SIZE BOX OF A CALENDER STACK; AND PUMPING MEANS CONNECTED TO SAID CONDUIT MEANS FOR CONTINUOUSLY SUPPLYING SAID SIZE BOX WITH SAID COOKED STARCH FOR USE IN SAID SIZING OPERATION.