Patent Grant
10801161
The present invention is related to processes for making strong, soft, 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, and absorbency. 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.
Through-air drying papermaking belts comprising a reinforcing member and a resinous framework, and/or fibrous webs made using these belts are known and described, for example, in the following commonly assigned U.S. Pat. No. 4,514,345, issued Apr. 30, 1985 to Johnson et al.; U.S. Pat. No. 4,637,859 issued Jan. 20, 1987 to Trokhan; and U.S. Pat. No. 6,660,129 issued Dec. 9, 2003 to Cabell et al.
In the aforementioned belts of prior art the resinous framework is joined to the fluid-permeable reinforcing member (such as, for example, a woven structure, or a felt). The resinous framework may be continuous, semi-continuous, comprise a plurality of discrete protuberances, or any combination thereof. The resinous framework extends outwardly from the reinforcing member to form a web-side of the belt (i.e., the surface upon which the paper web is disposed during a papermaking process), a backside opposite to the web-side, and deflection conduits extending therebetween. The deflection conduits provide spaces into which papermaking fibers deflect under application of a pressure differential during a papermaking process. The terms “papermaking belt,” and “forming member,” may be used herein interchangeably.
Paper produced on the papermaking belts disclosed in the aforementioned patents are generally characterized by having at least two physically distinct regions: a region having a first elevation and typically having a relatively high density, and a region extending from the first region to a second elevation and typically having a relatively low density. This is because papermaking belts on which the paper is produced generally have two distinct regions at two distinct elevations, a first region at a first elevation associated with the resinous framework, and a second region at a second elevation associated with the woven (or felt) reinforcing member. The first region is typically formed from the fibers that have not been deflected into the deflection conduits, and the second region is typically formed from the fibers deflected into the deflection conduits of the papermaking belt. The papers made using the belts having a continuous resinous framework and a plurality of discrete deflection conduits dispersed therethrough comprise a continuous high-density network region and a plurality of discrete low-density pillows (or domes), dispersed throughout, separated by, and extending from the network region. The continuous high-density network region is designed primarily to provide strength, while the plurality of the low-density pillows is designed primarily to provide softness and absorbency. Such belts have been used to produce commercially successful products, such as, for example, BOUNTY® paper towels, CHARMIN® toilet tissue, and PUFFS® facial tissue, all produced and sold by The Procter & Gamble Co.
Certain aspects of absorbency of a fibrous structure, as well as its ability to clean more effectively, are highly dependent on its three-dimensional surface area. By three-dimensional surface area is meant the surface area that includes out-of-plane three-dimensionality such that a sheet of fibrous structure of a given overall two-dimensional size has a three-dimensional surface area greater than its two-dimensional calculated area. Attempts have been made to increase the three-dimensional surface area by increasing the number and placement of different elevations of a papermaking belt. That is, for a given fibrous web, the greater the web's three-dimensional surface area the higher the web's absorbency and cleaning performance. In the three-dimensional structured webs made on the aforementioned papermaking belts, the low-density pillows and the transition areas between the pillows and the relatively high density regions, dispersed throughout the web, increase the web's three-dimensional surface area, thereby increasing the web's absorbency. However, increasing the web's surface area by increasing the area comprising the relatively low-density pillows would result in decreasing the web's area comprising the relatively high-density network area that imparts the strength.
Attempts to increase absorbency and cleaning performance of absorbent paper products by increasing the three-dimensional surface area include using two layers of a resinous framework of the forming member. One example of using two layers of a resinous framework is shown in U.S. Pat. No. 6,660,129 B1, issued Dec. 9, 2003 to Cabell et al. Cabell et al. discloses a fibrous structure having at least a first region defining a first plane and having a first elevation, and a second region outwardly extending from the first plane to define a second elevation, wherein the second region comprises a plurality of fibrous pillows. Due to the nature of the resinous framework on the forming member described in Cabell et al., one feature of a fibrous structure made thereon is fibrous cantilever portions laterally extending at a second elevation. This is believed to be because of the nature of the process of producing the resinous framework of Cabell et al., which includes randomly dispersed cantilevered portions of the second layer of the resinous framework of Cabell et al. It is believed that the cantilevered portions can be weakened and fail during prolonged use of the belt, and, as well, fail to produce increased surface area in the finished paper of a type not requiring the cantilevered portions.
There is a continuing unaddressed need for a papermaking belt that can produce fibrous structures having greater absorbency and cleaning performance, particularly cleaning of soils and other solids, due to increased three-dimensional surface area.
Additionally, there is a continuing unaddressed need for a papermaking belt that can produce fibrous structures having distinct three-dimensional features in discrete planes, but which are not cantilevered.
Additionally, there is a continuing unaddressed need for a method for making a papermaking belt having a multi-stage, three-dimensional structure in a single pass.
Further, there is an unaddressed need for a three-dimensional mask that can produce a papermaking belt that can produce fibrous structures having distinct three-dimensional features in discrete planes, but which are not cantilevered.
A textured mask comprising a film is disclosed. The film can have a first substantially continuously flat surface lying in a first plane and a second surface opposite the first surface lying in a second plane substantially parallel to the first plane. The second surface is interrupted by a plurality of cavities, each of the cavities having a first depth defined by a third surface lying in a third plane substantially parallel to the first and second planes. The depth of the cavities can be at a distance of from about 0.1 mm to about 5 mm from the second plane. The textured mask is at least partially coated with an opaque masking agent. The textured mask can make a correspondingly structured three-dimensional papermaking belt, which can make correspondingly structured three-dimensional fibrous structure.
Papermaking Belt
In
Patterns of knuckles and pillows can be made generally according to the methods and processes described in U.S. Pat. No. 6,610,173, issued to Lindsay et al. on Aug. 26, 2003, or U.S. Pat. No. 4,514,345 issued to Trokhan on Apr. 30, 1985, together with the improved techniques disclosed herein. The Lindsay and Trokhan disclosures describe belts that are representative of papermaking belts made with cured resin on a woven reinforcing member, of which the present invention is an improvement. But further, the present improvement can make papermaking belts useful as a fabric crepe belt as disclosed in U.S. Pat. No. 7,494,563, issued to Edwards et al. on Feb. 24, 2009 or U.S. Pat. No. 8,152,958, issued to Super et al. on Apr. 10, 2012, as well as belt crepe belts, as described in U.S. Pat. No. 8,293,072, issued to Super et al on Oct. 23, 2012. When utilized as a fabric crepe belt, a papermaking belt of the present invention can provide the relatively large recessed pockets and three-dimensional knuckle dimensions to redistribute the fiber to a greater degree upon high impact creping in a creping nip between a backing roll and the fabric to form additional bulk in conventional wet press processes. Likewise, when utilized as a belt in a belt crepe method, a papermaking belt of the present invention can provide three-dimensional fiber enriched dome regions arranged in a repeating pattern corresponding to the pattern of the papermaking belt, as well as the interconnected plurality of surround areas to form additional bulk and local basis weight distribution in a conventional wet press process.
Examples of papermaking belts 2 of the present invention are shown in
The papermaking belt 2 may be made from a variety of materials, including but not limited to: resinous material, metal, metal-impregnated resin, plastic, polymers such as a polyurethane material, or any combination thereof that can form a patterned framework of knuckles. As used herein, the term “patterned framework” or “framework” does not include a structure that is formed solely by mutually perpendicular interwoven filaments, such as, for example, a forming wire or a similarly formed structure. Such a structure, comprising a plurality of mutually perpendicular filaments, may be used as a reinforcing member 8 in the papermaking belt 2 of the present invention, as will be discussed below, but does not constitute the framework of knuckles 6 of the papermaking belt 2.
If the papermaking belt 2 is made with a resinous material or other material having a pattern that can be distorted when pulled in a machine direction, a reinforcing member 8 is typically used to reinforce the framework of the papermaking belt 2. The reinforcing member 8 may be necessary when the patterned framework comprises a semi-continuous pattern or a pattern comprising a plurality of discrete protuberances, as shown in
The papermaking belt 2 can be joined to the reinforcing member 8. The reinforcing member 8 has an upper side 18 and a lower side 20 opposite to the upper side 18. The web-side 14 of the papermaking belt 2 and the upper side 18 of the reinforcing member 8 face one direction, and the backside 16 of the papermaking belt 2 and the lower side 20 of the reinforcing member 8 face the opposite direction. As defined herein, the backside 16 of the papermaking belt 2 forms an X-Y plane. Since the reinforcing member 8 is typically near or adjacent to the backside 16 of the papermaking belt 2 (e.g.,
One skilled in the art will also appreciate that the reinforcing member 8, as well as the papermaking belt 2 as a whole, does not need to (and indeed cannot in some embodiments) have a planar configuration throughout its length, especially when used in a typical industrial process for making a fibrous structure 500 of the present invention, as shown in
In some embodiments, the reinforcing member 8 is substantially fluid-permeable. The fluid-permeable reinforcing member 8 may comprise a woven screen, or an apertured element, a felt, a film, or any combination thereof. Various types of the fluid-permeable reinforcing member 8 are described in several commonly assigned US Patents, for example, U.S. Pat. Nos. 5,275,700 and 5,954,097. The reinforcing member 8 may comprise a felt, also referred to as a “press felt” as is used in conventional papermaking. The framework may be applied to the reinforcing member 8, as taught by commonly assigned U.S. Pat. No. 5,549,790, issued Aug. 27, 1996 to Phan; U.S. Pat. No. 5,556,509, issued Sep. 17, 1996 to Trokhan et al.; U.S. Pat. No. 5,580,423, issued Dec. 3, 1996 to Ampulski et al.; U.S. Pat. No. 5,609,725, issued Mar. 11, 1997 to Phan; U.S. Pat. No. 5,629,052 issued May 13, 1997 to Trokhan et al.; U.S. Pat. No. 5,637,194, issued Jun. 10, 1997 to Ampulski et al.; U.S. Pat. No. 5,674,663, issued Oct. 7, 1997 to McFarland et al.; U.S. Pat. No. 5,693,187 issued Dec. 2, 1997 to Ampulski et al.; U.S. Pat. No. 5,709,775 issued Jan. 20, 1998 to Trokhan et al., U.S. Pat. No. 5,795,440 issued Aug. 18, 1998 to Ampulski et al., U.S. Pat. No. 5,814,190 issued Sep. 29, 1998 to Phan; U.S. Pat. No. 5,817,377 issued Oct. 6, 1998 to Trokhan et al.; and U.S. Pat. No. 5,846,379 issued Dec. 8, 1998 to Ampulski et al.
Alternatively, in some embodiments, the reinforcing member 8 may be fluid-impermeable. The fluid-impermeable reinforcing member 8 can comprise, for example, a polymeric resinous material, identical to, or different from, the material used for making a papermaking belt 2 of the present invention; a plastic material; a metal; a film, or any other suitable natural or synthetic material; or any combination thereof. One skilled in the art will appreciate that the fluid-impermeable reinforcing member 8 will cause the papermaking belt 2, as a whole, to be also fluid-impermeable.
If desired, the reinforcing member 8 comprising a Jacquard weave can be utilized. Illustrative belts having the Jacquard weave can be found in U.S. Pat. No. 5,429,686 issued Jul. 4, 1995 to Chiu, et al.; U.S. Pat. No. 5,672,248 issued Sep. 30, 1997 to Wendt, et al.; U.S. Pat. No. 5,746,887 issued May 5, 1998 to Wendt, et al.; and U.S. Pat. No. 6,017,417 issued Jan. 25, 2000 to Wendt, et al. It is believed that a Yankeeless process may benefit from using the papermaking belt 2 of the present invention by providing additional three-dimensionality to a fibrous structure during the web formation process.
It is to be understood that the present invention contemplates a papermaking belt 2 previously unachievable with prior techniques. Specifically, in general, the multi-elevational framework of knuckles of the invention comprises a plurality of Z-direction spatially separated surfaces defined in order spatially with respect to the backside 16 of the papermaking belt 2. Each surface can be substantially parallel to the X-Y plane. Further, each successive surface progressing in a Z-direction away from the backside 16 toward a web side 14 has a projected area less than the projected area of the surface adjacent and closer to the backside 16, and is bounded completely by the area of the projected area of the surface adjacent and closer to the backside 16. The concept of projected area and description of the framework of the invention as well as a mask to make the framework and fibrous structures made on the framework is described more fully below.
As shown in
By “projected area” is meant an area of a surface as it would be projected in the Z-direction onto an X-Y plane, 44, as shown in
“Draft angles” 46 of sidewalls the Z-direction-oriented three-dimensional features may be present in the structure of the knuckles 6 of the papermaking belt 2, as shown in
In an embodiment, the extended portion 28 can be designed to have a shape and predetermined position with respect to the base portion 26, such as being fully centrally registered with respect to the base portion 26 in the X-Y dimension, but in any configuration the extended portion 28 does not extend beyond the boundaries of the projected area of the base portion 26 to form a cantilevered, or overhanging, member. Any other configuration is contemplated, however, and several various embodiments of example configurations of base portions 26 and extended portions 28 are shown schematically in
In general, as shown in
Process for Making Papermaking Belt
A process for making the papermaking belt 2, according to one embodiment of the present invention, is shown in
If desired, the forming surface may comprise a deformable surface, as described in the commonly assigned U.S. Pat. No. 5,275,700. When the reinforcing member 8 is pressed into the deformable forming surface during the process of making, the deformable forming surface forms protrusions that exclude the curable material from certain areas which, when cured, will lie along the backside 16 of the papermaking belt 2. This causes the reinforcing member to extend at least partially beyond the back side of the framework of the papermaking belt 2 to form a so-called “textured” backside 16 having passageways providing texture irregularities therein. Those texture irregularities are beneficial in some embodiments of the papermaking belt 2, because they prevent formation of a vacuum seal between the backside of the papermaking belt 2 and a surface of the papermaking equipment (such as, for example, a surface of a vacuum box or a surface of a pick-up shoe), thereby creating a “leakage” there between and thus mitigating undesirable consequences of an application of a vacuum pressure in a through-air-drying process of making a fibrous structure 500 of the present invention. Other methods of creating such a leakage are disclosed in commonly assigned U.S. Pat. Nos. 5,718,806; 5,741,402; 5,744,007; 5,776,311; and 5,885,421.
The leakage can also be created using so-called “differential light transmission techniques” as described in commonly assigned U.S. Pat. Nos. 5,624,790; 5,554,467; 5,529,664; 5,514,523; and 5,334,289. The papermaking belt is made by applying a coating of photosensitive resin to a reinforcing member that has opaque portions, and then exposing the coating to light of an activating wavelength through a mask having transparent and opaque regions, and also through the reinforcing member 8.
Another way of creating backside surface irregularities comprises the use of a textured forming surface, or a textured barrier film, as described in commonly assigned U.S. Pat. Nos. 5,364,504; 5,260,171; and 5,098,522. The papermaking belt 2 is made by casting a photosensitive resin over and through the reinforcing member while the reinforcing member travels over a textured surface, and then exposing the coating to light of an activating wavelength through a mask which has transparent and opaque regions.
As shown in
In the embodiment shown in
The use herein of the term “machine direction” is consistent with the traditional use of the term in papermaking, where this term refers to a direction which is parallel to the flow of the paper web through the papermaking equipment. In the context of the continuous process of making the papermaking belt 2, the “machine direction” is a direction parallel to the flow of the coating of the curable material (or the reinforcing member where applicable) during the process of the present invention. It should be understood that the machine direction is a relative term defined in relation to the movement of the coating at a particular point of the process. Therefore, the machine direction may (and typically does) change several times during a given process of the present invention. A term “cross-machine direction” is a direction perpendicular to the machine direction and parallel to the general plane of the papermaking belt 2 being constructed, or the X-Y plane.
A coating of curable material 300, such as, for example, a liquid photosensitive resinous material, is applied to the reinforcing member 8, and specifically, to its upper side 18. Any technique by which the liquid curable material can be applied to the reinforcing member 8 is suitable. For example, a nozzle 260, schematically shown in
Suitable curable materials that can be readily selected from the many those commercially available. For example, the curable material may comprise liquid photosensitive resins, such as polymers that can be cured or cross-linked under the influence of a suitable radiation, typically an ultraviolet (UV) light. References containing more information about liquid photosensitive resins include Green et al., “Photocross-linkable Resin Systems,” J. Macro-Sci. Revs. Macro Chem., C21 (2), 187-273 (1981-82); Bayer, “A Review of Ultraviolet Curing Technology,” Tappi Paper Synthetics Conf. Proc., Sep. 25-27, 1978, pp. 167-172; and Schmidle, “Ultraviolet Curable Flexible Coatings,” J. of Coated Fabrics, 8, 10-20 (July, 1978). All the preceding three references are incorporated herein by reference.
The next step is optional and comprises controlling a thickness of the coating to a pre-selected value. In some embodiments, this pre-selected value is dictated by a desired thickness of resin layer and will influence the resulting thickness of the papermaking belt 2. This resulting thickness of the papermaking belt 2 is primarily dictated by the expected use of the papermaking belt 2. For example, when the papermaking belt 2 is to be used in a process for making a fibrous structure, described hereinafter, the papermaking belt 2 is typically from about 0.3 mm to about 10.0 millimeters thick. Any suitable means for controlling the thickness of the layer 300 can be used in the process. For example, illustrated in
The coating is then cured via UV light radiation through the mask. The intensity of the radiation and its duration depend upon the degree of curing required in the areas exposed to the radiation. In the instance of the photosensitive resin, the absolute values of the exposure intensity and time depend upon the chemical nature of the resin, its photo characteristics, the pattern selected, and the thickness of the coating, or of the desired depth of its areas, to be cured. Further, the intensity of the exposure and the angle of incidence of the curing radiation can have an important effect on the presence or absence of taper in the walls of the pre-selected pattern of the framework to be constructed. The disclosure of commonly assigned U.S. Pat. No. 5,962,860, issued Oct. 5, 1999 in the name of Trokhan et al. for teaching an apparatus for generating controlled radiation for curing a photosensitive resin, comprising a reflector having a plurality of elongate reflective facets that are adjustable such as to direct the curing radiation substantially to a desired direction. The patent further discloses a radiation management device comprising a mini-reflector juxtaposed with the source of radiation for controlling the direction and intensity of the curing radiation.
The reinforcing member 8 comprising so-called “fugitive tie yarns” may be beneficially used for the second layer 40. Commonly assigned PCT application WO 1999/14425, published on Mar. 25, 1999, and titled Multiple Layer Foraminous Belts With Fugitive Tie Yarns, discloses a belt for supporting a cellulosic fibrous structure in a papermaking process and a method of producing the belt. The belt comprises a reinforcing member having two layers, a web-contacting first layer and a machine-facing second layer, and a pattern layer comprising a cured photosensitive resin, the pattern layer having a plurality of conduits therethrough. The two layers of the reinforcing member are joined together by either integral or adjunct tie yarns such that at least a portion of the tie yarns which lies within the conduits is removable after the photosensitive resin has been cured. These “fugitive” tie yarns are substantially transparent to actinic radiation and can be removed by chemical or mechanical processes when they are no longer needed to stabilize the relationship between the web-facing layer and the machine-facing layer of the reinforcing member. In particular, the portion of the fugitive tie yarns that lies within the conduits can be removed so that belt properties, such as projected open area, are substantially isotropic across the belt. A means to remove the fugitive adjunct tie yarns may include a combination of solubilization and mechanical energy provided by showering systems that are part of the belt-making and papermaking processes. Suitable materials for the fugitive tie yarns comprise those that can be controllably removed by chemical or mechanical means.
Mask
A mask 110 is positioned between the coating of the curable material 300 and a source of curing radiation 120. In the instance of a photosensitive resin, the source of curing radiation 120 may comprise, for example, a mercury arc lamp or an LED source. The mask 110, a portion of which is shown in perspective view in
In the exemplary portion shown in
The portion of mask 110 shown in
With reference to
The purpose of the mask 110 is to shield certain areas of the curable material 300, i.e., those areas that are shielded by the opaque regions 114, from exposure to curing radiation and to form a three dimensional knuckle structure. The three-dimensional structure of the mask serves to mold a substantially identically shaped three-dimensional structure of a knuckle of a papermaking belt, which likewise serves to form the three-dimensional structure of a fibrous structure made on the papermaking belt. The novel three-dimensional structure of the fibrous structure so formed serves to increase the absorbency and cleaning performance of the fibrous structure by providing relatively more surface area in a given sheet of fibrous structure than was previously possible in prior structures.
One method for providing shielding is to apply an opaque coating, which can be an opaque ink, 118 to in a pattern to form transparent regions of the mask and opaque regions of the mask corresponding to the desired pattern of the resulting papermaking belt 2. The transparent regions 112 of the mask 110 allow other (unshielded or partially shielded) areas of the curable resin to be exposed to and receive the curing radiation which results in hardening, i. e., curing, of these unshielded portions. The opaque regions can be in a pattern such that the mask has a plurality of transparent regions, the transparent regions corresponding to and being coextensive with the cavities. The shielded areas of the coating thus form a pre-selected pattern corresponding to the desired pattern of knuckles 6 on the papermaking belt 2. Ink 118 can be applied on either surface of mask 110, that is, on either side 110a or 110b. As can be understood by the description herein, applying the coating 118 on first surface 110a requires registered application to ensure that light can penetrate the mask through the region of cavity 116. However, applying the coating 118 onto side 110b can be accomplished without registration with a printing process that for example, applies ink from a generally smooth-surface roller to second surface 110b, thereby applying ink to second mask plane 154, but not to third (or fourth, fifth, etc.) surface 156. In an embodiment, for example, ink 118 can be applied to second mask plane 154 in a gravure coating process.
Additionally, however, in the present invention the mask provides a dimensionally-stable, three-dimensional mold, so to speak, to form the knuckles 6 of the papermaking belt 2 in a corresponding three-dimensional shape. Prior masks utilized in the formation of papermaking belts, being flat or at the most having a single-elevation, possibly deformable, cavity, are incapable of forming the papermaking belt 2 or the fibrous structures of the present invention. The three-dimensional structure of the mask 110 can be used to form a papermaking belt having substantially the same three-dimensional geometry, as shown in
A source of curing radiation 120, i.e., a light source, radiates through the non-opaque transparent region 112 to cure a portion of the curable resin, which cured portion can include the base portion 26 and extended portion 28 of knuckles 6. Once the mask is removed, and the uncured resin is washed away, the resulting cured resin forms the patterned framework of knuckles 6, as shown, for example in
The mask 110 of the present invention may have multiple differential opacities, i.e., the mask 110 may have the opaque regions 114 that differ in opacity. Those differential opacities may comprise discrete opacities and/or gradient opacities. As used herein, the term “gradient opacity” means an opacity having a gradually changing intensity. Gradual opacity does not have a defined “border line” therein that would separate one opacity value from the other. That is, the gradient opacity is a non-monotone opacity, wherein the change in opacity in at least one direction is gradually incremental, as opposed to discrete.
One method of constructing the mask 10 having regions of differential opacities comprises printing a transparent film to form a pattern of opaque regions having a certain initial opacity, and then printing the film a second time to form a pattern of opaque regions having another opacity different from the initial opacity. For example, first the film can be printed with ink to form regions of the initial opacity, and then printed again to apply the ink to at least several of the regions already having the initial opacity, thereby increasing the opacity of said several regions. In another method, the differential opacities can be formed in one-step printing, by using a printing roll, such as, for example, a Gravure roll, having a differential-depths pattern therein for receiving ink. During printing, the ink deposited to the transparent film will have regions of differential intensities, reflecting the differential depths of the roll's pattern. Other methods of forming opaque regions can be used in the present invention. Such methods include, but are not limited to, chemical, electromagnetic, laser, heat, lamination of various transmission films, such as by combining multiple layers of film, at least two of the films having a difference in opacity. In one embodiment, the three-dimensional mask can be formed by the lamination of at least two film layers, with at least one being a flat, smooth film, and at least one being formed with a pattern of apertures, such that when laminated the apertures, in effect, form the cavity 116 of mask 110.
The mask 110 can be made in a form of an endless loop (all the details of which are not shown but should be readily apparent to one skilled in the art), or it can be supplied from a supply roll to a take-up roll. As shown in
The mask can be made the process described herein schematically in
The first step of the mask-making process, as shown schematically in
Once the desired repeating pattern for the patterned framework is machined into an individual master tool 212, the master tool 212 is immersed in an electrolyte solution 220 and acts as the cathode in an electroforming process 214 to form a nickel replica 216 of the master tool, as depicted schematically in
In an embodiment, a mask can be produced by casting an optically clear polymer film onto the nickel replica 216, thus forming a virtually exact copy of the cavity 116 or a plurality of cavities 116 in the film mask. Due to its size, the mask so formed would have limited usefulness in a commercial papermaking operation. But with an opaque ink coating 118 added in a desired pattern, the mask made from casting on a single nickel replica would have all the structural features for usefulness in making a papermaking belt 2 of the present invention. In commercial practice, however, it can be beneficial to use multiple nickel replicas of the master tool 212, each mounted to a rotating drum or belt or other continuous support loop, as discussed below with reference to
A mask can be cast on an embosser apparatus of the type developed by Avery Dennison Corporation, and described in U.S. Pat. No. 6,375,776. The process is briefly repeated below with respect to
Turning now to
In accordance with this embodiment of the invention, the mask is constructed with the aid of apparatus 130 by simultaneously feeding at least one lower layer polymer film 144, such as film, described above, together with at least one specialized carrier film 146 into the embosser 130 between pressure roller 138 and the embossing tool 132. The region of the embosser 130 in which embossing tool 132 is in contact with heating roller 134 functions as a heating station. The temperature of the heating roller 134 can be set such that the tool 132 is raised to a temperature above the glass transition temperature of the film 144. When acrylic is used, the heating roller temperature can be about 425° F., although one skilled in the art will recognize that the optimum temperature of the heating roller will depend on environmental conditions and the particular features of the specific embossing machine used. Heating of the roller 134 can be accomplished such as by circulating hot oil axially through the roller 134, or by electrically heating roller 134. The film 144 and carrier 146 pass between pressure rollers 138, 139 and 140 and the tool 132 whereupon the desired pattern of the tool 132 is impressed into the film 144. The carrier film 146 can be selected as to have a glass transition temperature higher than that of the film 144 and, therefore, can remain unaffected by the tool 132 as it passes beneath the pressure rollers 138, 139 and 140.
After the embossed film 144 and carrier film 146 pass roller 140, the carrier film 146 can be separated from superimposed relationship with film 144 and can be moved onto a wind-up roll (not shown). However, the film 144 continues to be adhered to the tool 132 and reaches pressure roller 141 at which point a superimposed top layer of polymer film 148 and a standard carrier film 150 can be joined with the film 144 and together pass beneath the rollers 141 and 142 with the film 144. Because the tool 132 is still in contact with the heating roller 134 at this point, the two polymer films 144 and 148 become bonded together. Like carrier film 146, the carrier film 150 is selected to have a glass transition temperature which is higher than that of both film 144 and film 148. The multi-layer laminate next moves through a cooling station, which can be a generally planar region 122 where the mask is cooled such as by a chilled fluid such as chilled air, and finally exits the embosser 130 at a stripper roller 124, which can strip the mask from the tool (such as disclosed in U.S. Pat. No. 4,601,861).
While lower layer polymer film 144 and top layer polymer film 148 have been illustrated in
Once the three-dimensional mask 110 is made on the apparatus described with respect to
One advantage of the mask of the present invention is that it facilitates single-pass formation of three-dimensional structures on a patterned framework 20 of papermaking belt 2. This provides commercial advantages in that a papermaking belt 2 having a three-dimensional patterned framework can be made more economically. Further, the mask of the present invention provides for better registration of the three-dimensional aspects of the patterned framework on papermaking belt 2. These features of the mask, and the papermaking belt 2 produced by the mask, translate into a fibrous structure having three-dimensional features that improve the absorbency and cleaning performance of the fibrous structure.
Process for Making Fibrous Structure
With reference to
The present invention contemplates the use of a variety of fibers, such as, for example, papermaking 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 each 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 papermaking belt 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.
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 papermaking belt 211 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 papermaking belt 211 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 papermaking belt and the void spaces formed between the suspended portions and the X-Y plane.
In
Then, a portion of the fibers 501 is deflected into the deflection portion of the papermaking belt such as to cause some of the deflected fibers or portions thereof to be disposed within the deflection conduits of the papermaking belt, and therefore, to take the shape of the knuckles 6, as shown in
Finally, a partly-formed fibrous structure associated with the papermaking belt 211 can be separated from the papermaking belt to form the fibrous structure 500 of the present invention.
The process may further comprise a step of impressing the papermaking belt 211 having the fibers therein against a pressing surface, such as, for example, a surface of a Yankee drying drum 228, thereby densifying portions of web. In
Fibrous Structure
When formed utilizing a papermaking belt 2 having a knuckle pattern of the invention, the fibrous structure can exhibit features corresponding to the features of the knuckles of the papermaking belt, as shown in
The fibrous structure can be further processed and converted to consumer goods, for example by joining together single plies to make a multi-ply fibrous structure, and/or by embossing to provided for an embossed fibrous structure, and/or by supplying in roll form to provide for a rolled fibrous structure which can be a roll of sheets separated by perforations as is commonly known in the field of bath tissue and paper towels. In an embodiment, the fibrous structure is a roll of embossed, multi-ply fibrous structure in the form of bath tissue or paper towels, as shown in
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any embodiment disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such embodiment. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the present disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.
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| Number | Date | Country | |
|---|---|---|---|
| 20180155873 A1 | Jun 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62076036 | Nov 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14932079 | Nov 2015 | US |
| Child | 15875064 | US |
