Patent Grant
10240296
The present invention relates to sanitary tissue products comprising fibrous structures that exhibit a novel combination of surface feel (surface mobility) as evidenced by average TS7 Emtec values of the sanitary tissue products and surface smoothness (glide vs. grip) as evidenced by slip stick coefficient of friction of the sanitary tissue product and/or a novel combination of surface feel (surface mobility) as evidenced by average TS7 Emtec values of the sanitary tissue products and cushiness as evidenced by compressibility of the sanitary tissue products and methods for making same.
Surface feel (surface mobility) and surface smoothness and/or cushiness are attributes that consumers desire in their sanitary tissue products, for example bath tissue products. However, there has been a surface feel and/or surface smoothness and/or cushiness dichotomy. Historically when the surface feel and/or surface smoothness of a sanitary tissue product, such as bath tissue product, have been increased, the cushiness of the sanitary tissue product has decreased and vice versa. A technical measure of surface feel is average TS7 Emtec values of the sanitary tissue product, which is measured by the Emtec Test Method described herein. A technical measure of surface smoothness is slip stick coefficient of friction values of the sanitary tissue product, which is measured by the Slip Stick Coefficient of Friction Test Method described herein. A technical measure of cushiness is compressibility values of the sanitary tissue product which is measured by the Stack Compressibility and Resilient Bulk Test Method described herein. Current sanitary tissue products fall short of consumers' expectations for surface feel and surface smoothness and cushiness, with and more importantly without surface softening agents.
Emtec TS7 values, as outlined in the Emtec Paper Testing Technology user manual, are “dependent on the softness/hardness of the fibers (stiffness of the individual fibers) and structure of the material (bulk, binding of the fibers). The height of this peak TS7 correlates with the real material softness”. “Excitation of horizontal vibrations of the blades itself (in resonance frequency at approximately 6,500 Hz), caused by momentary blocking and swinging back of the blades by the fibers when moving over the surface.” In order to achieve low average Emtec TS7 values as measured according to the Emtec Test Method described herein and thus good surface mobility/real material softness, it has in the past been necessary for the sanitary tissue product to exhibit low Slipstick Coefficient of Friction values as well.
It is also desired for the sanitary tissue product to have a high level of compressibility to give the consumer the “cushiness” that is desired. Historically, as compressibility is increased, surface mobility (as represented by average Emtec TS7 values) becomes worse, thus resulting in higher average TS7 values as measured according to the Emtec Test Method described herein.
Formulators in the past believed that a creped surface of a fibrous structure, such as by creping the fibrous structure off a dryer or Yankee and/or by other means of foreshortening the fibrous structure, such as rush transfer steps in making the fibrous structure, was needed to achieve improved softness of fibrous structure and to achieve low average TS7 values. Such formulators have tried to utilize the EMTEC Tissue Softness Analyzer from Emtec Electronic GmbH of Leipzig, Germany to measure the softness (TS7) of creped fibrous structures and/or surface smoothness (TS750) of the creped surfaces of the sanitary tissue products. In the past, the formulators of sanitary tissue products apparently believed that creped surfaces of wood pulp fiber-containing fibrous structures were needed in order to attempt to measure softness of the creped fibrous structures using the EMTEC Tissue Softness Analyzer. It has been unexpectedly found that uncreped surfaces of fibrous structures can be measured using the EMTEC Tissue Softness Analyzer to measure softness of such fibrous structures, which is contrary to the teachings of the past.
Another problem with the past formulators' measurements using the EMTEC Tissue Softness Analyzer is that the measurements are very dependent upon which of two calibration methods is used in calibrating the EMTEC Tissue Softness Analyzer. Apparently, the past formulators failed to appreciate this fact and didn't indicate which of the two calibration methods were used or even if the EMTEC Tissue Softness Analyzer was calibrated at all. As a result the values the past formulators reported for TS7 and TS750 and other EMTEC Tissue Softness Analyzer values obtained from the EMTEC Tissue Softness Analyzer on creped surfaces of wood pulp fiber-containing fibrous structures are suspect at best, if not worthless from an absolute value point of view. At most, the values obtained by past formulators for creped fibrous structures may have value internally to the formulator from a relative perspective to show which versions of the same creped surface, wood pulp-containing fibrous structures differ in softness.
Accordingly, one problem faced by sanitary tissue product manufacturers is how to improve (i.e., decrease) the average TS7 Emtec values and/or the slip stick coefficient of friction properties, with and more importantly without surface softening agents, and improve (i.e., increase) the compressibility of sanitary tissue products, for example bath tissue products, to make such sanitary tissue products smoother and cushier to better meet consumers' expectations for more clothlike, luxurious, and plush sanitary tissue products since the actions historically used to make a sanitary tissue product smoother negatively impact the cushiness of the sanitary tissue product and vice versa.
Accordingly, there exists a need for sanitary tissue products, for example bath tissue products, that exhibit improved average TS7 Emtec values and slip stick coefficient of friction properties and improved compressibility properties, to provide consumers with sanitary tissue products that fulfill their desires and expectations for more comfortable and/or luxurious sanitary tissue products, and methods for making such sanitary tissue products.
The present invention fulfills the need described above by providing sanitary tissue products, for example bath tissue products, that are smoother and cushier than known sanitary tissue products, for example bath tissue products, as evidenced by improved average TS7 Emtec values as measured according to the Emtec Test Method described herein and/or improved slip stick coefficient of friction values as measured according to the Slip Stick Coefficient of Friction Test Method described herein and improved compressibility values as measured according to the Stack Compressibility and Resilient Bulk Test Method described herein, and methods for making such sanitary tissue products.
It has been unexpectedly found that the following variables improve surface mobility (lower average TS7 values) without Slipstick Coefficient of Friction being as much of a factor and while providing good “cushiness” (increased Compressibility): 3D patterned fibrous structure (semi-continuous and/or discrete knuckles), angle of the semi-continuous and discrete knuckles (straight and greater than 45° from machine direction), and orientation of fibrous structure (uncreped surface forming an exterior surface of the fibrous structure and/or sanitary tissue product comprising the fibrous structure).
It has been unexpectedly found that discrete knuckle and/or semi-continuous knuckle fibrous structures improve surface mobility (lower average TS7 values) without Slipstick Coefficient of Friction being as much of a factor while still providing good “cushiness” (higher Compressibility). Not wishing to be bound by theory, it is believed that one of the reasons for the improved surface mobility without Slipstick Coefficient of Friction being as much of a factor and still providing good “cushiness” of the discrete and/or semi-continuous knuckle fibrous structures is the continuous or semi-continuous pillow network being available for surface feel and compression. The pillows are lower density regions which have higher stretch and are more flexible than the higher density knuckles. As a result, 3D patterned fibrous structures with a continuous and/or semi-continuous pillow portion will have better “cushiness” because under compressive load, the 3D patterned fibrous structures will be more likely to compress due to the higher flexibility/lower density of the semi-continuous and/or continuous pillow network. Further, the semi-continuous and/or continuous pillow network will also have better surface mobility, because the strain imparted on the surface of the 3D patterned fibrous structure will move through the pillow more easily than through a knuckle, providing less stress on the surface of the 3D patterned fibrous structure due to the lower density of the pillow structure. This will result in an improved surface mobility performance (lower average TS7 values).
It has also unexpectedly been found that the angle of the semi-continuous and/or discrete knuckles being greater than 45° (with respect to the cross-machine direction) and straight rather than curved improves surface mobility without Slipstick Coefficient of Friction being as much of a factor while providing good “cushiness”. Not wishing to be bound by theory, it is believed that one of the reasons for the improved surface mobility without Slipstick Coefficient of Friction being as much of a factor and good “cushiness” when the angle of the semi-continuous and/or discrete knuckles is greater than 45° (with respect to the cross-machine direction) and straight is the better molding that is possible when the orientation of the knuckle is greater than 45° (with respect to the cross-machine direction). Because the majority of fibers in the 3D patterned fibrous structure are substantially machine direction oriented, when the angle of the discrete and/or semi-continuous knuckles is greater than 45° (with respect to the machine direction) better molding into the pillows occurs. This better molding into the pillows creates a better continuous and/or semi-continuous pillow region. This more robust low density pillow region creates a better low density network which will lead to good “cushiness” and good surface mobility.
It has also unexpectedly been found that the orientation of the fibrous structure, specifically converting the fibrous structure such that its uncreped surface (the surface that has not contacted the dryer and/or Yankee and thus has not been creped off the dryer and/or Yankee) (low density pillow side out rather than high density knuckle side out) improves surface mobility without Slipstick Coefficient of Friction being as much of a factor while still providing good “cushiness”. Not wishing to be bound by theory, it is believed that one of the reasons for the improved surface mobility without Slipstick Coefficient of Friction being as much of a factor and good “cushiness” when the orientation of the fibrous structure is uncreped surface (low density pillow surface) side out is the fact that the lower density pillows are on the surface of the fibrous structure. When the fibrous structure undergoes compressive force with the lower density pillows on the surface of the fibrous structure, the fibrous structure will have increased “cushiness”. At the same time, having the low density pillows on the surface of the fibrous structure creates better surface mobility, because a strain imparted on the surface of the fibrous structure will move through the pillow more easily than through a knuckle, providing less stress on the surface of the 3D patterned fibrous structure due to the lower density of the pillow structure.
The combination of either a semi-continuous and/or discrete knuckle structure creating a continuous and/or semi-continuous low density pillow network, the angle of the discrete or semi-continuous knuckles allowing for the best possible molding into the pillows, and the uncreped side out orientation leading to the low density pillow network being on the surface of the fibrous structure leads to the best possible scenario for the best possible surface mobility due to the best possible low density pillow network allowing the strain imparted on the surface of the fibrous structure to move through the pillow most easily, providing less stress on the surface of the fibrous structure due to the lower density of the best possible low density pillow structure. In addition, this best possible low density pillow network will have better “cushiness” because under compressive load, the fibrous structure will be most likely to compress due to the higher flexibility/lower density of the best possible low density pillow structure.
Accordingly, one solution to the problem set forth above is achieved by making the sanitary tissue products or at least one fibrous structure ply employed in the sanitary tissue products on patterned molding members that impart three-dimensional (3D) patterns to the sanitary tissue products and/or fibrous structure plies made thereon, wherein the patterned molding members are designed such that the resulting sanitary tissue products, for example bath tissue products, made using the patterned molding members and/or the process conditions used during the making process, for example vacuum settings during the sanitary tissue product making process, are smoother and cushier than known sanitary tissue products as evidenced by the sanitary tissue products, for example bath tissue products, with or without surface softening agents, that exhibit average TS7 values as measured according to the Emtec Test Method described herein and slip stick coefficient of friction values as measured according to the Slip Stick Coefficient of Friction Test Method described herein such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values and/or as evidenced by the sanitary tissue products, for example bath tissue products, with or without surface softening agents, that exhibit average TS7 values less than 7.5 dB V2 rms as measured according to the Emtec Test Method described herein and Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Compressibility and Resilient Bulk Test Method described herein. Non-limiting examples of such patterned molding members include patterned felts, patterned forming wires, patterned rolls, patterned fabrics, and patterned belts utilized in conventional wet-pressed papermaking processes, air-laid papermaking processes, and/or wet-laid papermaking processes that produce 3D patterned sanitary tissue products and/or 3D patterned fibrous structure plies employed in sanitary tissue products. Other non-limiting examples of such patterned molding members include through-air-drying fabrics and through-air-drying belts utilized in through-air-drying papermaking processes that produce through-air-dried sanitary tissue products, for example 3D patterned through-air dried sanitary tissue products, and/or through-air-dried fibrous structure plies, for example 3D patterned through-air-dried fibrous structure plies, employed in sanitary tissue products. Non-limiting examples of such patterned molding members include patterned felts, patterned forming wires, patterned rolls, patterned fabrics, and patterned belts utilized in conventional wet-pressed papermaking processes, air-laid papermaking processes, and/or wet-laid papermaking processes that produce 3D patterned sanitary tissue products and/or 3D patterned fibrous structure plies employed in sanitary tissue products. Other non-limiting examples of such patterned molding members include through-air-drying fabrics and through-air-drying belts utilized in through-air-drying papermaking processes that produce through-air-dried sanitary tissue products, for example 3D patterned through-air dried sanitary tissue products, and/or through-air-dried fibrous structure plies, for example 3D patterned through-air-dried fibrous structure plies, employed in sanitary tissue products.
Unlike in the past, it has unexpectedly been found that a 3D patterned fibrous structure with its uncreped surface (the surface of the fibrous structure that has not been in contact with the dryer or Yankee and thus has not been creped off the dryer and/or Yankee) forming an exterior surface, for example a consumer-contacting surface, of the fibrous structure exhibits lower average TS7 values than non-3D patterned fibrous structures and even 3D patterned fibrous structures that have their creped surface (the surface of the fibrous structure that has been in contact with a dryer and/or Yankee and thus has been creped off the dryer and/or Yankee).
Further, it has unexpectedly been found that the 3D patterned fibrous structures of the present invention exhibit good surface mobility performance (low average TS7 values) without needing as low of a Slipstick Coefficient of Friction as has been needed in the past to achieve the same performance.
In addition, it has unexpectedly been found that the 3D patterned fibrous structures of the present invention exhibit both good surface mobility (low average TS7 values) and good “cushiness” (high compressibility).
In addition to the impact of the patterned molding members, the fibers utilized to make the sanitary tissue products of the present invention also may influence the average TS7 values and/or slip stick coefficient of friction values of the sanitary tissue products. It has unexpectedly been found that the use of non-wood pulp fibers, for example trichomes, positively impact the surface smoothness of the sanitary tissue products, for example when they form at least part of an exterior surface of the sanitary tissue products, as evidenced by a decrease in the slip stick coefficient of frictions compared to sanitary tissue products containing only wood pulp fibers, without negatively impacting the compressibility of the sanitary tissue products.
In one example of the present invention, a sanitary tissue product comprising a plurality of pulp fibers, wherein the sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In another example of the present invention, a sanitary tissue product comprising a plurality of pulp fibers, wherein the sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In another example of the present invention, a through-air-dried sanitary tissue product, such as a 3D patterned through-air-dried sanitary tissue product, for example bath tissue product, comprising a plurality of pulp fibers, wherein the through-air-dried sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In yet another example of the present invention, a sanitary tissue product, for example bath tissue product, comprising at least one through-air-dried fibrous structure ply comprising a plurality of pulp fibers, wherein the sanitary tissue product exhibits an average TS7 value of less than 7.5 db V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In still another example of the present invention, a sanitary tissue product, for example bath tissue product, comprising at least one 3D patterned through-air-dried fibrous structure ply comprising a plurality of pulp fibers, wherein the sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In even another example of the present invention, a multi-ply, for example two-ply, sanitary tissue product, for example bath tissue product, comprising a plurality of pulp fibers, wherein the multi-ply sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In even yet another example of the present invention, a multi-ply, for example two-ply, sanitary tissue product, for example bath tissue product, comprising at least one 3D patterned fibrous structure ply, for example a 3D patterned through-air-dried fibrous structure ply, comprising a plurality of pulp fibers, wherein the multi-ply sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In another example of the present invention, a creped sanitary tissue product comprising a plurality of pulp fibers, wherein the creped sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In another example of the present invention, a creped sanitary tissue product comprising a at least one 3D patterned creped fibrous structure ply comprising a plurality of pulp fibers, wherein the creped sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.92981 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In another example of the present invention, a creped through-air-dried sanitary tissue product, such as a 3D patterned creped through-air-dried sanitary tissue product, for example bath tissue product, comprising a plurality of pulp fibers, wherein the creped through-air-dried sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In yet another example of the present invention, a creped sanitary tissue product, for example bath tissue product, comprising at least one creped through-air-dried fibrous structure ply comprising a plurality of pulp fibers, wherein the creped sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In still another example of the present invention, a creped sanitary tissue product, for example bath tissue product, comprising at least one 3D patterned creped through-air-dried fibrous structure ply comprising a plurality of pulp fibers, wherein the creped sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In even another example of the present invention, a creped multi-ply, for example two-ply, sanitary tissue product, for example bath tissue product, comprising a plurality of pulp fibers, wherein the creped multi-ply sanitary tissue product exhibits an average TS7 value (dB V2 rms) as measured according to the Emtec Test Method and a Slip Stick Coefficient of Friction value as measured according to the Slip Stick Coefficient of Friction Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0096x+1.9291 graphed on a plot of Average TS7 values to Slip Stick Coefficient of Friction values where the x-axis is Slip Stick Coefficient of Friction values and the y-axis is Average TS7 values as shown in
In even yet another example of the present invention, a creped multi-ply, for example two-ply, sanitary tissue product, for example bath tissue product, comprising at least one 3D patterned creped fibrous structure ply, for example a 3D patterned creped through-air-dried fibrous structure ply, comprising a plurality of pulp fibers, wherein the creped multi-ply sanitary tissue product exhibits an average TS7 value of less than 7.5 dB V2 rms as measured according to the Emtec Test Method and a Compressibility value of greater than 38.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method as shown in
In still yet another example of the present invention, a method for making a single- or multi-ply sanitary tissue product according to the present invention, wherein the method comprises the steps of:
Accordingly, the present invention provides sanitary tissue products, for example bath tissue products, that are smoother and cushier than known sanitary tissue products, for example bath tissue products, and methods for making same.
“Sanitary tissue product” as used herein means a soft, low density (i.e. <about 0.15 g/cm3) article comprising one or more fibrous structure plies according to the present invention, wherein the sanitary tissue product is useful as a wiping implement for post-urinary and post-bowel movement cleaning (toilet tissue), for otorhinolaryngological discharges (facial tissue), and multi-functional absorbent and cleaning uses (absorbent towels). The sanitary tissue product may be convolutedly wound upon itself about a core or without a core to form a sanitary tissue product roll.
The sanitary tissue products and/or fibrous structures of the present invention may exhibit a basis weight of greater than 15 g/m2 to about 120 g/m2 and/or from about 15 g/m2 to about 110 g/m2 and/or from about 20 g/m2 to about 100 g/m2 and/or from about 30 to 90 g/m2. In addition, the sanitary tissue products and/or fibrous structures of the present invention may exhibit a basis weight between about 40 g/m2 to about 120 g/m2 and/or from about 50 g/m2 to about 110 g/m2 and/or from about 55 g/m2 to about 105 g/m2 and/or from about 60 to 100 g/m2.
The sanitary tissue products of the present invention may exhibit a sum of MD and CD dry tensile strength of greater than about 59 g/cm (150 g/in) and/or from about 78 g/cm to about 394 g/cm and/or from about 98 g/cm to about 335 g/cm. In addition, the sanitary tissue product of the present invention may exhibit a sum of MD and CD dry tensile strength of greater than about 196 g/cm and/or from about 196 g/cm to about 394 g/cm and/or from about 216 g/cm to about 335 g/cm and/or from about 236 g/cm to about 315 g/cm. In one example, the sanitary tissue product exhibits a sum of MD and CD dry tensile strength of less than about 394 g/cm and/or less than about 335 g/cm.
In another example, the sanitary tissue products of the present invention may exhibit a sum of MD and CD dry tensile strength of greater than about 196 g/cm and/or greater than about 236 g/cm and/or greater than about 276 g/cm and/or greater than about 315 g/cm and/or greater than about 354 g/cm and/or greater than about 394 g/cm and/or from about 315 g/cm to about 1968 g/cm and/or from about 354 g/cm to about 1181 g/cm and/or from about 354 g/cm to about 984 g/cm and/or from about 394 g/cm to about 787 g/cm.
The sanitary tissue products of the present invention may exhibit an initial sum of MD and CD wet tensile strength of less than about 78 g/cm and/or less than about 59 g/cm and/or less than about 39 g/cm and/or less than about 29 g/cm.
The sanitary tissue products of the present invention may exhibit an initial sum of MD and CD wet tensile strength of greater than about 118 g/cm and/or greater than about 157 g/cm and/or greater than about 196 g/cm and/or greater than about 236 g/cm and/or greater than about 276 g/cm and/or greater than about 315 g/cm and/or greater than about 354 g/cm and/or greater than about 394 g/cm and/or from about 118 g/cm to about 1968 g/cm and/or from about 157 g/cm to about 1181 g/cm and/or from about 196 g/cm to about 984 g/cm and/or from about 196 g/cm to about 787 g/cm and/or from about 196 g/cm to about 591 g/cm.
The sanitary tissue products of the present invention may exhibit a density (based on measuring caliper at 95 g/in2) of less than about 0.60 g/cm3 and/or less than about 0.30 g/cm3 and/or less than about 0.20 g/cm3 and/or less than about 0.10 g/cm3 and/or less than about 0.07 g/cm3 and/or less than about 0.05 g/cm3 and/or from about 0.01 g/cm3 to about 0.20 g/cm3 and/or from about 0.02 g/cm3 to about 0.10 g/cm3.
The sanitary tissue products of the present invention may be in the form of sanitary tissue product rolls. Such sanitary tissue product rolls may comprise a plurality of connected, but perforated sheets of fibrous structure, that are separably dispensable from adjacent sheets.
In another example, the sanitary tissue products may be in the form of discrete sheets that are stacked within and dispensed from a container, such as a box.
The fibrous structures and/or sanitary tissue products of the present invention may comprise additives such as surface softening agents, for example silicones, quaternary ammonium compounds, aminosilicones, lotions, and mixtures thereof, temporary wet strength agents, permanent wet strength agents, bulk softening agents, wetting agents, latexes, especially surface-pattern-applied latexes, dry strength agents such as carboxymethylcellulose and starch, and other types of additives suitable for inclusion in and/or on sanitary tissue products.
“Fibrous structure” as used herein means a structure that comprises a plurality of pulp fibers. In one example, the fibrous structure may comprise a plurality of wood pulp fibers. In another example, the fibrous structure may comprise a plurality of non-wood pulp fibers, for example plant fibers, synthetic staple fibers, and mixtures thereof. In still another example, in addition to pulp fibers, the fibrous structure may comprise a plurality of filaments, such as polymeric filaments, for example thermoplastic filaments such as polyolefin filaments (i.e., polypropylene filaments) and/or hydroxyl polymer filaments, for example polyvinyl alcohol filaments and/or polysaccharide filaments such as starch filaments. In one example, a fibrous structure according to the present invention means an orderly arrangement of fibers alone and with filaments within a structure in order to perform a function. Non-limiting examples of fibrous structures of the present invention include paper.
Non-limiting examples of processes for making fibrous structures include known wet-laid papermaking processes, for example conventional wet-pressed papermaking processes and through-air-dried papermaking processes, and air-laid papermaking processes. Such processes typically include steps of preparing a fiber composition in the form of a suspension in a medium, either wet, more specifically aqueous medium, or dry, more specifically gaseous, i.e. with air as medium. The aqueous medium used for wet-laid processes is oftentimes referred to as a fiber slurry. The fibrous slurry is then used to deposit a plurality of fibers onto a forming wire, fabric, or belt such that an embryonic fibrous structure is formed, after which drying and/or bonding the fibers together results in a fibrous structure. Further processing the fibrous structure may be carried out such that a finished fibrous structure is formed. For example, in typical papermaking processes, the finished fibrous structure is the fibrous structure that is wound on the reel at the end of papermaking, often referred to as a parent roll, and may subsequently be converted into a finished product, e.g. a single- or multi-ply sanitary tissue product.
The fibrous structures of the present invention may be homogeneous or may be layered. If layered, the fibrous structures may comprise at least two and/or at least three and/or at least four and/or at least five layers of fiber and/or filament compositions.
In one example, the fibrous structure of the present invention consists essentially of fibers, for example pulp fibers, such as cellulosic pulp fibers and more particularly wood pulp fibers.
In another example, the fibrous structure of the present invention comprises fibers and is void of filaments.
In still another example, the fibrous structures of the present invention comprises filaments and fibers, such as a co-formed fibrous structure.
“Co-formed fibrous structure” as used herein means that the fibrous structure comprises a mixture of at least two different materials wherein at least one of the materials comprises a filament, such as a polypropylene filament, and at least one other material, different from the first material, comprises a solid additive, such as a fiber and/or a particulate. In one example, a co-formed fibrous structure comprises solid additives, such as fibers, such as wood pulp fibers, and filaments, such as polypropylene filaments.
“Fiber” and/or “Filament” as used herein means an elongate particulate having an apparent length greatly exceeding its apparent width, i.e. a length to diameter ratio of at least about 10. In one example, a “fiber” is an elongate particulate as described above that exhibits a length of less than 5.08 cm (2 in.) and a “filament” is an elongate particulate as described above that exhibits a length of greater than or equal to 5.08 cm (2 in.).
Fibers are typically considered discontinuous in nature. Non-limiting examples of fibers include pulp fibers, such as wood pulp fibers, and synthetic staple fibers such as polyester fibers.
Filaments are typically considered continuous or substantially continuous in nature. Filaments are relatively longer than fibers. Non-limiting examples of filaments include meltblown and/or spunbond filaments. Non-limiting examples of materials that can be spun into filaments include natural polymers, such as starch, starch derivatives, cellulose and cellulose derivatives, hemicellulose, hemicellulose derivatives, and synthetic polymers including, but not limited to polyvinyl alcohol filaments and/or polyvinyl alcohol derivative filaments, and thermoplastic polymer filaments, such as polyesters, nylons, polyolefins such as polypropylene filaments, polyethylene filaments, and biodegradable or compostable thermoplastic fibers such as polylactic acid filaments, polyhydroxyalkanoate filaments and polycaprolactone filaments. The filaments may be monocomponent or multicomponent, such as bicomponent filaments.
In one example of the present invention, “fiber” refers to papermaking fibers. Papermaking fibers useful in the present invention include cellulosic fibers commonly known as wood pulp fibers. Applicable wood pulps include chemical pulps, such as Kraft, sulfite, and sulfate pulps, as well as mechanical pulps including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. Chemical pulps, however, may be preferred since they impart a superior tactile sense of softness to tissue sheets made therefrom. Pulps derived from both deciduous trees (hereinafter, also referred to as “hardwood”) and coniferous trees (hereinafter, also referred to as “softwood”) may be utilized. The hardwood and softwood fibers can be blended, or alternatively, can be deposited in layers to provide a stratified fibrous structure. U.S. Pat. No. 4,300,981 and U.S. Pat. No. 3,994,771 are incorporated herein by reference for the purpose of disclosing layering of hardwood and softwood fibers. Also applicable to the present invention are fibers derived from recycled paper, which may contain any or all of the above categories as well as other non-fibrous materials such as fillers and adhesives used to facilitate the original papermaking.
In one example, the wood pulp fibers are selected from the group consisting of hardwood pulp fibers, softwood pulp fibers, and mixtures thereof. The hardwood pulp fibers may be selected from the group consisting of: tropical hardwood pulp fibers, northern hardwood pulp fibers, and mixtures thereof. The tropical hardwood pulp fibers may be selected from the group consisting of: eucalyptus fibers, acacia fibers, and mixtures thereof. The northern hardwood pulp fibers may be selected from the group consisting of: cedar fibers, maple fibers, and mixtures thereof.
In addition to the various wood pulp fibers, other cellulosic fibers such as cotton linters, rayon, lyocell, trichomes, seed hairs, and bagasse can be used in this invention. Other sources of cellulose in the form of fibers or capable of being spun into fibers include grasses and grain sources.
“Trichome” or “trichome fiber” as used herein means an epidermal attachment of a varying shape, structure and/or function of a non-seed portion of a plant. In one example, a trichome is an outgrowth of the epidermis of a non-seed portion of a plant. The outgrowth may extend from an epidermal cell. In one embodiment, the outgrowth is a trichome fiber. The outgrowth may be a hairlike or bristlelike outgrowth from the epidermis of a plant.
Trichome fibers are different from seed hair fibers in that they are not attached to seed portions of a plant. For example, trichome fibers, unlike seed hair fibers, are not attached to a seed or a seed pod epidermis. Cotton, kapok, milkweed, and coconut coir are non-limiting examples of seed hair fibers.
Further, trichome fibers are different from nonwood bast and/or core fibers in that they are not attached to the bast, also known as phloem, or the core, also known as xylem portions of a nonwood dicotyledonous plant stem. Non-limiting examples of plants which have been used to yield nonwood bast fibers and/or nonwood core fibers include kenaf, jute, flax, ramie and hemp.
Further trichome fibers are different from monocotyledonous plant derived fibers such as those derived from cereal straws (wheat, rye, barley, oat, etc), stalks (corn, cotton, sorghum, Hesperaloe funifera, etc.), canes (bamboo, bagasse, etc.), grasses (esparto, lemon, sabai, switchgrass, etc), since such monocotyledonous plant derived fibers are not attached to an epidermis of a plant.
Further, trichome fibers are different from leaf fibers in that they do not originate from within the leaf structure. Sisal and abaca are sometimes liberated as leaf fibers.
Finally, trichome fibers are different from wood pulp fibers since wood pulp fibers are not outgrowths from the epidermis of a plant; namely, a tree. Wood pulp fibers rather originate from the secondary xylem portion of the tree stem.
“Basis Weight” as used herein is the weight per unit area of a sample reported in lbs/3000 ft2 or g/m2 (gsm) and is measured according to the Basis Weight Test Method described herein.
“Machine Direction” or “MD” as used herein means the direction parallel to the flow of the fibrous structure through the fibrous structure making machine and/or sanitary tissue product manufacturing equipment.
“Cross Machine Direction” or “CD” as used herein means the direction parallel to the width of the fibrous structure making machine and/or sanitary tissue product manufacturing equipment and perpendicular to the machine direction.
“Ply” as used herein means an individual, integral fibrous structure.
“Plies” as used herein means two or more individual, integral fibrous structures disposed in a substantially contiguous, face-to-face relationship with one another, forming a multi-ply fibrous structure and/or multi-ply sanitary tissue product. It is also contemplated that an individual, integral fibrous structure can effectively form a multi-ply fibrous structure, for example, by being folded on itself.
“Embossed” as used herein with respect to a fibrous structure and/or sanitary tissue product means that a fibrous structure and/or sanitary tissue product has been subjected to a process which converts a smooth surfaced fibrous structure and/or sanitary tissue product to a decorative surface by replicating a design on one or more emboss rolls, which form a nip through which the fibrous structure and/or sanitary tissue product passes. Embossed does not include creping, microcreping, printing or other processes that may also impart a texture and/or decorative pattern to a fibrous structure and/or sanitary tissue product.
“Differential density”, as used herein, means a fibrous structure and/or sanitary tissue product that comprises one or more regions of relatively low fiber density, which are referred to as pillow regions, and one or more regions of relatively high fiber density, which are referred to as knuckle regions.
“Densified”, as used herein means a portion of a fibrous structure and/or sanitary tissue product that is characterized by regions of relatively high fiber density (knuckle regions).
“Non-densified”, as used herein, means a portion of a fibrous structure and/or sanitary tissue product that exhibits a lesser density (one or more regions of relatively lower fiber density) (pillow regions) than another portion (for example a knuckle region) of the fibrous structure and/or sanitary tissue product.
“Non-rolled” as used herein with respect to a fibrous structure and/or sanitary tissue product of the present invention means that the fibrous structure and/or sanitary tissue product is an individual sheet (for example not connected to adjacent sheets by perforation lines. However, two or more individual sheets may be interleaved with one another) that is not convolutedly wound about a core or itself. For example, a non-rolled product comprises a facial tissue.
“Stack Compressibility and Resilient Bulk Test Method” as used herein means the Stack Compressibility and Resilient Bulk Test Method described herein.
“Slip Stick Coefficient of Friction Test Method” as used herein means the Slip Stick Coefficient of Friction Test Method described herein.
“Creped” as used herein means creped off of a Yankee dryer or other similar roll and/or fabric creped and/or belt creped. Rush transfer of a fibrous structure alone does not result in a “creped” fibrous structure or “creped” sanitary tissue product for purposes of the present invention.
Sanitary Tissue Product
The sanitary tissue products of the present invention may be single-ply or multi-ply sanitary tissue products. In other words, the sanitary tissue products of the present invention may comprise one or more fibrous structures. The fibrous structures and/or sanitary tissue products of the present invention are made from a plurality of pulp fibers, for example wood pulp fibers and/or other cellulosic pulp fibers, for example trichomes. In addition to the pulp fibers, the fibrous structures and/or sanitary tissue products of the present invention may comprise synthetic fibers and/or filaments.
As shown in
The sanitary tissue products of the present invention may exhibit an average TS7 value of less than 10 and/or less than 9 and/or less than 8 and/or less than 7 and/or less than 6 and/or less than 5.5 and/or greater than 4 and/or greater than 4.5 and/or greater than 5 dB V2 rms as measured according to the Emtec Test Method described herein.
The sanitary tissue products of the present invention may exhibit a Slip Stick Coefficient of Friction value (COF*10000) of greater than 230 and/or greater than 300 and/or greater than 350 and/or greater than 400 and/or greater than 425 and/or greater than 475 and/or greater than 500 and/or greater than 530 and/or greater than 600 and/or greater than 675 and/or less than 730 and/or less than 700 as measured according to the Slip Stick Coefficient of Friction Test Method described herein.
The sanitary tissue products of the present invention may exhibit a Compressibility of greater than 38.0 and/or greater than 40.0 and/or greater than 41.0 and/or greater than 42.0 and/or less than 60.0 and/or less than 55.0 and/or less than 50.0 and/or less than 45.0 [mils/(log(g/in2))] as measured according to the Stack Compressibility and Resilient Bulk Test Method described herein.
The fibrous structures and/or sanitary tissue products of the present invention may be creped or uncreped.
The fibrous structures and/or sanitary tissue products of the present invention may be wet-laid or air-laid.
The fibrous structures and/or sanitary tissue products of the present invention may be embossed.
The fibrous structures and/or sanitary tissue products of the present invention may comprise a surface softening agent or be void of a surface softening agent. In one example, the sanitary tissue product is a non-lotioned sanitary tissue product, such as a sanitary tissue product comprising a non-lotioned fibrous structure ply, for example a non-lotioned through-air-dried fibrous structure ply, for example a non-lotioned creped through-air-dried fibrous structure ply and/or a non-lotioned uncreped through-air-dried fibrous structure ply. In yet another example, the sanitary tissue product may comprise a non-lotioned fabric creped fibrous structure ply and/or a non-lotioned belt creped fibrous structure ply.
The fibrous structures and/or sanitary tissue products of the present invention may comprise trichome fibers and/or may be void of trichome fibers.
The fibrous structures and/or sanitary tissue products of the present invention may exhibit the compressibility values alone or in combination with the slip stick coefficient of friction values with or without the aid of surface softening agents. In other words, the sanitary tissue products of the present invention may exhibit the compressibility values described above alone or in combination with the slip stick coefficient of friction values when surface softening agents are not present on and/or in the sanitary tissue products, in other words the sanitary tissue product is void of surface softening agents. This does not mean that the sanitary tissue products themselves cannot include surface softening agents. It simply means that when the sanitary tissue product is made without adding the surface softening agents, the sanitary tissue product exhibits the compressibility and slip stick coefficient of friction values of the present invention. Addition of a surface softening agent to such a sanitary tissue product within the scope of the present invention (without the need of a surface softening agent or other chemistry) may enhance the sanitary tissue product's compressibility and/or slip stick coefficient of friction to an extent. However, sanitary tissue products that need the inclusion of surface softening agents on and/or in them to be within the scope of the present invention, in other words to achieve the compressibility and slip stick coefficient of friction values of the present invention, are outside the scope of the present invention.
Patterned Molding Members
The sanitary tissue products of the present invention and/or fibrous structure plies employed in the sanitary tissue products of the present invention are formed on patterned molding members that result in the sanitary tissue products of the present invention. In one example, the pattern molding member comprises a non-random repeating pattern. In another example, the pattern molding member comprises a resinous pattern.
A “reinforcing element” may be a desirable (but not necessary) element in some examples of the molding member, serving primarily to provide or facilitate integrity, stability, and durability of the molding member comprising, for example, a resinous material. The reinforcing element can be fluid-permeable or partially fluid-permeable, may have a variety of embodiments and weave patterns, and may comprise a variety of materials, such as, for example, a plurality of interwoven yarns (including Jacquard-type and the like woven patterns), a felt, a plastic, other suitable synthetic material, or any combination thereof.
As shown in
As shown in
Without wishing to be bound by theory, foreshortening (dry & wet crepe, fabric crepe, rush transfer, etc) is an integral part of fibrous structure and/or sanitary tissue paper making, helping to produce the desired balance of strength, stretch, softness, absorbency, etc. Fibrous structure support, transport and molding members used in the papermaking process, such as rolls, wires, felts, fabrics, belts, etc. have been variously engineered to interact with foreshortening to further control the fibrous structure and/or sanitary tissue product properties.
Non-limiting Examples of Making Sanitary Tissue Products
The sanitary tissue products of the present invention may be made by any suitable papermaking process so long as a molding member of the present invention is used to make the sanitary tissue product or at least one fibrous structure ply of the sanitary tissue product and that the sanitary tissue product exhibits an average TS7 value and slip stick coefficient of friction value and/or compressibility value of the present invention. The method may be a sanitary tissue product making process that uses a cylindrical dryer such as a Yankee (a Yankee-process) or it may be a Yankeeless process as is used to make substantially uniform density and/or uncreped fibrous structures and/or sanitary tissue products. Alternatively, the fibrous structures and/or sanitary tissue products may be made by an air-laid process and/or meltblown and/or spunbond processes and any combinations thereof so long as the fibrous structures and/or sanitary tissue products of the present invention are made thereby.
As shown in
The first foraminous member 40 may be supported by a breast roll 44 and a plurality of return rolls 46 of which only two are shown. The first foraminous member 40 can be propelled in the direction indicated by directional arrow 48 by a drive means, not shown. Optional auxiliary units and/or devices commonly associated fibrous structure making machines and with the first foraminous member 40, but not shown, include forming boards, hydrofoils, vacuum boxes, tension rolls, support rolls, wire cleaning showers, and the like.
After the aqueous dispersion of fibers is deposited onto the first foraminous member 40, embryonic fibrous structure 42 is formed, typically by the removal of a portion of the aqueous dispersing medium by techniques well known to those skilled in the art. Vacuum boxes, forming boards, hydrofoils, and the like are useful in effecting water removal. The embryonic fibrous structure 42 may travel with the first foraminous member 40 about return roll 46 and is brought into contact with a patterned molding member 50, such as a 3D patterned through-air-drying belt. While in contact with the patterned molding member 50, the embryonic fibrous structure 42 will be deflected, rearranged, and/or further dewatered.
The patterned molding member 50 may be in the form of an endless belt. In this simplified representation, the patterned molding member 50 passes around and about patterned molding member return rolls 52 and impression nip roll 54 and may travel in the direction indicated by directional arrow 56. Associated with patterned molding member 50, but not shown, may be various support rolls, other return rolls, cleaning means, drive means, and the like well known to those skilled in the art that may be commonly used in fibrous structure making machines.
After the embryonic fibrous structure 42 has been associated with the patterned molding member 50, fibers within the embryonic fibrous structure 42 are deflected into pillows and/or pillow network (“deflection conduits”) present in the patterned molding member 50. In one example of this process step, there is essentially no water removal from the embryonic fibrous structure 42 through the deflection conduits after the embryonic fibrous structure 42 has been associated with the patterned molding member 50 but prior to the deflecting of the fibers into the deflection conduits. Further water removal from the embryonic fibrous structure 42 can occur during and/or after the time the fibers are being deflected into the deflection conduits. Water removal from the embryonic fibrous structure 42 may continue until the consistency of the embryonic fibrous structure 42 associated with patterned molding member 50 is increased to from about 25% to about 35%. Once this consistency of the embryonic fibrous structure 42 is achieved, then the embryonic fibrous structure 42 can be referred to as an intermediate fibrous structure 58. During the process of forming the embryonic fibrous structure 42, sufficient water may be removed, such as by a noncompressive process, from the embryonic fibrous structure 42 before it becomes associated with the patterned molding member 50 so that the consistency of the embryonic fibrous structure 42 may be from about 10% to about 30%.
While applicants decline to be bound by any particular theory of operation, it appears that the deflection of the fibers in the embryonic fibrous structure and water removal from the embryonic fibrous structure begin essentially simultaneously. Embodiments can, however, be envisioned wherein deflection and water removal are sequential operations. Under the influence of the applied differential fluid pressure, for example, the fibers may be deflected into the deflection conduit with an attendant rearrangement of the fibers. Water removal may occur with a continued rearrangement of fibers. Deflection of the fibers, and of the embryonic fibrous structure, may cause an apparent increase in surface area of the embryonic fibrous structure. Further, the rearrangement of fibers may appear to cause a rearrangement in the spaces or capillaries existing between and/or among fibers.
It is believed that the rearrangement of the fibers can take one of two modes dependent on a number of factors such as, for example, fiber length. The free ends of longer fibers can be merely bent in the space defined by the deflection conduit while the opposite ends are restrained in the region of the ridges. Shorter fibers, on the other hand, can actually be transported from the region of the ridges into the deflection conduit (The fibers in the deflection conduits will also be rearranged relative to one another). Naturally, it is possible for both modes of rearrangement to occur simultaneously.
As noted, water removal occurs both during and after deflection; this water removal may result in a decrease in fiber mobility in the embryonic fibrous structure. This decrease in fiber mobility may tend to fix and/or freeze the fibers in place after they have been deflected and rearranged. Of course, the drying of the fibrous structure in a later step in the process of this invention serves to more firmly fix and/or freeze the fibers in position.
Any convenient means conventionally known in the papermaking art can be used to dry the intermediate fibrous structure 58. Examples of such suitable drying process include subjecting the intermediate fibrous structure 58 to conventional and/or flow-through dryers and/or Yankee dryers.
In one example of a drying process, the intermediate fibrous structure 58 in association with the patterned molding member 50 passes around the patterned molding member return roll 52 and travels in the direction indicated by directional arrow 56. The intermediate fibrous structure 58 may first pass through an optional predryer 60. This predryer 60 can be a conventional flow-through dryer (hot air dryer) well known to those skilled in the art. Optionally, the predryer 60 can be a so-called capillary dewatering apparatus. In such an apparatus, the intermediate fibrous structure 58 passes over a sector of a cylinder having preferential-capillary-size pores through its cylindrical-shaped porous cover. Optionally, the predryer 60 can be a combination capillary dewatering apparatus and flow-through dryer. The quantity of water removed in the predryer 60 may be controlled so that a predried fibrous structure 62 exiting the predryer 60 has a consistency of from about 30% to about 98%. The predried fibrous structure 62, which may still be associated with patterned molding member 50, may pass around another patterned molding member return roll 52 and as it travels to an impression nip roll 54. As the predried fibrous structure 62 passes through the nip formed between impression nip roll 54 and a surface of a Yankee dryer 64, the pattern formed by the top surface 66 of patterned molding member 50 is impressed into the predried fibrous structure 62 to form a 3D patterned fibrous structure 68. The imprinted fibrous structure 68 can then be adhered to the surface of the Yankee dryer 64 where it can be dried to a consistency of at least about 95%.
The 3D patterned fibrous structure 68 can then be foreshortened by creping the 3D patterned fibrous structure 68 with a creping blade 70 to remove the 3D patterned fibrous structure 68 from the surface of the Yankee dryer 64 resulting in the production of a 3D patterned creped fibrous structure 72 in accordance with the present invention. As used herein, foreshortening refers to the reduction in length of a dry (having a consistency of at least about 90% and/or at least about 95%) fibrous structure which occurs when energy is applied to the dry fibrous structure in such a way that the length of the fibrous structure is reduced and the fibers in the fibrous structure are rearranged with an accompanying disruption of fiber-fiber bonds. Foreshortening can be accomplished in any of several well-known ways. One common method of foreshortening is creping. The 3D patterned creped fibrous structure 72 may be subjected to post processing steps such as calendaring, tuft generating operations, and/or embossing and/or converting.
Another example of a papermaking process for making the sanitary tissue products of the present invention is illustrated in
The embryonic fibrous structure 80 is then transferred to a molding member 50 of the present invention, such as a through-air-drying fabric, and passed over through-air-dryers 86 and 58 to dry the embryonic fibrous structure 80 to form a 3D patterned fibrous structure 90. While supported by the molding member 50, the 3D patterned fibrous structure 90 is finally dried to a consistency of about 94% percent or greater. After drying, the 3D patterned fibrous structure 90 is transferred from the molding member 50 to fabric 92 and thereafter briefly sandwiched between fabrics 92 and 94. The dried 3D patterned fibrous structure 90 remains with fabric 94 until it is wound up at the reel 96 (“parent roll”) as a finished fibrous structure. Thereafter, the finished 3D patterned fibrous structure 90 can be unwound, calendered and converted into the sanitary tissue product of the present invention, such as a roll of bath tissue, in any suitable manner.
Yet another example of a papermaking process for making the sanitary tissue products of the present invention is illustrated in
The embryonic fibrous structure 122 is advanced to a papermaking felt 126 which is supported by a plurality of rolls 114 and the felt 126 is in contact with a shoe press roll 128. The embryonic fibrous structure 122 is of low consistency as it is transferred to the felt 126. Transfer may be assisted by vacuum; such as by a vacuum roll if so desired or a pickup or vacuum shoe as is known in the art. As the embryonic fibrous structure 122 reaches the shoe press roll 128 it may have a consistency of 10-25% as it enters the shoe press nip 130 between shoe press roll 128 and transfer roll 132. Transfer roll 132 may be a heated roll if so desired. Instead of a shoe press roll 128, it could be a conventional suction pressure roll. If a shoe press roll 128 is employed it is desirable that roll 114 immediately prior to the shoe press roll 128 is a vacuum roll effective to remove water from the felt 126 prior to the felt 126 entering the shoe press nip 130 since water from the furnish will be pressed into the felt 126 in the shoe press nip 130. In any case, using a vacuum roll at the roll 114 is typically desirable to ensure the embryonic fibrous structure 122 remains in contact with the felt 126 during the direction change as one of skill in the art will appreciate from the diagram.
The embryonic fibrous structure 122 is wet-pressed on the felt 126 in the shoe press nip 130 with the assistance of pressure shoe 134. The embryonic fibrous structure 122 is thus compactively dewatered at the shoe press nip 130, typically by increasing the consistency by 15 or more points at this stage of the process. The configuration shown at shoe press nip 130 is generally termed a shoe press; in connection with the present invention transfer roll 132 is operative as a transfer cylinder which operates to convey embryonic fibrous structure 122 at high speed, typically 1000 feet/minute (fpm) to 6000 fpm to the patterned molding member section 106 of the present invention, for example a through-air-drying fabric section, also referred to in this process as a creping fabric section.
Transfer roll 132 has a smooth transfer roll surface 136 which may be provided with adhesive and/or release agents if needed. Embryonic fibrous structure 122 is adhered to transfer roll surface 136 which is rotating at a high angular velocity as the embryonic fibrous structure 122 continues to advance in the machine-direction indicated by arrows 138. On the transfer roll 132, embryonic fibrous structure 122 has a generally random apparent distribution of fiber.
Embryonic fibrous structure 122 enters shoe press nip 130 typically at consistencies of 10-25% and is dewatered and dried to consistencies of from about 25 to about 70% by the time it is transferred to the molding member 140 according to the present invention, which in this case is a patterned creping fabric, as shown in the diagram.
Molding member 140 is supported on a plurality of rolls 114 and a press nip roll 142 and forms a molding member nip 144, for example fabric crepe nip, with transfer roll 132 as shown.
The molding member 140 defines a creping nip over the distance in which molding member 140 is adapted to contact transfer roll 132; that is, applies significant pressure to the embryonic fibrous structure 122 against the transfer roll 132. To this end, backing (or creping) press nip roll 142 may be provided with a soft deformable surface which will increase the length of the creping nip and increase the fabric creping angle between the molding member 140 and the embryonic fibrous structure 122 and the point of contact or a shoe press roll could be used as press nip roll 142 to increase effective contact with the embryonic fibrous structure 122 in high impact molding member nip 144 where embryonic fibrous structure 122 is transferred to molding member 140 and advanced in the machine-direction 138. By using different equipment at the molding member nip 144, it is possible to adjust the fabric creping angle or the takeaway angle from the molding member nip 144. Thus, it is possible to influence the nature and amount of redistribution of fiber, delamination/debonding which may occur at molding member nip 144 by adjusting these nip parameters. In some embodiments it may by desirable to restructure the z-direction interfiber characteristics while in other cases it may be desired to influence properties only in the plane of the fibrous structure. The molding member nip parameters can influence the distribution of fiber in the fibrous structure in a variety of directions, including inducing changes in the z-direction as well as the MD and CD. In any case, the transfer from the transfer roll to the molding member is high impact in that the fabric is traveling slower than the fibrous structure and a significant velocity change occurs. Typically, the fibrous structure is creped anywhere from 10-60% and even higher during transfer from the transfer roll to the molding member.
Molding member nip 144 generally extends over a molding member nip distance of anywhere from about ⅛″ to about 2″, typically ½″ to 2″. For a molding member 140, for example creping fabric, with 32 CD strands per inch, embryonic fibrous structure 122 thus will encounter anywhere from about 4 to 64 weft filaments in the molding member nip 144.
The nip pressure in molding member nip 144, that is, the loading between roll 142 and transfer roll 132 is suitably 20-100 pounds per linear inch (PLI).
After passing through the molding member nip 144, and for example fabric creping the embryonic fibrous structure 122, a 3D patterned fibrous structure 146 continues to advance along MD 138 where it is wet-pressed onto Yankee cylinder (dryer) 148 in transfer nip 150. Transfer at nip 150 occurs at a 3D patterned fibrous structure 146 consistency of generally from about 25 to about 70%. At these consistencies, it is difficult to adhere the 3D patterned fibrous structure 146 to the Yankee cylinder surface 152 firmly enough to remove the 3D patterned fibrous structure 146 from the molding member 140 thoroughly. This aspect of the process is important, particularly when it is desired to use a high velocity drying hood as well as maintain high impact creping conditions.
In this connection, it is noted that conventional TAD processes do not employ high velocity hoods since sufficient adhesion to the Yankee dryer is not achieved.
It has been found in accordance with the present invention that the use of particular adhesives cooperate with a moderately moist fibrous structure (25-70% consistency) to adhere it to the Yankee dryer sufficiently to allow for high velocity operation of the system and high jet velocity impingement air drying. In this connection, a poly(vinyl alcohol)/polyamide adhesive composition as noted above is applied at 154 as needed.
The 3D patterned fibrous structure is dried on Yankee cylinder 148 which is a heated cylinder and by high jet velocity impingement air in Yankee hood 156. As the Yankee cylinder 148 rotates, 3D patterned fibrous structure 146 is creped from the Yankee cylinder 148 by creping doctor blade 158 and wound on a take-up roll 160. Creping of the paper from a Yankee dryer may be carried out using an undulatory creping blade, such as that disclosed in U.S. Pat. No. 5,690,788, the disclosure of which is incorporated by reference. Use of the 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 of the undulatory blade tend to correlate with improved softness perception of the tissue products.
When a wet-crepe process is employed, 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: U.S. Pat. No. 5,865,955 of Ilvespaaet et al. U.S. Pat. No. 5,968,590 of Ahonen et al. U.S. Pat. No. 6,001,421 of Ahonen et al. U.S. Pat. No. 6,119,362 of Sundqvist et al. U.S. patent application Ser. No. 09/733,172, entitled Wet Crepe, Impingement-Air Dry Process for Making Absorbent Sheet, now U.S. Pat. No. 6,432,267. A throughdrying unit as is well known in the art and described in U.S. Pat. No. 3,432,936 to Cole et al., the disclosure of which is incorporated herein by reference as is U.S. Pat. No. 5,851,353 which discloses a can-drying system.
There is shown in
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a fibrous structure according to the present invention on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and equally distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then directed to the NSK fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.28% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 34% of the top side is made up of the eucalyptus fibers, about 34% is made of the eucalyptus fibers on the bottom side and about 32% is made up of the NSK fibers in the center. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is an 84M (84 by 76 5A, Albany International). The speed of the Fourdrinier wire is about 763 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 18-22% at the point of transfer, to a 3D patterned, semi-continuous knuckle, through-air-drying belt as shown in
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 80% polyvinyl alcohol (PVA 88-44), about 20% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-99% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 45° and is positioned with respect to the Yankee dryer to provide an impact angle of about 101°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 650 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 583 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 650 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.50″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.5% of a softening agent is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a fibrous structure according to the present invention on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 1.5% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe and mixed with the aqueous slurry of Northern Softwood Kraft (NSK), described in the next paragraph, to a fan pump where the slurry consistency is reduced from about 1.5% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus/NSK slurry is then pumped and distributed in the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then mixed with the 1.5% aqueous slurry of Eucalyptus fibers (described in the preceding paragraph) and directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% Eucalyptus/NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.25% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK/Eucalyptus fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 40% of the top side is made up of the eucalyptus fibers, about 15% is made of the eucalyptus fibers on the bottom side, about 40% is made up of the NSK fibers in the center, and about 5% is made up of the eucalyptus fiber in the center. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is a Legent 866A Dual Layer (0.11 mm×0.18 mm, Asten Johnson). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 18-22% at the point of transfer, to a 3D patterned, discrete knuckle, through-air-drying belt as shown in
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 78% polyvinyl alcohol (PVA 88-44), about 22% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 640 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 550 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.56″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.75% of a softening agent is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a fibrous structure according to the present invention on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.17% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the top layer Euc fiber stock pipe at a rate sufficient to deliver 0.14% temporary wet strengthening additive based on the dry weight of the top layer Euc fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 35% of the top side is made up of the eucalyptus fibers, about 19% is made of the eucalyptus fibers on the bottom side, and about 46% is made up of the NSK fibers in the center. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is a Legent 866A Dual Layer (0.11 mm×0.18 mm, Asten Johnson). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 18-22% at the point of transfer, to a 3D patterned, discrete knuckle, through-air-drying belt as shown in
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 40-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 78% polyvinyl alcohol (PVA 88-44), about 22% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 644 fpm. Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 750 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.51″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.5% of a proprietary quaternary amine softener is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a fibrous structure according to the present invention on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.17% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the top headbox Euc layer fiber stock pipe at a rate sufficient to deliver 0.14% temporary wet strengthening additive based on the dry weight of the top layer Euc fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 36% of the top side is made up of the eucalyptus fibers, about 17% is made of the eucalyptus fibers on the bottom side, and about 47 is made up of the NSK fibers in the center. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is a Legent 866A Dual Layer (0.11 mm×0.18 mm, Asten Johnson). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 18-22% at the point of transfer, to a 3D patterned, discrete knuckle, through-air-drying belt as shown in
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 78% polyvinyl alcohol (PVA 88-44), about 22% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 95-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 640 fpm. Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 750 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.5″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.5% of a proprietary quaternary amine softener is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a Semi-Continuous Knuckle, Fabric Side Out, variable angle (with average 0 Degree) Knuckle relative to CD fibrous structure according to the Points of Comparison in the Data Table on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then mixed with the 1.5% aqueous slurry of Eucalyptus fibers (described in the preceding paragraph) and directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.41% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the bottom layer Euc fiber stock pipe at a rate sufficient to deliver 0.06% temporary wet strengthening additive based on the dry weight of the bottom layer Euc fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the top layer Euc fiber stock pipe at a rate sufficient to deliver 0.06% temporary wet strengthening additive based on the dry weight of the top layer Euc fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 39.5% of the sheet is made up of the eucalyptus fibers in the bottom headbox chamber, about 21.0% is made of the NSK fibers in the center layer, and about 39.5% is made up of the Euc fibers in the top layer. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is an 84M (84 by 76 5A, Albany International). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 14-25% at the point of transfer, to a 3D patterned, semi-continuous knuckle, through-air-drying belt as shown in Prior Art
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-70% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 60% polyvinyl alcohol (PVA 88-44), about 40% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 325° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 703 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 550-600 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.5″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.5% of a proprietary quaternary amine softener is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above, under the “Points of Comparison” Label.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a Continuous Knuckle, Fabric Side Out, various angle Knuckle relative to CD fibrous structure according to the Points of Comparison in the Data Table on a full-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3-6% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to an additional Hardwood stock check and then to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the Fabric-side chamber and Wire-Side chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3-6% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is directed to a Mix Tank, where it is mixed with a Broke stream (described in the paragraph below). The refined NSK fiber slurry is directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of a mixture of Eucalyptus and NSK fibers that have been reprocessed from scrap Charmin is prepared at about 3-6% fiber by weight using a conventional repulper, then transferred to a Broke storage chest. The Broke fiber slurry is then directed to a Mix Tank where it is mixed with the refined NSK referenced in the paragraph above. The Broke fiber slurry is directed to a fan pump where the Broke slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% Broke slurry is then directed and distributed to the center chamber of a multi-layered three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Parez® 750C commercially available from Kemira) is prepared and is added to the combined NSK/Broke fiber stock pipe coming out of the Mix Tank referenced in the preceding two paragraphs at a rate sufficient to deliver 0.8%-2.5 temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber and Broke fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 20-40% of the sheet is made up of the eucalyptus fibers in the fabric-layer headbox chamber, about 20-40% is made of the NSK fibers in the center layer, and about 20-40% is made up of the Euc fibers in the wire layer. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is a 84M (84 by 76 5A, Albany International). The speed of the Fourdrinier wire is about 2800-4000 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 14-25% at the point of transfer, to a 3D patterned, discrete knuckle, through-air-drying belt as shown in Prior Art
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-70% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 90% polyvinyl alcohol (PVA 88-44), about 10% Crepertrol® 6115. Crepetrol® 6115 is commercially available from Hercules Inc. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 94-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 2800-4000 fpm. Approximately 1.0% of a proprietary quaternary amine softener is sprayed onto the sheet, therefore being added to both sides of a 2 ply sheet. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 2200-3400 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee). The line speed is 750-1500 ft/min. Both parent roll of the fibrous structure are unwound and transported to a combiner where the fibrous structure is combined with a hot-melt adhesive to make a multi-ply (2-ply) sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above, under the “Points of Comparison” Label.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a Semi-Continuous Knuckle, Wire Side Out, 85 Degree Knuckle relative to CD fibrous structure according to the Points of Comparison in the Data Table on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to a hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and distributed in the top, center, and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then mixed with the 1.5% aqueous slurry of Eucalyptus fibers (described in the preceding paragraph) and directed to a fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the top and center chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.17% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the Euc fiber stock pipe at a rate sufficient to deliver 0.14% temporary wet strengthening additive based on the dry weight of the Euc fibers in the bottom chamber of the headbox. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber, center headbox chamber, and bottom headbox chamber. The NSK fiber slurry is directed to the center and top headbox chambers. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 35% of the sheet is made up of the eucalyptus fibers in the bottom headbox chamber, about 21.5% is made of the NSK fibers in the center layer, about 11% is made up of the Euc fibers in the center layer, about 21.5% is made up of the NSK fibers in the top layer, and about 11% is made up of the Euc fibers in the top layer. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is a Legent 866A Dual Layer (0.11 mm×0.18 mm, Asten Johnson). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 14-25% at the point of transfer, to a 3D patterned, discrete knuckle, through-air-drying belt as shown in
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-70% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 78% polyvinyl alcohol (PVA 88-44), about 22% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.10-0.20% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 632 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The two parent rolls are converted with the high density knuckle side out, the creped surface (the surface that contacts the dryer and/or Yankee). The line speed is 550-600 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.56″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. Approximately 0.25% of a proprietary quaternary amine softener is added to the top side only of the multi-ply sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above, under the “Points of Comparison” Label.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a Discrete Knuckle, Fabric Side Out, various angle Knuckle with average of 45 degrees relative to CD fibrous structure according to the Points of Comparison in the Data Table on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and equally distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then directed to the NSK fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Parez® commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.3% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 50% of the top side is made up of the eucalyptus fibers, about 20% is made of the eucalyptus fibers on the bottom side and about 30% is made up of the NSK fibers in the center.
Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is an 84M (84 by 76 5A, Albany International). The speed of the Fourdrinier wire is about 800 feet per minute (fpm).
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 16-20% at the point of transfer, to a 3D patterned through-air-drying belt as shown in Prior Art
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 80% polyvinyl alcohol (PVA 88-50), about 20% CREPETROL® 457T20. CREPETROL® 457T20 is commercially available from Ashland (formerly Hercules Incorporated of Wilmington, Del.). The creping adhesive is delivered to the Yankee surface at a rate of about 0.15% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 97% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 275° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 680 fpm.
Two parent rolls of the fibrous structure are then converted with the low density pillow side out, the uncreped surface (the surface that doesn't contact the dryer and/or Yankee) into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The line speed is 400 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. The multi-ply sanitary tissue product is then transported over a slot extruder through which a surface chemistry may be applied. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
The following Example illustrates a non-limiting example for a preparation of a sanitary tissue product comprising a discrete and semi-continuous Knuckle Dual-Cast, Fabric Side Out, fibrous structure according to the Points of Comparison in the Data Table on a pilot-scale Fourdrinier fibrous structure making (papermaking) machine.
An aqueous slurry of eucalyptus (Fibria Brazilian bleached hardwood kraft pulp) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the hardwood fiber stock chest. The eucalyptus fiber slurry of the hardwood stock chest is pumped through a stock pipe to a hardwood fan pump where the slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% eucalyptus slurry is then pumped and equally distributed in the top and bottom chambers of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
Additionally, an aqueous slurry of NSK (Northern Softwood Kraft) pulp fibers is prepared at about 3% fiber by weight using a conventional repulper, then transferred to the softwood fiber stock chest. The NSK fiber slurry of the softwood stock chest is pumped through a stock pipe to be refined to a Canadian Standard Freeness (CSF) of about 630. The refined NSK fiber slurry is then directed to the NSK fan pump where the NSK slurry consistency is reduced from about 3% by fiber weight to about 0.15% by fiber weight. The 0.15% NSK slurry is then directed and distributed to the center chamber of a multi-layered, three-chambered headbox of a Fourdrinier wet-laid papermaking machine.
In order to impart temporary wet strength to the finished fibrous structure, a 1% dispersion of temporary wet strengthening additive (e.g., Fennorez® 91 commercially available from Kemira) is prepared and is added to the NSK fiber stock pipe at a rate sufficient to deliver 0.23% temporary wet strengthening additive based on the dry weight of the NSK fibers. The absorption of the temporary wet strengthening additive is enhanced by passing the treated slurry through an in-line mixer.
The wet-laid papermaking machine has a layered headbox having a top chamber, a center chamber, and a bottom chamber where the chambers feed directly onto the forming wire (Fourdrinier wire). The eucalyptus fiber slurry of 0.15% consistency is directed to the top headbox chamber and bottom headbox chamber. The NSK fiber slurry is directed to the center headbox chamber. All three fiber layers are delivered simultaneously in superposed relation onto the Fourdrinier wire to form thereon a three-layer embryonic fibrous structure (web), of which about 26% of the top side is made up of the eucalyptus fibers, about 26% is made of the eucalyptus fibers on the bottom side and about 48% is made up of the NSK fibers in the center. Dewatering occurs through the Fourdrinier wire and is assisted by a deflector and wire table vacuum boxes. The Fourdrinier wire is an 84M (84 by 76 5A, Albany International). The speed of the Fourdrinier wire is about 800 feet per minute (fpm). The one-ply Basis Weight for this condition was 11.3 pounds per 3000 square feet. The one-ply caliper (at 95 gsi) was 10.65 mils.
The embryonic wet fibrous structure is transferred from the Fourdrinier wire, at a fiber consistency of about 18-22% at the point of transfer, to a 3D patterned through-air-drying belt as shown in Prior Art
Further de-watering of the fibrous structure is accomplished by vacuum assisted drainage until the fibrous structure has a fiber consistency of about 20% to 30%.
While remaining in contact with the 3D patterned through-air-drying belt, the fibrous structure is pre-dried by air blow-through pre-dryers to a fiber consistency of about 50-65% by weight.
After the pre-dryers, the semi-dry fibrous structure is transferred to a Yankee dryer and adhered to the surface of the Yankee dryer with a sprayed creping adhesive. The creping adhesive is an aqueous dispersion with the actives consisting of about 80% polyvinyl alcohol (PVA 88-44), about 20% UNICREPE® 457T20. UNICREPE® 457T20 is commercially available from GP Chemicals. The creping adhesive is delivered to the Yankee surface at a rate of about 0.15% adhesive solids based on the dry weight of the fibrous structure. The fiber consistency is increased to about 96-98% before the fibrous structure is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25° and is positioned with respect to the Yankee dryer to provide an impact angle of about 81°. The Yankee dryer is operated at a temperature of about 300° F. and a speed of about 800 fpm. The fibrous structure is wound in a roll (parent roll) using a surface driven reel drum having a surface speed of about 655 fpm.
Two parent rolls of the fibrous structure are then converted into a sanitary tissue product by loading the roll of fibrous structure into an unwind stand. The line speed is 400 ft/min. One parent roll of the fibrous structure is unwound and transported to an emboss stand where the fibrous structure is strained to form the emboss pattern in the fibrous structure via a 0.75″ Pressure Roll Nip and then combined with the fibrous structure from the other parent roll to make a multi-ply (2-ply) sanitary tissue product. The multi-ply sanitary tissue product is then transported to a winder where it is wound onto a core to form a log. The log of multi-ply sanitary tissue product is then transported to a log saw where the log is cut into finished multi-ply sanitary tissue product rolls. The multi-ply sanitary tissue product of this example exhibits the properties shown in Table 1, above.
Test Methods
Unless otherwise specified, all tests described herein including those described under the Definitions section and the following test methods are conducted on samples that have been conditioned in a conditioned room at a temperature of 23° C.±1.0° C. and a relative humidity of 50%±2% for a minimum of 2 hours prior to the test. The samples tested are “usable units.” “Usable units” as used herein means sheets, flats from roll stock, pre-converted flats, and/or single or multi-ply products. All tests are conducted in such conditioned room. Do not test samples that have defects such as wrinkles, tears, holes, and like. All instruments are calibrated according to manufacturer's specifications.
Emtec Test Method
TS7 and TS750 values are measured using an EMTEC Tissue Softness Analyzer (“Emtec TSA”) (Emtec Electronic GmbH, Leipzig, Germany) interfaced with a computer running Emtec TSA software (version 3.19 or equivalent). According to Emtec, the TS7 value correlates with the real material softness, while the TS750 value correlates with the felt smoothness/roughness of the material. The Emtec TSA comprises a rotor with vertical blades which rotate on the test sample at a defined and calibrated rotational speed (set by manufacturer) and contact force of 100 mN. Contact between the vertical blades and the test piece creates vibrations, which create sound that is recorded by a microphone within the instrument. The recorded sound file is then analyzed by the Emtec TSA software. The sample preparation, instrument operation and testing procedures are performed according the instrument manufacture's specifications.
Sample Preparation
Test samples are prepared by cutting square or circular samples from a finished product. Test samples are cut to a length and width (or diameter if circular) of no less than about 90 mm, and no greater than about 120 mm, in any of these dimensions, to ensure the sample can be clamped into the TSA instrument properly. Test samples are selected to avoid perforations, creases or folds within the testing region. Prepare 8 substantially similar replicate samples for testing. Equilibrate all samples at TAPPI standard temperature and relative humidity conditions (23° C.±2 C.° and 50%±2%) for at least 1 hour prior to conducting the TSA testing, which is also conducted under TAPPI conditions.
Testing Procedure
Calibrate the instrument according to the manufacturer's instructions using the 1-point calibration method with Emtec reference standards (“ref.2 samples”). If these reference samples are no longer available, use the appropriate reference samples provided by the manufacturer. Calibrate the instrument according to the manufacturer's recommendation and instruction, so that the results will be comparable to those obtained when using the 1-point calibration method with Emtec reference standards (“ref.2 samples”).
Mount the test sample into the instrument, and perform the test according to the manufacturer's instructions. When complete, the software displays values for TS7 and TS750. Record each of these values to the nearest 0.01 dB V2 rms. The test piece is then removed from the instrument and discarded. This testing is performed individually on the top surface (outer facing surface of a rolled product) of four of the replicate samples, and on the bottom surface (inner facing surface of a rolled product) of the other four replicate samples.
The four test result values for TS7 and TS750 from the top surface are averaged (using a simple numerical average); the same is done for the four test result values for TS7 and TS750 from the bottom surface. Report the individual average values of TS7 and TS750 for both the top and bottom surfaces on a particular test sample to the nearest 0.01 dB V2 rms. Additionally, average together all eight test value results for TS7 and TS750, and report the overall average values for TS7 and TS750 on a particular test sample to the nearest 0.01 dB V2 rms.
Basis Weight Test Method
Basis weight of a fibrous structure and/or sanitary tissue product is measured on stacks of twelve usable units using a top loading analytical balance with a resolution of ±0.001 g. The balance is protected from air drafts and other disturbances using a draft shield. A precision cutting die, measuring 3.500 in±0.0035 in by 3.500 in±0.0035 in is used to prepare all samples.
With a precision cutting die, cut the samples into squares. Combine the cut squares to form a stack twelve samples thick. Measure the mass of the sample stack and record the result to the nearest 0.001 g.
The Basis Weight is calculated in lbs/3000 ft2 or g/m2 as follows:
Basis Weight=(Mass of stack)/[(Area of 1 square in stack)×(No. of squares in stack)]
For example,
Basis Weight (lbs/3000 ft2)=[[Mass of stack (g)/453.6 (g/lbs)]/[12.25 (in2)/144 (in2/ft2)×12]]×3000
or,
Basis Weight (g/m2)=Mass of stack (g)/[79.032 (cm2)/10,000 (cm2/m2)×12]
Report result to the nearest 0.1 lbs/3000 ft2 or 0.1 g/m2. Sample dimensions can be changed or varied using a similar precision cutter as mentioned above, so as at least 100 square inches of sample area in stack.
Caliper Test Method
Caliper of a fibrous structure and/or sanitary tissue product is measured using a ProGage Thickness Tester (Thwing-Albert Instrument Company, West Berlin, N.J.) with a pressure foot diameter of 2.00 inches (area of 3.14 in2) at a pressure of 95 g/in2. Four (4) samples are prepared by cutting of a usable unit such that each cut sample is at least 2.5 inches per side, avoiding creases, folds, and obvious defects. An individual specimen is placed on the anvil with the specimen centered underneath the pressure foot. The foot is lowered at 0.03 in/sec to an applied pressure of 95 g/in2. The reading is taken after 3 sec dwell time, and the foot is raised. The measure is repeated in like fashion for the remaining 3 specimens. The caliper is calculated as the average caliper of the four specimens and is reported in mils (0.001 in) to the nearest 0.1 mils.
Density Test Method
The density of a fibrous structure and/or sanitary tissue product is calculated as the quotient of the Basis Weight of a fibrous structure or sanitary tissue product expressed in lbs/3000 ft2 divided by the Caliper (at 95 g/in2) of the fibrous structure or sanitary tissue product expressed in mils. The final Density value is calculated in lbs/ft3 and/or g/cm3, by using the appropriate converting factors.
Stack Compressibility and Resilient Bulk Test Method
Stack thickness (measured in mils, 0.001 inch) is measured as a function of confining pressure (g/in2) using a Thwing-Albert (14 W. Collings Ave., West Berlin, N.J.) Vantage Compression/Softness Tester (model 1750-2005 or similar) or equivalent instrument, equipped with a 2500 g load cell (force accuracy is +/−0.25% when measuring value is between 10%-100% of load cell capacity, and 0.025% when measuring value is less than 10% of load cell capacity), a 1.128 inch diameter steel pressure foot (one square inch cross sectional area) which is aligned parallel to the steel anvil (2.5 inch diameter). The pressure foot and anvil surfaces must be clean and dust free, particularly when performing the steel-to-steel test. Thwing-Albert software (MAP) controls the motion and data acquisition of the instrument.
The instrument and software is set-up to acquire crosshead position and force data at a rate of 50 points/sec. The crosshead speed (which moves the pressure foot) for testing samples is set to 0.20 inches/min (the steel-to-steel test speed is set to 0.05 inches/min). Crosshead position and force data are recorded between the load cell range of approximately 5 and 1500 grams during compression. The crosshead is programmed to stop immediately after surpassing 1500 grams, record the thickness at this pressure (termed Tmax), and immediately reverse direction at the same speed as performed in compression. Data is collected during this decompression portion of the test (also termed recovery) between approximately 1500 and 5 grams. Since the foot area is one square inch, the force data recorded corresponds to pressure in units of g/in2. The MAP software is programmed to the select 15 crosshead position values (for both compression and recovery) at specific pressure trap points of 10, 25, 50, 75, 100, 125, 150, 200, 300, 400, 500, 600, 750, 1000, and 1250 g/in2 (i.e., recording the crosshead position of very next acquired data point after the each pressure point trap is surpassed). In addition to these 30 collected trap points, Tmax is also recorded, which is the thickness at the maximum pressure applied during the test (approximately 1500 g/in2).
Since the overall test system, including the load cell, is not perfectly rigid, a steel-to-steel test is performed (i.e., nothing in between the pressure foot and anvil) at least twice for each batch of testing, to obtain an average set of steel-to-steel crosshead positions at each of the 31 trap points described above. This steel-to-steel crosshead position data is subtracted from the corresponding crosshead position data at each trap point for each tested stacked sample, thereby resulting in the stack thickness (mils) at each pressure trap point during the compression, maximum pressure, and recovery portions of the test.
StackT(trap)=StackCP (trap)−SteelCP (trap)
Where:
trap=trap point pressure at either compression, recovery, or max
StackT=Thickness of Stack (at trap pressure)
StackCP=Crosshead position of Stack in test (at trap pressure)
SteelCP=Crosshead position of steel-to-steel test (at trap pressure)
A stack of five (5) usable units thick is prepared for testing as follows. The minimum usable unit size is 2.5 inch by 2.5 inch; however a larger sheet size is preferable for testing, since it allows for easier handling without touching the central region where compression testing takes place. For typical perforated rolled bath tissue, this consists of removing five (5) sets of 3 connected usable units. In this case, testing is performed on the middle usable unit, and the outer 2 usable units are used for handling while removing from the roll and stacking. For other product formats, it is advisable, when possible, to create a test sheet size (each one usable unit thick) that is large enough such that the inner testing region of the created 5 usable unit thick stack is never physically touched, stretched, or strained, but with dimensions that do not exceed 14 inches by 6 inches.
The 5 sheets (one usable unit thick each) of the same approximate dimensions, are placed one on top the other, with their MD aligned in the same direction, their outer face all pointing in the same direction, and their edges aligned +/−3 mm of each other. The central portion of the stack, where compression testing will take place, is never to be physically touched, stretched, and/or strained (this includes never to ‘smooth out’ the surface with a hand or other apparatus prior to testing).
The 5 sheet stack is placed on the anvil, positioning it such that the pressure foot will contact the central region of the stack (for the first compression test) in a physically untouched spot, leaving space for a subsequent (second) compression test, also in the central region of the stack, but separated by ¼ inch or more from the first compression test, such that both tests are in untouched, and separated spots in the central region of the stack. From these two tests, an average crosshead position of the stack at each trap pressure (i.e., StackCP(trap)) is calculated for compression, maximum pressure, and recovery portions of the tests. Then, using the average steel-to-steel crosshead trap points (i.e., SteelCP(trap)), the average stack thickness at each trap (i.e., StackT(trap) is calculated (mils).
Stack Compressibility is defined here as the absolute value of the linear slope of the stack thickness (mils) as a function of the log(10) of the confining pressure (grams/in2), by using the 15 compression trap points discussed previously (i.e., compression from 10 to 1250 g/in2), in a least squares regression. The units for Stack Compressibility are [mils/(log(g/in2))], and is reported to the nearest 0.1 [mils/(log(g/in2))].
Resilient Bulk is calculated from the stack weight per unit area and the sum of 8 StackT(trap) thickness values from the maximum pressure and recovery portion of the tests: i.e., at maximum pressure (Tmax) and recovery trap points at R1250, R1000, R750, R500, R300, R100, and R10 g/in2 (a prefix of “R” denotes these traps come from recovery portion of the test). Stack weight per unit area is measured from the same region of the stack contacted by the compression foot, after the compression testing is complete, by cutting a 3.50 inch square (typically) with a precision die cutter, and weighing on a calibrated 3-place balance, to the nearest 0.001 gram. The weight of the precisely cut stack, along with the StackT(trap) data at each required trap pressure (each point being an average from the two compression/recovery tests discussed previously), are used in the following equation to calculate Resilient Bulk, reported in units of cm3/g, to the nearest 0.1 cm3/g.
Where:
StackT=Thickness of Stack (at trap pressures of Tmax and recovery pressures listed above), (mils)
M=weight of precisely cut stack, (grams)
A=area of the precisely cut stack, (cm2)
Slip Stick Coefficient of Friction Test Method
Background
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Of particular interest here, ‘dry’ friction resists relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction between non-moving surfaces, and kinetic friction between moving surfaces. “Slip Stick”, as applied here, is the term used to describe the dynamic variation in kinetic friction.
Friction is not itself a fundamental force but arises from fundamental electromagnetic forces between the charged particles constituting the two contacting surfaces. Textured surfaces also involve mechanical interactions, as is the case when sandpaper drags against a fibrous substrate. The complexity of these interactions makes the calculation of friction from first principles impossible and necessitates the use of empirical methods for analysis and the development of theory. As such, a specific sled material and test method was identified, and has shown correlation to human perception of surface feel.
This Slip Stick Coefficient of Friction Test Method measures the interaction of a diamond file (120-140 grit) against a surface of a test sample, in this case a fibrous structure and/or sanitary tissue product, at a pressure of about 32 g/in2 as shown in
Equipment and Set-up
A Thwing-Albert (14 W. Collings Ave., West Berlin, N.J.) friction/peel test instrument (model 225-1) or equivalent if no longer available, is used, equipped with data acquisition software and a calibrated 2000 gram load cell that moves horizontally across the platform. Attached to the load cell is a small metal fitting (defined here as the “load cell arm”) which has a small hole near its end, such that a sled string can be attached (for this method, however, no string will be used). Into this load cell arm hole, insert a cap screw (¾ inch #8-32) by partially screwing it into the opening, so that it is rigid (not loose) and pointing vertically, perpendicular to the load cell arm.
After turning instrument on, set instrument test speed to 2 inches/min, test time to 10 seconds, and wait at least 5 minutes for instrument to warm up before re-zeroing the load cell (with nothing touching it) and testing. Force data from the load cell is acquired at a rate of 52 points per second, reported to the nearest 0.1 gram force. Press the ‘Return’ button to move crosshead 201 to its home position.
A smooth surfaced metal test platform 200, with dimensions of 5 inches by 4 inches by ¾ inch thick, is placed on top of the test instrument platen surface, on the left hand side of the load cell 203, with one of its 4 inch by ¾ inch sides facing towards the load cell 203, positioned 1.125 inches d from the left most tip of the load cell arm 202 as shown in
Sixteen test sleds 204 are required to perform this test (32 different sled surface faces). Each is made using a dual sided, wide faced diamond file 206 (25 mm×25 mm, 120/140 grit, 1.2 mm thick, McMaster-Carr part number 8142A14) with 2 flat metal washers 208 (approximately 11/16th inch outer diameter and about 11/32nd inch inner diameter). The combined weight of the diamond file 206 and 2 washers 208 is 11.7 grams+/−0.2 grams (choose different washers until weight is within this range). Using a metal bonding adhesive (Loctite 430, or similar), adhere the 2 washers 208 to the c-shaped end 210 of the diamond file 206 (one each on either face), aligned and positioned such that the opening 212 is large enough for the cap screw 214 to easily fit into, and to make the total length of sled 204 to approximately 3 inches long. Clean sled 204 by dipping it, diamond face end 216 only, into an acetone bath, while at the same time gently brushing with soft bristled toothbrush 3-6 times on both sides of the diamond file 206. Remove from acetone and pat dry each side with Kimwipe tissue (do not rub tissue on diamond surface, since this could break tissue pieces onto sled surface). Wait at least 15 minutes before using sled 204 in a test. Label each side of the sled 204 (on the arm or washer, not on the diamond face) with a unique identifier (i.e., the first sled is labeled “1a” on one side, and “1b” on its other side). When all 16 sleds 204 are created and labeled, there are then 32 different diamond face surfaces for available for testing, labeled 1a and 1b through 16a and 16b. These sleds 204 must be treated as fragile (particularly the diamond surfaces) and handled carefully; thus, they are stored in a slide box holder, or similar protective container.
Sample Prep
If sample to be tested is bath tissue, in perforated roll form, then gently remove 8 sets of 2 connected sheets from the roll, touching only the corners (not the regions where the test sled will contact). Use scissors or other sample cutter if needed. If sample is in another form, cut 8 sets of sample approximately 8 inches long in the MD, by approximately 4 inches long in the CD, one usable unit thick each. Make note and/or a mark that differentiates both face sides of each sample (e.g., fabric side or wire side, top or bottom, etc.). When sample prep is complete, there are 8 sheets prepared with appropriate marking that differentiates one side from the other. These will be referred to hereinafter as: sheets #1 through #8, each with a top side and a bottom side.
Test Operation
Press the ‘Return’ button to ensure crosshead 201 is in its home position.
Without touching test area of sample, place sheet #1 218 on test platform 200, top side facing up, aligning one of the sheet's CD edges (i.e. edge that is parallel to the CD) along the platform 218 edge closest to the load cell 202 (+/−1 mm). This first test (pull), of 32 total, will be in the MD direction on the top side of the sheet 218. Place a brass bar weight or equivalent 220 (1 inch diameter, 3.75 inches long) on the sheet 218, near its center, aligned perpendicular to the sled pull direction, to prevent sheet 218 from moving during the test. Place test sled “1a” 204 over cap screw head 214 (i.e., sled washer opening 212 over cap screw head 214, and sled side 1a is facing down) such that the diamond file 206 surface is laying flat and parallel on the sheet 218 surface and the cap screw 214 is touching the inside edge of the washers 208.
Gently place a cylindrically shaped brass 20 gram (+/−0.01 grams) weight 222 on top of the sled 204, with its edge aligned and centered with the sled's back end. Initiate the sled movement m and data acquisition by pressing the ‘Test’ button on the instrument. The test set up is shown in
If the test pull was set-up correctly, the diamond file 206 face (25 mm by 25 mm square) stays in contact with the sheet 218 during the entire 10 second test time (i.e., does not overhang over the sheet 218 or test platform 200 edge). Also, if at any time during the test the sheet 218 moves, the test is invalid, and must be rerun on another untouched portion of the sheet 218, using a heavier brass bar weight or equivalent 220 to hold sheet 218 down. If the sheet 218 rips or tears, rerun the test on another untouched portion of the sheet 218 (or create a new sheet 218 from the sample). If it rips again, then replace the sled 204 with a different one (giving it the same sled name as the one it replaced). These statements apply to all 32 test pulls.
For the second of 32 test pulls (also an MD pull, but in the opposite direction on the sheet), first remove the 20 gram weight 222, the sled 204, and the brass bar weight or equivalent 220 from the sheet 218. Press the ‘Return’ button on the instrument to reset the crosshead 201 to its home position. Rotate the sheet 218 180° (with top side still facing up), and replace the brass bar weight or equivalent 220 onto the sheet 218 (in the same position described previously). Place test sled “1b” 204 over the cap screw head 214 (i.e., sled washer opening 212 over cap screw head 214, and sled side 1b is facing down) and the 20 gram weight 222 on the sled 204, in the same manner as described previously. Press the ‘Test’ button to collect the data for the second test pull.
The third test pull will be in the CD direction. After removing the sled 204, weights 220, 222, and returning the crosshead 201, the sheet 218 is rotated 90° from its previous position (with top side still facing up), and positioned so that its MD edge is aligned with the test platform 200 edge (+/−1 mm). Position the sheet 218 such that the sled 204 will not touch any perforation, if present, or touch the area where the brass bar weight or equivalent 220 rested in previous test pulls. Place the brass bar weight or equivalent 220 onto the sheet 218 near its center, aligned perpendicular to the sled pull direction m. Place test sled “2a” 204 over the cap screw head 214 (i.e., sled washer opening 212 over cap screw head 214, and sled side 2a is facing down) and the 20 gram weight 222 on the sled 204, in the same manner as described previously. Press the ‘Test’ button to collect the data for the third test pull.
The fourth test pull will also be in the CD, but in the opposite direction and on the opposite half section of the sheet 218. After removing the sled 204, weights 220, 222, and returning the crosshead 201, the sheet 218 is rotated 180° from its previous position (with top side still facing up), and positioned so that its MD edge is again aligned with the test platform 200 edge (+/−1 mm). Position the sheet 218 such that the sled 204 will not touch any perforation, if present, or touch the area where the brass bar weight or equivalent 220 rested in previous test pulls. Place the brass bar weight or equivalent 220 onto the sheet 218 near its center, aligned perpendicular to the sled pull direction m. Place test sled “2b” 204 over the cap screw head 214 (i.e., sled washer opening 212 over cap screw head 214, and sled side 2b is facing down) and the 20 gram weight 222 on the sled 204, in the same manner as described previously. Press the ‘Test’ button to collect the data for the fourth test pull.
After the fourth test pull is complete, remove the sled 204, weights 220, 222, and return the crosshead 201 to the home position. Sheet #1 218 is discarded.
Test pulls 5-8 are performed in the same manner as 1-4, except that sheet #2 218 has its bottom side now facing upward, and sleds 3a, 3b, 4a, and 4b are used.
Test pulls 9-12 are performed in the same manner as 1-4, except that sheet #3 218 has its top side facing upward, and sleds 5a, 5b, 6a, and 6b are used.
Test pulls 13-16 are performed in the same manner as 1-4, except that sheet #4 218 has its bottom side facing upward, and sleds 7a, 7b, 8a, and 8b are used.
Test pulls 17-20 are performed in the same manner as 1-4, except that sheet #5 218 has its top side facing upward, and sleds 9a, 9b, 10a, and 10b are used.
Test pulls 21-24 are performed in the same manner as 1-4, except that sheet #6 218 has its bottom side facing upward, and sleds 11a, 11b, 12a, and 12b are used.
Test pulls 25-28 are performed in the same manner as 1-4, except that sheet #7 218 has its top side facing upward, and sleds 13a, 13b, 14a, and 14b are used.
Test pulls 29-32 are performed in the same manner as 1-4, except that sheet #8 218 has its bottom side facing upward, and sleds 15a, 15b, 16a, and 16b are used.
Calculations and Results
The collected force data (grams) is used to calculate Slip Stick COF for each of the 32 test pulls, and subsequently the overall average Slip Stick COF for the sample being tested. In order to calculate Slip Stick COF for each test pull, the following calculations are made. First, the standard deviation is calculated for the force data centered on 131st data point (which is 2.5 seconds after the start of the test)+/−26 data points (i.e., the 53 data points that cover the range from 2.0 to 3.0 seconds). This standard deviation calculation is repeated for each subsequent data point, and stopped after the 493rd point (about 9.5 sec). The numerical average of these 363 standard deviation values is then divided by the sled weight (31.7 g) and multiplied by 10,000 to generate the Slip Stick COF*10,000 for each test pull. This calculation is repeated for all 32 test pulls. The numerical average of these 32 Slip Stick COF*10,000 values is the reported value of the Slip Stick COF*10,000 for the sample. For simplicity, it is referred to as just Slip Stick COF, or more simply as Slip Stick, without units (dimensionless), and is reported to the nearest 1.0.
Outliers and Noise
It is not uncommon, with this described method, to observe about one out of the 32 test pulls to exhibit force data with a harmonic wave of vibrations superimposed upon it. For whatever reason, the pulled sled periodically gets into a relatively high frequency, oscillating ‘shaking’ mode, which can be seen in graphed force vs. time. The sine wave-like noise was found to have a frequency of about 10 sec-1 and amplitude in the 3-5 grams force range. This adds a bias to the true Slip Stick result for that test; thus, it is appropriate for this test pull be treated as an outlier, the data removed, and replaced with a new test of that same scenario (e.g., CD top face) and sled number (e.g. 3a).
To get an estimate of the overall measurement noise, ‘blanks’ were run on the test instrument without any touching the load cell (i.e., no sled). The average force from these tests is zero grams, but the calculated Slip Stick COF was 66. Thus, it is speculated that, for this instrument measurement system, this value represents that absolute lower limit for Slip Stick COF.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
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