US3153378A

US3153378A - Method of calendering

Info

Publication number: US3153378A
Application number: US314229A
Authority: US
Inventors: Benjamin J H Nelson
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-12-04
Filing date: 1963-10-07
Publication date: 1964-10-20
Anticipated expiration: 1981-10-20

Description

Oct. 20, 1964 B. J. H. NELSON 3,153,378

METHOD OF CALENDERING Original Filed Dec. 4. 1961 s Sheets-Sheet 1 INVENTOR. BENJAMIN J.|'l. NELSON ATTORNEYS Oct. 20, 1964 B. J. H. NELSON 3,

METHOD OF CALENDERING Original Filed Dec. 4. 1961 5 Sheets-Sheet 3 nnnnnnnn nr lOl l2 8 I127 I52 I24 I25 21 ms INVENTOR. BENJAMIN J. H. NELSON Wm #W ATTO RNEYS United States Patent 6 Claims. (Cl. Nil-38) This application is a division of my co-pending application Serial No. 156,827, filed December 4, 1961, and entitled Paper Finishing Mechanism and Method, which application is a continuation-in-part of my prior applica- Generally speaking, the calendering technique provided a by the present invention comprises nipping a web of paper having a substantial moisture content between a smooth metal master roll and at least one resilient auxiliary roll frictionally driven by the master roll at essendaily the same peripheral speed as the master roll, maintaining a nip pressure of from about 180 to about 1100 pounds per lineal inch, maintaining the master roll at a temperature of at least 250 F., and driving the master roll at a peripheral speed of at least about 525 feet per minute.

'In known conventional methods of calendering ink receptive papers, it has been necessary to reduce the moisture content of the paper down to approximately 45% prior to the actual calendering. In contrast, a paper web to be calendered by the process of the present invention may have a moisture content up to about This results in a significant saving in the manufacturing costs of the paper, as the removal of water from the paper Web is a costly operation. In the calendering process of the present invention, at least most of the moisture content of the paper is vaporized solely by contact of the Web with the heated master roll.

In conventional calenders and supercalenders, each type of which involves a vertical stack of rolls, the nip pressure may reach 3000 pounds per lineal inch of roll. Nip pressures of this magnitude may result in a crushing of the fibers and a consequent blackening of the surface. Also, with the higher pressures the fibers are squeezed together so as to become more dense. In contrast, in the calendering technique of the present invention the nip pressure is maintained at about 180 to about 1100 pounds per lineal inch. I have found that with the lower pressures there is less crushing of the fibers, and a better finish is produced. Also, since less crushing is experienced there is less fiber per unit volume of the finished paper. As Will be appreciated, this means a reduction in the cost of fiber per unit volume of paper produced, resulting in an additional saving in the total manufacturing cost of the paper.

According to the present invention, the paper web can be calendered at the rate of at least about 525 feet per minute to about 2250 feet per minute, when using the presently available equipment for handling the calendered web of paper after it leaves the calendering machine.

These and other important objects and advantages of my invention will be more clearly brought forth with reference to the following drawings, specification and claims.

In the drawings:

Patented Get. 20, 1964 "ice FIGURE 1 is an end elevational view of a specific embodiment of my invention in accordance with the preferred teachings thereof.

FIGURE 2 is a fragmentary plan View looking down on the calender and illustrates the central roll with the central section removed to more clearly depict the heating element in the roll.

FIGURE 3, on an enlarged scale, is a fragmentary end elevational view illustrating the means for adjusting the nip between the central roll and the auxiliary roll.

FIGURE 4, taken on line 44 of FIGURE 3, is a plan view looking down on the means for adjusting the nip between the central roll and the auxiliary roll.

FIGURE 5 is a fragmentary lateral cross-sectional view taken on line 5-5 of FIGURE 4 and illustrates the bearing means for maintaining the auxiliary roll in position in the calender frame.

FIGURE 6 is a schematic end elevational view illustrating the arrangement of the central calender roll and the three auxiliary rolls, and illustrates and shows the heating element in the central roll.

FIGURE 7 is a schematic diagram illustrating the hydraulic system for adjusting and controlling the pressures between each auxiliary roll and the central roll.

FIGURE 8 is a longitudinal diametrical cross-sectional view of another master roll and illustrates the details of construction of the same;

FIGURE 9, taken on line 99 of FIGURE 8, is a lateral cross-sectional view of the master roll.

Referring to the drawings it is seen that the invention comprises a calender 10 having a base 11. Supported on this base 11 is a roll frame 12. This roll frame 12 comprises two end members 13 and two side members 14. The upper edge of each end member 13 is recessed to receivebearing blocks and a top frame member 15. More particularly, the members 13 near their outer edges are stepped at 16. This step runs into an inwardly directed horizontal ledge 17. In the lower center portion of the member 13 is a slot having a bottom wall 18 and side walls 20. Each side wall 20 connects with the adjacent ledge 17 by means of curved wall 21. The top frame member 15 is in the configuration of a rectangular frame having longitudinal sides 22 and ends 23. In the central portion of the end 23 is a depending curved bearing support 24. Journalled in each of these two bearing supports 24 is a shaft 25. This shaft 25 is not a continuous shaft but is two independent shafts. In the support 24 is a drilled passageway 25 and in this passageway is a bearing 2.7. The end of each shaft 25 is journalled in said bearing 27.

On the inner end of each of the shafts 25 is a circular hub 28. This circular hub co-fits with a hollow central roll 30. This roll may be of metal. In the interior of this roll is a heating element 31 in a configuration of a U-bend. The ends of this heating element are in an electrical adapter base 32 at the left of the roll as illustrated in FIGURE 2.

On the outside left face of the frame member 23 and overlying the central part of the depending support 24- is a commutator 33. This commutator 33 is attached to the frame member 23 by screws 34. Leading into the commutator 33 are

electrical Wires

35 and 36. The shafts 25 are hollow. The commutator 33 connects with the electrical adapter 32 through the hollow shaft 25 by suitable electrical connectors.

The top frame member 15 is supported on the upper and outer edges of the end members 13. The lower surface of the upper member 15, the step 16 and the ledge 1'7 define a guide channel for a bearing block 40. The bearing block has a main body 41. In the bottom surface is a groove 42 for co-fitting with the ledge 17, and in the upper surface is a groove 43 for co-fitting with the lower surface of the end member 23. On the outer edge oft .e block is an outwardly directed lug 44. I And, projecting out of the lug 4 4 is a pin 45 having a drilled passageway 4-6 therein.

In the body 41 is a lateral drilled passageway 47. In

' this passageway-is a bearing 48.

As is seen in FIGURE 2 there are three sets of hearing blocks with'two' blocks in each set. Also the two blocks in each set are aligned with one block associated withone end member and'the other block with the other end member.

Journalled in'the bearings 48 of a set of the blocks is ashaft 50. The central part of this shaft is of a larger cylindrical configuration51. Surrounding the configuration'51 is acylindrical fibrous mat 52 of the type employed in supercalenderrolls. In fact, mat 52 makes this roll a supercalender roll.

On the upper and outer surface of the end member 13 and adjacentto the step 16 is a ing 49." In this lug is a central passageway 53. Positioned in the passageway 53 is a hydraulic cylinder 54 having a plunger 55.

The hydraulic cylinder 54 can be positioned in the bearing block-by means of a pressure fit, a set'screw or by-welding.

The plunger 55 contacts the outer face of the lug 44 so as tomove inwardly the bearing'block 49.

' On the-outer edgeof the lug 49 is a pin 56. A spring with a main feeder line 64. In each line 61 the gauge 62 In each pipe 61 is a' can be readily varied. Also, the pressure between one is positioned between the hydraulic cylinder 54 and the main line 64, and the valve 63 is positioned between the gauge 62' and the main line 64. branches into areservoir line 65. This line connects with a hydraulic fluid reservoir 66. In the line between the reservoir 66- and the main line 64 is a valve 67.

The main line 64also connects with a pressure line 68. A motor and pump combination 70 connects with the pressure line. In the line 63*between the main line 64 and the pump7i1 are a valve 71 and a pressure gauge 72.

The motor and pump combination 70 are electrically actuated and controlled. There are two lead wires 73 and 74' leading to the motor 715; In the lead 73 is a switch 78; It is to be understood that connecting with the wiper 77 and the switch 751 is an appropriate'source of. electrical energy.

In the lead 35 there is a rheostat 75 having a number of resistances 76-and a wiper 77. In the lead 36 there is a switch 79;

In regard .to details of constructionof the calender it is seen that the end members are connected at their base by lower braces 81 These members are connected at their upper edges by the top frame member 15. The upper edges of the end members 13.are drilled and tapped as at 82. In the end 23 is a drilled passageway '83. The tapped hole 82 and the drilled passageway 83 arealigned. A bolt 84 is screwed into the tapped hole 32 so as to firmly position the frame members 15 on the roll frame 12. The central roll 3tl'can be removed by unscrewing the bolts 84 and removing the top frame member 15.

From this specific description of theinvention it is seen that there is a central heated roll and three auxiliary rolls 52. Referring to FIGURE 2 it is seen that the right end of the shaft 25 of the central roll 36 connects with an output shaft 85 of a motor 86. This motor drives the roll3tl. The motor connects with an appropriate source of electrical power by means of wires 87 and $3. The central roll is of metal and may be heated to an appropriate temperature of 250-500 F. The auxiliary rolls may be of metal or may be fiber filled, depending on the surface to be imparted to the paper.

The main line 64 auxiliary roll and the central roll can be different than the pressure between another auxiliary roll and the wntral roll.

Referring to FIGURE 6 it is seen that paper 91) is threaded between thethree auxiliary rolls 52 and the central roll 31). As seen in this figure the central roll 36 rotates in a counterclockwise direction while the three auxiliary rolls rotate in a clockwise direction.

In FIGURE 1 the elements 9.2, 93, .94, 95 are airjet forming means used to assist in the threading of the paper web into the calendering machine. The preferred threading technique, and the apparatus for its practice, form the subject matter ofand areclaimed in my pending application Serial No. 292,804, filed July 1, 1963, entitled Calender and Method of Threading Same, and also a division of my aforementioned application Serial No. 156,827.

In FIGURE 8 there is illustrated another master or metal roll 1%. This roll'comprises a first hub 101 and a second hub 1%2. The exposed face of thehub has a shoulder 1113 and which shoulder1tl3 tapers down to a shaft or axle 1114. In the inner or hidden face of the hub 1111 there is a-peripheral recess 1115. This recess is in the outer edge of the hub. In the more central portion of the hub 101 there is a circular recess 106. Between the outer recess 1115 and the-circular groove 106 there is drilled inthe hub a plurality of holes or openings 1117. In the hub 101 are a'plurality-ofvent holes 168. These vent holes 108 are between the shoulder 1G3 and the circular groove 106. Also, drilled in the axle 1414 and the shoulder 103 is a recess 110.

In the hub 102, and on the exposed face, there is a shoulder 111. The shoulder 111 is-reduced to an axle 112. In the axle 112 and the shoulder 111 there is a drilled recess 113. In the inner or hidden face and at the outer periphery there-is a recess 114. This recess 114 corresponds tothecircular recess in the hub 101.

Also, there is a ci'rcular'recess 115 inthe hub 102. The recess 1'15 corresponds to the recesslti6 in the hub 161. There are vent holes 116 in the hub-112. These vent holes are between the shoulder 111 and the circular recess1115.

In the circular recessesltl6-and 115 there is positioned a cylinder 117. The cylinder'117 has the outer'wall recessed at 118 so as to receive in an assembled positiona gasket or an O-ring 1213. In the end-walls of the cylinder 117 are a number of drilled tapped passageways 121. In the hubs 1G1- and-102 are a number of drilled-holes 122. The drilled holes 122' are aligned with the tapped holes 121. As'is readily appreciated, bolt 123 can be inserted through the holes 122 and screwed into the tapped holes 121. In this manner the

hubs

101 and 102 are positioned with'respect to the cycinder'117;

In the circular recess 1051there is positioned a metal cylinder 124. It is seen that this'cylinder 124 is larger in diameter than the cylinder 117. The inner-outer edge of the cylinder 124 is recessed at 125. The roll 180 in assembled position has an O-ring 126 in this recess 125. The ends of the cylinder 124-have a plurality of tapped holes 127. The

hubs

101 and 102. have a plurality of drilled passageways 128; It is to be understood that the .tapped holes 127 and the drilled passageway 128 are in A bolt 130'projeots through the hole .128-

alignment. and is screwed into the tapped hole 127. It is to be realized that by tightening the bolt 130 thehubs 101- and 192 are drawn closer'together and the O-ring 126 is squeezed so as to function as a gasket.

In thehub 1111, and positioned between the

holes

122 and 128 there are a plurality of drilled holes 131. Inserted in these holesis an electric heating element 13-2. On the outside of the hub. 101 there is attached electric lead ends 133 and 134. In the toroidal space between the

hubs

101 and 102 and the cylinders 117 and 12d there may be a compound which can withstand relatively high temperature without decomposing, having a low coefficient of expansion and which is a liquid at the higher temperatures, and is perfectly at liquid at room temperature. One such compound is tetraiodotetrasilane. The reason for a liquid in the toroidal space is that better results are achieved by having a liquid in contact with the cylinder 124 instead of depending upon convection from a gas and radiation.

The vent holes 108 allow the pre-passage of air in the central part of the metal roll 100. A beneficial result of this is that there is not created undue pressure due to the expansion of heated gas inside of the roll.

It is noted that the

shafts

104 and 112 have drilled

holes

110 and 113. This is so that the cooling liquid may be pumped into the drilled holes and th reby cool down the hubs. A longer life is realized by this.

Having described my invention Iiwill now present some examples illustrating the use of my calender and the product realized therefrom. These examples are by Way of illustration only and are not to be taken as limitations on the invention.

Example I The paper was a 45 pound naw stock having a pound coating, i.e., latex and clay, to make :a 60 pound paper.

Invention Conventional Calender Calender Nlps Temperature, F 3 Less than 200. Speed of paper, feet per minute 1,0721,200. Pressure, pounds per lineal inch 79 0. smoothness (glare, Bekk reading)-.." A 43 14. Appearance Like wax paper.

The paper was a 45 pound raw stock having a 15 pound coating, i.e., latex and clay to make a 60 pound paper.

Invention Conventional Calender Calender Nips. 7. Temperature, F Less than 200. Speed of paper, feet per minute. 800. Pressure, pounds per lineal inc 5,500. smoothness 45 i4 (blackened). Appearance White .L-ilre Wax paper.

The results of this example show that a better quality paper, e.g., a white appearance as contrasted with a wax paper appearance is realized at approximately two and one-half to three times the output, viz., 2200 i.p.m. as contrasted with 800 f.p.m., with my calender than with the conventional calender. Also, the product of the conventional calender is of an undesirable nature as the appearance is blackened, i.e. the fibers of the paper have been crushed. As contrasted with this the fibers in the product of the calender are not crushed. Also, it 'is possible to realize these advantages with three nips instead of a larger number of nips as employed on a conventional calender.

Example III This paper was a 45 pound raw stock having a 15 pound coating, i.e. latex and clay to make a 60 pound paper.

6 This paper was run through my calender under four different sets of conditions. These sets were:

Pressure ,pounds per lineal 1,110 900 555 1,110 260 260 300 45 45 48. 5 84 84 Satis- Satis- Satisfacfacfactory. tory. tory.

In order to pass the paper through the six nips it was necessary to run the paper through the machine two times. The bulk of the paper was checked by a micrometer, and the thickness of the paper is in thousandths of an inch. With the conventional supercalender there is a 6 to 8 point loss in bulk while with my calender there is only about a 2.5 point loss in bulk. It is pointed out that a variation in the speed from 525 f.p.m. to 2250 f.p.m.; a variation in temperature from 250 F. to 380 F.; a variation in lineal pressure from 555 pounds per lineal inch to 1110 pounds per lineal inch; and a variation in bulk from 260 to 800 do not appreciably affect the glare and the varnish on the paper. All of the papers from these four runs were of satisfactory commercial quality. From this, it is seen that it is possible to manufacture on my calender a satisfactory commercial paper with a wide range of operating conditions.

Example IV The paper was a 45 pound raw stock having a 15 pound coating, i.e., latex and clay, to make a 60 pound paper.

Invention Conven- Calender tional Calender Nips 3 6 7 Temperature, F 350 -120 Speed of paper, ieet per minut 1, 000 800 Pressure, pounds per lineal inch 1, 500-3, 000 Moisture, Percent:

Like wax paper paper paper With the invention calender there was employed a label grade of paper having a high clay content or a high ller content. With one pass through the invention calender the paper passed through three nips. With two passes through the calender the paper passed through six nips. The temperature of the invention calender was set at approximately 350 F.; the speed of the paper was approximately 1000 feet per minute; the pressure was 180 pounds per lineal inch and the moisture content for the three-nip paper was at approximately 6 percent initial moisture and 5 percent final moisture. For the six-nip paper the initial moisture content was approximately 10 percent and the final moisture content was approximately 6 percent. In contrast with this the conventional calender may employ seven nips; have an operating temperature of approximately 110120 F.; a speed of approximately 800 feet per minute; a pressure of approximately 1500 to 3000 pounds per lineal inch; and, a moisture content in the range of 4 to 5 percent. It is seen that the 1I1VIl tion calender has fewer nips, a higher operating temperature, a higher speed of the paper passing through the calender, a lower pressure in pounds per lineal inch and a higher moisture content. It is my opinion that this high moisture content along with the higher temperature makes it possible to operate at a lower pressure and to achieve a liner finish than can be achieved with the conventional calender.

'1 Example V A reproduction of copier paper capableof. being used for xerography Work wascfinished;

1 Chilled calender.

It is seen that in this .examplethe invention calender employsthree nips while the .conventional calender employs seven nips. In addition, the. temperature of the invention calender isv approximately 350 'F. as compared with about-80 F. for theconventional. calender. speed at which the 'paper maypass through the inventioncalendercan. be as high as 2200 feetper minute as compared :with 350feet perminutefor the conventional calender. The pressure in pounds per lineal inch for the inventional calender is about-180.. Unfortunately, the pressure for the conventional calender is not known. Finally,-the moisture content of the paper entering the invention calender may range from approximately 8 to 10 percent while for theconventional calender it may range. from approximately f44 /2 percent. The paper manufactured on the invention calender has a somewhat better appearance and is moresatisfactory for reproduction work than paper manufactured on the conventional calender.

ExampleVl ln this example, I mounted a cloth on thecotton filled. rolls or. the fiberfilledrolls and moistened it. In effect, the ,water was wicked %onto the mounted cloth. The paper was passed through the three nips and steam formed on the metal roll. The metal roll was operated at a temperature of approximately 450 F.; a paper speed of approximately 1000 feet per minute; and,'a pressure of approximately 180 p0unds--per lineal inch. It may be assumed that thersteam functio'ned as a lubricant on the metal surface and, also; as asoftener for the surface of thesized sheets Theresult was a stiffer sheet than. pro duced by the conventional calender and, also a brighter sheet With'a heavier caliper. as with. the conventional-calender. This lack of the crushing of thexfibers inconjunetion-withithe heavier calipermakes it. possible. to'use less fiber weight than with: the conventional calender and, therefore, have a savingin; the fiber content of the paper. Naturally, the paper is less costly from the fiber-content standpoint. Further, the, super-label paper manufactured by this method had less glare and a better varnish'than the label paper manufactured by thev conventional calender.

Example VII' The paper was 2.45 pound raw stock having a poundcoating, i.e-., latex and'clay, tomake a 60-poundv paper.

In this example there was used one-side-coated label paper. This paper was passed through three nips in the The The fibers were not crushed- 8. invention calender as compared to seven nips for the conventional calender. The temperature in the invention calender as approximately500 F. was compared with the conventional calender temperature l10--120 R, viz., approximatelyfour times the conventional calender temperature. The speed .ofthe paper passing through the invention calender was 2200 feet per minute as compared with -800feet per minute for the conventional calander, approximately three times the speed of paperin the conventionalcalenderz. The pressurein pounds per lineal inch is approximately 180 as compared with the conventional calender of about 1500 to 3000 pounds per lineal inch. Further, the, moisturecontentinitially was considerably higher being in the range of about 15 percent as compared with the conventional calender range of about 4 to 5 percent.

From the above descriptionof my calender and theexamples it is seen that it ispossible to have both a ln'gh bulk and a good finish. As contrasted with this the bulk and finish factors are usually at cross purposes, i.e., in order to realize good finishit is necessary to have a poor bulk quality. A contributing factor to good finish While simultaneously realizing good bulk may be the higher temperature of operation of my calender as contrasted with the'operat-ing temperature of the conventional calender. Another advantage of my calender is that it is possible to realize a good finish without applying too much pressure. possibility of crushing the fibers and blackening the paper. As contrasted with this inthe use of a conventional calender there is a continual struggle to give a good finish without crushing the fibers and blackening the paper. The difference in theblackening of the two calenders may be explained by the difference inthe pressure of the rolls.

With my calender there isasmall pressure of-about 500 to 1100 pounds per lineal inch which with the conventional calender having a large number of rolls the pressure may reach about 5500 pounds per lineal inch.

In the manufacture of label and letter-press papers with conventional'equipment, thepaper is run through a regular'calender and then 'run through a supercalender. It is possible to realize the same results by processing the paper in my calender. In other words, it is possible to accomplish the same results withmy one calender as is now accomplished by two calenders,

Another contrasting feature of the paper product is inthe. foldingability. Withthe conventional calender the fibers are crushed and the foldingability is lessened because the fibers structure has been damaged. As contrasted with-this the folding ability of my paper product is much superior as the structure of the fibers has not been damaged.

Also, with my calender the porosity of the fibrous product is not decreased as with a conventional calender. As a result it is .possibleto usemore filler and less fiber with my calender. Because filler is not as expensive as fiber, it is possible to manufacturea lower priced product.

With my calender it is possible to have good temperature control'at speeds up to 10,000'feet per minute. This is because of' the external heating of the central metal roll. However, in the conventional calender there is not this good temperature control as the heat is generated by the rolls-and is not externally supplied.

From my experience in the paper manufacturing industry and working on Fourdrinier-machines'and calenders and the finishing of paper, I consider that some of the major factors in the'manufacture of paper are the temperature of the calender, the moisture content in the paper, the pressure of the calender rolls-and the speed in which the paper passes through thecalender. In regard to temperature, the conventional process for manufacturing paper employs calender rolls which are not heated. The temperature of the calender rolls is determined by the friction of thecalender rollsas they contact the paper. The normally employed'temperature has been Therefore, there is only a small 9 less than 200 F. and in the range of 1l0-120 F. As contrasted with this, my master roll is a heated roll and may achieve a temperature of approximately 500 F. Some of the beneficial results of this higher temperature are that this temperature vaporizes the moisture inside the sheet. Also, the sheet becomes more pliable and easier to work by the calender rolls. In regard to the moisture, the conventional process has been to use paper having a moisture content of approximately 45% Now,

as is well-known in the manufacture of paper, the fibers,

are held in water and are laid down on a wire. A large percentage of the water drains through the wire and the fibers are on this continuously moving wire to form somewhat of a sheet of fibers. Then, the sheet of fibers is transferred to a continuous felt and passed through the dryer. As is readily appreciated, the removal of the water in this sheet of fibers on the felt is a tremendous operation. The removal of one percent of the water in the paper by a drying apparatus is costly and requires additional floor space and expensive equipment. As contrasted with this, paper entering my machine may have a moisture content of up to percent. This is approximately three times the moisture content of paper which enters the conventional stacked roll calender. Therefore, it is possible with my machine to cut down on the size of the drying equipment for the paper sheet or to run the paper sheet at a higher velocity through the drying equipment so as to allow the sheet to have the 15 percent moisture. Now, the moisture in the paper, in conjunction with the relatively high temperature on the master roll, produces the beneficial effect from the pressure standpoint. At the incoming nip to the master roll and the auxiliary rolls, the moisture is heated and expands. Some of the moisture may become a vapor or the moisture may remain a liquid. In effect, this expansion of the moisture creates a counter pressure to the pressure being applied by the calender rolls. The counter pressure is in the sheet and keeps the sheet from collapsing. Actually, the expanded moisture in the sheet is substantially trapped in the sheet and cannot escape at the nip. In effect, it may be considered that the moisture in both the vapor form and in the liquid form functions as a solid and I refer to it as a gas-solid. This gas-solid prevents crushing of the paper by the calender rolls. At the nip center point of the master rolls and the auxilairy rolls there is build-up of the compression and the nip of the rolls functions as a gate. To repeat, in the incoming nip, the moisture is trapped in the paper and cannot escape. Once, the paper is passed the nip center line, the moisture is allowed to escape or to be exhausted with the release of moisture vapor. This results in a reduction of the amount of moisture in the paper. In regard to the pressure of the rolls, I have found that a lower pressure is beneficial to the results of the paper product. With the conventional stacked-roll, vertical calender pressure may reach 3000 pounds per lineal inch of roll. With this high pressure there is a crushing of the fibers of the paper and a consequent blackening of these fibers with the crushing. Also, with the higher pressure the fibers are squeezed together so as to become more dense. As contrasted with this, I found that with a lower pressure, such as may be used with my calender, there is less crushing of the fibers and a better finish. Also, with less crushing there is a higher caliper of the paper which means that there may be less fiber per unit volume of paper. Naturally, with less fiber per unit volume there is a lower cost of fiber per unit volume and, therefore, a lower cost of the final paper product as compared with the conventional stacked-roll vertical calender. Finally, in regard to the speed of operation of the calender, it is possible with my calender to realize a high output speed of approximately 2200 feet per minute. I believe that it is possible to achieve a higher output speed than 2200 feet per minute; however, I have not been able to test this as, at the present time, I do not have a machine capable of feeding paper to my calender at a velocity higher than 2200 feet per minute, and I do not have a machine for winding paper at a velocity higher than 2200 feet per minute. I firmly believe that, under proper conditions, paper can pass through my calender at a velocity of up to 10,000 feet per minute. However, it will be necessary to provide feeding apparatus and also winding apparatus for such velocity.

Although I have described my invention as having a central roll having three auxiliary rolls, it is to be realized that in certain instances it may be desirable to have a central roll and. only one or two auxiliary rolls or a central roll and more than three auxiliary rolls. The number of rolls is not as important as the ability to control the temperature of the central roll at a higher than the conventionally used calender; the ability to exert pressure between the rolls without stacking one roll on another roll and the ability to control said pressure; and, the ability to operate said machine at much higher temperature than presently used.

What is claimed is:

1. A method for gloss calendering a web of ink-receptive paper having a substantial moisture content, said method comprising nipping the paper between a heated, positively driven smooth metal master roll and at least one resilient auxiliary roll frictionally driven by said master roll at essentially the same peripheral speed as the master roll, maintaining a nip pressure of from about to about 1100 pounds per lineal inch, maintaining the master roll at a temperature of at least 250 F., and driving the master roll at a peripheral speed of at least about 525 feet per minute so as to vaporize at least most of the moisture content of the paper solely by contact with the said heated master roll without charring of the paper.

2. The method of calendering a web of porous, inkreceptive paper having a substantial moisture content to provide a high gloss on a surface thereof without blackening and without substantial loss of caliper, said method comprising; nipping a web of the paper between a smooth metal master roll and a smaller, resilient auxiliary roll, positively driving said master roll and frictionally driving said auxiliary roll by contact with the master roll so that the web speed and the peripheral speed of each roll are all substantially equal, maintaining the web movement at a speed of at least about 525 feet per minute, maintaining the nip at an effective glossing pressure of less than about 1100 pounds per lineal inch, and heating the metal roll to heat the moisture containing paper in the nip to a temperature of at least about 250 F.

3. The method of claim 2, wherein the paper web being calendered is raw paper stock with a latex and clay coating.

4. A method for calendering a web of pervious paper stock, said method comprising passing the paper between the hips of a smooth metal central roll and a plurality of resilient rolls, positioned around the central roll and being frictionally driven by the central roll at essentially the same peripheral speed as the central roll, maintaining the web speed at a velocity of up to 2250 feet per minute with a pressure between the nips in the range of 180-1100 pounds per lineal inch, said paper having the same surface facing the central roll while being calendered, said resilient rolls being spaced apart to allow the paper to be exposed to the surrounding atmosphere, and heating said central roll so as to heat the paper in the nips to a temperature in the range of about 250-500 F.

5. A method for calendering a web of pervious paper stock with a moisture content up to about 15% by weight, said method comprising passing the paper between the nips of a smooth metal central roll and a plurality of resilient rolls positioned around the central roll and being frictionally driven by the central roll at essentially the same peripheral speed as the central roll, maintaining the web speed at a velocity of up to 2250 feet per minute with a pressure between the nips in the range of 180-1110 1 1 poundsh per lineal inch, said paper having the same surface'facing the central roll while being calendered, said resilient rolls being spaced apart to allow the paper to be exposed to the surrounding atmosphere, and heating said central roll so as to heat the paper in the nips to a temperature in the range of about 250-500 F.

6. The method of gloss calendering a non-laminant paper web having a substantial moisture content up to about 15% :by weight and uniformly producing a noncr-ushed, ,high gloss and non-Waxy appearance in the calendered paper, said method comprising:

'(a) nipping the paper between a smooth metal roll and a resilient roll at a substantially uniform pres sure of about 180-1100 pounds per lineal inch;

surface temperature of about 250-500" F.; and

(d) moving the paper web through the nip at a speed of about 525-2250 -feet per minute.

References Cited in the file of this patent UNITED STATES PATENTS Parks Jan. 14, 1919 Muench Aug. 15, 1950

Claims

1. A METHOD FOR GLOSS CALENDERING A WEB OF INK-RECEPTIVE PAPER HAVING A SUBSTANTIAL MOISTURE CONTENT, SAID METHOD COMPRISING NIPPING THE PAPER BETWEEN A HEATED, POSITIVELY DRIVEN SMOOTH METAL MASTER ROLL AND AT LEAST ONE RESILIENT AUXILARY ROLL FRICTIONALLY DRIVEN BY SAID MASTER ROLL AT ESSENTIALLY THE SAME PERIPHERAL SPEED AS THE MASTER ROLL, MAINTAINING A NIP PRESSURE OF FROM ABOUT 180 TO ABOUT 1100 POUNDS PER LINEAL INCH, MAINTAINING THE MASTER ROLL AT A TEMPERATURE OF AT LEAST 250*F., AND DRIVING THE MASTER ROLL AT A PERIPHERAL SPEED OF AT LEST ABOUT 525 FEET PER MINUTE SO AS T VAPORIZE AT LEAST MOST OF THE MOISTURE CONTENT OF THE PAPER SOLELY BY CONTACT WITH SAID HEATED MASTER ROLL WITHOUT CHARRING OF THE PAPER.