Patent Application
20170275821
The present disclosure is related to deflection members for making absorbent fibrous webs, such as, for example, paper webs. More particularly, this invention is concerned with structured fibrous webs, equipment used to make such structured fibrous webs, and processes therefor.
Products made from a fibrous web are used for a variety of purposes. For example, paper towels, facial tissues, toilet tissues, napkins, and the like are in constant use in modern industrialized societies. The large demand for such paper products has created a demand for improved versions of the products. If the paper products such as paper towels, facial tissues, napkins, toilet tissues, mop heads, and the like are to perform their intended tasks and to find wide acceptance, they must possess certain physical characteristics.
Among the more important of these characteristics are strength, softness, absorbency, and cleaning ability. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation consumers perceive when they use the paper for its intended purposes. Absorbency is the characteristic of the paper that allows the paper to take up and retain fluids, particularly water and aqueous solutions and suspensions. Important not only is the absolute quantity of fluid a given amount of paper will hold, but also the rate at which the paper will absorb the fluid. Cleaning ability refers to a fibrous structures' capacity to remove and/or retain soil, dirt, or body fluids from a surface, such as a kitchen counter, or body part, such as the face or hands of a user.
Through-air drying papermaking belts comprising a reinforcing element and a resinous framework, and/or fibrous webs made using these belts are known. The resinous framework may be continuous or semi-continuous. The resinous framework extends outwardly from the reinforcing element to form a web-side of the belt (i. e., the surface upon which the web is disposed during a papermaking process), a backside opposite to the web-side, and deflection conduits extending therebetween. Sometimes called deflection members, the reinforcing element is always a woven (or felt) substrate in which woven filaments are oriented in either the machine direction (MD) or cross machine direction (CD) in a relatively closely spaced woven pattern.
An improvement on deflection members is disclosed in commonly owned co-pending U.S. Provisional Application 62/155,517, entitled Unitary Deflection Member for Making Fibrous Structures Having Increased Surface Area and Process for Making Same, filed by Manifold et al. on May 1, 2015. The reinforcing member of Manifold et al. can mimic a woven substrate in which filaments are oriented in either the machine direction (MD) or cross machine direction (CD) in a relatively closely spaced woven pattern.
However, there remains an unmet need for a papermaking surface, including the type described as deflection members, having a three-dimensional topography that permits greater degrees of freedom with respect to open area, air permeability, strength, and paper structures.
Additionally, there is an unmet need for a method for making a papermaking surface, including the type described as deflection members, having a three-dimensional topography that permits greater degrees of freedom with respect to open area, air permeability, strength, and paper structures.
A deflection member is disclosed. The deflection member can be a unitary structure having a plurality of discrete primary elements and a plurality of secondary elements. At least one of the secondary elements can be an elongate member having a major axis having both a machine direction vector component and a cross machine direction vector component. Each discrete primary element can be an open structure having at least two linking segments, with at least one of the plurality of linking segments having a Z-direction vector component. In an example, either of the secondary elements or the linking segments can be arranged in a Voronoi pattern.
The deflection member of the present invention can be a unitary structure manufactured by additive manufacturing processes, including what is commonly described as “3-D printing.” As such, the unitary deflection member is not achieved by the use of a mask and UV-curable resin, in which a resin and a reinforcing member are provided as separate parts and joined as separate components in a non-unitary manner.
The deflection member of the present invention includes discrete primary elements connected by secondary elements in a unitary structure which does not necessarily have a portion resembling a woven structure of interwoven MD and CD elements. The term “deflection member” as used herein refers to a structure useful for making fibrous webs such as absorbent paper products, but which has protuberances that define deflection conduits not formed by any underlying woven or grid-like structure. Woven papermaking fabrics or papermaking fabrics based on a structure of woven filaments are not deflection members as used in the instant disclosure.
By “unitary” as used herein is meant that the deflection member does not constitute a unit comprised of previously separate components joined together. Unitary can mean that all the portions described herein are formed as a single unit, and not as separate parts being joined to form a unit. Deflection members as described herein can be manufactured in a process of additive manufacturing such that they are unitary, as contrasted by processes in which deflection members are manufactured joining together or otherwise modifying separate components. A unitary deflection member may comprise different features and different materials for the different features as described below.
As can be understood from
As shown in
For any of the secondary elements 118, as shown in
The illustrated deflection member of
As can be understood from the above description, the number, size, and spacing of secondary elements 118 can be designed in to integrate and optimize a deflection member having a plurality of discrete primary elements 112. The optimization can be achieved by utilizing the principles of a Voronoi pattern. Specifically, as shown in
Referring again to
The number of points 320, and, in turn, the number of cells 310, which in turn can determine the number of secondary elements, can be predetermined and designed into the structure based on desired parameters such as strength and air permeability of the resulting deflection member. For example, a value for air permeability, as well as an arrangement that facilitates uniform air permeability, can be designed based on the number and spacing of desired primary elements and secondary elements. Better uniformity of air permeability across the area of a deflection member facilitates improved drying efficiency when the deflection member is utilized for papermaking. Likewise, the number, size, spacing and orientation of secondary elements can be designed for optimal fiber support during papermaking. By way of example, the number, size, spacing and orientation of secondary elements can be designed to minimize or eliminate pin holing, which can happen when the juxtaposition of polymer elements on a woven reinforcing member results in a randomly situated large opening, through which fibers can pass during papermaking.
The unitary deflection members shown in
The arrangement of secondary elements can have an open area sufficient to allow water to pass through during drying stages of a papermaking process, but nevertheless prevent fibers from being drawn through in dewatering processes, including pressing and vacuum processes. As fibers are molded into the deflection member during production of fibrous substrates such as absorbent tissue paper, the secondary elements can serve as a “backstop” to prevent, or minimize fiber loss through the unitary deflection member.
Utilizing the numbering of
As used herein, the term “Z-direction” designates any direction perpendicular to the X-Y plane. Analogously, the term “Z-dimension” means a dimension, distance, or parameter measured parallel to the Z-direction and can be used to refer to dimensions such as the height of discrete primary elements or the thickness (or height or caliper), of the secondary elements. It should be carefully noted, however, that an element that “extends” in the Z-direction does not need itself to be oriented strictly parallel to the Z-direction; the term “extends in the Z-direction” in this context merely indicates that the element extends in a direction which is not parallel to the X-Y plane. Analogously, an element that “extends in a direction parallel to the X-Y plane” does not need, as a whole, to be parallel to the X-Y plane; such an element can be oriented in the direction that is not parallel to the Z-direction.
One skilled in the art will also appreciate that the unitary deflection member 200 as a whole does not need to (and indeed cannot in some embodiments) have a planar configuration throughout its length, especially if sized for use in a commercial process for making a fibrous structure 850 of the present invention, and in the form of an flexible member or belt that travels through the equipment in a machine direction (MD) indicated by a directional arrow “B” (
As used herein, the terms containing “macroscopical” or “macroscopically” refer to an overall geometry of a structure under consideration when it is placed in a two-dimensional configuration. In contrast, “microscopical” or “microscopically” refer to relatively small details of the structure under consideration, without regard to its overall geometry. For example, in the context of the unitary deflection member 200, the term “macroscopically planar” means that the unitary deflection member 200, when it is placed in a two-dimensional configuration, has—as a whole—only minor deviations from absolute planarity, and the deviations do not adversely affect the unitary deflection member's performance. At the same time, the patterned framework 12 of the unitary deflection member 200 can have a microscopical three-dimensional pattern of deflection conduits and suspended portions, as will be described below.
As shown in
As depicted in
There are virtually an infinite number of shapes, sizes, spacing and orientations that may be chosen for discrete primary elements 212 and secondary elements 218. The actual shapes, sizes, orientations, and spacing can be specified and manufactured by additive manufacturing processes based on a desired design of the end product, such as a fibrous structure having a regular pattern of substantially identical “knuckles” regions separated by “pillow” regions, as discussed in more detail below. The improvement of the present invention is that the shapes, sizes, spacing, and orientations of the discrete primary elements 212, and shapes, sizes, spacing, and orientations of the secondary elements 218 is decoupled from the imposed limitations of woven or grid-like structures of generally MD- and CD-oriented elements. In general, the discrete primary elements can take any of the forms disclosed in the aforementioned commonly owned co-pending U.S. Provisional Application 62/155,517.
In addition to solid forms for discrete primary elements, the discrete primary elements can have an open structure. In an example, the open structure can be such that the discrete primary elements exhibit air permeability in a direction parallel to the plane of the MD and CD directions of the deflection member. In an example, the open structure can be cage-like. The open structure discrete primary elements can be joined to a traditional woven reinforcing member, or built up in a unitary structure on secondary elements, as discussed herein.
The difference in the discrete primary elements on the deflection member shown in
Linking segments 330 can be manufactured by additive manufacturing processes in virtually any configuration desired. In general, linking segments 330 can be generally linear members having a first end and a second end and uniform or variable cross sections. At least two linking segments 330 are present for each discrete primary element 312, with each joined on at least one end to reinforcing member 326, and joined at the other end to each other or to another of the plurality of linking segments 330, in a configuration that permits fluid permeability in a plane of the MD and CD directions.
For example, as shown in
Likewise, by way of example, three linking segments 330 can be utilized to make a generally pyramid-shaped discrete primary member 312, as shown in
Further, by way of example, linking segments 330 can be configured in a cube-shape as shown in
Referring again to
Linking segments 430 and secondary elements 418 can be manufactured by additive manufacturing processes in virtually any configuration desired. In general, linking segments 430 can be generally linear members having a first end and a second end and uniform or variable cross sections. At least two linking segments 330 are present for each discrete primary element 412, with being integral on at least one end to a secondary element 430, and joined at the other end to each other or to another of secondary elements 430, in a configuration that permits fluid permeability in a plane of the MD and CD directions. In practice, a unitary deflection member can have any configuration of primary elements as can the deflection member describe with reference to
By way of example shown in the enlarged view of a discrete primary element 412 shown in
A unitary deflection member can be made by a 3-D printer as the additive manufacturing making apparatus. Unitary deflection members of the invention were made using a MakerBot Replicator 2, available from MakerBot Industries, Brooklyn, N.Y., USA. Other alternative methods of additive manufacturing include, by way of example, selective laser sintering (SLS), stereolithography (SLA), direct metal laser sintering, or fused deposition modeling (FDM, as marketed by Stratasys Corp., Eden Prairie, Minn.), also known as fused filament fabrication (FFF).
The material used for the unitary deflection member of the invention is poly lactic acid (PLA) provided in a 1.75 mm diameter filament in various colors, for example, TruWhite and TruRed. Other alternative materials can include liquid photopolymer, high melting point filament (50 degrees C. to 120 degrees C. above Yankee temperature), flexible filament (e.g., NinjaFlex PLA, available from Fenner Drives, Inc, Manheim, Pa., USA), clear filament, wood composite filament, metal/composite filament, Nylon powder, metal powder, quick set epoxy. In general, any material suitable for 3-D printing can be used, with material choice being determined by desired properties related to strength and flexibility, which, in turn, can be dictated by operating conditions in a papermaking process, for example. In the present invention, the method for making fibrous substrates can be achieved with relatively stiff deflection members.
A 2-D image of a repeat element of a desired unitary deflection member, created in, for example, AutoCad, DraftSight, or Illustrator, can be exported to a 3-D file such as a drawing file in SolidWorks 3-D CAD or other NX software. The repeat unit has the dimensional parameters for wall angles, protrusion shape, and other features of the deflection member. Optionally, one can create a file directly in the a 3-D modeling program, such as Google SketchUp or other solid modeling programs that can, for example, create standard tessellation language (STL) file. The STL file for a repeat element and repeat element dimensions for the present invention was exported to, and imported by, the MakerWare software utilized by the MakerBot printer. Optionally, Slicr3D software can be utilized for this step.
The next step is to assemble objects for the various features of a deflection member, such as the secondary elements, transition portions, and protuberances, assign Z-direction dimensions for each. Once all the objects are assembled, they are imported and used to make an x3g print file. An x3g file is a binary file that the MakerWare machine reads which contains all of the instructions for printing. The output x3g file can be saved on an SD card, or, optionally connect via a USB cable directly to the computer. The SD card with the x3g file can be inserted into the slot provided on the MakerBot 3-D printer. In general, any numerical control file, such as G-code files, as is known in the art, can be used to import a print file to the additive manufacturing device.
Prior to printing, the build platform of the MakerBot 3-D printer can be prepared. If the build plate is unheated, it can be prepared by covering it with 3M brand Scotch-Blue Painter's Tape #2090, available from 3M, Minneapolis, Minn., USA. For a heated build plate, the plate is prepared by using Kapton tape, manufactured by DuPont, Wilmington, Ddel., USA, and water soluble glue stick adhesive, hair spray, with a barrier film. The build platform should be clean and free from oil, dust, lint, or other particles.
The printing nozzle of the MakerBot 3-D printer used to make the invention was heated to 230 degrees C.
The printing process is started to print the deflection member, after which the equipment and deflection member are allowed to cool. Once sufficiently cooled, the deflection member can be removed from the build plate by use of a flat spatula, a putty knife, or any other suitable tool or device. The deflection member can then be utilized to a process for making a fibrous structure, as described below.
Each of the unitary deflection members shown in
The unitary deflection members disclosed herein can have a specific resulting open area R. As used herein, the term “specific resulting open area” (R) means a ratio of a cumulative projected open area (ΣR) of all deflection conduits of a given unit of the unitary deflection member's surface area (A) to that given surface area (A) of this unit, i.e., R=ΣR/A, wherein the projected open area of each individual conduit is formed by a smallest projected open area of such a conduit as measured in a plane parallel to the X-Y plane. The specific open area can be expressed as a fraction or as a percentage. For example, if a hypothetical layer has two thousand individual deflection conduits dispersed throughout a unit surface area (A) of thirty thousand square millimeters, and each deflection conduit has the projected open area of five square millimeters, the cumulative projected open area (ΣR) of all two thousand deflection conduits is ten thousand square millimeters, (5 sq. mm×2.000=10,000 sq. mm), and the specific resulting open area of such a hypothetical layer is R=⅓, or 33.33% (ten thousand square millimeters divided by thirty thousand square millimeters).
The cumulative projected open area of each individual conduit is measured based on its smallest projected open area parallel to the X-Y plane, because some deflection conduits may be non-uniform throughout their length, or thickness of the deflection member. For example, some deflection conduits may be tapered as described in commonly assigned U.S. Pat. Nos. 5,900,122 and 5,948,210. In other embodiments, the smallest open area of the individual conduit may be located intermediate the top surface and the bottom surface of the unitary deflection member.
The specific resulting open area of the unitary deflection member can be at least ⅕ (or 20%), more specifically, at least ⅖ (or 40%), and still more specifically, at least ⅗ (or 60%). According to the present invention, the first specific resulting open area R1 may be greater than, substantially equal to, or less than the second resulting open area R2.
The deflection members shown in
One purpose of the deflection member disclosed herein is to provide a forming surface on which to mold fibrous structures, including sanitary tissue products, such as paper towels, toilet tissue, facial tissue, wipes, dry or wet mop covers, and the like. When used in a papermaking process, the deflection member can be utilized in the “wet end” of a papermaking process, as described in more detail below, in which fibers from a fibrous slurry are deposited on the web side of the deflection member. As discussed below, a portion of the fibers can be deflected into the deflection conduits of the unitary deflection member to cause some of the deflected fibers or portions thereof to be disposed within the void spaces, i.e., the deflection conduits, formed by, i.e., between, the discrete primary elements of the unitary deflection member.
Thus, as can be understood from the description above, a fibrous structure an mold to the general shape of the deflection member, including the deflection conduits such that the shape and size of the knuckles and pillow features of the fibrous structure are a close approximation of the size and shape of the discrete primary elements and deflection conduits. Fibers can be pressed or otherwise introduced over the protuberances and into the deflection conduits at a constant basis weight to form relatively low density pillows in the finished fibrous structure.
With reference to
The present invention contemplates the use of a variety of fibers, such as, for example, cellulosic fibers, synthetic fibers, or any other suitable fibers, and any combination thereof. Papermaking fibers useful in the present invention include cellulosic fibers commonly known as wood pulp fibers. Fibers derived from soft woods (gymnosperms or coniferous trees) and hard woods (angiosperms or deciduous trees) are contemplated for use in this invention. The particular species of tree from which the fibers are derived is immaterial. The hardwood and softwood fibers can be blended, or alternatively, can be deposited in layers to provide a stratified web. U.S. Pat. No. 4,300,981 issued Nov. 17, 1981 to Carstens and U.S. Pat. No. 3,994,771 issued Nov. 30, 1976 to Morgan et al. are incorporated herein by reference for the purpose of disclosing layering of hardwood and softwood fibers.
The wood pulp fibers can be produced from the native wood by any convenient pulping process. Chemical processes such as sulfite, sulfate (including the Kraft) and soda processes are suitable. Mechanical processes such as thermomechanical (or Asplund) processes are also suitable. In addition, the various semi-chemical and chemi-mechanical processes can be used. Bleached as well as unbleached fibers are contemplated for use. When the fibrous web of this invention is intended for use in absorbent products such as paper towels, bleached northern softwood Kraft pulp fibers may be used. Wood pulps useful herein include chemical pulps such as Kraft, sulfite and sulfate pulps as well as mechanical pulps including for example, ground wood, thermomechanical pulps and Chemi-ThermoMechanical Pulp (CTMP). Pulps derived from both deciduous and coniferous trees can be used.
In addition to the various wood pulp fibers, other cellulosic fibers such as cotton linters, rayon, and bagasse can be used in this invention. Synthetic fibers, such as polymeric fibers, can also be used. Elastomeric polymers, polypropylene, polyethylene, polyester, polyolefin, and nylon, can be used. The polymeric fibers can be produced by spunbond processes, meltblown processes, and other suitable methods known in the art. It is believed that thin, long, and continuous fibers produces by spunbond and meltblown processes may be beneficially used in the fibrous structure of the present invention, because such fibers are believed to be easily deflectable into the pockets of the unitary deflection member of the present invention.
The paper furnish can comprise a variety of additives, including but not limited to fiber binder materials, such as wet strength binder materials, dry strength binder materials, and chemical softening compositions. Suitable wet strength binders include, but are not limited to, materials such as polyamide-epichlorohydrin resins sold under the trade name of KYMENE™ 557H by Hercules Inc., Wilmington, Del. Suitable temporary wet strength binders include but are not limited to synthetic polyacrylates. A suitable temporary wet strength binder is PAREZ™ 750 marketed by American Cyanamid of Stanford, Conn. Suitable dry strength binders include materials such as carboxymethyl cellulose and cationic polymers such as ACCO™ 711. The CYPRO/ACCO family of dry strength materials are available from CYTEC of Kalamazoo, Mich.
The paper furnish can comprise a debonding agent to inhibit formation of some fiber to fiber bonds as the web is dried. The debonding agent, in combination with the energy provided to the web by the dry creping process, results in a portion of the web being debulked. In one embodiment, the debonding agent can be applied to fibers forming an intermediate fiber layer positioned between two or more layers. The intermediate layer acts as a debonding layer between outer layers of fibers. The creping energy can therefore debulk a portion of the web along the debonding layer. Suitable debonding agents include chemical softening compositions such as those disclosed in U.S. Pat. No. 5,279,767 issued Jan. 18, 1994 to Phan et al., the disclosure of which is incorporated herein by reference Suitable biodegradable chemical softening compositions are disclosed in U.S. Pat. No. 5,312,522 issued May 17, 1994 to Phan et al. U.S. Pat. Nos. 5,279,767 and 5,312,522, the disclosures of which are incorporated herein by reference. Such chemical softening compositions can be used as debonding agents for inhibiting fiber to fiber bonding in one or more layers of the fibers making up the web. One suitable softener for providing debonding of fibers in one or more layers of fibers forming the web 20 is a papermaking additive comprising DiEster Di (Touch Hardened) Tallow Dimethyl Ammonium Chloride. A suitable softener is ADOGEN® brand papermaking additive available from Witco Company of Greenwich, Conn.
The embryonic web can be typically prepared from an aqueous dispersion of papermaking fibers, though dispersions in liquids other than water can be used. The fibers are dispersed in the carrier liquid to have a consistency of from about 0.1 to about 0.3 percent. Alternatively, and without being limited by theory, it is believed that the present invention is applicable to moist forming operations where the fibers are dispersed in a carrier liquid to have a consistency less than about 50 percent. In yet another alternative embodiment, and without being limited by theory, it is believed that the present invention is also applicable to airlaid structures, including air-laid webs comprising pulp fibers, synthetic fibers, and mixtures thereof.
Conventional papermaking fibers can be used and the aqueous dispersion can be formed in conventional ways. Conventional papermaking equipment and processes can be used to form the embryonic web on the Fourdrinier wire. The association of the embryonic web with the unitary deflection member can be accomplished by simple transfer of the web between two moving endless belts as assisted by differential fluid pressure. The fibers may be deflected into the unitary deflection member by the application of differential fluid pressure induced by an applied vacuum. Any technique, such as the use of a Yankee drum dryer, can be used to dry the intermediate web. Foreshortening can be accomplished by any conventional technique such as creping.
The plurality of fibers can also be supplied in the form of a moistened fibrous web (not shown), which should preferably be in a condition in which portions of the web could be effectively deflected into the deflection conduits of the unitary deflection member and the void spaces formed between the suspended portions and the X-Y plane.
In
A portion of the fibers 850 is deflected into the deflection portion of the unitary deflection member such as to cause some of the deflected fibers or portions thereof to be disposed within the void spaces formed by the discrete primary elements of the unitary deflection member. Depending on the process, mechanical and fluid pressure differential, alone or in combination, can be utilized to deflect a portion of the fibers 850 into the deflection conduits of the unitary deflection member. For example, in a through-air drying process a vacuum apparatus 48c can apply a fluid pressure differential to the embryonic web disposed on the unitary deflection member, thereby deflecting fibers into the deflection conduits of the unitary deflection member. The process of deflection may be continued with additional vacuum pressure, if necessary, to even further deflect the fibers into the deflection conduits of the unitary deflection member.
Finally, a partly-formed fibrous structure associated with the unitary deflection member can be separated from the unitary deflection member at roll 19k at the transfer to a Yankee dryer 128. By doing so, the unitary deflection member having the fibers thereon is pressed against a pressing surface, such as, for example, a surface of a Yankee drying drum 128, thereby densifying generally high density knuckles. In some instances, those fibers that are disposed within the deflection conduits can also be at least partially densified.
After being creped off the Yankee dryer, a fibrous structure 850 of the present invention can result and can be further processed or converted as desired.
| Number | Date | Country | |
|---|---|---|---|
| 62312528 | Mar 2016 | US |
