US3647618A - Method and apparatus for improving formation uniformity of paper - Google Patents

Method and apparatus for improving formation uniformity of paper Download PDF

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Publication number
US3647618A
US3647618A US850861A US3647618DA US3647618A US 3647618 A US3647618 A US 3647618A US 850861 A US850861 A US 850861A US 3647618D A US3647618D A US 3647618DA US 3647618 A US3647618 A US 3647618A
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United States
Prior art keywords
web
rolls
formation
paper
nip
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Expired - Lifetime
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US850861A
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English (en)
Inventor
Sangho E Back
Rueben A Marti
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James River Corp of Nevada
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Crown Zellerbach Corp
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G1/00—Calenders; Smoothing apparatus
    • D21G1/0073—Accessories for calenders
    • D21G1/0093—Web conditioning devices

Definitions

  • the pressure nip compaction also contributes to densifi cation, improved surface smoothness and improved uniformity of fiber distribution.
  • a dandy roll Another mode which has been suggested to improve formation, especially in heavier sheets, is through the use of a dandy roll.
  • the dandy roll is positioned over the fourdrinier wire and turns in light contact with the top of the web in what has been described as a light stirring action on the fibers.
  • the use of a dandy roll has generally been limited to web speeds of less than 1,000 feet per minute.
  • Another object is to provide method and apparatus for treating a moving web to densify and smooth the web while improving the formation properties.
  • Still another object is to provide a method and apparatus for treating a nonwoven web so as to produce a web having potential to develop improved grease-resistant properties with a decrease in the amount of grease-resistant coating that need be applied to the web.
  • the above and other objects are obtained, according to a broader aspect of the present invention, by providing a method and apparatus for advancing the web at a moisture content of between about 18% and 40% through a pressure nip between a pair of pressure rolls.
  • the surface hardness of the rolls at room temperature is such that the rolls are very hard but have some slight compressibility and resilience at the pressures used; and, more specifically, the roll surface hardness of each roll is between 0 and 10 P & I Plastometer ball).
  • FIG. 1 is a side view, mostly diagrammatic, of a paper machine with the apparatus of the present invention located therein;
  • FIG. 2 is a partially diagrammatic side view of the apparatus of the present invention in place between dryer sections of a paper machine;
  • FIG. 3 is a diagrammatic, sectional side view illustrating a web passing between pressure rolls, as provided by the present invention.
  • FIG. 4 is a graphical approximation of curves taken from charts of a QNS/M Formation Tester comparing the formation curves of a web given a treatment according to the present invention with a web not treated.
  • cellulosic pulp stock flows through a slice opening 11 in a headbox onto a traveling endless screen 12 called a fourdrinier wire which is entrained for rotation at one end about a breast roll 13 and at the opposite end about a couch roll 14.
  • the stock in the headbox conventionally includes more than 99% water and less than 1% fiber.
  • Water is removed from the Web 15 through the screen 12, and the fibers become intermixed and matted together on the screen so that by the time the web reaches the couch roll 14 it has a water content of typically between about 80-85% water.
  • a felt press section 16 is conventionally used to remove additional water, and it is common for the web to contain from 60-70% water when it leaves the press section.
  • the moving web is advanced through at least one dryer section 17 for removing additional moisture from the Web.
  • This dryer section 17 or sections is used to bring the moisture content of the web down to between about 18-40% moisture.
  • the present invention is concerned with apparatus and method for treatment of the web at a station indicated by the numeral 18 (FIGS. 1, 2 and 3). After treatment at station 18, the web may pass through an additional conventional dryer 19 or dryers and the web may then be wound into a roll 20. Of course, additional treatments such as calendering or coating could be applied to the web after the web leaves dryer 19.
  • the web 15 is advanced over an upper guide roll 21 and then through a pressure nip 22 between a pair of opposed rolls 23 and 24; thence around a lower guide roll 25 to dryer section 19.
  • the roll 23 is provided with an appropriate drive mechanism (not shown) to turn the surface of the roll in the direction of the arrow at the speed of the web 15 being advanced through the nip 22.
  • the shaft forming the axis of the roll 23 is, of course, journalled for rotation and supportedat opposite ends thereof by an appropriate supporting means.
  • each arm 27 is pivotallysecured to a main horizontal supporting frame member 28 which is, in turn, supportedfrom the floor by vertical frame member 29.
  • the lower end of each arm has a pivotal connection 30 to the end of a piston rod 31, the rod 31 being attached to a piston which is movable lengthwise within a cylinder 32 in accordance with fluid under pressure being supplied to 4 the cylinder at either of opposite ends of the piston by fluid lines 33 and 34.
  • the end of the cylinder 32 remote from the piston rod is pivotally connected to a bracket 35 which is secured to vertical frame member 29.
  • the roll 24 is, therefore, movable toward the roll so as to permit the surface of the roll 24 to be pressureloaded against the surface of roll 23 so that when web 15 is in the nip between the rolls there will be pressure exerted by the roll surfaces on the web 15.
  • the specific manner of supporting the rolls 23 and 24 is not critical, however, and any conventional supporting mechanism may be used so long as there is provided means to urge the surface of one roll in a direction toward the surface of the other roll to provide a pressure nip.
  • each of the rolls should each have a surface hardness of between 0 and 10 P -& J Plastometer (%a" ball) at room temperature of 70 F. This does not necessarily mean that the rolls will be operated at room temperatures, but only specifies the surface hardness of the rolls when the rolls are at room temperature. With the hardness just specified, the rolls are very slightly compressible and slightly resilient at the nip pressures utilized.
  • the preferred surface hardness range for each roll 23 and 24 is between 0 and 5 P & J Plastometer 0A3 ball) at room temperature.
  • each roll 23 and 24 have a surface hardness between 0 and 10 P' & I Plastometer ball) and preferably between 0 and 5 P & J.
  • the roll may be constructed by applying, for example, a /8 inch thick covering material 36 (FIG. 3) having the desired surface hardness characteristics to the exterior surface of a steel core 37. It is desirable that the steel core be hollow so that a cooling fluidmay be circulated therethrough to provide some degree of cooling to the roll. This cooling effect is particularly desirable at high operating speeds where the nip action might cause undue heating and shorten the effective life of the rolls.
  • One material which has been found to be particularly desirablefor a roll cover 36 to provide the exterior surface for each of the rolls 23 and 24 is manufactured and sold by Stowe-Woodward Co. under the trademark Microrok. This material is a natural rubber compounded with a finely ground stone aggregate to provide the desired hardness properties.
  • the surface hardness of the rolls is important. This may be further expressed in terms of nip width of particular diameter rolls at particular loading pressures.
  • the nip width should be between about .07 inch and about .42 inch when 23-inch diameter rolls are loaded to provide a nip pressure of about pounds per lineal inch.
  • the nip width may be measured by using impression foil that is available for this purpose and pressure-loading the two rolls together (not rotating) with the foil in between. The impression width on the foil can be measured to obtain an indication of the nip width.
  • the moisture content of the web at the time it enters the nip 22 is too low, the position of the fibres has already been set, and the improvement in formation does not occur. If the moisture content of the web 15 at the time it enters the nip 22 is too high, it has been found that irregular glossy spots, perhaps due to excess mobility of fibers and fibrils, are formed on the web so that the formation does not improve.
  • the moisture content of the web should therefore be great enough so that a rearrangement of fibers and fibrils to a certain extent is possible, but not so great as to cause excessive, uneven glossy spots or mass movement of large massive areas.
  • the moisture content of the web should be between about 18-40%, and preferably between -35% when the web enters the nip 22 between the two rolls 23 and 24.
  • the pressure should be great enough to exert the desired compacting and fiber re-arranging action. It has been found that formation improvement is obtained with nip pressures as low as 50 pounds per lineal inch at the nip 22 between the rolls 23 and 24.
  • the maximum pressure which may be utilized is not critical and depends mostly on the physical limitations of the structure of the rolls themselves. Pressures up to 1,350 pounds per lineal inch have successfully been tried.
  • the desired amount of pressure utilized will vary with the basis weight of the web being treated, the heavier Webs utilizing greater pressure.
  • the optimum pressure range for paper having a basis weight of 25-45 pounds/ 3000 ft. is between about 100 and 250 pounds per lineal inch at the nip 22.
  • comparison of the uniformity of fiber distribution (formation) in sample sheets can be judged by looking through the samples at a light source.
  • the instrument graphically charts a formation curve and operates on the general principle of a scanning light source-photometer arrangement with the sample to be tested positioned between the light source and the photometer.
  • the abscissa (X axis) of the plotted curve represents thirty steps
  • Steps 3 through 28 utilize a filter in the machine at each step to provide a series of measurements corresponding to floc separation in inches (distance between centers of adjacent fiocs in the direction being scanned).
  • the filter at step 3 provides a reading which corresponds to a floc separation of 4.0 inches
  • the filter at step 16 provides a reading which corresponds to a floc separation of 0.21 inch (frequency of 800 cycles per second)
  • the filter at step 28 provides a reading which corresponds to 0.013 inch (frequency of 12,500 c.p.s.).
  • Steps 2 and 29 provide what is described as an LIN reading. In the LIN position, the signal bypasses the filters so the reading represents the integrated variation represented by the individual filters.
  • the ordinate (Y axis) of the curve provided by the instrument just mentioned is the relative intensity 'of the signal seen by the photometer.
  • the curve which is plotted by the instrument, in testing a sample for formation usually has its minimum ordinate, or Y axis values, at steps 3 and 28 (because the frequency of occurrence of flocs having the separations measured at steps 3 and 28 is not as great as at other steps) and the maximum ordinate value occurs at a filter-setting somewhere between steps 3 and 28.
  • Predominant floc size index the highest peak in the formation curve.
  • the step in the X axis at which the highest peak occurs is the floc separation step that occurs most often (i.e., the floc size that is most predominant).
  • Skewness the location of the predominant floc size relative to the step which is the center of the general formation curve (such center step being chosen as step 16 along the X axis of the curve).
  • the skewness is equal to the step number where the predominant floc size occurs (highest peak) minus 16.
  • a positive skewness number indicates the predominant floc size is to the left of the center of the general formation curve and is in the range of floc sizes less than 0.21 inch. Having the predominant floc size occur in the range of small floc sizes is an indication of good formation. Therefore, as a general rule, the higher the skewness number, the better the formation.
  • Example 1 A pulp containing 60% Douglas fir kraft, bleached to a brightness of 80 G.E.R.S. (General Electric Recording Spectrophotometer), and 40% bleached cottonwood sulfite was refined at high consistency (power input to refiner of 10.8 horsepower day/air dry ton of pulp) to 442 cc. CSF (Canadian Standard Freeness). The consistency was then reduced for conventional Claflin refining to 330 cc. CSF, followed by conventional Jordan refining to 195 cc. CSF.
  • G.E.R.S. General Electric Recording Spectrophotometer
  • the pulp was diluted to conventional papermaking consistency and formed into paper on a papermaking machine such as diagrammatically illustrated at FIG. 1.
  • the basis weight of the paper formed was about 32 lb./ream (3000 wt.
  • the moisture content of the web entering the nip between rolls 23 and 24 was about 28.0%.
  • the web bypassed the nip between rolls 23 and 24 (O nip pressure so no inventive treatment) and during other parts of the run the web was fed through the nip between rolls 23 and 24 at a pressure of about 175 lbs/lineal inch.
  • Example 2 A pulp containing 60% strong bleached sulfite, bleached to 81-84 G.E.R.S. (predominantly hemlock), and 40% ENSO birch kraft, bleached to 8-5 G.E.R.S., was refined at high consistency (power input to refiner of 7.1 horsepower day/air dry ton pulp) to 460 cc. CSF (Canadian Standard Freeness) followed by conventional Claflin and Jordan refining to 357 cc. CSF and 235 cc. CSF respectively.
  • the pulp was dilutedand made into paper as in Example 1 except that the moisture content at the nip between rolls 23 and 24 was slightly different, and a broader range of nip pressures was utilized.
  • ToP 280 168 173 166 165 Wire 319 173 175 171 172 Opac y, percent (Banseh & Lomb 49. 4 45.0 43. 5 44.3 43. 9 Densometer, cc./min.
  • Example 3 A pulp containing 60% Douglas fir kraft, bleached to a brightness of G.E.R.S., and 40% ENSO birch kraft, bleached to G.E.R.S., was refined at high consistency (power input to refiner of 9.2 horsepower day/air dry ton pulp) to 480 cc. CSF, followed by conventional Claflin to 345 cc. CSF and Jordan to 231 cc. CSF. The pulp was made into paper and samples obtained substantially in the same manner as was reported in'regard to Example 2 above. The data obtained from the samples is indicated at the following table.
  • Example 4 Substantially the same procedure as Example 2 was followed except in this Example 4 the pulp used was a mixture of 15% Douglas fir kraft, bleached to 80 G.E.R.S. brightness, 45% strong bleached kraft, and 40% ENSO birch kraft. The pulp was refined at high consistency (power input of 8.3.5 horsepower day/ air dry ton pulp) to 420 cc. CSF, followed by Claflin to 351 cc. CSF and Jordan to 222 cc. CSF.
  • Example 5 This example is presented to compare the grease-resistant properties of a web which has been given a rollcompacting treatment according to the present invention with a web which has not been given the roll-compacting inventive treatment, after both such webs having also been given a conventional size press barrier coating. This illustrates the inventive process requires less coating material to obtain even greater grease-resistant properties than a web which has not been given the inventive treatment.
  • Penford Gum 280 is a hydroxy ethyl ether derivative of corn starch and is sold by Penick and Ford Limited of Cedar Rapids, Iowa. When each of these samples was given the same coating treatment, it was found that Sample A picked up 2.7 lb./ream coating while Sample B picked up 1.6 lb./ream coating.
  • the 3M Kit has twelve Kit numbers (Kit Nos. 1-12), each containing varying amounts of castor oil, toluene and heptane.
  • Kit No. 1 the volume of castor oil is 200. with zero toluene and heptane.
  • the volume of castor oil decreases and the volume of toluene and heptane increases gradually through the sequential Kit Numbers, and Kit.
  • No. 12 has a volume of zero castor oil, 90 toluene and 11 0 heptane.
  • the 3M Kit value is defined as the highest Kit Number solution that will stand on the surface of a sheet for 15 seconds in the form of a drop without failing. The idea is that the higher the Kit Number a paper can stand without failure, the better the oil resistance.
  • both Samples A and B were given a size press coating. Then, each sample was given a conventional machine finish (calendering operation) after coating.
  • the calendered Sample A had a 3M Kit Rating of 4, but the calendered Sample B had a 3M Kit Rating of 8.
  • Additional coated Samples A and B were, instead of being calendered after coating, dampened and supercalendered, and a coated, supercalendered Sample A had a 3M Kit Rating of 3, while a coated, supercalendered Sample B had a 3M Kit Rating of 5.
  • inventive treatment in itself does not produce a slgnificant improvement in greaseproofing effect until a barrier coating is applied, there is a positive correlation between oil absorption of a base paper and grease resist ance of the paper after treatment with a size press formulation. Oil absorption properties then become a convenient tool to use in judging the base papers value for potential greaseproof applications without going through the actual step of applying a barrier coating. It is noted that in all examples the inventive treatment improved the oil absorption properties.
  • the QNS/M Formation Tester was used to graphically judge the samples in the examples above, the data was obtained from a CMD (cross machine direction) scan of the sample. Improvements were also noted in scanning the sample in a machine direction (WMD). Also, the improved formation was apparent in the invention-treated samples by visual inspection thereof.
  • CMD cross machine direction
  • Cellulosic material which is useful as a starting material in accordance with this invention may be derived from any species of coniferous pulp wood, such as spruce, hemlock, fir, pine and others; deciduous pulp wood, such as poplar, birch, cottonwood, alder and others; as well as from fibrous, nonwoody plants suitable for paper making, such as cereal straws, bagasse, corn stalks, grasses and the like, and also the usual waste cellulosic sources. Blegds of pulp from the mentioned sources may also be use It is to be noted that an improvement in formation was noted in connection with each of the pulp sources utilized in Examples 1-4 when treated according to the inventive process.
  • the web was, in each instance, made smoother and densified by the inventive process.
  • a method of improving the uniformity of fiber distribution in a process for forming a wet-laid web of nonwoven fibers wherein the improvement comprises:
  • a method of making a web of nonwoven cellulosic fibers by wet-laying a fiber-liquid slurry on a moving forming wire and thereafter removing moisture from the slurry to form a finished web, wherein the improvement comprises:

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US850861A 1969-08-18 1969-08-18 Method and apparatus for improving formation uniformity of paper Expired - Lifetime US3647618A (en)

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US (1) US3647618A (fr)
BE (1) BE754025A (fr)
DE (1) DE2036949C3 (fr)
FR (1) FR2057945A5 (fr)
GB (1) GB1266658A (fr)
NL (1) NL167744C (fr)
SE (1) SE368729B (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4612231A (en) * 1981-10-05 1986-09-16 James River-Dixie Northern, Inc. Patterned dry laid fibrous web products of enhanced absorbency
US5505820A (en) * 1995-01-11 1996-04-09 Westvaco Corporation Method for providing enhanced smoothness for a paper web
US20090056894A1 (en) * 2007-08-30 2009-03-05 Michael Alan Hermans Tissue machine parent roll with a Z-direction intensive property profile

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2525650A1 (fr) * 1982-04-22 1983-10-28 Condat Papeteries Procede et dispositif pour la fabrication de papiers ou cartons
DE4335053A1 (de) * 1993-10-14 1995-04-20 Kleinewefers Gmbh Verfahren und Vorrichtung zum Veredeln einer Papierbahn

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4612231A (en) * 1981-10-05 1986-09-16 James River-Dixie Northern, Inc. Patterned dry laid fibrous web products of enhanced absorbency
US5505820A (en) * 1995-01-11 1996-04-09 Westvaco Corporation Method for providing enhanced smoothness for a paper web
US20090056894A1 (en) * 2007-08-30 2009-03-05 Michael Alan Hermans Tissue machine parent roll with a Z-direction intensive property profile
US8277609B2 (en) * 2007-08-30 2012-10-02 Kimberly-Clark Worldwide, Inc Tissue machine parent roll having variable intrinsic sheet dryness

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DE2036949A1 (de) 1971-03-04
DE2036949C3 (de) 1980-06-12
DE2036949B2 (de) 1978-10-05
NL7011922A (fr) 1971-02-22
SE368729B (fr) 1974-07-15
GB1266658A (fr) 1972-03-15
BE754025A (fr) 1970-12-31
NL167744C (nl) 1982-01-18
FR2057945A5 (fr) 1971-05-21
NL167744B (nl) 1981-08-17

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