US3833466A - Manufacture of hardwood printing paper - Google Patents

Manufacture of hardwood printing paper Download PDF

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Publication number
US3833466A
US3833466A US00153381A US15338171A US3833466A US 3833466 A US3833466 A US 3833466A US 00153381 A US00153381 A US 00153381A US 15338171 A US15338171 A US 15338171A US 3833466 A US3833466 A US 3833466A
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United States
Prior art keywords
web
percent
hardwood
paper
drying
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00153381A
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English (en)
Inventor
Carty E Mc
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Svenska Flaktfabriken AB
Original Assignee
Svenska Flaktfabriken AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Svenska Flaktfabriken AB filed Critical Svenska Flaktfabriken AB
Priority to US00153381A priority Critical patent/US3833466A/en
Priority to ZA723352A priority patent/ZA723352B/xx
Priority to IT25019/72A priority patent/IT955982B/it
Priority to AU42909/72A priority patent/AU470597B2/en
Priority to CA144,086A priority patent/CA967360A/en
Priority to ES403729A priority patent/ES403729A1/es
Priority to AR242512A priority patent/AR195283A1/es
Priority to PL1972156000A priority patent/PL83664B1/pl
Priority to FR7221458A priority patent/FR2142450A5/fr
Priority to BR3826/72A priority patent/BR7203826D0/pt
Priority to JP5872672A priority patent/JPS544403B1/ja
Application granted granted Critical
Publication of US3833466A publication Critical patent/US3833466A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper

Definitions

  • the invention is concerned with a process for making newsprint from 100 percent or near 100 percent hardwood groundwood pulp.
  • FIGS. 1 and 2 are graphs of shrinkage versus moisture content for samples of paper made from 100 percent hardwood groundwood;
  • FIG. 3 is a schematic flowsheet illustrating results obtained by the process of this invention and results obtained by the conventional process
  • FIG. 4 is a schematic view of a drying apparatus suitable for carrying out the process of the invention.
  • FIG. 6 is a schematic plan view of a portion of a blow box which forms part of apparatus of FIGS. 4 and 5;
  • FIG. 7 is a schematic sectional view on the line 77 of FIG. 6; and I FIG. 8 is a graph illustrating the web tension in the drying apparatus of FIG. 4.
  • Hardwood mechanical pulps are of course not new per se, inasmuch as such pulps have found use in the past in a variety'of uncoated and coated grades of paper. These pulps, when used correctly, cut costs and improve printing quality of uncoated papers. While these latter tend to have good opacity and printing quality, their lack of strength has limited their use in all grades, but especially in newsprint.
  • paper suitable for newsprint must have sufficient strength to feed at high speed and run properly at high speed during the various mechanical operations involved in unrolling the paper received from the papermill, calendering the paper to obtain a smooth printable surface and movement through the printing machine.
  • the required combination of physical characteristics such as stiffness, toughness, tensile strength,
  • softwood and hardwood respectively designate trees having needle or scale-like leaves and trees having broad leaves, deciduous in the Temperate Zone.
  • Hardness or density of wood is not involved. All woods are composed of three basic components: cellulose, ligmin and extractives. While there are differences between the chemical structure of hardwood and softwood lignins, the important difference, as far as this patent is concerned, lies in the variation in cell structure.
  • Softwoods for the most part are made up of cells whose length is several hundred times their diameter. That is, while barely visible to the eye, they are threadlike.
  • Hardwoods are made up of a wider variety of cell types characterized by a length to diameter ratio which may run from 1:1 to 20:1.
  • the quality of individual hardwood fibers, by papermaking standards, is inferior to softwood.
  • Hardwood fiber is stiffer, because its ratio of length to diameter being smaller and bonding between fibers is poorer, since the inter-fiber crossings per fiber are fewer and the bond area of each is smaller. Consequently, the sheet is weaker when it contains hardwood. Hardwood mechanicalpulp is even weaker than chemical hardwood pulp.
  • Cockling is the formation of waves and ripples on the surface and within the body of a sheet of paper during the last stages of the drying of the sheet.
  • the art has long recognized that cockling occurs during drying in the range below about 15 percent by weight moisture unless special procedures are used. While some papers are deliberately cockled to produce special surface effects, cockling is totally unacceptable for most papers requiring any further surface finishing or high-speed printing.
  • drying in the range below about 15 percent by weight moisture is carried out by physically restraining the sheet during this stage, usually by drying the sheet while in contact with heated rolls (known as machine drying). The surface contact between the rolls and the sheet prevents deformation of the sheet, but at the same time this prevents further shrinkage, and therefore there is no further increase in strength.
  • the present invention is based to a considerable extent onthe discovery that paper made from hard wood groundwood does not cockle and on the more surprising discovery that this absence of cockling permits an unexpectedly high degree of stretch, and hence strength, to be imparted to this paper by drying under low-restraint conditions in the range below about 15 percent moisture.
  • low-restraint conditions is meant primarily the previously referred to airborne conveying technique in which the continuous sheet is supported and conveyed by a gaseous medium free of restraint except for such tension as is required to make the sheet travel. This permits free fiber shrinkage to occur which is translated into web shrinkage. This latter appears in the form of stretch at a later time during use.
  • FIGS. 1 and 2 are plots of shrinkage versus moisture content, under conditions of substantially no physical restraint, for percent hardwood groundwood machine-made papers.
  • the data were obtained by air-drying individual 18- inch square sheets of paper resting on beds of sand in an enclosure and by periodically measuring the dimensions of the sheets and weighing the sheets to determine loss of water.
  • FIG. 1 shows the relationship for paper which has never been dried during its manufacture
  • FIG. 2 shows the relationship for paper which has been fully dried and then rewet.
  • the significance of the curves is that they clearly illustrate the great additional shrinkage which is introduced when the sheets are dried in the range below about 15 percent moisture. Specifically, it will be seen from the slopes of the curves that, during the last stages of drying, a further small reduction in moisture content effects a relatively large increase in shrinkage.
  • the production of this high shrinkage characteristic, with no cockling, is the essential feature of the present invention, because it has been found that hardwood groundwood papers dried under little or no restraint in continuous drying machines of proper design can be converted to newsprint.
  • the process of the present invention makes the difference between success and failure in the manufacture of newsprint and the like from groundwood hardwood.
  • the invention is not, however, limited to 100 percent hardwood groundwood papers, and in fact a manufacturer in the temperate zone would usually not expect to continually obtain a furnish which is always completely 100 percent groundwood hardwood;
  • the present invention is broadly applicable to any furnishes which are sufficiently noncockling when unrestrainedly dried above the percent to percent dry range to permit calendering, printing or other surface sensitive converting or use operations.
  • suitable furnishes are those which consist essentially of hardwood groundwood, that is, furnishes which contain sufficient hardwood to render the initial paper web too weak and brittle for calendering and printing when dried in the range below about 15 percent moisture under such restraint that no significant shrinkage occurs.
  • FIG. 3 illustrates schematically and in flow sheet form a group of papermaking, drying and printing runs carried out with a percent hardwood groundwood furnish for the purpose of comparing the properties of the paper dried under low restraint with theproperties of the same paper dried in a conventional manner.
  • a furnish of 100 percent Aspen refinergroundwood was prepared by a conventional refining operation.
  • the furnish was then pulped with water, and the resulting slurry was supplied to a conventional papermaking machine which formed the slurry into a running. web and dewatered the web.
  • the wet web was then partially dried to about 40 percent-50 percent by weight moisture by. passing it over internally steamheated cylinders. Severaltons of this still wet paper were wound up into rolls during several different runs under substantially identical conditions.
  • Batch CRWS was first conventionally cylinderdried to less than 5 percent by weight moisture, re-wet to 50 percent moisture and then airborne-dried to less than 5 percent moisture, under substantially no physical restraint in either the machine direction or the cross machine direction, on a drying machine of the'type illustrated in simplified form in, FIGS. 4, 5, 6 and 7.
  • the resulting dry paper was processed without any unusual difficulties on a three-nip calender without applied pressure.
  • Batch III still containing about 40 percent 50 percent moisture, was dried to less than 5 percent moisture on the same airborne drying machine as was batch CRWS.
  • the resulting drypaper was processed without difficulty on a two-nip calender without applied pressure.
  • the calendered paper was transported to the same printing plant as batch I and was successfully fed to the same high-speed'printing press.
  • the press was run at the rate of 50,000 impressions per hour for 14 minutes to produce a different four-page centerfold for each of two sections of a newspaper. No unusual difiiculties were encountered in threading up oroperating the press.
  • TEA Tensile Energy Absorption
  • the special unrestrained drying operation of the present invention not only renders the hardwood groundwood paper capable of subsequent conventional calendering but also complements the'calendering operation by enabling the latter toimpart improved properties to the paper.
  • the improved properties are generally the same as those of conventional commercial newsprint (for example newsprint made from 25 percent spruce sulfite pulp and percent spruce groundwood pulp), in terms of tear strength, opacity and tensile strength. Individual properties may vary between the two types of paper, however. Calendered paper of batch III, for example, was found to have a tear strength slightly lower and a tensile strength slightly higher than a typical conventional newsprint.
  • the special low-restraint drying operation is preferably carried out in a machine of the type illustrated in FIGS. 4, 5, 6 and7 wherein the wet or moist web 10 passes through a heating zone while being supported upon a gaseous medium so that the web is permitted to shrink freely in the machine direction and cross direction of the web 10.
  • the heating zone includes a plurality of blow boxes 12 arranged in tiers, each tier consisting of horizontal parallel boxes disposed within a given horizontal plane and having a length equal to the width of the web 10. Heated air or other heated gaseous medium is supplied under pressure to the interior of each box-l2 and is discharged as jets 14 (FIG. 6) directed alternately in the forward and backward direction relative to the direction of web travel.
  • Eyelid openings 15 are provided in the top'wall of each box 12 and evenly distributed along its length for the purpose of generating the jets 14.
  • the web 10 is led back and forth over the tiers of blow boxes 12 by rolls 16 located at opposite ends of the heating zone.
  • the heated air jets 14 form cushions of air upon which the web 10 floats freely so that the weight of the web 10 is supported by the air cushion, not by the rolls 16. Due to interaction between the static and the dynamic air pressure upon the web, the paper web will be held at a constant distance, determined essentially by the velocity of the air, from the tops of the blow boxes 12.
  • An overpressure in the boxes for example, of the order 1 inch water column, has proven to give stable running conditions. There is only a very slight friction between the web and the air cushions and therefore the paper web is fully or almost fully unrestricted to shrink in the cross machine direction.
  • Unrestricted shrinking of the web 10 in the machine direction is permitted, in spite of the tension force which must be applied to the web 10, by driving each of the rolls 16 at a peripheral speed appropriate to the respective portion of the web.
  • This can be accom plished by driving each roll 16 with a variable speed electric motor M the speed of which is adjusted to give a roll speed equal to the web speed, the latter being essentially based on the initial entry speed of the web decreased by an amount dependent on the amount of machine direction shrink imparted to the web at the location of the particular roll 16.
  • the same result can be obtained with a single motor connected to each roll 16 through a variable speed transmission. In practice the rolls will be arrived at by on stream adjustment of the motors M to about the lowest speed at which the web will travel smoothly through the machine.
  • the effect of adjusting the roll speed in the manner described is to reduce the force, called the draw tension, required to move the web 10.
  • the tension in the web leaving each driven roll 16 is very close to zero but increases as that portion of the web approaches the next downstream roll. If that next roll and the subsequent rolls, are merely idlers, the tension in the web continues to increase until the web is finally discharged from the machine by whatever nip roll arrangement or driven roll is employed to pull the web through the machine. While the increase in tension between any two idler rolls in sequence may be small, the overall tension in the whole machine is significant and would adversely affect the machine direction shrink required by the present invention.
  • the difference between the use of idlers and the use of independently driven rolls is illustrated graphically in FIG. 8 wherein the solid line shows the increase in tension between rolls 16 and the dashed line illustrates the increase in tension which would occur if the rolls 16 were idlers and if the nips 20 and 22 were the only means for driving the web 10 through the machine.
  • a calender 24 is shown for purposes of simplicity as being adjacent the drying machine, although in the actual tests described above the calendering operation was carried out in a different plant from the drying operation.
  • a process for making newsprint comprising: preparing a pulp-in-water dispersion in which the pulp contains a major proportion of hardwood groundwood fibers, said fibers being present in an amount sufficient to render the web too weak and brittle for calendering and printing when dried under physical restraint; forming a continuous wet web of said fibers by extracting water, subsequently drying the web to below about 15 percent by weight moisture and simultaneously shrinking the web in its machine direction and in the cross machine direction, said drying and shrinking being carried out by supporting the moving web on a heated gaseous medium in a drying zone whereby free shrinkage occurs in both of said directions; and calendering the resulting dried paper to produce a surface receptive to printing.
  • Machine-made printing paper containing at least percent hardwood groundwood fibers and having a calendered surface receptive to printing, said printing paper being capable of being processed by high-speed printing presses and having been formed by drying a continuous moist web of the fibers under substantially no physical restraint to less than 15 percent by weight moisture the proportion of hardwood ground wood fibers in the web being sufficient to render the web too weak and brittle for calendering and printing when dried under physical restraint.

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US00153381A 1971-06-15 1971-06-15 Manufacture of hardwood printing paper Expired - Lifetime US3833466A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
US00153381A US3833466A (en) 1971-06-15 1971-06-15 Manufacture of hardwood printing paper
ZA723352A ZA723352B (en) 1971-06-15 1972-05-17 Manufacture of printing paper
IT25019/72A IT955982B (it) 1971-06-15 1972-05-29 Fabbricazione di carta da stampa
AU42909/72A AU470597B2 (en) 1971-06-15 1972-05-31 Manufacture of printing paper
CA144,086A CA967360A (en) 1971-06-15 1972-06-07 Manufacture of printing paper
ES403729A ES403729A1 (es) 1971-06-15 1972-06-10 Un procedimiento para fabricar papel calandrado e impre- sion.
AR242512A AR195283A1 (es) 1971-06-15 1972-06-13 Un procedimiento para fabricar papel y el papel obtenido por este procedimiento
PL1972156000A PL83664B1 (oth) 1971-06-15 1972-06-13
FR7221458A FR2142450A5 (oth) 1971-06-15 1972-06-14
BR3826/72A BR7203826D0 (pt) 1971-06-15 1972-06-14 Processo de fabricar papel apropriado para calandragem e impressao processo de fabricar papel de imprensa e papel de impressao feito a maquina
JP5872672A JPS544403B1 (oth) 1971-06-15 1972-06-14

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00153381A US3833466A (en) 1971-06-15 1971-06-15 Manufacture of hardwood printing paper

Publications (1)

Publication Number Publication Date
US3833466A true US3833466A (en) 1974-09-03

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Application Number Title Priority Date Filing Date
US00153381A Expired - Lifetime US3833466A (en) 1971-06-15 1971-06-15 Manufacture of hardwood printing paper

Country Status (11)

Country Link
US (1) US3833466A (oth)
JP (1) JPS544403B1 (oth)
AR (1) AR195283A1 (oth)
AU (1) AU470597B2 (oth)
BR (1) BR7203826D0 (oth)
CA (1) CA967360A (oth)
ES (1) ES403729A1 (oth)
FR (1) FR2142450A5 (oth)
IT (1) IT955982B (oth)
PL (1) PL83664B1 (oth)
ZA (1) ZA723352B (oth)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5320334A (en) * 1992-06-23 1994-06-14 Deangelis Andrew V Method of printing a book having pages of newsprint and pages of coated enamel pages
WO1995009733A1 (en) * 1992-06-23 1995-04-13 Deangelis Andrew V Multi-colored book printing method and apparatus
US5542193A (en) * 1992-04-24 1996-08-06 Beloit Technologies, Inc. Dryer group for curl control
US5884415A (en) * 1992-04-24 1999-03-23 Beloit Technologies, Inc. Paper making machine providing curl control

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2802610C2 (de) * 1978-01-21 1983-05-05 Vits-Maschinenbau Gmbh, 4018 Langenfeld Blaskasten zum schwebenden Führen und/oder Fördern von Bahnen oder Bogen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA614598A (en) * 1961-02-14 Allander Claes Method in manufacturing paper to increase its strength
US3331138A (en) * 1965-06-21 1967-07-18 Int Paper Co Papermaking method and apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA614598A (en) * 1961-02-14 Allander Claes Method in manufacturing paper to increase its strength
US3331138A (en) * 1965-06-21 1967-07-18 Int Paper Co Papermaking method and apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Casey, Pulp and Paper, Vol. I, (1952), p. 196, 450. *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5542193A (en) * 1992-04-24 1996-08-06 Beloit Technologies, Inc. Dryer group for curl control
US5884415A (en) * 1992-04-24 1999-03-23 Beloit Technologies, Inc. Paper making machine providing curl control
US5320334A (en) * 1992-06-23 1994-06-14 Deangelis Andrew V Method of printing a book having pages of newsprint and pages of coated enamel pages
WO1995009733A1 (en) * 1992-06-23 1995-04-13 Deangelis Andrew V Multi-colored book printing method and apparatus
US5547225A (en) * 1992-06-23 1996-08-20 Deangelis; Andrew V. Printing method and apparatus
US5749567A (en) * 1992-06-23 1998-05-12 Deangelis; Andrew V. Printing method and apparatus

Also Published As

Publication number Publication date
AU470597B2 (en) 1976-03-25
JPS544403B1 (oth) 1979-03-06
IT955982B (it) 1973-09-29
FR2142450A5 (oth) 1973-01-26
ZA723352B (en) 1973-03-28
CA967360A (en) 1975-05-13
BR7203826D0 (pt) 1973-05-31
AR195283A1 (es) 1973-09-28
PL83664B1 (oth) 1975-12-31
AU4290972A (en) 1973-12-06
ES403729A1 (es) 1976-01-01

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