Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/02—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/006—Making patterned paper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F1/00—Mechanical deformation without removing material, e.g. in combination with laminating
  • B31F1/12—Crêping
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F1/00—Mechanical deformation without removing material, e.g. in combination with laminating
  • B31F1/12—Crêping
  • B31F1/126—Crêping including making of the paper to be crêped
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
  • D21H11/20—Chemically or biochemically modified fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/002—Tissue paper; Absorbent paper
  • D21H27/004—Tissue paper; Absorbent paper characterised by specific parameters
  • D21H27/005—Tissue paper; Absorbent paper characterised by specific parameters relating to physical or mechanical properties, e.g. tensile strength, stretch, softness
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/002—Tissue paper; Absorbent paper
  • D21H27/008—Tissue paper; Absorbent paper characterised by inhomogeneous distribution or incomplete coverage of properties, e.g. obtained by using materials of chemical compounds

Definitions

• Fabric creping has been employed in connection with papermaking processes which include mechanical or compactive dewatering ofthe paper web as a means to influence product properties. See United States Patent Nos. 4,689,119 and 4,551,199 of Weldon; 4,849,054 and 4,834,838 of Klowak; and 6,287,426 of Edwards et al. Operation of fabric creping processes has been hampered by the difficulty of effectively transferring a web of high or intermediate consistency to a dryer. Note also United States Patent No. 6,350,349 to Hermans et al. which discloses wet transfer of a web from a rotating transfer surface to a fabric. Further patents relating to fabric creping more generally include the following: 4,834,838; 4,482,4294,445,638 as well as 4,440,597 to Wells et al.
• the absorbency, bulk and stretch of a wet-pressed web can be vastly improved by wet fabric creping a web and rearranging the fiber on a creping fabric, while preserving the high speed, thermal efficiency, and furnish tolerance to recycle fiber of conventional wet press processes
• an absorbent sheet of cellulosic fibers including a mixture of hardwood fibers and softwood fibers arranged in a reticulum having: (i) a plurality of pileated fiber enriched regions of relatively high local basis weight interconnected by way of (ii) a plurality of lower local basis weight linking regions.
• the fiber orientation ofthe linking regions is biased along the direction between pileated regions interconnected thereby.
• the relative basis weight, degree of pileation, hardwood to softwood ratio, fiber length distribution, fiber orientation, and geometry ofthe reticulum are controlled such that the sheet exhibits a percent CD stretch of at least about 2.75 times the dry tensile ratio ofthe sheet.
• the sheet exhibits a void volume of at least about 5 g/g, a CD stretch of at least about 5 percent and a MD/CD tensile ratio of less than about 1.75. In another preferred embodiment the MD/CD tensile ratio is less than about 1.5. In another preferred embodiment the • sheet has an absorbency of at least about 5 g/g, a CD stretch of at least about 10 percent and a MD/CD tensile ratio of less than about 2.5. In a still further preferred embodiment the sheet exhibits an absorbency of at least about 5 g/g, a CD stretch of at least about 15 percent and a MD/CD tensile ratio of less than about 3.5. A CD stretch of at least about 20 percent and a MD/CD tensile ratio of less than about 5 is believed achievable in accordance with the present invention.
• a percent CD stretch of at least about 4 and a dry tensile ratio of from about 0.4 to about 4 are typical of products ofthe invention.
• the products Preferably, the products have a CD stretch of least about 5 or 6. In some cases a CD stretch of at least about 8 or at least about 10 is preferred.
• the inventive products typically have a void volume of at least about 5 or 6 g/g. Void volumes of at least about 7 g/g, 8 g/g, 9 g/g or 10 g/g are likewise typical.
• the inventive sheet may consist predominantly (more than 50%) of hardwood fiber or softwood fiber. Typically the sheet includes a mixture of these two fibers.
• a method of making a cellulosic web for tissue or towel products including the steps of: (a) preparing an aqueous cellulosic papermaking furnish; (b) providing the papermaking furnish to a forming fabric as a jet issuing from a head box at a jet speed; (c) compactively dewatering the papermaking furnish to form a nascent web having an apparently random distribution of papermaking fiber; (d) applying the dewatered web having an apparently random fiber distribution to a translating transfer surface moving at a first speed; (e) belt creping the web from the transfer surface at a consistency of from about 30 to about 60 percent utilizing a patterned creping belt, the creping step occurring under pressure in a belt creping nip defined between the transfer surface ofthe creping belt wherein the belt is traveling at a second speed slower than the speed of said transfer surface.
• the belt pattern, nip parameters, velocity delta and web consistency are selected such that the web is creped from the transfer surface and redistributed on the creping belt to form a web with a reticulum having a plurality of interconnected regions of different local basis weights including at least (i) a plurality of fiber enriched regions of relatively high local basis weight, interconnected by way of (ii) a plurality of lower local basis weight regions.
• the web is then dried. It will be seen that the hardwood to softwood ratio, fiber length distribution, overall crepe, jet speed, drying and belt creping steps are controlled and the creping belt pattern is selected such that the web is characterized in that it has a percent CD stretch which is at least about 2.75 times the dry tensile ratio ofthe web.
• inventive process may be practiced with predominantly hardwood fiber for producing base sheet for tissue manufacture or the inventive process may be practiced with a furnish consisting predominantly of softwood fiber when it is desired to make towel. It will be appreciated by one of skill in the art that other additives are selected as so desired. It has been found in accordance with the present invention that the webs having a local variation in basis weight are preferably calendered between steel calender rolls when calendering is desirable.
• the belt creped web ofthe invention is typically characterized in that the fibers ofthe fiber enriched regions are biased in the cross direction as will be appreciated from the attached photomicrographs.
• the process is operated at a fabric crepe of from about 10 to about 100 percent.
• Preferred embodiments include those wherein the process is operated at a fabric crepe of at least about 40, 60, 80 or 100 percent or more.
• the inventive process may be operated at a fabric crepe of 125 percent or more.
• the process ofthe present invention is exceedingly furnish tolerant, and can be operated with large amounts of secondary fiber if so desired.
• Figure 1 is a photomicrograph (120X) in section along the machine direction of a fiber enriched region of a fabric creped sheet
• Figure 2 is a plot of MD/CD dry tensile ratio versus jet/wire velocity delta in feet per minute;
• Figure 3 is a photomicrograph (10X) ofthe fabric side of a fabric creped web
• Figure 4 is a schematic diagram illustrating a paper machine which may be used to produce the products and practice the process ofthe present invention
• Figures 5 and 6 are plots of CD stretch versus MD/CD tensile ratio for 13 lb sheet produced with various fabrics and crepe ratios;
• Figures 7 through 9 are plots of CD stretch versus dry tensile ratio for various 24 lb sheets ofthe invention.
• Figure 10 is a plot of caliper reduction versus calender load for various combinations of steel and rubber calender rolls.
• Te ⁇ ninology used herein is given its ordinary meaning with the exemplary definitions set forth immediately below.
• Absorbency ofthe inventive products is measured with a simple absorbency tester.
• the simple absorbency tester is a particularly useful apparatus for measuring the hydrophilicity and absorbency properties of a sample of tissue, napkins, or towel.
• a sample of tissue, napkins, or towel 2.0 inches in diameter is mounted between a top flat plastic cover and a bottom grooved sample plate.
• the tissue, napkin, or towel sample disc is held in place by a 1/8 inch wide circumference flange area.
• the sample is not compressed by the holder.
• De- ionized water at 73 °F is introduced to the sample at the center ofthe bottom sample plate through a 1 mm. diameter conduit. This water is at a hydrostatic head of minus 5 mm.
• Flow is initiated by a pulse introduced at the start ofthe measurement by the instrument mechanism. Water is thus imbibed by the tissue, napkin, or towel sample from this central entrance point radially outward by capillary action. When the rate of water imbibation decreases below 0.005 gm water per 5 seconds, the test is terminated. The amount of water removed from the reservoir and absorbed by the sample is weighed and reported as grams of water per square meter of sample unless otherwise indicated. In practice, an M/K Systems Inc. Gravimetric Absorbency Testing System is used. This is a commercial system obtainable from M/K Systems Inc., 12 Garden Street,
• WAC or water absorbent capacity also referred to as SAT is actually determined by the instrument itself.
• WAC is defined as the point where the weight versus time graph has a "zero" slope, i.e., the sample has stopped absorbing.
• the termination criteria for a test are expressed in maximum change in water weight absorbed over a fixed time period. This is basically an estimate of zero slope on the weight versus time graph.
• the program uses a change of 0.005 g over a 5 second time interval as termination criteria; unless "Slow Sat" is specified in which case the cut off criteria is 1 mg in 20 seconds.
• Basis weight refers to the weight of a 3000 square foot ream of product. Consistency refers to percent solids of a nascent web, for example, calculated on a bone dry basis. "Air dry” means including residual moisture, by convention up to about 10 percent moisture for pulp and up to about 6% for paper. A nascent web having 50 percent water and 50 percent bone dry pulp has a consistency of 50 percent.
• cellulosic cellulosic sheet
• papermaking fibers include virgin pulps or recycle (secondary) cellulosic fibers or fiber mixes comprising cellulosic fibers.
• Fibers suitable for making the webs of this invention include: nonwood fibers, such as cotton fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and wood fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, aspen, or the like.
• Papermaking fibers can be liberated from their source material by any one of a number of chemical pulping processes familiar to one experienced in the art including sulfate, sulfite, polysulfide, soda pulping, etc.
• the pulp can be bleached if desired by chemical means including the use of chlorine, chlorine dioxide, oxygen and so forth.
• the products ofthe present invention may comprise a blend of conventional fibers
• the term compactively dewatermg the web or furnish refers to mechanical dewatering by wet pressing on a dewatering felt, for example, in some embodiments by use of mechanical pressure applied continuously over the web surface as in a nip between a press roll and a press shoe wherein the web is in contact with a papermaking felt.
• Compactively dewatering a web thus refers, for example, to removing water from a nascent web having a consistency of less than 30 percent or so by application of pressure thereto and/or increasing the consistency ofthe web by about 15 percent or more by application of pressure thereto.
• Fabric side and like terminology refers to the side ofthe web which is in contact with the creping and drying fabric.
• Dryer side or the like is the side of the web opposite the fabric side ofthe web.
• Fpm refers to feet per minute while consistency refers to the weight percent fiber of the web.
• MD machine direction
• CD cross-machine direction
• Nip parameters include, without limitation, nip pressure, nip length, backing roll hardness, fabric approach angle, fabric takeaway angle, uniformity, and velocity delta between surfaces ofthe nip.
• Nip length means the length over which the nip surfaces are in contact.
• On line and like terminology refers to a process step performed without removing the web from the papermachine in which the web is produced. A web is drawn or calendered on line when it is drawn or calendered without being severed prior to wind-up.
• a translating transfer surface refers to the surface from which the web is creped into the creping fabric.
• the translating transfer surface may be the surface of a rotating drum as described hereafter, or may be the surface of a continuous smooth moving belt or another moving fabric which may have surface texture and so forth.
• the translating transfer surface needs to support the web and facilitate the high solids creping as will be appreciated from the discussion which follows.
• Calipers and or bulk reported herein may be 1, 4 or 8 sheet calipers.
• the sheets are stacked and the caliper measurement taken about the central portion of the stack.
• the test samples are conditioned in an atmosphere of 23° ⁇ 1.0°C (73.4° ⁇ 1.8°F) at 50% relative humidity for at least about 2 hours and then ⁇ measured with a Thwing-Albert Model 89-11- JR or Progage Electronic Thicl ⁇ iess Tester with 2-in (50.8-mm) diameter anvils, 539 ⁇ 10 grams dead weight load, and 0.231 in./sec descent rate.
• each sheet of product to be tested must have the same number of plies as the product is sold.
• eight sheets are selected and stacked together.
• napkins are enfolded prior to stacking.
• each sheet to be tested must have the same number of plies as produced off the winder.
• basesheet testing off of the papermachine reel single plies must be used. Sheets are stacked together aligned in the MD. On custom embossed or printed product, try to avoid taking measurements in these areas if at all possible. Bulk may also be expressed in units of volume/weight by dividing caliper by basis weight.
• Dry tensile strengths (MD and CD), stretch, ratios thereof, break modulus, stress and strain are measured with a standard Instron test device or other suitable elongation tensile tester which may be configured in various ways, typically using 3 or 1 inch wide strips of tissue or towel, conditioned at 50% relative humidity and 23 °C (73.4), with the tensile test run at a crosshead speed of 2 in/min.
• Tensile ratios are simply ratios ofthe values determined by way ofthe foregoing methods. Tensile ratio refers to the MD/CD dry tensile ratio unless otherwise stated. Unless otherwise specified, a tensile property is a dry sheet property. Tensile strength is sometimes referred to simply as tensile. Unless otherwise specified, break tensile strength, stretch and so forth are reported herein. "Fabric crepe ratio" is an expression ofthe speed differential between the creping fabric and the forming wire and typically calculated as the ratio ofthe web speed immediately before creping and the web speed immediately following creping, because the forming wire and transfer surface are typically, but not necessarily, operated at the same speed:
• Line crepe (sometimes referred to as overall crepe), reel crepe and so forth are similarly calculated as discussed below.
• PLI or pli means pounds force per linear inch.
• Predominantly means more than about 50%, typically by weight; bone dry basis when referring to fiber.
• Pusey and Jones (P+J) hardness (indentation) sometimes referred to as P+J is measured in accordance with ASTM D 531, and refers to the indentation number (standard specimen and conditions).
• Velocity delta means a difference in linear speed.
• the void volume and /or void volume ratio as referred to hereafter, are determined by saturating a sheet with a nonpolar POROFIL ® liquid and measuring the amount of liquid absorbed.
• the volume of liquid absorbed is equivalent to the void volume within the sheet structure.
• the percent weight increase (PWI) is expressed as grams of liquid absorbed per gram of fiber in the sheet structure times 100, as noted hereinafter. More specifically, for each single- ply sheet sample to be tested, select 8 sheets and cut out a 1 inch by 1 inch square (1 inch in the machine direction and 1 inch in the cross-machine direction). For multi-ply product samples, each ply is measured as a separate entity. Multiple samples should be separated into individual single plies and 8 sheets from each ply position used for testing.
• the PWI for all eight individual specimens is determined as described above and the average ofthe eight specimens is the PWI for the sample.
• the void volume ratio is calculated by dividing the PWI by 1.9 (density of fluid) to express the ratio as a percentage, whereas the void volume (gms/gm) is simply the weight increase ratio; that is, PWI divided by 100.
• an absorbent paper web is made by dispersing papermaking fibers into aqueous furnish (slurry) and depositing the aqueous furnish onto the forming wire of a papermaking machine, typically by way of a jet issuing from a headbox.
• aqueous furnish slurry
• Any suitable forming scheme might be used.
• an extensive but non-exhaustive list in addition to Fourdrinier formers includes a crescent former, a C-wrap twin wire former, an S-wrap twin wire former, or a suction breast roll former.
• the forming fabric can be any suitable foraminous member including single layer fabrics, double layer fabrics, triple layer fabrics, photopolymer fabrics, and the like.
• Non-exhaustive background art in the forming fabric area includes United States Patent Nos.
• One forming fabric particularly useful with the present invention is Voith Fabrics Forming Fabric 2164 made by Voith Fabrics Corporation, Shreveport, LA.
• Foam- forming ofthe aqueous furnish on a forming wire or fabric may be employed as a means for controlling the permeability or void volume ofthe sheet upon fabric-creping. Foam-forming techniques are disclosed in United States Patent No. 4,543,156 and Canadian Patent No. 2,053,505, the disclosures of which are incorporated herein by reference.
• the foamed fiber furnish is made up from an aqueous sluny of fibers mixed with a foamed liquid earner just prior to its introduction to the headbox.
• the pulp slurry supplied to the system has a consistency in the range of from about 0.5 to about 7 weight percent fibers, preferably in the range of from about 2.5 to about 4.5 weight percent.
• the pulp slurry is added to a foamed liquid comprising water, air and surfactant containing 50 to 80 percent air by volume forming a foamed fiber furnish having a consistency in the range of from about 0.1 to about 3 weight percent fiber by simple mixing from natural turbulence and mixing inherent in the process elements.
• the addition ofthe pulp as a low consistency slurry results in excess foamed liquid recovered from the forming wires.
• the excess foamed liquid is discharged from the system and may be used elsewhere or treated for recovery of surfactant therefrom.
• the furnish may contain chemical additives to alter the physical properties ofthe paper produced. These chemistries are well understood by the skilled artisan and may be used in any known combination. Such additives may be surface modifiers, softeners, debonders, strength aids, latexes, opacifiers, optical brighteners, dyes, pigments, sizing agents, barrier chemicals, retention aids, insolubilizers, organic or inorganic crosslinkers, or combinations thereof; said chemicals optionally comprising polyols, starches, PPG esters, PEG esters, phospholipids, surfactants, polyamines, HMCP or the like;
• the pulp can be mixed with strength adjusting agents such as wet strength agents, dry strength agents and debonders/softeners and so forth. Suitable wet strength agents are known to the skilled artisan. A comprehensive but non- exhaustive list of useful strength aids include urea-formaldehyde resins, melamine formaldehyde resins, glyoxylated polyacrylamide resins, polyamide- epichlorohydrin resins and the like.
• Thermosetting polyacrylamides are produced by reacting acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to produce a cationic polyacrylamide copolymer which is ultimately reacted with glyoxal to produce a cationic cross-linking wet strength resin, glyoxylated polyacrylamide.
• DMDMAC diallyl dimethyl ammonium chloride
• a cationic polyacrylamide copolymer which is ultimately reacted with glyoxal to produce a cationic cross-linking wet strength resin, glyoxylated polyacrylamide.
• Suitable temporary wet strength agents may likewise be included.
• a comprehensive but non-exhaustive list of useful temporary wet strength agents includes aliphatic and aromatic aldehydes including glyoxal, malonic dialdehyde, succinic dialdehyde, glutaraldehyde and dialdehyde starches, as well as substituted or reacted starches, disaccharides, polysaccharides, chitosan, or other reacted polymeric reaction products of monomers or polymers having aldehyde groups, and optionally, nitrogen groups.
• Representative nitrogen containing polymers which can suitably be reacted with the aldehyde containing monomers or polymers, includes vinyl-amides, acrylamides and related nitrogen containing polymers.
• the temporaiy wet strength resin may be any one of a variety of water- soluble organic polymers comprising aldehydic units and cationic units used to increase dry and wet tensile strength of a paper product. Such resins are described in United States Patent Nos. 4,675,394; 5,240,562; 5,138,002; 5,085,736; 4,981,557; 5,008,344; 4,603,176; 4,983,748; 4,866,151; 4,804,769 and 5,217,576. Modified starches sold under the trademarks CO-BOND® 1000 and CO-BOND® 1000 Plus, by National Starch and Chemical Company of Bridgewater, N.J. may be used.
• the cationic aldehydic water soluble polymer can be prepared by preheating an aqueous slu ⁇ y of approximately 5% solids maintained at a temperature of approximately 240 degrees Fahrenheit and a pH of about 2.7 for approximately 3.5 minutes. Finally, the slurry can be quenched and diluted by adding water to produce a mixture of approximately 1.0% solids at less than about 130 degrees Fahrenheit.
• Other temporary wet strength agents also available from National Starch and Chemical Company are sold under the trademarks CO-BOND® 1600 and CO-BOND® 2300. These starches are supplied as aqueous colloidal dispersions and do not require preheating prior to use.
• Temporary wet strength agents such as glyoxylated polyacrylamide can be used.
• Temporary wet strength agents such glyoxylated polyacrylamide resins are produced by reacting acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to produce a cationic polyacrylamide copolymer which is ultimately reacted with glyoxal to produce a cationic cross-linking temporary or semipermanent wet strength resin, glyoxylated polyacrylamide.
• DMDMAC diallyl dimethyl ammonium chloride
• acrylamide/DADMAC/glyoxal can be used to produce cross-linking resins, which are useful as wet strength agents.
• dialdehydes can be substituted for glyoxal to produce wet strength characteristics.
• Suitable dry strength agents include starch, guar gum, polyacrylamides, carboxymethyl cellulose and the like. Of particular utility is carboxymethyl cellulose, an example of which is sold under the trade name Hercules CMC, by Hercules Incorporated of Wilmington, Delaware.
• the pulp may contain from about 0 to about 15 lb/ton of dry strength agent.
• the pulp may contain from about 1 to about 5 lbs/ton of dry strength agent.
• Suitable debonders are likewise known to the skilled artisan. Debonders or softeners may also be incorporated into the pulp or sprayed upon the web after its formation.
• the present invention may also be used with softener materials including but not limited to the class of amido amine salts derived from partially acid neutralized amines. Such materials are disclosed in United States Patent No. 4,720,383. Evans, Chemistry and Industry, 5 July 1969, pp. 893-903; Egan, J.Am. Oil Chemist's Soc. Vol. 55 (1978), pp. 118-121; and Trivedi et al, J.Am.Oil Chemist's Soc, June 1981, pp. 754-756, incorporated by reference in their entirety, indicate that softeners are often available commercially only as complex mixtures rather than as single compounds. While the following discussion will focus on the predominant species, it should be understood that commercially available mixtures would generally be used in practice.
• Quasoft 202-JR is a suitable softener material, which may be derived by alkylating a condensation product of oleic acid and diethylenetriamine. Synthesis conditions using a deficiency of alkylation agent (e.g., diethyl sulfate) and only one alkylating step, followed by pH adjustment to protonate the non-ethylated species, result in a mixture consisting of cationic ethylated and cationic non- ethylated species. A minor proportion (e.g., about 10%) ofthe resulting amido amine cyclize to imidazoline compounds.
• alkylation agent e.g., diethyl sulfate
• the compositions as a whole are pH-sensitive. Therefore, in the practice ofthe present invention with this class of chemicals, the pH in the head box should be approximately 6 to 8, more preferably 6 to 7 and most preferably 6.5 to 7.
• Quaternary ammonium compounds such as dialkyl dimethyl quaternary ammonium salts are also suitable particularly when the alkyl groups contain from about 10 to 24 carbon atoms. These compounds have the advantage of being relatively insensitive to pH.
• Biodegradable softeners can be utilized. Representative biodegradable cationic softeners/debonders are disclosed in United States Patent Nos. 5,312,522; 5,415,737; 5,262,007; 5,264,082; and 5,223,096, all of which are incorporated herein by reference in their entirety.
• the compounds are biodegradable diesters of quaternary ammonia compounds, quatemized amine-esters, and biodegradable vegetable oil based esters functional with quaternary ammonium chloride and diester dierucyldimethyl ammonium chloride and are representative biodegradable softeners.
• a particularly preferred debonder composition includes a quaternary amine component as well as a nonionic surfactant.
• the nascent web is typically dewatered on a papermaking felt.
• Any suitable felt may be used.
• felts can have double-layer base weaves, triple-layer base weaves, or laminated base weaves.
• Preferred felts are those having the laminated base weave design.
• a wet-press-felt which may be particularly useful with the present invention is Vector 3 made by Voith Fabric. Background art in the press felt area includes United States Patent Nos. 5,657,797; 5,368,696; 4,973,512; 5,023,132; 5,225,269; 5,182,164; 5,372,876; and 5,618,612.
• a differential pressing felt as is disclosed in United States Patent No. 4,533,437 to Curran et al. may likewise be utilized.
• Suitable creping fabrics include single layer, multi-layer, or composite preferably open meshed structures. Fabrics may have at least one ofthe following characteristics: (1) on the side of the creping fabric that is in contact with the wet web (the "top” side), the number of machine direction (MD) strands per inch (mesh) is from 10 to 200 and the number of cross-direction (CD) strands per inch (count) is also from 10 to 200; (2) The strand diameter is typically smaller than 0.050 inch; (3) on the top side, the distance between the highest point ofthe MD knuckles and the highest point on the CD knuckles is from about 0.001 to about 0.02 or 0.03 inch; (4) In between these two levels there can be knuckles formed either by MD or CD strands that give the topography a three dimensional hill/valley appearance which is imparted to the sheet during the wet molding step; (5) The fabric may be oriented in any suitable way so as to achieve the desired effect on processing and
• the creping fabric may thus be ofthe class described in United States Patent No. 5,607,551 to Farrington et al, Cols. 7-8 thereof, as well as the fabrics described in United States Patent No. 4,239,065 to Trokhan and United States Patent No. 3,974,025 to Ayers.
• Such fabrics may have about 20 to about 60 meshes per inch and are formed from monofilament polymeric fibers having diameters typically ranging from about 0.008 to about 0.025 inches. Both warp and weft monofilaments may, but need not necessarily be ofthe same diameter.
• the filaments are so woven and complimentarily serpentinely configured in at least the Z-direction (the thickness ofthe fabric) to provide a first grouping or array of coplanar top-surface-plane crossovers of both sets of filaments; and a predetermined second grouping or array of sub-top-surface crossovers.
• the arrays are interspersed so that portions ofthe top-surface-plane crossovers define an array of wicker-basket-like cavities in the top surface ofthe fabric which cavities are disposed in staggered relation in both the machine direction (MD) and the cross-machine direction (CD), and so that each cavity spans at least one sub-top-surface crossover.
• the cavities are discretely perimetrically enclosed in the plan view by a picket-like-lineament comprising portions of a plurality ofthe top-surface plane crossovers.
• the loop of fabric may comprise heat set monofilaments of thermoplastic material; the top surfaces ofthe coplanar top-surface-plane crossovers may be monoplanar flat surfaces.
• Specific embodiments ofthe invention include satin weaves as well as hybrid weaves of three or greater sheds, and mesh counts of from about 10 X 10 to about 120 X 120 filaments per inch (4 X 4 to about 47 X 47 per centimeter). Although the preferred range of mesh counts is from about 18 by 16 to about 55 by 48 filaments per inch (9 X 8 to about 22 X 19 per centimeter).
• a dryer fabric may be used as the creping fabric if so desired.
• Suitable fabrics are described in United States Patent Nos. 5,449,026 (woven style) and 5,690,149 (stacked MD tape yam style) to Lee as well as United States Patent No. 4,490,925 to Smith (spiral style).
• a creping adhesive used on the Yankee cylinder is preferably capable of cooperating with the web at intermediate moisture to facilitate transfer from the creping fabric to the Yankee and to firmly secure the web to the Yankee cylinder as it is dried to a consistency of 95% or more on the cylinder preferably with a high volume drying hood.
• the adhesive is critical to stable system operation at high production rates and is a hygroscopic, re-wettable, substantially non- crosslinking adhesive. Examples of preferred adhesives are those which include poly(vinyl alcohol) ofthe general class described in United States Patent No. 4,528,316 to Soerens et al. Other suitable adhesives are disclosed in co-pending United States Provisional Patent Application Serial No.
• Suitable adhesives are optionally provided with modifiers and so forth. It is preferred to use crosslinker sparingly or not at all in the adhesive in many cases; such that the resin is substantially non-crosslinkable in use.
• Figure 1 shows a cross-section (120X) along the MD of a fabric-creped, sheet 10 illustrating a fiber-enriched, pileated region 12. It is seen that the web has microfolds transverse to the machine direction, i.e., the ridges or creases extend in the CD (into the photograph). It will be appreciated that fibers ofthe fiber-enriched region 12 have orientation biased in the CD, especially at the right side of region 12, where the web contacts a knuckle ofthe creping fabric.
• the jet/forming wire velocity delta jet velocity-wire velocity
• Figure 2 is a plot of MD/CD tensile ratio (strength at break) versus the difference between headbox jet velocity and forming wire speed (fpm).
• the upper U-shaped curve is typical of conventional wet-press absorbent sheet.
• the lower, broader curve is typical of fabric-creped product ofthe invention. It is readily appreciated from Figure 2 that MD/CD tensiles of below 1.5 or so are achieved in accordance with the invention over a wide range of jet to wire velocity deltas, a range which is more than twice that ofthe CWP curve shown.
• control ofthe headbox jet forming wire velocity may be used to achieve desired sheet properties.
• MD/CD ratios below square i.e. below 1
• square or below sheets are formed by way ofthe invention without a lot of fiber aggregates or "floes" which is not the case with the CWP products with low MD/CD tensile ratios.
• This difference is due, in part, to the relatively low velocity deltas required to achieve low tensiles in CWP products and may be due in part to the fact that fiber is redistributed on the creping fabric when the web is creped from the transfer surface in accordance with the invention.
• CD relative tensiles may be selectively elevated by control ofthe headbox to forming wire velocity delta and fabric creping.
• Figure 3 is a photomicrograph (10X) ofthe fabric side of a fabric-creped web. It is again seen in Figure 2 that sheet 10 has a plurality of very pronounced high basis weight, fiber-enriched regions 12 having fiber with orientation biased in the cross-machine direction (CD) linked by relatively low basis weight-linking regions 14, which have fiber orientation biased in a direction between pileated or fiber-enriched regions.
• CD cross-machine direction
• Figure 4 is a schematic diagram of a papermachine 15 having a conventional twin wire forming section 17, a felt run 19, a shoe press section 16, a creping fabric 18 and a Yankee dryer 20 suitable for practicing the present invention.
• Forming section 12 includes a pair of forming fabrics 22, 24 supported by a plurality of rolls 26, 28, 30, 32, 34, 36 and a forming roll 38.
• a headbox 40 provides papermaking furnish in the form of a jet to a nip 42 between forming roll 38 and roll 26 and the fabrics. Control ofthe jet velocity relative to the forming fabrics is an important aspect of controlling tensile ratio as will be appreciated by one of skill in the art.
• the furnish forms a nascent web 44 which is dewatered on the fabrics with the assistance of vacuum, for example, by way of vacuum box 46.
• the nascent web is advanced to a papermaking felt 48 which is supported by a plurality of rolls 50, 52, 54, 55 and the felt is in contact with a shoe press roll 56.
• the web is of low consistency as it is transferred to the felt. Transfer may be assisted by vacuum; for example roll 50 may be a vacuum roll if so desired or a pickup or vacuum shoe as is known in the art.
• Transfer roll 60 may be a heated roll if so desired.
• roll 56 could be a conventional suction pressure roll.
• roll 54 is a vacuum roll effective to remove water form the felt prior to the felt entering the shoe press nip since water from the furnish will be pressed into the felt in the shoe press nip.
• using a vacuum roll or STR at 54 is typically desirable to ensure the web remains in contact with the felt during the direction change as one of skill in the art will appreciate from the diagram.
• Web 44 is wet-pressed on the felt in nip 58 with the assistance of pressure shoe 62.
• the web is thus compactively dewatered at 58, typically by increasing the consistency by 15 or more points at this stage ofthe process.
• the configuration shown at 58 is generally termed a shoe press; in connection with the present invention cylinder 60 is operative as a transfer cylinder which operates to convey web 44 at high speed, typically 1000 fpm-6000 fpm to the creping fabric.
• Cylinder 60 has a smooth surface 64 which may be provided with adhesive and/or release agents if needed. Web 44 is adhered to transfer surface 64 of cylinder 60 which is rotating at a high angular velocity as the web continues to advance in the machine-direction indicated by arrows 66. On the cylinder, web 44 has a generally random apparent distribution of fiber.
• Direction 66 is referred to as the machine-direction (MD) ofthe web as well as that of papermachine 10; whereas the cross-machine-direction (CD) is the direction in the plane ofthe web perpendicular to the MD.
• MD machine-direction
• CD cross-machine-direction
• Web 44 enters nip 58 typically at consistencies of 10-25 percent or so and is dewatered and dried to consistencies of from about 25 to about 70 by the time it is transferred to creping fabric 18 as shown in the diagram.
• Fabric 18 is supported on a plurality of rolls 68, 70, 72 and a press nip roll or solid pressure roll 74 such that there is formed a fabric crepe nip 76 with transfer cylinder 60 as shown in the diagram.
• the creping fabric defines a creping nip over the distance in which creping fabric 18 is adapted to contact roll 60; that is, applies significant pressure to the web against the transfer cylinder.
• backing (or creping) roll 70 may be provided with a soft deformable surface which will increase the length ofthe creping nip and increase the fabric creping angle between the fabric and the sheet and the point of contact or a shoe press roll could be used as roll 70 to increase effective contact with the web in high impact fabric creping nip 76 where web 44 is transferred to fabric 18 and advanced in the machine-direction.
• a shoe press roll could be used as roll 70 to increase effective contact with the web in high impact fabric creping nip 76 where web 44 is transferred to fabric 18 and advanced in the machine-direction.
• the creping nip parameters can influence the distribution of fiber in the web in a variety of directions, including inducing changes in the z- direction as well as the MD and CD.
• the transfer from the transfer cylinder to the creping fabric is high impact in that the fabric is traveling slower than the web and a significant velocity change occurs.
• the web is creped anywhere from 10-60 percent and even higher during transfer from the transfer cylinder to the fabric.
• Creping nip 76 generally extends over a fabric creping nip distance of anywhere from about 1/8" to about 2", typically Vz" to 2". For a creping fabric with 32 CD strands per inch, web 44 thus will encounter anywhere from about 4 to 64 weft filaments in the nip.
• the nip pressure in nip 76, that is, the loading between backing roll 70 and transfer roll 60 is suitably 20-100, preferably 40-70 pounds per linear inch (PLI).
• nip 82 occurs at a web consistency of generally from about 25 to about 70 percent. At these consistencies, it is difficult to adhere the web to surface 84 of cylinder 80 firmly enough to remove the web from the fabric thoroughly.
• a poly(vinyl alcohol)/polyamide adhesive composition as noted above is applied at 86 as needed.
• a vacuum box may be employed at 67 in order to increase caliper.
• a vacuum typically, a vacuum of from about 5 to about 30 inches of Mercury is employed.
• the web is dried on Yankee cylinder 80 which is a heated cylinder and by high jet velocity impingement air in Yanlcee hood 88.
• Yankee cylinder 80 which is a heated cylinder and by high jet velocity impingement air in Yanlcee hood 88.
• web 44 is creped from the cylinder by creping doctor 89 and wound on a take-up roll 90.
• Creping ofthe paper from a Yankee dryer may be carried out using an undulatory creping blade, such as that disclosed in United States Patent No. 5,690,788, the disclosure of which is incorporated by reference.
• Use ofthe undulatory crepe blade has been shown to impart several advantages when used in production of tissue products. In general, tissue products creped using an undulatory blade have higher caliper (thickness), increased CD stretch, and a higher void volume than do comparable tissue products produced using conventional crepe blades. All of these changes effected by use ofthe undulatory blade tend to correlate with improved softness perception ofthe tissue products.
• calender station 85 with rolls 85(a), 85(b) to calender the sheet if so desired.
• an impingement air dryer, a through-air dryer, or a plurality of can dryers can be used instead of a Yankee. Impingement air dryers are disclosed in the following patents and applications, the disclosure of which is incorporated herein by reference:
• absorbent sheet was prepared at various weights, crepe ratios and so forth. This material exhibited high CD stretch at low dry tensile ratios as is seen particularly in Figures 5 through 9.
• the relative basis weight ofthe fiber enriched regions and linking regions, degree of pileation, fiber orientation and geometry ofthe reticulum are controlled by appropriate selection of materials and fabrics, as well as controlling the fabric crepe ratio, nip parameters and jet to wire velocity delta.
• BRT Bath tissue CD refers to tensile strength CD%, MD% - Stretch at break in the direction indicated CMC Carboxy methyl cellulose CWP Conventional Wet Press FC Fabric crepe or fabric crepe ratio GM, GMT - Geometric Mean, typically tensile Mod Modulus Ratio Dry Tensile Ratio, MD/ CD SPR Solid pressure roll, roll 74 seen in Figure 4 STR Suction turning roll, roll 54 as seen in Figure 4 T Ton TAD Through Air Dried '819 Refers to emboss pattern of USP 6,827,819
• Tissue Products Tissue Products (non-permanent wet strength grades where softness is a key parameter) made with a high solids fabric crepe process as described herein can use many ofthe same process parameters as would be used to make towel products (permanent wet strength grades where absorbency is important, strength in use is critical, and softness is less important than in tissue grades.) In either category, 1- ⁇ ly and 2-ply products can be made.
• Fibers Soft tissue products are optimally produced using high amounts of hardwood fibers. These fibers are not as coarse as the longer, stronger, softwood fibers. Further, these finer, shorter, fibers exhibit much higher counts per gram of fiber. On the negative side, these hardwood pulps generally contain more fines that are a result ofthe wood structures from which the pulp was made. Removing these fines can increase the numbers of actual fibers present in the final paper sheets. Also, removing these fines reduces the bonding potential during the drying process, making it easier to debond the sheet either with chemicals or with blade creping at the dry end ofthe paper machine. The key benefit derived from high fiber counts per gram of pulp is sheet opacity or lack of transparency.
• Softwood fibers are usually needed to provide a mesh-like structure on which the hardwood fibers can be arranged to optimize softness and optical properties. But even in the case of softwoods, fiber coarseness and fibers per gram are important properties. Long, thin, flexible, softwood fibers like northern softwoods present many more fibers per gram than do the long, coarse, thick, stiff southern softwoods.
• Tissue sheets generally employ a variety of chemicals to help meet consumer demands for performance and softness.
• a dry strength chemical to the long fiber portion ofthe pulp blend than to use a refiner to develop tensile. Refining generates fines and tends to make more bonds of higher bonding strength because refining makes the fibers more flexible, which increases the potential for fiber-fiber contacts during drying.
• dry strength additives increase the strengths ofthe available bonds without increasing the number of bonds.
• Such a sheet then ends up being inherently more flexible even before the fabric creping step ofthe fabric crepe process.
• Applying a debonding chemical to the hardwood portion is desirable so that these hardwood fibers have a lower propensity of bonding to each other, but retain the capability of being bonded to the network of softwood fibers that is primarily responsible for the working tensile strengths ofthe paper.
• a temporary wet strength agent can also be added along with the softwood and hardwood fibers to improve the perception of wet strength performance without sacrificing flush ability or septic tank safeness.
• Fabric Creping This process step is primarily responsible for the unique and desirable properties of a tissue sheet. Increased fabric creping increases caliper and decreases tensiles. Further, fabric creping changes the tensile ratios measured in the base sheets allowing sheets with equal MD/CD tensiles or sheets with lower MD than CD tensiles. However, it is desirable for tissue sheets to exhibit equal tensiles in the two directions as most products are used in a manner independent of sheet direction. For example, "poke through" in a toilet paper is influenced by this tensile ratio along with the fact that fabric creping develops higher CD stretch, especially at lower MD/CD ratios than conventional technology.
• Fabrics The design of the fabrics is a salient aspect of the process. But the parameters ofthe fabric go beyond the size and depth ofthe depressions woven into it. Their shape and placement is also very important. Diameters of the strands making up the woven fabric are also important. For example, the size ofthe knuckle that stands at the leading edge ofthe depression into which the sheet will be creped determines the parameters of fabric crepe ratio and basis weight at which holes will appear in the sheet.
• the challenge is to make these depressions as deep as possible with finest possible strand diameters, thereby allowing greater fabric crepe ratios resulting in higher sheet calipers at a given ratio.
• fabric designs need to change based upon the weight ofthe sheet being produced. For example, a very high quality, premium, 2-ply bathroom tissue exhibiting high strength, caliper, and softness can be made on a 44M-design fabric. The 44G can also be used to make a heavier (up to 2x) weight single ply sheet with very good results.
• Another property ofthe fabric design is to impart a pattern into the sheet. Some fabric designs can impart a very noticeable pattern while others produce a pattern that seems to disappear into the background.
• Calendering By all accounts, more calendering is better insofar as a reasonable level of caliper is maintained in the sheet for subsequent converting. Too little caliper requires too much embossing which then degrades the overall quality. Therefore, one strategy for producing for quality toilet paper is use the coarsest fabric without putting holes in the sheet, reducing the fabric creping level so that more ofthe MD stretch will come from the reel crepe portion and still get sufficient caliper prior to calendering so that at least about 20-40%o of this caliper may be removed during the calendering step. These calendering levels tend to reduce the sidedness of sheets. Alternatively, a quality sheet can be made with a finer fabric but with a lower reel crepe/fabric crepe ratio.
• Towel Products behave in a fashion similar to the tissue sheets to various process parameters. However, in many cases towel products utilize the same parameters but in an opposite direction with some in the same direction. For example, both product forms desire caliper as caliper relates directly to softness in tissue products and absorbency in towel products. In the following parameters, only the differences from tissue situations will be discussed.
• Towels require functional strength in use, which usually means when wetted. To reach these needed tensiles, long softwood fibers are used in ratios about opposite that of tissue products. Ratios of 70 to 90 percent softwood fibers are common. Refining can be used but tends to close up the sheet so much so that the subsequent fabric creping cannot "open" the structure. This results in slower absorbency rates and lower capacities. Unlike tissue products, fines can be utilized in towel sheets providing that not too much hardwood is used as this again would tend to close the sheet and also to reduce its tensile capability.
• debonders can also be used in towels! But their use must be done judiciously. Likewise, refining ofthe fibers needs to be regulated to lower levels to keep the sheet open and a quick absorber. Therefore chemical strength agents are routinely added. Of course wet strength chemicals must be added to prevent sliredding in use. But to get to high wet tensile levels the ratio of wet to dry tensiles must be maximized. If diy tensile levels get too high the towel sheet becomes too "papery” and is judged as low quality by consumers. Therefore, wet strength agents and CMC are added to increase the CD wet/dry ratio from the typical 25%> up to the desired 30-35% range.
• Fabric Creping Increasing the fabric creping increases the absorbency directly. Therefore it is desirable to maximize fabric creping.
• FC also reduces tensiles so there is the balance that must be maintained.
• Towel sheets sometimes cannot exhibit high levels of MD stretch because ofthe type of dispensers that are used. In these cases FC must also be limited. Therefore, towels require a coarser fabric design on average than do tissue sheets. Further, since these wet sheets will typically exhibit considerable wet strength, they may be more difficult to mold at the same consistency as a tissue sheet.
• Coarse fabrics are desirable for towels in general.
• Two-ply towel sheets are typically made on a 44G or 36G fabric or coarser with good results, although good results can be obtained with finer fabrics, particularly if the fabric crepe ratio is increased.
• One-ply sheets often require an even coarser fabric along with other technology to make and acceptable sheet. The longer fibers in the sheets and the higher strengths permit the use of these fabrics and higher FC ratios before holes appear in the sheets.
• Creping Very little creping is done on towel sheets. Creping does increase caliper but does so in a manner similar to CWP sheets. This caliper disappears when wetted and the sheet expands. Caliper from fabric creping acts like a dry sponge when wetted. The sheet expands in the Z-direction and can shrink in the MD & CD directions. This behavior adds greatly to the perceived absorbency ofthe towels and makes them look similar to TAD towels.
• using the serrated blades of Taurus technology in conjunction with fabric crepe process improves the absorbency, caliper, and softness ofthe towel sheet. The CD stiffness is reduced while the CD stretch is increased. The higher caliper produced at the blade allows more calendering and hence more sheet smoothness.
• Calendering Towel sheets benefit from calendering for two key reasons. First, calendering smoothes the sheets and improves the tactile feel. Second, it "crushes" the domes produced by the fabrics imparting more Z-direction depth to the feel ofthe sheet and often improve the absorbent properties at a given caliper.
• the commercial 1-ply BRT sensory softness objective of 17.0 was achieved at 20 lb basis weight. Consumer testing will determine the effect of reduced basis weight on consumer acceptance ofthe product.
• Southern HW and S W to make 1 -ply retail tissue at 21.4 lb/3000 sq. ft. the highest sensory softness achieved at 450 GMT was 16.9.
• calendering at higher than 65 PLI may decrease softness when using virgin HW and recycled fiber.
• 80 PLI may be the upper limit.
• creping fabrics used in this study affected basesheet caliper, but did not significantly affect sensory softness.
• the fabric crepe process ofthe invention produces a very low modulus sheet that is acceptable for retail or commercial BRT. However, because the sheet is attached to the Yankee with a fabric, there is less contact area on the dryer. During the Yanlcee creping process, less smoothing ofthe sheet surface occurs compared to conventional attachment to the Yankee with a felt. This results in a flannel-like feel compared to the silky feel of conventional creping.
• the airside ofthe sheet is less smooth than the dryerside.
• the airside contributes to overall softness, since it cannot be hidden to the inside as in a 2-ply product. This combination results in a lower sensory softness rating.
• the current approach to improving softness is to build caliper with a relatively coarse creping fabric, add a softening agent and calender with "high" load to smooth the sheet and reduce two- sidedness.
• the tissue (commercial) furnish, for 1-ply BRT, will be 40% Northern HW and 60% recycled fiber.
• FRF is Fox River recycled wet- lap.
• FRF is a high brightness recycled fiber. With only a few data points, 17.5 sensory softness is the best so far.
• Rubber/Steel Calendering To reduce the two-sidedness of 1-ply BRT, a rubber roll and a conventional steel calender roll were compared to conventional steel/steel calendering. The rubber roll was placed against the dryerside ofthe sheet. Tables 5-7 below show the effect of calender load on basesheet caliper using rubber rolls of different hardness's. Both rubber rolls gave similar levels of caliper reduction for equivalent calender load. The steel/steel rolls gave significantly higher caliper reduction at equivalent load as seen in the chart below. The 56 P+J roll, which is harder than the (nominal) 80 P+J roll, should have given more caliper loss at equivalent load.
• the (nominal) 80 P+J roll had been used previously and its actual measured P+J value was 70. Its cover thickness was 5/8 inches compared to 1 inch for the 56 P+J roll. The calculated nip width for a 70 P+J roll with a 5/8-inch'cover thickness is slightly less than for the 56 P+J roll with a 1-inch cover. This explains the higher caliper reduction seen with the "80 P+J" roll.
• Fabric Crepe Versus Reel Crepe Basesheet was produced at constant line crepe, but with a wide range of fabric crepe percents.
• Line crepe or overall crepe is calculated by dividing transfer cylinder speed (also appx forming speed) by reel speed. From this value, 1 is subtracted. The resulting value is multiplied by 100 and is expressed as percent.
• transfer cylinder speed is divided by Yanlcee speed, because this is also the creping fabric speed, and then 1 is subtracted and multiplied by 100.
• the Yanlcee speed is divided by the reel speed and then 1 is subtracted and multiplied by 100.
• the transfer cylinder speed and reel speed were held constant and Yanlcee speed varied to create the different fabric/reel crepe conditions.
• MD/CD Tensile Ratio Effect The fabric crepe process has the ability to easily control MD/CD tensile ratio over a much wider range than conventional wet-press and TAD processes. Ratios of 4.0 to 0.4 have been produced without pushing the process to its limits. Traditionally, tissue products required that MD tensile be higher than CD tensile to maximize formation. For maximum softness, CD tensile was kept as low as possible. This increases the risk of failure in use by consumers. If CD tensile could be increased and MD tensile decreased, GMT would remain constant. Therefore, at equivalent overall strength there would be less chance of failure. The table below shows 1-ply finished BRT data for two separate trials in which MD/CD tensile ratio was varied.
• Southern HW Level The effect of Southern HW level on sensory softness is shown in Table 19 below. No softness improvement at 75% HW was observed. In both cases softness was well below the target of 17.0. The 80 P+J rubber/steel calendering rolls were used. Table 19
• Fabric Crepe Versus Spray Softener Process variables were manipulated to determine which, if any, would result in a finished product sensory softness of 17.0 using Southern HW and SW. One such comparison was between a basesheet with no spray softener using high fabric crepe to control strength and low fabric crepe using spray softener to control strength. Table 20 shows that softness was equivalent when adjusted for GMT. In both cases softness was well below the target of 17.0. The 80 P+J rubber/steel calendering rolls were used.
• the molding box was located on the creping fabric, between the crepe roll and the solid pressure roll. Sheet solids were usually between 38 and 44% at this point. The effect of vacuum on sheet caliper can be seen in the table. An increase of almost 8 mils of "8-sheet caliper" was observed with 21 inches of mercury vacuum at the molding box. This is about a 14% increase. Both rolls were calendered at 50 PLI with steel/steel rolls. The amount of caliper development is dependent on the coarseness ofthe fabric weave and the amount of vacuum applied. Other sheet properties were not significantly affected. Drying was affected by use ofthe molding box. Without a significant change in Yanlcee hood temperature, sheet moisture after the Yankee increased from 2.66 to 3.65%. Vacuum pulls the sheet deeper into the creping fabric, therefore, there is less contact with the Yanlcee and more drying is required to maintain sheet moisture. See Table 21. In this case the Yanlcee hood temperatures were not adjusted.

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