Patent Application
20100155004
Absorbent fibrous articles such as paper towels, facial tissues, bath tissues and other similar products, for example, are designed to include several characteristics. One such characteristic is a soft feel. Softness is typically increased by decreasing or reducing cellulosic fiber bonding within the fibrous product. Inhibiting or reducing fiber bonding, however, can adversely affect properties, such as the strength of the fibrous web.
In other instances, softness can be enhanced by the topical addition of a softening agent to the outer surfaces of the fibrous web. The softening agent may comprise, for instance, a silicone chemistry. The silicone chemistry may be applied to the web by printing, coating or spraying. Although silicone chemistries make the fibrous webs feel softer, silicone chemistries can be relatively expensive, reduce absorbent rate and capacity, and may lower sheet durability as measured by other strength properties.
Recent technology has enabled a significant improvement in the tactile perception of tissue products as a result of the unique surface modification brought about by creping with a water insoluble surface modifying material. The surface modification consists of the deposition of a thin but discontinuous film onto the surface of the pulp fiber matrix. This film deposition results from a unique mode of cohesive failure at a creping blade such that a portion of the creping composition remains bonded to the tissue surface.
While the recent surface modifying technology has generated a significant improvement in tissue tactile properties (e.g. it is softer than conventionally-creped tissues), the water insoluble nature of these materials introduces changes in tissue machine operations which can reduce manufacturing efficiency. Specifically, the surface modification material dispersion is not stable in mill water resulting in deposition of the material on parts of the tissue machine which require removal and disposal. This material further has to be removed out of the mill waste water system due to its insolubility and instability in hard water.
Previous research efforts on developing water soluble alternatives indicated that while they did not have the same technical challenges in terms of ease of processing, they also seemed not effective in terms of improving soft hand feel. Therefore, there is a need to develop alternative chemistries to replace the current water-insoluble chemistry. Desirably, the new chemistry would be affordable, absorbent, and water soluble, while exhibiting a good hand feel as determined by one or more tests, e.g. an In-Hand Ranking Test (“IHR,” see below), absorbent rate and capacity, etc.
In one aspect is a fibrous article composed of a creped fibrous web having a first side and an opposite second side. The fibrous web includes pulp fibers with an additive composition disposed on the pulp fibers. The additive composition includes a first polymer and a second polymer, wherein the first and second polymers are each water-soluble and non-crosslinked. The first polymer has a LCST of >40 C, and the second polymer has a melting point of <90 C.
In a second aspect is a fibrous article composed of a creped fibrous web having a first side and an opposite second side. The fibrous web includes pulp fibers with an additive composition disposed on the pulp fibers. The additive composition includes a first polymer and a second polymer, wherein the first and second polymers are each water-soluble and non-crosslinked. The fibrous article has a water soluble extractable of at least 0.35% as determined by the Water Extractable test described herein.
In another aspect is a fibrous article composed of a creped fibrous web having a first side and an opposite second side, wherein the fibrous web includes pulp fibers. An additive composition is disposed on the pulp fibers. The additive composition includes a first polymer and a second polymer, wherein the first and second polymers are each water-soluble and non-crosslinked. The fibrous article has a fuzz on edge greater than 1.25 as determined by the Fuzz on Edge test described herein.
In a further aspect is a method of applying an additive composition for a fibrous material including the following steps (not necessarily in order):
(a) preparing the additive composition including a first polymer and a second polymer, wherein the first and second polymers are each water-soluble and non-crosslinkable, and wherein the first polymer has a LCST of <40 C, and the second polymer has a melting point of >90 C;
(b) mixing the first polymer and the second polymer in a water solution to create a solute having a concentration of >30%;
(c) applying the solute to a heated dryer surface;
(d) allowing the solute to phase separate;
(e) applying the fibrous material to the phase separated solute; and
(f) removing the fibrous material from the heated dryer surface.
The foregoing and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where:
Repeated use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention. The drawings are representational and are not necessarily drawn to scale. Certain proportions thereof may be exaggerated, while others may be minimized.
The In-Hand Ranking Test (IHR) is a basic assessment of in-hand feel of fibrous webs and assesses attributes such as softness and stiffness. It can provide a measure of generalizability to the consumer population.
The softness test involves evaluating the velvety, silky or fuzzy feel of a tissue sample when rubbed between the thumb and fingers. The stiffness test involves gathering a flat sample into one's hand and moving the sample around in the palm of the hand by drawing the fingers toward the palm and evaluating the amount of pointed, rigid or cracked edges or peaks felt.
Rank data generated for each sample code by the panel are analyzed using a proportional hazards regression model. This model assumes computationally that the panelist proceeds through the ranking procedure from most of the attribute being assessed to the least of the assessed attribute. The softness and stiffness test results are presented as log odds values. The log odds are the natural logarithm of the risk ratios that are estimated for each code from the proportional hazards regression model. Larger log odds indicate the attribute of interest is perceived with greater intensity.
The IHR is employed to obtain a holistic assessment of softness and stiffness, or to determine if product differences are humanly perceivable. This panel is trained to provide assessments more accurately than an average untrained consumer might provide. The IHR is useful in obtaining a quick read as to whether a process change is humanly detectable and/or affects the softness or stiffness perception, as compared to a control.
The data from the IHR can also be presented in rank format. The data can generally be used to make relative comparisons within tests as a product's ranking is dependent upon the products it is ranked with. Across-test comparisons can be made when at least one product is tested in both tests.
The STFI mottling program has been written to run with Matlab computer software for computation and programming. A grayscale image is uploaded to the program where an image of the tissue in question had been generated under controlled, low-angle lighting conditions with a video camera, frame grabber and an image acquisition algorithm. Images are generated according to the method described below. The resulting image has a pixel resolution of 1024×1024 and represents a 12.5 mm×12.5 mm field of view.
The STFI mottling software analyzes the grayscale variation of the image in both the MD and CD directions by using FFT (Fast Fourier Transform). The FFT is used to develop gray-scale images at different wavelength ranges based on the frequency information present within the FFT. The gray-scale coefficient-of-variation (% COV) is then calculated from each of the images (e.g. inverse FFT's) corresponding to the wavelengths which were pre-determined by the STFI software. Since these images are generated with low-angle lighting, the tissue surface structure is shown as areas of light and dark, due to shadowing, and consequently the grayscale variation can be related to the tissue surface structure. For each code, 3 tissues are analyzed with 5 images from each tissue, resulting in a total of 15 images analyzed per code.
The test method involves retaining tissues, from which samples will be cut, at room temperature of between 68° F. to 72° F., and a relative humidity between 45 to 55%, for a time period of 24 hours. After the tissues have been acclimated, samples are prepared for imaging. Three randomly sampled, wrinkle-free tissues specimens are mounted on a 10×12-inch glass plate by adhering with an adhesive tape at their corners and along their sides. The tissues are drawn snug under mild tension during this tape adhering step. The specimens are cut and mounted so that the machine direction runs parallel with the longer dimension of the 2×3 inch piece. The basesheet samples are one-ply, and finished product samples are two-ply. For basesheet and finished product samples, each sample specimen is mounted with the creped side of the tissue in an upward position. Each sample specimen is “painted” with a 50:50 mixture of PENTEL® Correction Pen™ fluid and n-butanol, using a top quality camel's hair brush, applying in one direction parallel to the machine direction. This preparation will reduce light reflection and refraction. A 20 minute drying time is sufficient.
Referring to the schematic representation of the image acquisition apparatus shown in
The Dage 81 video camera 236 is mounted on a Polaroid MP-4 Land Camera (Polaroid Resource Center, Cambridge, Mass.) standard support 242. The support is attached to a KREONITE macro-viewer 244 available from Kreonite, Inc., having an office in Wichita, Kans. An auto-stage Model HM-1212, 246 is placed on the upper surface of the KREONITE macro-viewer. The auto-stage 246 is a motorized apparatus known to those skilled in the analytical arts which can be purchased from Design Components Incorporated (DCI), having an office in Franklin, Mass. The auto stage 246 is used to move the sample 222 in order to obtain five separate and distinct, non-overlapping images from the approximately 3×2 inch size specimen. The glass plates 224 with painted tissue are placed on the auto macro-stage (DCI 12×12 inch) of a Leica Microsystems Quantimet 600 Image Analysis system, under the optical axis of a 40 mm El-Nikkor lens 238 with a 30-mm extension tube 240. The sample is illuminated at 20 degrees with a slide projector to form shadows.
Referring again to
The image analysis system used to acquire images may be a Quantimet 600 Image Analysis System available from Leica Microsystems, having an office in Heerbrugg, Switzerland. The system is controlled and run by QWIN Version 1.06A software. The image analysis algorithm ‘OSC6C’ is used to acquire and process gray-scale monochrome images using Quantimet User Interactive Programming System (QUIPS) language. Alternatively, the OSC6C program could be used with a Quantimet 550 IW Image Analysis System or newer QWIN Pro platforms which run newer versions of the software (e.g. QWIN Pro Version 3.2.1). The custom image acquisition program is shown below.
Prior to acquiring the first sample images, shading correction is performed using QWIN software and a white, 803 Polaroid film positive (or equivalent white material) covered with an opaque, translucent film. Alternatively, other non-glossy white films or sheets could be used. The shading correction is performed using a ‘live’ mode. The system and images are accurately calibrated using QWIN software and a standard ruler with metric markings. The calibration is performed in the horizontal dimension of the video camera image.
After calibrating, the QUIPS algorithm OSC6C is executed via the QWIN software and this initially prompts the analyst to place the sample specimen within the field-of-view of the video camera. After positioning the specimen so the machine direction is parallel to the light source and the specimen is properly aligned for auto-stage motion, the analyst will then be prompted to adjust the light level setting (via the POWERSTAT variable auto transformer) to register between Gray-Level readings of 190-194. During this process of light adjustment, a QUIPS algorithm OSC6C will automatically display the current Gray-Level value on the video screen.
After the light has been properly adjusted, the QUIPS algorithm OSC6C will then automatically acquire the five images for a single tissue specimen. The analyst will then be prompted to reposition the plate, so that the next specimen can be imaged accordingly. This repositioning step will re-occur again for the third tissue specimen as well. The Gray-Level scale used on the Quantimet 600 system, or equivalent, is 8-bit and ranges from 0-255 (0 represents ‘black’ and 255 represents ‘white’).
Using the set-up described above, an image representing a 12.5 mm×12.5 mm field of view is generated and saved as *.tif image file. Typically, 3 tissue specimens are selected per sample code and 5 images generated per tissue specimen resulting in 15 images generated per sample or code.
The STFI Mottling software used for this analysis is STFI-Mottling v2.61 created by INNVENTIA (BOX 5604, SE-114 86, Stockholm, Sweden +46 8 676 7000—formerly STFI-Packforsk), designed for use with Matlab v7.x for Windows 95/98/2000/XP. The following inputs are entered in the STFI Mottling user interface.
No. of measuring areas: 4
Wavelength, mm—min: 2
Wavelength, mm—max: 64
Images are uploaded to the software by clicking the Select TIFF-file button and then choosing the appropriate file. The image then appears in the image window and the “Mark two corners” button is chosen. Diagonally opposite corners of the image are selected resulting in 4 regions on the tissue image boxed to denote the 4 measuring areas 250, 252, 253, and 254. The image analysis areas are illustrated in
The “Add to batch” button is then clicked to ready the measuring areas for analysis. All images for a sample are “added to batch” prior to clicking the “Start evaluation” button. Once the evaluation is complete, data files are then saved automatically for summary and analysis. A data file is saved for each image analyzed. A FFT calculation is completed for each analysis area and the average of the four FFTs is used for the image. Since there is a magnification difference of 29× between the actual images used and what the STFI mottling software normally uses from an image provided by a flatbed scanner, the wavelength ranges provided by the STFI software has to be recalculated to reflect this difference.
The data file for each image contains % COV for 2-4 mm, 4-8 mm, 8-16 mm, 16-32 mm, and 32-64 mm wavelengths for each of the four image areas 250-256 and the mean of those areas. The total variation and gray level is also included in each data file. The mean of the 4 image analysis areas for the 8-16 mm wavelength % COV is used for each image for data analysis. Since there are 15 images total per code, 15% COV is used to calculate a mean for the code or sample. Since images are acquired at a magnification of 29×, the 8-16 mm wavelength reported by the STFI software is actually 0.28-0.55 mm on the tissue specimens. 0.28-0.55 mm is generally considered by those skilled in the art to reflect good crepe. In the case of this analysis technique, lower % COV numbers in this wavelength area suggest less variation in the surface or a smoother surface.
This test is used to determine the amount of water-soluble creping blend component transferred from a facial tissue to a collagen film which serves as a model for skin. Collagen film may be obtained from Viscofan Group (located in Pomplona, Spain). An Ink Rub Tester Model #10-18-01, manufactured by Testing Machines Inc. (located in Ronkonkoma, N.Y.) is used in this test method. A block 5 cm by 10 cm and 2 cm thick, with a weight of 908 grams, is covered with the collagen film which is secured with magnets. The prepared block, covered by the collagen film is rubbed against the stable base of the instrument, which is covered by the tissue sample which is secured to the base with tape on the edges.
One set of films are equilibrated at 50% Relative Humidity (RH), and another set at an equilibration of 100% RH. Conditioning to 100% RH can be achieved by placing the collagen in a closed container containing water, without immersing the collagen in the water, and equilibrating the collagen in the closed container for 24 hours. Each sample is rubbed 8 cycles at a speed of 85 cycles per minute.
Prior to sample analysis, collagen is extracted and analyzed to ensure that no possible components could interfere with the quantification of PEG. Also, addition/recovery experiments are conducted to determine the extraction efficiency of the PEG from collagen. A stock ethanol solution of PEG is generated and a known amount (20 μL) is applied to collagen. The ethanol is allowed to evaporate and the samples are analyzed as per the methodology specified below. The addition/recovery results indicate that the methodology is sufficient for the accurate determination of PEG transferred to collagen.
Following the transfer procedure, each collagen sample is placed into a 20-mL vial. To each vial, 5-mL water is added and the contents sonicated for 10 minutes and shaken for 10 minutes. The ultrasonic action may be performed using a BRANSON Ultrasonic Cleaner, Model BRANSONIC 52, from the Branson Company in Danbury, Conn. The resulting solutions are filtered through a filter such as a PALL ACRODISC Syringe filter, 25 mm with 5 micron VERSAPOR membrane. These solutions are used for quantification. A PEG 8,000 calibration curve is generated for quantification purposes.
Mobile Phase: 85:15 (IPA: 0.1% acetic acid)
Flow rate: 0.7 mL/min.
Injection volume: 100 microliters
ELS detection: 70C nebulizer, 90C evaporator, 1 Liter N2
Lubricious or lubricated hand feel can be demonstrated by a significant reduction in coefficient of friction on a skin simulant of collagen film. Collagen film can be obtained from various sources such as Viscofan Group (located in Pomplona, Spain). The films are conditioned to 100% RH. Each collagen sample is rubbed against a tissue sample as follows:
An Ink Rub Tester Model #10-18-01, manufactured by Testing Machines Inc. (located in Ronkonkoma, N.Y.) functions by rubbing a block 5 cm by 10 cm and 2 cm thick, with a weight of 908 grams, covered with the collagen film (secured with magnets), against the stable base of the instrument, covered by a tissue sample (secured with tape on the edges). Conditioning the collagen films to 100% RH is achieved by placing the collagen in a closed container containing water, without immersing the collagen in the water, and equilibrating the collagen in the closed container for 24 hours. Each sample is rubbed 8 cycles at a speed of 85 cycles per minute.
The coefficient of friction for the tissue-rubbed collagen film samples is determined with a Lab Master Friction and Slip tester, Model 32-90, available from Testing Machines Inc., Ronkonkoma, N.Y. The films are tested under TAPPI conditions (50% relative humidity and 23° C.) at a test speed of 122 cm/minute, with a sled weight of 250 grams and a contact area of 38.4 cm2. A first film is placed, treated side up, on the base platform and secured with tape. A second identically treated film is secured on the sled with the treated side facing the first film. Identical collagen films, which are not rubbed with the tissue, are tested in the same manner.
Sheet bulk is calculated as the quotient of the sheet caliper of a conditioned fibrous sheet, expressed in microns, divided by the conditioned basis weight, and expressed in grams per square meter. The resulting sheet bulk is expressed in cubic centimeters per gram. More specifically, the sheet caliper is the representative thickness of a single sheet measured in accordance with TAPPI test methods T402 “Standard Conditioning and Testing Atmosphere For Paper, Board, Pulp Handsheets and Related Products” and T411 om-89 “Thickness (caliper) of Paper, Paperboard, and Combined Board” with Note 3 for stacked sheets. The micrometer used for carrying out T411 om-89 is an Emveco 200-A Tissue Caliper Tester available from Emveco, Inc., Newberg, Oreg. The micrometer has a load of 2 kilo-Pascals, a pressure foot area of 2500 square millimeters, a pressure foot diameter of 56.42 millimeters, a dwell time of 3 seconds and a lowering rate of 0.8 millimeters per second.
As used herein, the “geometric mean tensile (GMT) strength” is the square root of the product of the machine direction tensile strength multiplied by the cross-machine direction tensile strength. The “machine direction (MD) tensile strength” is the peak load per 3 inches (76.2 mm) of sample width when a sample is pulled to rupture in the machine direction. Similarly, the “cross-machine direction (CD) tensile strength” is the peak load per 3 inches (76.2 mm) of sample width when a sample is pulled to rupture in the cross-machine direction. The “stretch” is the percent elongation of the sample at the point of rupture during tensile testing. The procedure for measuring tensile strength is as follows.
Samples for tensile strength testing are prepared by cutting a 3 inch (76.2 mm) wide by a 5 inch (127 mm) long strip in the machine direction (MD) or cross-machine direction (CD) orientation using a JDC Precision Sample Cutter (Thwing-Albert Instrument Company, Philadelphia, Pa., Model No. JDC 3-10, Serial No. 37333). Samples must be conditioned to 50% relative humidity at a temperature of 23° C. and handled with rubber gloves. The instrument used for measuring tensile strengths is an MTS Systems Insight 1 Material Testing Work Station. The data acquisition software is MTS TestWorks® 4 (MTS Systems Corp., 14000 Technology Driver, Eden Prairie, Minn. 55344). The load cell is selected from either a 50 Newton or 100 Newton maximum (S-Beam TEDS ID Load Cell), depending on the strength of the sample being tested, such that the majority of peak load values fall between 10-90% of the load cell's full scale value.
The gauge length between jaws is 4±0.04 inches (101.6±1 mm). The jaws are operated using pneumatic-action and are rubber coated. The minimum grip face width is 3 inches (76.2 mm), and the approximate height of a jaw is 0.5 inches (12.7 mm).
The crosshead speed is 10±0.4 inches/min (254±1 mm/min), and the break sensitivity is set at 65%. The data is recorded at 100 hz. The sample is placed in the jaws of the instrument, centered both vertically and horizontally. The test is then started and ends when the specimen breaks. The peak load is recorded as the “MD tensile strength” or the “CD tensile strength” of the specimen. At least six (6) representative specimens are tested for each product or sheet, taken “as is”, and the arithmetic average of all individual specimen tests is the MD or CD tensile strength for the product or sheet.
The “Basis Weight” test is used to determine the mass of tissue fibers per unit area of the tissue sheet for napkins, towels, facial and bath tissue product. The basis weight can be measured in As-Is (no conditioning), Conditioned (equilibrated to laboratory conditions of 23+/−3.0° C. and 50+/−5% relative humidity) or Bone Dry (oven dried at 105+/−2.0° C. for 25 minutes for a sample weight less than 10.0 grams and a minimum of 8 hours for a sample weighing more than 10 grams). To carry out the test, 16 sheets are stacked and cut to a dimension of 76.2×76.2+/−1 mm using a die cutter capable of cutting the specimen to the specified dimensions such as a Hudson Machinery part number SE-25 or equivalent with an appropriately designed die. Weigh the cut specimen in grams for as-is, conditioned or bone dry basis weight after appropriate conditions of previously mentioned preparations are completed. If bone dry basis weight is required, the oven dried sample will be placed into an air-tight can after drying to prevent moisture from penetrating the sample—the weight of the can is then removed from the calculation of the sample weight. This weight in grams is then multiplied by 6.3492 to report the finished product basis weight in pounds per ream or multiply the sample weight in grams by 10.764 to report the finished product basis weight in grams per square meter (gsm).
The “Absorbency Rate (Wet-Out Time) Test” is used to determine the absorbency wet out time of napkins, towels, facial and bath tissue product. To carry out the test, the test product is first equilibrated to ambient conditions for at least four hours at 23+/−3.0° C. and 50+/−5% relative humidity. 20 sheets are stacked and cut to a sixty three millimeter by sixty three millimeter (+/−three millimeters) square using a device capable of cutting to the specified dimensions such as a Hudson Machinery part number se-25 or equivalent. The square is then fixed in each corner by staples delivered by a standard, commercially available manual office stapler. The staples are placed diagonally across each corner far enough into the sheet so that the staples are completely contacting the tissue sheets, staples should not wrap the corner of the sample. The sample is then held horizontally and approximately 25 mm (1 inch) over a container containing distilled or de-ionized water at 23.0° C.±3.0° C. The container should be of sufficient size and depth to ensure that the saturated specimen does not contact the sides, bottom of the container, and the top surface of the water at the same time. The container should contain a minimum depth of 51 mm of water to ensure complete saturation of the test specimen and this depth should be maintained throughout the testing. The specimen is then dropped flat onto the water surface and a timing device is started when the specimen contacts the water surface. As soon as the specimen is completely saturated, stop the timing device and record the absorbency wet out time in seconds.
A 1-2 gram sample of the tissue to be tested is weighed and placed in a 100 mL specimen cup. Fifty milliliters of room temperature deionized water is added to each specimen cup. The specimen cup is capped and extracted on a flat-bed shaker at 150 rpm for one hour.
After extraction the sample is filtered through a Buchner funnel containing a Whatman 934-AH glass microfiber filter (Whatman Catalog Number 1827-055, Whatman Inc., GE Healthcare, www.whatman.com) using vacuum. The specimen cup is rinsed twice with deionized water and poured into the funnel. The tissue is then rinsed an additional two times with deionized water. The extract is transferred to a tared 100 mL beaker and the filter flask is rinsed twice with deionized water and combined with the extract in the beaker. The total volume in the beaker is nearly 100 mL. The beaker is dried in an oven at 105° C., cooled, and weighed. The % water soluble extractables are calculated from the tissue weight and the tare and final weights of the beaker.
Three tests are completed per sample. The average, % water soluble extractables is reported for each sample.
The fuzz-on-edge methodology measures the amount of fibers that protrude from the surface of a fibrous material. The measurement is performed using image analysis to detect and then measure the total perimeter of protruding surface fibers observed when the material in question is wrapped over an ‘edge’ to that allow the fibers to be viewed from the side using transmitted light. An image analysis algorithm was developed to detect and measure the perimeter length of the fibers per edge length of material, where the perimeter length is defined as the total length of the boundaries of all of the protruding fibers (i.e. Perimeter/Edge Length or PR/EL for short). For example, an edge along the majority of the length of a fibrous material (e.g. facial tissue) can be measured by acquiring and analyzing multiple, adjacent fields-of-view to arrive at a single PR/EL value. Typically, several such material specimens are analyzed for a sample to arrive at a mean PR/EL value.
A tissue sample is allowed to equilibrate at laboratory temperature conditions ranging from 68-72 degrees Fahrenheit, and a relative humidity between 45 to 55% for at least 24 hours. A sample specimen 400 of the tissue is first prepared by cutting it into a strip that is approximately 20 cm in length. The width is cut to approximately 4-5 cm. A folded edge is imparted along the machine-direction (MD) length of the tissue strip by taping down one end onto a piece of beveled glass plate 402 using a common, transparent tape (e.g., SCOTCH® tape) so that approximately half the width of the material hangs over the beveled glass edge 404.
See
After taping down the entire long edge stretching between the two ends, the beveled glass plate 402 and holding apparatus 424 is inverted. The loose specimen portion sticking out past the beveled edge 404 is then gently pulled over the edge 404 and taped onto the opposite side of the glass relative to the first specimen edge. When taping down the second edge on the opposite glass surface, the material is again lightly stretched in an effort to remove any macro wrinkles.
A Dage 81 video camera (Dage-MTI, Michigan City, Ind.) 420 is mounted on a Polaroid MP-4 Land Camera (Polaroid Resource Center, Cambridge, Mass.) standard support 422. The support is attached to a KREONITE macro-viewer available from Kreonite, Inc., having an office in Wichita, Kans. An auto-stage, DCI Model HM-1212, is placed on the upper surface of the KREONITE macro-viewer and the sample mounting apparatus was placed atop the auto-stage. The auto-stage is a motorized apparatus known to those skilled in the analytical arts which was purchased from Design Components Incorporated (DCI), having an office in Franklin, Mass. The auto stage is used to move the sample in order to obtain 15 separate and distinct, non-overlapping images from the specimen. The sample mounting apparatus 424 is placed on the auto macro-stage (DCI 12×12 inch) of a Leica Microsystems Quantimet 600 Image Analysis system, under the optical axis of a 60-mm AF Micro Nikkor lens (Nikon Corp., Japan) fitted with a 30-mm extension tube. The lens focus is adjusted to provide the maximum magnification and the camera position on the Polaroid MP-4 support is adjusted to provide optimum focus of the tissue edge. The sample is illuminated from beneath the auto-stage using a Chroma Pro 45 (Circle 2, Inc., Tempe, Ariz.). The Chroma Pro settings are such that the light is ‘white’ and not filtered in any way to bias the light's spectral output. The Chroma Pro may be connected to a POWERSTAT Variable Auto-transformer, type 3PN117C, which may be purchased from Superior Electric, Co. having an office in Bristol, Conn. The auto-transformer is used to adjust the Chroma Pro's illumination level.
The image analysis system used to acquire images and perform the PR/EL measurements may be a Quantimet 600 Image Analysis System available from Leica Microsystems, having an office in Heerbrugg, Switzerland. The system is controlled and run by QWIN Version 1.06A software. The image analysis algorithm ‘FOE2’ is used to acquire and process gray-scale monochrome images using Quantimet User Interactive Programming System (QUIPS) language. Alternatively, the FOE2 program could be used with a Quantimet 550 IW Image Analysis System or newer QWIN Pro platforms which run newer versions of the software (e.g. QWIN Pro Version 3.2.1). The custom image analysis program is shown below.
Prior to acquiring the first sample images, shading correction is performed using the QWIN software and blank field-of-view illuminated only by the Chromo Pro 45. The shading correction is performed using the ‘live’ mode. The system and images are also accurately calibrated using the QWIN software and a standard ruler with metric markings. The calibration is performed in the horizontal dimension of the video camera image.
After calibrating, the QUIPS algorithm FOE2 is executed via the QWIN software and this initially prompts the analyst to place the sample specimen 400 within the field-of-view of the video camera. After positioning the specimen so the machine direction runs horizontally in the image the specimen is properly aligned for auto-stage motion, the analyst will then be prompted to adjust the light level setting (via the POWERSTAT variable auto transformer) to register a white level reading of 1.0. During this process of light adjustment, the QUIPS algorithm FOE2 will automatically display the current white level value within a small window on the video screen.
After the light has been properly adjusted, the QUIPS algorithm FOE 2 will then automatically acquire the 15 images and make corresponding PR/EL measurements for a single tissue specimen. The analyst will then be prompted to reposition the tissue mounting apparatus, so that the next specimen can be imaged accordingly. This repositioning step will occur two more times so that a third and forth tissue specimen will be measured as well. The Gray-Level scale used on the Quantimet 600 system, or equivalent, is 8-bit and ranges from 0-255 (0 represents ‘black’ and 255 represents ‘white’).
The PR/EL data are exported directly to an EXCEL® spreadsheet. The data are then processed so that the mean PR/EL value obtained from each of the four tissue specimens are then combined together resulting in a final mean PR/EL value. This final sample mean PR/EL value is based on an N=4 analysis from the four tissue specimens. A comparison between different tissue samples is performed using a Student's T analysis at the 90% confidence level.
This test method is directed to a single-ply creped tissue sample. The dryer-side and felt-side of the sample must be identified. Machine direction (MD) and Cross-machine direction (CD) must also be known.
SCOTCH® Box Sealing Tape 373, available from 3M, St. Paul, Minn., is used to split the tissue sheet samples. The tape is supplied at 48 mm wide. Five samples of the tape alone, each 102 mm long, are weighed and averaged to determine an average weight per length. This is used as the tare weight of the tape.
A 48 mm by 102 mm piece of the SCOTCH® 373 tape is applied to the felt-side of the tissue sample, with the longer dimension aligned with the MD of the tissue sample. The actual tape length is longer than 102 mm in order to create a tab at one end by folding over the tape end. However, the actual effective applied length to the tissue is 102 mm. A 2.0 kg roller, which is approximately the same width as the tape, is rolled once over the taped portion at a speed of 305 mm per minute, down and back.
In the same manner, another 48 mm by 102 mm piece of SCOTCH® 373 tape is applied to the dryer-side of the tissue sample, over the same exact area, but on the opposite side of the tissue sample. After the 2.0 kg roller is rolled over the taped portion, on the dryer-side, as described above, the sample is equilibrated at TAPPI conditions (23 degrees C. and 50% relative humidity) for 12 hours.
After conditioning, the tissue sample is pulled apart by grasping the two tape tabs and pulling them apart at a speed of about 102 mm per minute. The result is a split tissue sheet sample, with a portion attached to each piece of tape.
Each of the two 48 mm by 102 mm tape/tissue samples is weighed. The tare weight of the tape is subtracted from the tape/tissue sample weight to obtain the weight of tissue and additive composition that is attached to each piece of tape.
Each of the two tape/tissue samples is placed in a 100-mL specimen cup and 15 ml of a 90:10 (isopropyl alcohol:water) mixture is added by pipette. The specimen cup was capped and then placed on a flatbed shaker at 150 rpm for 2 hours.
The amount of PEG extracted is determined by the HPLC procedure as described as follows:
The resulting extraction solutions are filtered through a PALL ACRODISC Syringe filters 25 mm with a 5 micron VERSAPOR membrane and used for quantification. A PEG 8,000 calibration curve was generated for quantification purposes.
The amounts of PEG isolated are normalized by the tissue/additive composition weight for that split and recorded as weight percent of PEG in the tissue split:
It should be noted that, when employed in the present disclosure, the terms “comprises,” “comprising” and other derivatives from the root term “comprise” are intended to be open-ended terms that specify the presence of any stated features, elements, integers, steps, or components, and are not intended to preclude the presence or addition of one or more other features, elements, integers, steps, components, or groups thereof.
The term “Lower Critical Solution Temperature” (hereinafter “LCST”) refers to a water soluble composition that is water soluble until it reaches a threshold temperature. Once the threshold temperature has been met, the composition's polymer chains shrivel into an insoluble mass as the hydrophobic components interact with each other and the polymer chains become dehydrated.
“Conventional” creping chemistries for tissue manufacturing have typically included an adhesive which comprises an aqueous admixture of polyvinyl alcohol (PVOH) and a water-soluble, thermosetting, cationic polyamide-epihalohydrin resin, as described in Soerens U.S. Pat. No. 4,501,640. The polyvinyl alcohol can be, for instance, Celvol 523, available from Celanese Corporation (Dallas, Tex.). The polyamide-epihalohydrin resin can be Kymene 557-H, available from Ashland Corporation (Covington, Ky.). Additional variations of conventional creping chemistries also include Rezosol 1095, available from Ashland Corporation (Covington, Ky.). The ratio of chemicals included in the conventional creping mixtures has varied over a large range. However, a typical mixture can be 40% PVOH, 40% Kymene 557-H, and 20% Rezosol 1095.
Other water soluble creping chemistries can include an additive composition having a water insoluble polyolefin dispersion as described in U.S. Pat. Pub. No. 2007/0144697, incorporated herein to the extent that it is consistent with the present invention.
Unless otherwise specified, all comparisons made with respect to webs are compared to webs of the same base substrates, but with a conventional treatment or other treatments. In other words, with the exception of the treatment, all other aspects of the web are the same.
These terms may be defined with additional language in the remaining portions of the specification.
It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary aspects only, and is not intended as limiting the broader aspects of the present disclosure.
In general, the present disclosure is directed to the incorporation of an additive composition onto at least the surface of a fibrous article in order to maintain or improve certain physical characteristics such softness and absorbency, while improving the related manufacturing efficiency. The additive composition is made from a water-soluble film-forming component and a water-soluble modifier component. In some aspects, the additive may also contain additional water-soluble modifier components.
Polymers which have the property of a Lower Critical Solution Temperature (LCST) are particularly beneficial as a non-uniform coating of the present invention because they are soluble in water at an ambient temperature of about 22° C. The composition quickly precipitates at the relatively high temperature of the dryer surface, which is greater than 50° C. This property allows discrete deposition onto the tissue fibers while increasing efficiency of processing. The polymers having the desired LCST property generally have both hydrophobic and hydrophilic segments in their macromolecular structure which results in the solubility change at a LCST.
Below the LCST, the polymer chains hydrophilic segments interact with water and are elongated. At the critical solution temperature, the polymer chains shrivel into an insoluble mass as the hydrophobic segments interact each other and the polymer chains become dehydrated. The composition examples from this group include, but are not limited to, hydroxypropyl cellulose (HPC), hydroxypropyl starch (HPS), hydroxyethyl cellulose (HEC), poly-N-isopropylacrylamide (poly-NIPAAm), polyethylene oxide-polypropylene oxide block copolymers (such as Pluronic F127), poly(2 ethyl oxazoline).
When a LCST polymer solution hits the hot surface of the Yankee dryer (temperature above 50° C.), the LCST polymer will precipitate and the transparent solution will become milky. In order to demonstrate this phenomenon, a metal plate was heated in an oven at 150° C. for 2 hours and then taken out of the oven. A 5 wt % of KLUCEL solution, available from Ashland, Inc. (Covington, Ky.), was sprayed onto its hot surface immediately. As a control, the solution was also sprayed onto a similar metal plate at room temperature. When a LCST polymer solution hits the hot surface of the Yankee dryer (temperature above 50° C.) the LCST polymer will be precipitated. See
Blends of the present invention consist of water soluble, polymers with melting points in the range of 35° C. to 95° C., which are utilized to crepe a fibrous web. These polymers are in the molten state at temperatures 20° C. to 80° C. above their melting point of the components. The molten state refers to a polymer or blend of polymers that is above the melting point of all components and has a water content of less than 5% by weight and a melt viscosity of 400-600,000 centipoise at 120° C., as measured by the Melt Viscosity test method, ASTM D 3236, 2004 version.
Blends of the present invention at the creping blade function like a hot melt adhesive with a high affinity for the metal surface and the cellulosic fiber web along with a low cohesive strength which facilitates failure, at least partially within the creping blend layer on the Yankee dryer, resulting in significant transfer of the creping blend to cellulosic fiber web. Since the blends of the present invention have relatively low melting points and have no functionality to promote crosslinking they are relatively stable and provide consistent creped tissue properties because there is less tendency for chemical transformation during the process by crosslinking or decomposition. Furthermore, if the polymer blends are nonionic (without charge) they are less sensitive to the ionic content of the process water. These properties enhance stability which provides for a robust process window.
In some aspects, the additive composition is non-ionic. However, cationic and anionic polymers may be used if they produce a similar effect as the non-ionic polymers.
Referring now to
Due to the water soluble nature of the present invention, the process may provide among other advantages, the advantage of not having to remove the polymer from the process waste water. Other process advantages include but are not limited to: (1) solubility at ambient temperature prevents unwanted deposition on tissue machine felts or fabrics; (2) insolubility at high temperature enables surface deposition onto the tissue surface; and (3) hydrophobic segment interaction at high temperature encourages the hydrophobic segment to stay on the surface of deposited material. This morphological conformation may be related to improved tissue tactile properties.
The moisture sensitivity of the creping composition can also be used to modify the frictional properties of the tissue as well as control coating transfer to the skin. At least a portion of the creping composition will dissolve in the presence of water. Creping compositions of the present invention when applied at levels greater than 100 mg/m2 have water soluble extractives greater than 0.35% at a conditioned basis weight of about 28 gsm.
Four biodegradable and water soluble modified polysaccharides were selected to demonstrate this invention. They are hydroxypropyl cellulose, hydroxyethyl cellulose, methyl cellulose, all available from Ashland, Inc. (Covington, Ky.) with commercial names of KLUCEL, NATROSOL, BENECEL respectively, and hydroxypropyl starch which is available from Chemstar (Minneapolis, Minn.) with a trade name of GLUCOSOL 800 (hereinafter referred to as GLUCOSOL). Of course, there may be other LCST materials, and this invention is not to be limited to these four compositions. Other LCST materials are listed herein. The examples from this group include, but are not limited to, hydroxypropyl cellulose (HPC), hydroxypropyl starch (HPS), hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC), polyethylene oxide, polyethylene oxide-polypropylene oxide block polymers (such as PLUCONIC F127) poly(2 ethyl oxazoline, vinyl caprolactone-vinyl pyrrolidone copolymers, and polyethylene glycol methacrylates.
The additive composition of the present invention includes at least one water-soluble film forming component capable of forming a coating on the surface of a dryer. When applied to a hot dryer surface the composition goes from a liquid solution to a suspension containing a precipitate. When transferred to a fibrous web, the additive composition in the form of a precipitate forms a deposit that not only stays on top of the tissue, but penetrates beyond the tissue surface as well.
Thus, of particular advantage, the deposit allows liquids to be absorbed therethrough and into the interior of the fibrous web. Furthermore, the polymer network is wettable due to the water soluble nature of the additive composition. As such, the additive composition does not significantly interfere with the liquid absorption properties of the web while increasing the softness of the web.
The water-soluble film forming components contained within the additive composition may vary depending upon the particular application and the desired result. In one particular aspect, for instance, the water-soluble film forming component is GLUCOSOL 800. The water-soluble film forming component can be present in the additive composition in any operative amount and will vary based on the chemical component selected, as well as on the end properties that are desired. For example, in the exemplary case of GLUCOSOL 800, the water-soluble film forming component can be present in the additive composition in an amount of about 10-90 wt %, such as 20-80 wt % or 30-70 wt % based on the total weight of the additive composition, to provide improved benefits.
An additional water-soluble film forming component is poly(ethylene oxide) such as POLYOX N3000, available from Dow Chemical, having a place of business located in Midland, Mich. For example, in the exemplary case of POLYOX N3000, the second water-soluble film forming component can be present in the additive composition in an amount of about 1-30 wt %, such as 5-20% or 10-15% based on the total weight of the additive composition, to provide improved benefits.
Suitable water-soluble film forming components also include, cellulose ethers and esters, poly(acrylic acid) and salts thereof, poly(acrylate esters), and poly(acrylic acid) copolymers. Other suitable water-soluble film forming components include polysaccharides of sufficient chain length to form films such as, but not limited to, pullulan and pectin. The water soluble film-forming polymer can also contain additional monoethylenically unsaturated monomers that do not bear a pendant acid group, but are copolymerizable with monomers bearing acid groups. Such compounds include, for example the monoacrylic esters and monomethacrylic esters of polyethylene glycol or polypropylene glycol, the molar masses (Mn) of the polyalkylene glycols being up to about 2,000, for example.
In some aspects, the water-soluble film forming component is dissolved into a 1 wt % aqueous solution, and diluted further as required to provide the desired dosage in mg/m2 of tissue surface. The dosage is estimated based on the volume of film forming solution multiplied by the film forming concentration and divided by the square meters of tissue treated per unit time. In one particular aspect, the water-soluble film forming component is hydroxypropyl cellulose (HPC) sold by Ashland, Inc. under the brand name of KLUCEL. The water-soluble film forming component can be present in the additive composition in any operative amount and will vary based on the chemical component selected, as well as on the end properties that are desired. For example, in the exemplary case of KLUCEL, the biodegradable, water-soluble modifier component can be present in the additive composition in an amount of about 1-70 wt %, or at least about 1 wt %, such as at least about 5 wt %, or least about 10 wt %, or up to about 30 wt %, such as up to about 50 wt % or up to about 75 wt % or more, based on the total weight of the additive composition, to provide improved benefits. Other examples of suitable first water-soluble biodegradable film forming components include methyl cellulose (MC) sold by Ashland, Inc. under the brand name of BENECEL; hydroxyethyl cellulose sold by Ashland, Inc. under the brand name of NATROSOL; and hydroxypropyl starch sold by Chemstar (Minneapolis, Minn.) under the brand name of GLUCOSOL 800. Any of these chemistries, once diluted in water, are disposed onto a Yankee dryer surface with a spray boom 22 to ultimately transfer to the web surface.
In addition to a water-soluble film forming component, the additive composition can include a first water-soluble modifier component. The first water-soluble modifier component is used, among other things, to adjust adhesion of the web to a paper drying surface. The water-soluble modifier component can also improve paper machine cleanliness (e.g., the paper machine dryer surface and paper machine felts or fabrics). In some aspects, the water-soluble modifier component is a first water-soluble modifier component. In one particular aspect, the water-soluble modifier component is Carbowax PEG 8000, available from Dow Chemical, having a place of business located in Midland, Mich. The water-soluble modifier component can be present in the additive composition in any operative amount and will vary based on the chemical component selected, as well as on the end properties that are desired. For example, in the exemplary case of Carbowax PEG 8000, the water-soluble modifier component can be present in the additive composition in an amount of about 1-90 wt %, or at least about 1 wt %, such as at least about 5 wt %, or least about 10 wt %, or up to about 30 wt %, such as up to about 50 wt % or up to about 75 wt %, or more, based on the total weight of the additive composition, to provide improved benefits. Examples of suitable first water-soluble modifier components include ethylene oxide-propylene oxide block copolymers.
The additive composition of the present invention can also include an additional water-soluble modifier component. The additional water-soluble modifier component can be utilized, among other things, as a plasticizer for the water-soluble film forming component thereby reducing the stiffness and cohesive strength of the water-soluble film forming component. The additional water-soluble modifier component can also contribute to improved end-properties of the web, including but not limited to, increased void volume of the sheet and/or improved perceived softness. Desirably, the additional water-soluble modifier component is different than the first water-soluble modifier component. In one particular aspect, the additional water-soluble modifier component is. The additional water-soluble modifier component can be present in the additive composition in any operative amount and will vary based on the chemical component selected, as well as on the end properties of the web that are desired. For example, in the exemplary case of glycerol, the additional water-soluble modifier component can be present in the additive composition in an amount of up to about 10 wt %, such as up to about 20 wt % or up to about 40 wt % or more, based on the total weight of the additive composition, to provide improved benefits. Examples of suitable additional water-soluble modifier components include sorbitol, sucrose, glycerol, glycerol esters, and propylene glycol.
In some aspects, the additive composition can be diluted prior to application. The pH of the aqueous solution is generally less than about 12, such as from about 5 to about 9, and preferably about 6 to about 8. In this aspect, the additive composition can be diluted to between 0.20 wt % to 10 wt %, desirably to between 4 to 7 wt %.
In one aspect, the additive composition may be applied topically to the web during a creping process. For instance, the additive composition may be sprayed onto a heated dryer drum in order to adhere the web to the dryer drum. The web can then be creped from the dryer drum.
Referring to
The range of operation is a much wider window of chemistry addition than conventional creping chemistry packages. A conventionally creped sheet uses a multi-component creping chemistry package including one component which is a polymer that forms a relatively hard solid after drying and water removal, such as a cross-linking or non-crosslinking resin, and a material such as low molecular weight organic compound which does not form a solid after drying and water removal, such as an emulsified oil. This total chemistry package addition range is generally below a level of 30 milligrams per square meter of the Yankee surface. This operating range for traditional coating chemistry is desired because the Yankee dryer coating typically becomes compromised at higher addition rates. This compromised condition can include excessively thick coating, discontinuous coating and high coating variability in both the machine and cross direction of the Yankee dryer which may result in reduced blade life, sheet quality issues, increased drying load and low machine efficiency due to breaks and poor winding. The desirable combinations of the alternative chemistries of the present invention have been successfully applied to the Yankee dryer at levels from about 50 to about 1000 milligrams per square meter of Yankee surface. The sheet and process have been acceptable at these addition ranges. The coating build up has not been excessive, sheet quality has remained acceptable at high addition rate and the machine efficiency has not been affected.
In general, any suitable fibrous web may be treated in accordance with the present disclosure. For example, in one aspect, the base sheet can be a tissue product, such as a bath tissue, a facial tissue, a paper towel, a napkin, dry and moist wipes, and the like. In some aspects, the fibrous products may have a bulk density of at least 3 cc/g. Fibrous products can be made from any suitable types of fiber. Fibrous products made according to the present disclosure may include single-ply fibrous products or multiple-ply fibrous products. For instance, in some aspects, the product may include two plies, three plies, or more.
Fibers suitable for making fibrous webs comprise any natural or synthetic fibers including, but not limited to nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and woody or pulp fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, and aspen. Pulp fibers can be prepared in high-yield or low-yield forms and can be pulped in any known method, including kraft, sulfite, high-yield pulping methods and other known pulping methods. Fibers prepared from organosolv pulping methods can also be used, including the fibers and methods disclosed in U.S. Pat. No. 4,793,898, issued Dec. 27, 1988 to Laamanen et al.; U.S. Pat. No. 4,594,130, issued Jun. 10, 1986 to Chang et al.; and U.S. Pat. No. 3,585,104. Useful fibers can also be produced by anthraquinone pulping, exemplified by U.S. Pat. No. 5,595,628 issued Jan. 21, 1997, to Gordon et al.
The fibrous webs of the present invention can also include synthetic fibers. For instance, the fibrous webs can include up to about 10%, such as up to about 30% or up to about 50% or up to about 70% or more by dry weight, to provide improved benefits. Suitable synthetic fibers include rayon, polyolefin fibers, polyester fibers, bicomponent sheath-core fibers, multi-component binder fibers, and the like. Synthetic cellulose fiber types include rayon in all its varieties and other fibers derived from viscose or chemically-modified cellulose.
Chemically treated natural cellulosic fibers can be used, for example, mercerized pulps, chemically stiffened or crosslinked fibers, or sulfonated fibers. For good mechanical properties in using web forming fibers, it can be desirable that the fibers be relatively undamaged and largely unrefined or only lightly refined. While recycled fibers can be used, virgin fibers are generally useful for their mechanical properties and lack of contaminants. Mercerized fibers, regenerated cellulosic fibers, cellulose produced by microbes, rayon, and other cellulosic material or cellulosic derivatives can be used. Suitable web forming fibers can also include recycled fibers, virgin fibers, or mixes thereof.
In general, any process capable of forming a web can also be utilized in the present disclosure. For example, a web forming process of the present disclosure can utilize creping, wet creping, double creping, recreping, double recreping, embossing, wet pressing, air pressing, through-air drying, hydroentangling, creped through-air drying, co-forming, air laying, as well as other processes known in the art. For hydroentangled material, the percentage of pulp is about 70-85%.
Also suitable for articles of the present disclosure are fibrous sheets that are pattern densified or imprinted, such as the fibrous sheets disclosed in any of the following U.S. Pat. No. 4,514,345 issued on Apr. 30, 1985, to Johnson et al.; U.S. Pat. No. 4,528,239 issued on Jul. 9, 1985, to Trokhan; U.S. Pat. No. 5,098,522 issued on Mar. 24, 1992; U.S. Pat. No. 5,260,171 issued on Nov. 9, 1993, to Smurkoski et al.; U.S. Pat. No. 5,275,700 issued on Jan. 4, 1994, to Trokhan; U.S. Pat. No. 5,328,565 issued on Jul. 12, 1994, to Rasch et al.; U.S. Pat. No. 5,334,289 issued on Aug. 2, 1994, to Trokhan et al.; U.S. Pat. No. 5,431,786 issued on Jul. 11, 1995, to Rasch et al.; U.S. Pat. No. 5,496,624 issued on Mar. 5, 1996, to Steltjes, Jr. et al.; U.S. Pat. No. 5,500,277 issued on Mar. 19, 1996, to Trokhan et al.; U.S. Pat. No. 5,514,523 issued on May 7, 1996, to Trokhan et al.; U.S. Pat. No. 5,554,467 issued on Sep. 10, 1996, to Trokhan et al.; U.S. Pat. No. 5,566,724 issued on Oct. 22, 1996, to Trokhan et al.; U.S. Pat. No. 5,624,790 issued on Apr. 29, 1997, to Trokhan et al.; and, U.S. Pat. No. 5,628,876 issued on May 13, 1997, to Ayers et al., the disclosures of which are incorporated herein by reference to the extent that they are non-contradictory herewith. Such imprinted fibrous sheets may have a network of densified regions that have been imprinted against a drum dryer by an imprinting fabric, and regions that are relatively less densified (e.g., “domes” in the fibrous sheet) corresponding to deflection conduits in the imprinting fabric, wherein the fibrous sheet superposed over the deflection conduits was deflected by an air pressure differential across the deflection conduit to form a lower-density pillow-like region or dome in the fibrous sheet.
The fibrous web can also be formed without a substantial amount of inner fiber-to-fiber bond strength. In this regard, the fiber furnish used to form the base web can be treated with a chemical debonding agent. The debonding agent can be added to the fiber slurry during the pulping process or can be added directly to the headbox. Suitable debonding agents that may be used in the present disclosure include cationic debonding agents such as fatty dialkyl quaternary amine salts, mono fatty alkyl tertiary amine salts, primary amine salts, imidazoline quaternary salts, silicone, quaternary salt and unsaturated fatty alkyl amine salts. Other suitable debonding agents are disclosed in U.S. Pat. No. 5,529,665 to Kaun which is incorporated herein by reference. In particular, Kaun discloses the use of cationic silicone compositions as debonding agents.
Optional chemical additives may also be added to the aqueous web forming furnish or to the formed embryonic web to impart additional benefits to the product and process and are not antagonistic to the intended benefits of the invention. The following chemicals are included as examples and are not intended to limit the scope of the invention.
The types of chemicals that may be added to the paper web include, but are not limited to, absorbency aids usually in the form of cationic, anionic, or non-ionic surfactants, humectants and plasticizers such as low molecular weight polyethylene glycols and polyhydroxy compounds such as glycerin and propylene glycol. Materials that supply skin health benefits such as mineral oil, aloe extract, vitamin-E, silicone, lotions in general and the like may also be incorporated into the finished products. Such chemicals may be added at any point in the web forming process.
In general, the products of the present invention can be used in conjunction with any known materials and chemicals that are not antagonistic to its intended use. Examples of such materials include but are not limited to odor control agents, such as odor absorbents, activated carbon fibers and particles, baby powder, baking soda, chelating agents, zeolites, perfumes or other odor-masking agents, cyclodextrin compounds, oxidizers, and the like. Superabsorbent particles, synthetic fibers, or films may also be employed. Additional options include cationic dyes, optical brighteners, humectants, emollients, and the like.
Fibrous webs that may be treated in accordance with the present disclosure may include a single homogenous layer of fibers or may include a stratified or layered construction. For instance, the fibrous web ply may include two or three layers of fibers. Each layer may have a different fiber composition. For example, referring to
Each of the fiber layers comprise a dilute aqueous suspension of papermaking fibers. The particular fibers contained in each layer generally depend upon the product being formed and the desired results. For instance, the fiber composition of each layer may vary depending upon whether a bath tissue product, facial tissue product or paper towel is being produced. In one aspect, for instance, middle layer 21 contains southern softwood kraft fibers either alone or in combination with other fibers such as high yield fibers. Outer layers 23 and 25, on the other hand, contain softwood fibers, such as northern softwood kraft.
In an alternative aspect, the middle layer may contain softwood fibers for strength, while the outer layers may comprise hardwood fibers, such as eucalyptus fibers, for a perceived softness.
An endless traveling forming fabric 26, suitably supported and driven by rolls 28 and 30, receives the layered papermaking stock issuing from headbox 10. Once retained on fabric 26, the layered fiber suspension passes water through the fabric as shown by the arrows 32. Water removal is achieved by combinations of gravity, centrifugal force and vacuum suction depending on the forming configuration.
Forming multi-layered paper webs is also described and disclosed in U.S. Pat. No. 5,129,988 to Farrington, Jr., which is incorporated herein by reference in a manner that is consistent herewith.
The basis weight of fibrous webs made in accordance with the present disclosure can vary depending upon the final product. For example, the process may be used to produce bath tissues, facial tissues, paper towels, and the like. In general, the basis weight of such fibrous products may vary from about 5 gsm to about 110 gsm, such as from about 10 gsm to about 90 gsm. For bath tissue and facial tissues, for instance, the basis weight may range from about 10 gsm to about 40 gsm. For paper towels, on the other hand, the basis weight may range from about 25 gsm to about 80 gsm or more.
Fibrous products made according to the above processes can have relatively good bulk characteristics. For instance, the fibrous web bulk may also vary from about 1-20 cc/g, such as from about 3-15 cc/g or from about 5-12 cc/g.
In multiple-ply products, the basis weight of each fibrous web present in the product can also vary. In general, the total basis weight of a multiple ply product will generally be the same as indicated above, such as from about 20 gsm to about 200 gsm. Thus, the basis weight of each ply can be from about 10 gsm to about 60 gsm, such as from about 20 gsm to about 40 gsm.
Once the aqueous suspension of fibers is formed into a fibrous web, the fibrous web may be processed using various techniques and methods. For example, referring to
The wet web is then transferred from the forming fabric to a transfer fabric 40. In one aspect, the transfer fabric can be traveling at a slower speed than the forming fabric in order to impart increased stretch into the web. This is commonly referred to as a “rush” transfer. Preferably the transfer fabric can have a void volume that is equal to or less than that of the forming fabric. The relative speed difference between the two fabrics can be from 0-60%, more specifically from about 15-45%. Transfer is preferably carried out with the assistance of a vacuum shoe 42 such that the forming fabric and the transfer fabric simultaneously converge and diverge at the leading edge of the vacuum slot.
The web is then transferred from the transfer fabric to the throughdrying fabric 44 with the aid of a vacuum transfer roll 46 or a vacuum transfer shoe, optionally again using a fixed gap transfer as previously described. The throughdrying fabric can be traveling at about the same speed or a different speed relative to the transfer fabric. If desired, the throughdrying fabric can be run at a slower speed to further enhance stretch. Transfer can be carried out with vacuum assistance to ensure deformation of the sheet to conform to the throughdrying fabric, thus yielding desired bulk and appearance if desired. Suitable throughdrying fabrics are described in U.S. Pat. No. 5,429,686 issued to Kai F. Chiu et al. and U.S. Pat. No. 5,672,248 to Wendt et al., which are incorporated by reference.
In one aspect, the throughdrying fabric contains high and long impression knuckles. For example, the throughdrying fabric can have from about 5 to about 300 impression knuckles per square inch which are raised at least about 0.005 inches above the plane of the fabric. During drying, the web can be macroscopically arranged to conform to the surface of the throughdrying fabric and form a three-dimensional surface. Flat surfaces, however, can also be used in the present disclosure.
The side of the web contacting the throughdrying fabric is typically referred to as the “fabric side” of the paper web. The fabric side of the paper web, as described above, may have a shape that conforms to the surface of the throughdrying fabric after the fabric is dried in the throughdryer. The opposite side of the paper web, on the other hand, is typically referred to as the “air side”. The air side of the web is typically smoother than the fabric side during normal throughdrying processes.
The level of vacuum used for the web transfers can be from about 3 to about 15 inches of mercury (75 to about 380 millimeters of mercury), preferably about 5 inches (125 millimeters) of mercury. The vacuum shoe (negative pressure) can be supplemented or replaced by the use of positive pressure from the opposite side of the web to blow the web onto the next fabric in addition to or as a replacement for sucking it onto the next fabric with vacuum. Also, a vacuum roll or rolls can be used to replace the vacuum shoe(s).
While supported by the throughdrying fabric, the web is finally dried to a consistency of about 94 percent or greater by the throughdryer 48 and thereafter transferred to a carrier fabric 50. The dried basesheet 52 is transported to the reel 54 using carrier fabric 50 and an optional carrier fabric 56. An optional pressurized turning roll 58 can be used to facilitate transfer of the web from carrier fabric 50 to fabric 56. Suitable carrier fabrics for this purpose are Albany International 84M or 94M and Asten 959 or 937, all of which are relatively smooth fabrics having a fine pattern. Although not shown, reel calendering or subsequent off-line calendering can be used to improve the smoothness and softness of the basesheet.
In one aspect, the reel 54 shown in
In one aspect, the paper web 52 is a textured web which has been dried in a three-dimensional state such that the hydrogen bonds joining fibers were substantially formed while the web was not in a flat, planar state. For instance, the web can be formed while the web is on a highly textured throughdrying fabric or other three-dimensional substrate. Processes for producing uncreped throughdried fabrics are, for instance, disclosed in U.S. Pat. No. 5,672,248 to Wendt, et al.; U.S. Pat. No. 5,656,132 to Farrington, et al.; U.S. Pat. No. 6,120,642 to Lindsay and Burazin; U.S. Pat. No. 6,096,169 to Hermans, et al.; U.S. Pat. No. 6,197,154 to Chen, et al.; and U.S. Pat. No. 6,143,135 to Hada, et al., all of which are herein incorporated by reference in their entireties.
Referring now to
From fabric 70, web 68, in this aspect, is transferred to the surface of a rotatable heated dryer drum 76, such as a Yankee dryer.
In accordance with the present disclosure, the additive composition can be incorporated into the fibrous web 68 by topically applying the additive composition during the drying process. In one particular aspect, the additive composition of the present disclosure may be applied to the surface of the dryer drum 76 for transfer onto one side of the fibrous web 68. In this manner, the additive composition is used to adhere the fibrous web 68 to the dryer drum 76. In this aspect, as web 68 is carried through a portion of the rotational path of the dryer surface, heat is imparted to the web causing most of the moisture contained within the web to be evaporated. Web 68 is then removed from dryer drum 76 by a creping blade 78. Creping the web as it is formed further reduces internal bonding within the web and increases softness. Applying the additive composition to the web during creping can, in some aspects, increase the strength of the web.
In addition to applying the additive composition during formation of the fibrous web, the additive composition may also be used in post-forming processes. For example, in one aspect, the additive composition may be used during a print-creping process, forming patterns including but not limited to those patterns shown in
For example, once a fibrous web is formed and dried, in one aspect, the additive composition may be applied to at least one side of the web and the at least one side of the web may then be creped. In general, the additive composition may be applied to only one side of the web and only one side of the web may be creped, the additive composition may be applied to both sides of the web and only one side of the web is creped, or the additive composition may be applied to each side of the web and each side of the web may be creped.
The additive composition can penetrate the fibrous web. The degree of such penetration is dependent upon degree of solubility of the additive composition. In general, a water soluble additive composition has a higher degree of penetration. On the other hand, the precipitate of a LCST polymer at the hot Yankee dryer's surface and has a much reduced degree of penetration. Creping the fibrous web increases the softness of the web by breaking apart fiber-to-fiber bonds contained within the fibrous web.
In one aspect, fibrous webs made according to the present disclosure can be incorporated into multiple-ply products. For instance, in one aspect, a fibrous web made according to the present disclosure can be attached to one or more other fibrous webs for forming a wiping product having desired characteristics. The other webs laminated to the fibrous web of the present disclosure can be, for instance, a wet-creped web, a calendered web, an embossed web, a through-air dried web, a creped through-air dried web, an uncreped through-air dried web, an airlaid web, and the like.
In one aspect, when incorporating a fibrous web made according to the present disclosure into a multiple-ply product, it may be desirable to only apply the additive composition to one side of the fibrous web and to thereafter crepe the treated side of the web. The creped side of the web is then used to form an exterior surface of a multiple-ply product. The untreated and uncreped side of the web, on the other hand, is attached by any suitable means to one or more plies.
Like cellulose, the materials used for the inventive creping chemistries are classified as humectants. This means they promote the adsorption and retention of water, including water vapor from the atmosphere. It is hypothesized that the creping chemistries used in this invention retain a higher percentage, by-weight, of water than cellulose under a given set of conditions (temperature, relative humidity). Under conditions of 23° C. and 50% relative humidity, for example, wood pulp fibers typically equilibrate at about 5% moisture by weight. Humectant creping chemistries in the tissue sheet that equilibrate at a higher level of moisture than cellulose will serve to bring, and hold, additional water within the structure. It is further hypothesized that the humectant creping chemistries are present in a concentration gradient within the tissue structure, having a high concentration on the creped tissue surface and decreasing in concentration as you move in the z-direction away from the creped surface. This chemical concentration gradient will result in an adsorbed moisture concentration gradient within the tissue thickness. The dryer side of the tissue, containing the highest concentration of humectant creping chemistry will have the highest localized moisture content.
Tissue sheets made according to the present disclosure may possess a desirable crepe structure. The crepe structure is very fine, where the crepe folds are small in both frequency and amplitude. This results in a smoother and softer tissue sheet. The crepe structure is characterized using tissue images and the STFI mottling program, as described in the Test Method section.
Tissue sheets made according to the present disclosure may possess a desirable surface structure. In addition to having a fine crepe structure, individual fibers protrude from the surface of the tissue while still being attached. These individual fibers protruding from the surface are called free fiber ends and provide enhanced softness, due to both the fuzziness of the tissue surface, as well as by the softening of the fibers from the coating of the additive composition. This results in a velvety soft tissue sheet. Evidence for free fiber ends are provided by visual images generated with SEM and the “Fuzz on Edge” test, as described in the Test Method section. See
Tissue sheets made according to the present disclosure may possess a desirable lubricious hand feel. The additive composition disposed on the fibers provides a smooth and slippery quality. Lubricious or lubricated hand feel is demonstrated by a significant reduction in coefficient of friction on a skin stimulant of collagen film, as described in the Test Method section.
Tissue sheets made according to the present disclosure may possess a desirable quality whereby some of the additive composition chemistry is transferred to moist surfaces, such as human skin. Additive compositions of the present disclosure are able to transfer PEG to (moist) skin, which is perceived to be smooth and having lotion. The method used to determine the amount of water soluble creping blend component transferred from the facial tissue to a skin stimulant of collagen film is described in the Test Method section.
Tissue sheets made according to the present disclosure may possess a desirable water absorption rate. The water absorption rate of cellulose based tissue products affects functional performance. In one example, facial tissue must be sufficiently strong in use and also wet out very fast in order to absorb liquids, such as nasal discharge. Facial tissue with outstanding softness but delayed absorbent (wet out) rate may not be acceptable for optimum performance. Absorbent rate is measured as described in the Test Method section.
By using readily water soluble Yankee dryer coating chemicals, in the additive composition of the present disclosure, to improve softness, we have maintained very quick water wet out rate. Hydrophobic topical chemicals tend to reduce water absorption rate and capacity, especially when a significant amount of the surface fiber area is coated with hydrophobic chemicals. Additive compositions of the present disclosure are readily water soluble.
In this example, fibrous webs were made generally according to the process illustrated in
For purposes of comparison, samples were also produced using a conventional creping chemistry treatment as a control. In addition, samples were also produced using an additive composition having a water insoluble polyolefin dispersion as described in U.S. Pat. Pub. 2007/0144697, incorporated herein to the extent that it is consistent with the present invention. Finally, various commercially available products were also sampled.
For reference, tissues manufactured with additive compositions made according to the present disclosure will be referred to as Technology A tissues. Likewise, tissues manufactured with conventional creping chemistry will be referred to as Technology B tissues. Finally, tissues manufactured with an additive composition having a water insoluble polyolefin dispersion as described in U.S. Pat. Pub. 2007/0144697 will be referred to as Technology C tissues. Competitive commercially available products are not classified.
In this example, 2-ply facial tissue products were produced and tested according to the same tests described in the Test Methods section. The following tissue manufacturing process was used to produce the samples.
Initially, northern softwood kraft (NSWK) pulp was dispersed in a pulper for 30 minutes at 4% consistency at about 100° F. The NSWK pulp was then transferred to a dump chest and subsequently diluted to approximately 3% consistency. The NSWK pulp was refined at 4.5-5.5 hp-days/metric ton. The softwood fibers were used as the inner strength layer in a 3-layer tissue structure. The NSWK layer contributed approximately 34-38% of the final sheet weight.
Two kilograms KYMENE® 6500 and 2-5 kilograms Hercobond® 1366 (Ashland, Incorporated, Covington, Ky., U.S.A.) per metric ton of wood fiber was added to the NSWK pulp prior to the headbox.
Aracruz ECF, a eucalyptus hardwood Kraft (EHWK) pulp (Aracruz, Rio de Janeiro, RJ, Brazil) was dispersed in a pulper for 30 minutes at about 4% consistency at about 100 degrees Fahrenheit. The EHWK pulp was then transferred to a dump chest and subsequently diluted to about 3% consistency. The EHWK pulp fibers were used in the two outer layers of the 3-layered tissue structure. The EHWK layers contributed approximately 62-66% of the final sheet weight.
Two kilograms KYMENE® 6500 per metric ton of wood fiber was added to the EHWK pulp prior to the headbox.
The pulp fibers from the machine chests were pumped to the headbox at a consistency of about 0.1%. Pulp fibers from each machine chest were sent through separate manifolds in the headbox to create a 3-layered tissue structure. The fibers were deposited onto a felt in a Crescent Former, as depicted similar to the process illustrated in FIG. 3 of U.S. Pat. No. 6,379,498.
The wet sheet, about 10-20% consistency, was adhered to a Yankee dryer, traveling at about 2000 to about 5000 fpm, (600 mpm-1500 mpm) through a nip via a pressure roll.
The consistency of the wet sheet after the pressure roll nip (post-pressure roll consistency or PPRC) was approximately 40%. The wet sheet is adhered to the Yankee dryer due to the additive composition that is applied to the dryer surface. Spray booms situated underneath the Yankee dryer sprayed the creping/additive composition, described in the present disclosure, onto the dryer surface at addition levels ranging from 50 to 1000 mg/m2.
The creping compositions of GLUCOSOL 800, PEG 8000, and POLYOX N3000 that were applied to the Yankee dryer were prepared by dissolution of the solid polymers into water followed by stirring until the solution was homogeneous. Each polymer was dissolved and pumped separately to the process. Glucosol 800 and PEG 8000 were prepared at 5% solids. POLYOX N3000 was prepared at 2% solids. The flow rates of the GLUCOSOL 800, PEG 8000, or POLYOX N3000 solutions were varied to deliver a total addition of 50 to 1000 mg/m2 spray coverage on the Yankee Dryer at the desired component ratio. Varying the flow rates of the polymer solutions also varies the amount of solids incorporated into the base web. For instance, at 100 mg/m2 spray coverage on the Yankee Dryer, it is estimated that about 1% additive composition solids is incorporated into the tissue web. At 200 mg/m2 spray coverage on the Yankee Dryer, it is estimated that about 2% additive composition solids is incorporated into the tissue web. At 400 mg/m2 spray coverage on the Yankee Dryer, it is estimated that about 4% additive composition solids is incorporated into the tissue web.
The sheet was dried to about 95%-98% consistency as it traveled on the Yankee dryer and to the creping blade. The creping blade subsequently scraped the tissue sheet and a portion of the additive composition off the Yankee dryer. The creped tissue basesheet was then wound onto a core traveling at about 1570 to about 3925 fpm (480 mpm to 1200 mpm) into soft rolls for converting. The resulting tissue basesheet had an air-dried basis weight of about 14.2 g/m2. Two or three soft rolls of the creped tissue were then rewound, calendared, and plied together so that both creped sides were on the outside of the 2- or 3-ply structure. Mechanical crimping on the edges of the structure held the plies together. The plied sheet was then slit on the edges to a standard width of approximately 8.5 inches and folded, and cut to facial tissue length. Tissue samples were conditioned and tested. See Table 1 for the Inventive Sample Code Descriptions.
For purposes of comparison, a 2-ply sample was also produced according to the same process. Instead of using an additive composition in accordance with the present disclosure, however, a conventional creping chemistry (Technology B) was applied to the Yankee dryer. Thus, the samples that were tested included Sample Codes 1 to 6 containing the additive composition in amounts from 1% by weight to 10% by weight, and a Control not containing the additive composition. In addition, commercially available facial tissues were also tested. Particularly, standard KLEENEX® facial tissues, PUFFS® facial tissues, PUFFS PLUS® facial tissues, HOMELIFE Whisper Soft facial tissues, and SCOTTIES® facial tissues were also tested. All of the commercially available facial tissues contain 2 plies. PUFFS PLUS® facial tissue is treated with a silicone. See Table 2 for sample descriptions.
Prior to testing, all of the samples were conditioned according to TAPPI standards. In particular, the samples were placed in an atmosphere at 50% relative humidity and 23° C. for at least four hours.
The following results are shown in Table 3. (Note that Controls 1-7 are the same in all of the test results show in Tables 3-5 and 7-9.)
Some of the water soluble additive composition (of the present disclosure) is transferred to the tissue web during the creping process and is disposed on portions of the web/pulp fibers. At least a portion of the additive composition will dissolve in the presence of water. Additive compositions of the present invention, when applied at levels greater than 100 mg/m2, have water soluble extractives greater than 0.35%, as measured by the test method described in the Test Method section. See Table 4 for test results.
The tissue sheets made according to the present disclosure possess an equivalent or faster water absorbent rate, as well as several other unique properties. Tissue sheets made according to the present disclosure may possess a desirable water absorption rate. The water absorption rate of cellulose based tissue products affects functional performance. In one example, facial tissue must be sufficiently strong in use and also wet out very fast in order to absorb liquids, such as nasal discharge. Facial tissue with outstanding softness but delayed absorbent (wet out) rate may not be acceptable for optimum performance. Absorbent rate is measured as described in the Test Method section.
Technology C tissues have slow wet out times, likely due to the water insoluble creping chemistry that is transferred to the surface of the tissue. Compared to Technology B (conventional creping chemistry) and other competitive commercially available tissues, Technology C tissues have a wet out time that is at least 2 times slower. By contrast the wet out times of the Technology A tissues are all under 3 seconds. Technology A tissue wet out time is independent of the spray application rate.
Tissue sheets made according to the present disclosure may possess a desirable crepe structure. The crepe structure is very fine, where the crepe folds are small in both frequency and amplitude. This results in a smoother and softer tissue sheet. The crepe structure is characterized using tissue images and the STFI mottling program, as described in the Test Method section.
Tissue sheets made according to the present disclosure may possess a desirable surface structure. In addition to having a fine crepe structure, individual fibers protrude from the surface of the tissue while still being attached. These individual fibers protruding from the surface are called free fiber ends and provide enhanced softness, due to both the fuzziness of the tissue surface, as well as by the softening of the fibers from the coating of the additive composition. This results in a velvety soft tissue sheet. Evidence for free fiber ends are provided by visual images generated with SEM and the “Fuzz on Edge” test, as described in the Test Method section. See Table 5 for test results.
The Fine Crepe Structure values of the Technology A tissues are all better (lower) than or equal to the Control codes. Additionally, the Fuzz on Edge values of the Technology A tissues are all much higher (better) than any of the Control codes.
The moisture sensitivity (water solubility) of the creping composition, present on the creped tissue, enables the coating to be used for controlled delivery of ingredients that have been mixed into the composition. Under low moisture conditions ingredients remain trapped within the composition's matrix. Under high moisture conditions, the ingredients are released as the composition dissolves.
Tissue sheets were prepared as described in Example 1.
Tissue sheets made according to the present disclosure may possess a desirable quality whereby some of the additive composition chemistry is transferred to moist surfaces, such as human skin. Additive compositions of the present disclosure are able to transfer PEG to moist skin, which is perceived to be smooth with the feel of lotion. The method used to determine the amount of water soluble creping blend component transferred from the facial tissue to a skin stimulant of collagen film is described in the Test Method section. See Table 6 for test results.
These results indicate that PEG 8000 is transferred to the skin model material (collagen film), but only when the film is well hydrated (100% RH equilibration) and when PEO (POLYOX N3000) is incorporated into the creping blend. Because the creping blend consists of water soluble components the transfer is enabled by contact with a slightly moist surface, as in the samples equilibrated at 100% RH.
A possible explanation for the PEG transfer happening only when PEO is incorporated is that the blend with high molecular weight PEO has higher viscosity so more of the creping blend remains on the tissue surface where it can be transferred to the skin.
Tissue sheets made according to the present disclosure may possess a desirable lubricious hand feel. The additive composition disposed on the fibers provides a smooth and slippery quality. Lubricious or lubricated hand feel is demonstrated by a significant reduction in coefficient of friction on a skin stimulant of collagen film, as described in the Test Method section.
Lubricious or lubricated hand feel was demonstrated by a significant reduction in coefficient of friction on a skin stimulant of collagen film. Samples were produced as described in Example 1. As shown in the Table below, treatment of the collagen film skin stimulant results in a significant reduction of kinetic coefficient of friction indicative of a lubricated hand feel. See Table 7 for test results.
Tissues were prepared as described in Example 1. Fibrous webs made according to the present disclosure (Technology A tissues) can have a perceived softness and/or strength that is similar to or better than fibrous webs treated with a conventional treatment (Technology B tissues) or with recent technology treatments (Technology C tissues). See Table 8 for test results.
The data from the IHR Softness test show that the tissues of the present invention (Technology A tissues) have higher Log Odds and Highest Statistical Groupings than Control 1 or 2, which are Technology B and C tissues respectively. This is achieved with GMT strengths which are about equal to or greater than the control tissue codes. Additionally, this is achieved with wet-out times which are lower than the control codes.
In a separate test, this softness ranking was verified as shown in Table 9.
Tissues were prepared as described in Example 1. Fibrous webs made according to the present disclosure (Technology A tissues) can have a perceived softness greater than conventional tissues largely due to the amount of additive composition available at the surface of the dryer-side of the tissue surface. This dryer-side of the tissue is typically the externally-facing surface of the facial tissue product. See Table 10 for sample descriptions.
Single plies of the fibrous webs made according to the present disclosure were split into two portions and then analyzed to determine the amount of PEG in each of the portions, as described in the Sheet Split PEG Analysis Test Method in the Test Method section. The resulting data demonstrate that the amount of PEG in the dryer-side portion is much greater than the felt-side portion, and can be influenced by the composition of the additive composition sprayed on the Yankee dryer. See Table 11 for test results.
The Dryer/Felt Ratios demonstrate that a larger portion of the PEG is in the Dryer-Side portion of the tissue sheet, also meaning that most of the additive composition remains in the dryer-side portion and less penetrates through to the felt-side. Finally, the incorporation of POLYOX N3000 also appears to increase the amount of PEG which is retained in the dryer-side portion. This is also a benefit as the perceived softness is improved.
This application is a continuation-in-part of application Ser. No. 12/317,137 filed on Dec. 19, 2008.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12317137 | Dec 2008 | US |
| Child | 12557969 | US |
