Embossed tissue paper products and methods of manufacturing

Abstract

Embossed tissue products having improved caliper, sheet bulk and reduced tensile degradation may be produced using a conventional unheated embossing nip by preheating the sheet immediately before embossing. The tissue sheet may be preheated using steam or a heated liquid. The surface temperature of the tissue sheet is heated to at least about 60 °C, such as from about 60 °C to about to 90 °C after treatment. Preferably the web path between treatment and the unheated embossing nip is sufficient short, such as about two meters or less, that the sheet surface temperature remains elevated as it is conveyed through the embossing nip. Preferably the temperature tissue sheet ranges from about 30 °C to about 50 °C as it is conveyed through the embossing nip.

Description

[0001] EMBOSSED TISSUE PAPER PRODUCTS AND METHODS OF MANUFACTURING BACKGROUND

[0002] It is well known in the art to emboss bond multiple plies of lightweight cellulosic material to form tissue products such as bath tissues, facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, and other similar products. The embossed tissue products may comprise one, two, three or more plies. Embossing not only plies multiple plies together but may also impart the tissue product with an aesthetically pleasing pattern. Examples of apparatus and methods for embossing multiply paper products are disclosed, for example, in U. S. Patent Nos. 6,733,866, 7,871,692 and 8,287,986 and U. S. Publication No. 2012 / 0156447.

[0003] Embossing may also be used to alter or improve certain tissue product properties such as sheet bulk and perceived softness. For example, tissue products manufactured using conventional creped wet press technology can be embossed after creping to improve bulk and perceived softness. Embossing often increases the surface area of the sheets by introducing a plurality of protuberances and thereby enhances the bulk and handfeel of the product. Examples of apparatus and methods for embossing multi-ply paper products to improve handfeel and bulk are disclosed, for example, in U. S. Publication Nos. 2005 / 0103456, 2018 / 0142422 and 2018 / 0135254.

[0004] Often tissue products marketed in rolls, contain a specified number of sheets per roll. Tissue embossed in conventional patterns of dot embossments, when packaged in roll form, exhibit a tendency to be non-uniform in appearance often due to compressing of the embossments as the sheet is wound onto the roll, detracting from the appearance of the rolls.

[0005] SUMMARY

[0006] The present invention provides novel embossed tissue products and methods of manufacturing the same. In certain embodiments the invention provides embossed tissue products, produced as described herein, having novel embossing patterns, enhanced embossed pattern clarity, and improved physical properties. In particularly preferred embodiments the present invention provides an apparatus for manufacturing an embossed, multi-ply tissue product, such as toilet paper or household towel, the apparatus comprising a moisturizing station configured to dispense a heated liquid or steam and an embossing unit comprising a first embossing roll and a first counter roll arranged in opposition to one another and forming a first embossing nip therebetween. The first embossing roll is generally provided with a plurality of male embossing elements, which may be arranged to form a decorative pattern on atissue ply as it passes through the first embossing nip. It is generally preferred that the embossing nip is unheated and has a temperature less than about 30 °C, such as from about 15 to about 20 °C.

[0007] Thus, in certain instances, the present disclosure provides an apparatus for the manufacture of a multi-ply embossed tissue product comprising: a first unwind for unwinding a first spirally wound tissue ply; a second unwind for unwinding a second spirally wound tissue ply; an embossing unit comprising an anvil roll and an embossing roll arranged in opposition to one another and defining an embossing nip therebetween and configured to emboss a moistened and heated tissue ply and yield an embossed tissue ply; and a moisturizing station disposed between the first unwind and the embossing nip, the moisturizing station configured to moisten and heat at least the first or second tissue ply such that the surface of the first or second tissue ply is at least about 30 °C and the basis the basis weight of the first or second ply is increased by at least about 2 wt%.

[0008] The moisturizing station is generally positioned upstream of the embossing nip such that the tissue ply is treated prior to being embossed. It may be desirable to arrange the moisturizing station a relatively short distances, such as a web distance less than two meters, upstream of the embossing station such that the temperature of the ply remains elevated as it is conveyed through the unheated embossing nip. In certain instances, it may be preferable that the surface temperature of the ply is at least about 60 °C, such as at least about 65 °C, such as at least about 70 °C, such as from about 60 °C to about 90 °C, such as from about 65 °C to about 75 °C, immediately after treatment with steam or a heated liquid. Thereafter the treated ply may cool slightly as it conveyed through the unheated embossing nip, however, the ply preferably continues to maintain a surface temperature of at least about 30 °C, such as at least about 32 °C, such as at least about 35 °C, such as at least about 40 °C such as from about 30 °C to about 50 °C, such as from about 32 °C to about 45 °C, such as from about 35 °C to about 40 °C, as it is conveyed through the unheated embossing nip.

[0009] In certain instances, the foregoing apparatus may further comprise an adhesive supplying unit for applying adhesive, such as lamination glue, to the tissue ply as it is supported by the male embossing elements disposed on the first embossing roll. The adhesively treated and embossed tissue ply may be brought into facing arrangement with a second tissue ply to join the first and second tissue plies and form a multi-ply, embossed tissue product. The first and second plies may be joined by passing the plies through the nip formed between the first embossing roll and the marrying roll.

[0010] In other instances, the foregoing apparatus may further comprise a micro-embossing unit. The micro-embossing unit may comprise a micro-embossing cylinder and a counter cylinder facing the microembossing cylinder to form a micro-embossing nip therebetween. Either the first or the second tissueply, or both, may be microembossed. In certain instances, the second tissue ply is microembossed prior to being joined with the first embossed tissue ply.

[0011] In certain instances, the apparatus of the present invention comprises a steam station, which may be configured for apply steam to the first and / or second tissue prior to being embossed. Preferably the steam station comprises one or more steaming units configured to apply steam to the first and / or second tissue plies. The steam station may comprise a shower or nozzle system for spraying steam onto the ply. Regardless, it is generally preferred that the steam station is configured to both moisten and heat the ply such that prior to embossing the temperature and moisture of the ply is increased. For example, the steam station may be configured to increase the basis weight of the ply by at least about 1 percent, based upon the weight of the tissue web (wt%), such as at least about 2 wt%, such as at least about 5 wt%.

[0012] In other instances, the steam station may be configured to increase the surface temperature of the ply by at least about 10 °C, such as at least about 20 °C, such as at least about 30 °C, such as at least about 40 °C, such as at least about 50 °C. Accordingly, upon treatment, the treated surface of the tissue ply may have a temperature of about 60 °C, such as at least about 65 °C, such as at least about 70 °C, such as from about 60 °C to about 90 °C, such as from about 65 °C to about 75 °C,

[0013] In other instances, the apparatus of the present invention may comprise a means for applying heated water to the ply prior to it being passed through the embossing nip. For example, water having a temperature from about 70 °C to about 100 °C may be applied to the ply by spraying immediately prior to the ply being conveyed through the embossing nip. The addition of heated water to the ply increases the temperature of the ply as well as the moisture content and results in less tensile degradation when the ply is embossed.

[0014] Regardless of whether moisture content and temperature of the sheet is increased by the addition of heated water or steam, it is generally preferred that the ply is subsequently embossed without the addition of heat. For example, in certain instances, it may be preferable to convey the ply through an unheated embossing nip, such as a nip having a temperature ranging from about 15 to about 20 °C after the ply has been treated with steam. Surprisingly, embossing the ply in this manner decreases the amount of tensile degradation caused by embossing without negatively affecting the clarity and quality of the embossing pattern. Thus, in certain instances, the present process may be used to moderate tensile degradation such that the finished product geometric tensile strength is equal to, or greater than, the geometric mean tensile strength of a substantially similar product prepared without the addition of steam or heated liquid. In other instances, the sheet bulk may be increased compared to a substantiallysimilar product prepared without the addition of steam or heated liquid, such as a sheet bulk increase ranging from 2 to about 10%.

[0015] In still other instances, the present disclosure provides a method of manufacturing an embossed, tissue product comprising the steps of: conveying a first tissue ply having a first and a second surface; applying steam or a heated liquid to the first or second surface of the conveyed first tissue ply to yield a heated first tissue ply having a surface temperature of at least about 60 °C; conveying the heated first tissue ply through a first embossing nip formed between a first embossing roll and a first counter roll wherein the surface temperature of the first embossing roll and the first counter roll is less than about 30 °C; and embossing the heated first tissue ply as it is conveyed through the first embossing nip to yield an embossed first tissue ply having an embossing pattern disposed thereon.

[0016] DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a plan view of one embodiment of a tissue product made in accordance with the present disclosure;

[0018] Figure 2A is an enlarged view of the tissue product illustrated in Figure 1; and

[0019] Figure 2B is a cross-sectional view along line 6B shown in Figure 2A; and

[0020] Figure 3 is a schematic illustration of an embossing apparatus and process for manufacturing an embossed tissue product of the present disclosure.

[0021] DEFINITIONS

[0022] As used herein the term “machine direction” or “MD” generally refers to the direction in which a tissue ply or product is produced. The term “cross-machine direction” or “CD” refers to the direction perpendicular to the machine direction.

[0023] As used herein the term “basesheet" refers to a tissue ply formed by any one of the papermaking processes described herein that has not been subjected to further processing, such as embossing, calendering, treatment with a binder or softening composition, perforating, plying, folding, or rolling into individual rolled products.

[0024] As used herein the term “tissue product” refers to products made from basesheets and includes, bath tissues, facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, and other similar products.

[0025] As used herein the terms “ply” and “web" refer to a discrete sheet of tissue used to form a tissue product. Individual plies or webs may be arranged in juxtaposition to each other. In a preferredembodiment, tissue products prepared according to the present invention comprise two or more plies or webs arranged in facing relation to one another.

[0026] As used herein, the term "layer” refers to a plurality of strata of fibers, chemical treatments, or the like, within a ply. A “layered tissue web” generally refers to a tissue web formed from two or more layers of aqueous papermaking furnish. In certain instances, the aqueous papermaking furnish forming two or more of the layers comprises different fiber types.

[0027] As used herein the term “basis weight” generally refers to the conditioned weight per unit area of a tissue and is generally expressed as grams per square meter (gsm). While the basis weights of tissue products prepared according to the present invention may vary, in certain embodiments the products have a total basis weight of about 30 gsm or greater, such as about 34 gsm or greater, such as about 36 gsm or greater, such as from about 30 to about 65 gsm, such as from about 32 to about 60 gsm, such as from about 38 to about 48 gsm.

[0028] As used herein, the term “caliper” refers to the thickness of a tissue product, web, sheet, or ply, typically having units of microns (pm).

[0029] As used herein, the term “sheet bulk” refers to the quotient of the caliper (pm) divided by the basis weight (gsm) and having units of cubic centimeters per gram (cc / g). Tissue products prepared according to the present invention may, in certain embodiments, have a sheet bulk of about 6.0 cc / g or greater, such as about 8.0 cc / g or greater, such as about 10.0 cc / g or greater, such as from about 6.0 to about 14.0 cc / g.

[0030] As used herein, the term “geometric mean tensile” (GMT) refers to the square root of the product of the machine direction tensile strength and the cross-machine direction tensile strength of the web.

[0031] As used herein the term “micro-embossments” generally refers to a plurality of discrete embossments disposed on a tissue ply where the number of embossments per square centimeter of tissue surface area (embossment density) is at least 25 embossments / cm2, such as at least about 30 embossments / cm2, such as at least about 40 embossments / cm2, such as from 25 to about 80 embossments / cm2. In certain embodiments the micro-embossments may consist of small protuberances on a given tissue ply and be formed by small protrusions on an embossing roll which press against and into the tissue ply to be embossed. The micro-embossments may be arranged in a pattern and may cover at least about 6 percent of the ply surface area, such as from about 6 to about 15 percent of the ply surface area.As used herein the term "pattern” generally refers to the arrangement of one or more design elements. Within a given pattern the design elements may be the same or may be different, further the design elements may be the same relative size or may be different sizes. For example, in one embodiment, a single design element may be repeated in a pattern, but the size of the design element may be different from one design element to the next within the pattern.

[0032] As used herein, the term “Embossing Pattern or Design” generally refers to a decorative shape disposed across at least one dimension of a fibrous structure surface, the pattern may comprise a line element, discrete elements or other shapes. The embossing pattern comprises a portion of the fibrous structure lying out of plane with the surface plane of the fibrous structure. In general, the embossing pattern results from embossing the fibrous structure resulting in protrusions having a z-directional elevation on one side of the fibrous structure and raised areas on the opposite side of the fibrous structure.

[0033] As used herein, the term “Continuous Element” refers to an element, such as an embossing element or portion, disposed on a fibrous structure that extends without interruption throughout one dimension of the fibrous structure.

[0034] As used herein, the term “Discrete Element or Shape” refers to an element or shape, such as an embossed portion or non-embossed portion, disposed on a fibrous structure that does not extend continuously in any dimension of the fibrous structure.

[0035] DESCRIPTION

[0036] It has now been discovered that embossed tissue products having improved physical properties and embossed pattern clarity may be produced by heating the tissue ply prior to conveyance through an unheated embossing nip. The apparatus may employ novel embossing patterns, particularly embossing pattern having embossed portions that surround and form a pattern of discrete shapes on the first surface of the first tissue ply. The pattern may be designed such that the discrete shapes have a top surface lying in a first surface plane and the embossed portions form raised areas on the second surface of the first tissue ply. Further, the apparatus may be used to produce tissue products having improved bulk, particularly when compared to conventional embossing techniques.

[0037] Accordingly, in one particularly preferred embodiment, embossed tissue products of the present invention are embossed using an embossing apparatus comprising a means for heating and moistening the tissue ply prior to the ply entering the embossing nip. Preferably the surface temperature of the ply is increased to at least about 60 °C before it is conveyed through an embossing nip having a temperatureless than about 30 °C. Embossing the tissue ply in this manner may reduce tensile degradation, improve embossing pattern clarity and enable the use of novel embossing patterns. Further, the present process may facilitate the use of lower embossing nip loads and increase the sheet bulk of the resulting tissue product.

[0038] Heating and moistening of the tissue ply may be carried out by one or moisturizing station that may be configured to heat and moisten one or both outer surfaces of the ply. The moisturizing station may consist of water showers (e.g., hydraulic, air atomized or ultrasonic showers) or steam showers or combination of water showers and steam showers. Heating and moisturizing ofthe ply may be performed by a liquid, water emulsion, liquid mixture, dispersion, water sprays, steam, or other means known in the art, such that the moisture content of the web is raised (measured after the moisturizing station and before the embossing nip) to a level of about 1 to about 15 weight percent (wt%), more preferably from about 2 to about 10 wt%. Generally, the moisturizing station are positioned, depending on the configuration of the embossing unit, very close before the embossing nip such that the ply remains heated and moistened as it passes through the embossing nip and is embossed. The location of the moisturizing station may be adjusted such that the imbibition time after wetting at a desired running speed before the nip is less than about 2 seconds and more preferably less than about 1 second.

[0039] The present method of heating and moisturizing the ply prior to embossing may adapted to a variety of embossing process. The method may also be suitable for use with embossing and lamination processes for forming multi-ply tissue products. Regardless of the embossing and / or lamination process used to impart an embossed pattern to the tissue ply and join multiple tissue plies together to form a multi-ply tissue product, it is generally preferred that at least one ply is treated with steam and / or heated liquid immediately prior to being conveyed through an embossing nip.

[0040] Generally, the embossing nip through which the heated tissue ply is passed, comprises an embossing roll having a plurality of male protrusions, also referred to as embossing elements, which are arranged to form an embossing pattern. Generally, any embossing pattern may be adapted for use with the present invention. In certain embodiments, the embossing pattern can be a negative engraved embossing pattern that creates embossed portions that surround non-embossed, discrete shapes that form “pillow areas” on the opposite side of the sheet. In this manner, the resulting tissue product not only has aesthetic appeal but is also soft to the touch.

[0041] In one embodiment, the embossing pattern includes embossed portions that surround and form a pattern of discrete shapes on the first surface of the first tissue ply. The discrete shapes have a top surface lying in a first surface plane. The embossed portions form raised areas on the second surfaceof the first tissue ply. An upper surface of the raised areas lies in a second surface plane that is spaced from the first surface plane. The second surface of the first tissue ply is adhered to a first surface of a second tissue ply by applying an adhesive registered with the raised areas on the second surface of the first tissue ply. In certain embodiments, the embossed portions occupy greater than about 10% of the surface area of the second surface of the first ply.

[0042] In certain embodiments, the embossed portions form enclosed shapes such that the embossed portions form a perimeter around the non-embossed discrete shapes. In one embodiment, the embossed portions can form a pattern of first shapes and second shapes corresponding to first pillow areas and second pillow areas on the first surface of the first ply. The embossing design can have an embossing depth of greater than about 0.4 mm, such as greater than about 0.6 mm, such as greater than about 0.8 mm, and less than about 2.5 mm, such as less than about 2 mm, such as less than about 1.5 mm. The embossing depth is measured from a top surface of a raised area of an embossed portion to a top surface of a discrete shape. In one aspect, the embossed portions can be continuous and intersecting. The second tissue ply can be a non-embossed sheet that is adhered to the first tissue ply. Alternatively, the second ply can be embossed with a pattern

[0043] One example of an embossing pattern suitable for use in the present invention is shown in FIG.

[0044] 1. As illustrated in FIG. 1, the embossing pattern includes embossed portions 16 that surround and define non-embossed discrete shapes 18. The embossed portion 16, for instance, can comprise a background pattern that forms the discrete shapes 18. In one aspect, the background pattern of the embossed portions 16 can surround and enclose the discrete shapes 18, forming a perimeter around each shape In one aspect, the embossed portions 16 form a continuous and interconnected pattern.

[0045] With reference now to FIGS. 2A and 2B, a detailed view of the embossing pattern of FIG. 1 is shown in FIG. 2A and FIG. 2B is a cross-sectional view of the embossing pattern and of the multi-ply tissue product 10. The embossed portions 16 form raised areas on the back side of the first tissue ply 12. The non-embossed discrete shapes 18, on the other hand, can form raised areas on the first side or top surface of the first tissue ply 12. In this manner, the thickness and bulk of the first tissue ply 12 can be greatly enhanced.

[0046] As shown in FIG. 2B, the first tissue ply 12 is laminated to the second tissue ply 14 to form the multi-ply tissue product 10. For instance, the first tissue ply 12 can be adhered to the second tissue ply 14 by applying an adhesive or water (to promote hydrogen bonding) in a pattern that is registered with the raised areas formed by the embossed portions 16. In this manner, the first tissue ply 12 is adhered to the second tissue ply 14 where the embossed portions 16 contact the second tissue ply 14 as shownparticularly in FIG. 1 B. The embossing pattern can produce a three-dimensional configuration in which the discrete shapes 18 have a top surface lying in a first surface plane 20. The raised areas of the embossed portions 16, on the other hand, lie in a second surface plane 22 that is spaced from the first surface plane 20. The first surface plane 20 can be parallel with the second surface plane 22. The distance between the first surface plane 20 and the second surface plane 22 represents the depth of the embossing pattern formed into the first tissue ply 12.

[0047] Tissue plies embossed in accordance with this invention can be any suitable tissue basesheet, which for purposes herein means tissue basesheets intended for use as facial tissue, bath tissue, table napkins and paper towels, the tissue basesheet may be layered or nonlayered, creped or uncreped, wet pressed or throughdried and can comprise natural and / or synthetic fibers.

[0048] Tissue basesheets useful in the present invention may be made by any well-known wet-laid papermaking processes such as, for example, creped wet pressed, modified wet pressed, creped through-air dried (CTAD) or uncreped through-air dried (UCTAD). For example, creped tissue basesheet may be formed using either a wet pressed or a modified wet pressed process such as those disclosed in U. S. Patent Nos. 3,953,638, 5,324,575 and 6,080,279, the disclosures of which are incorporated herein in a manner consistent with the instant application. In these processes the embryonic tissue basesheet is transferred to a Yankee dryer, which completes the drying process, and then creped from the Yankee surface using a doctor blade or other suitable device.

[0049] In other instances, the tissue basesheet may be manufactured by a through-air dried process known in the art. In such processes the embryonic tissue basesheet is noncompressively dried. For example, textured tissue plies may be formed by either creped or uncreped through-air dried processes. Particularly preferred are uncreped through-air dried tissue basesheets, such as those described in U. S. Patent No. 5,779,860, the contents of which are incorporated herein in a manner consistent with the present disclosure.

[0050] In still other instances the tissue basesheet may be manufactured by a process including the step of using pressure, vacuum, or air flow through the wet web (or a combination of these) to conform the wet web into a shaped fabric and subsequently drying the shaped sheet using a Yankee dryer, or series of steam heated dryers, or some other means, including but not limited to tissue made using the ATMOS process developed by Voith or the NTT process developed by Metso; or fabric creped tissue, made using a process including the step of transferring the wet web from a carrying surface (belt, fabric, felt, or roll) moving at one speed to a fabric moving at a slower speed (at least 5 percent slower) andsubsequently drying the sheet. Those skilled in the art will recognize that these processes are not mutually exclusive, e.g., an uncreped TAD process may include a fabric crepe step in the process.

[0051] Multi-ply tissue products may be constructed from two or more plies that are manufactured using the same or different tissue making techniques. In a particularly preferred embodiment, the multi-ply tissue product comprises two or three plies wherein at least one of the plies is a through-air dried ply. In certain instances, the multi-ply tissue products may be converted into rolled tissue products, such as rolled bath tissue or towel products, comprising a multi-ply embossed tissue spirally wound about a core. Such rolled tissue products may comprise a plurality of connected, but perforated, multi-ply tissue sheets that may be separated from adjacent sheets.

[0052] The multi-ply embossed tissue products of the present invention generally have a total product basis weight of at least about 20 gsm, such as at least about 30 gsm, such as at least about 40 gsm, such as from about 20 to about 100 gsm, such as from about 30 to about 65 gsm, such as about 40 to about 60 gsm. In certain instances, the multi-ply embossed tissue products may comprise two, three or four tissue plies where the basis weight of each individual tissue ply is less than about 50 gsm, such as from about 10 to about 50 gsm, such as from about 20 to about 35 gsm.

[0053] The tensile strength of the multi-ply embossed tissue products of the present invention may vary depending on their intended end use and product configuration. For example, the multi-ply embossed tissue products may be intended for use as bath tissue and have a geometric mean tensile (GMT) of about 800 g / 3” or greater, such as about 900 g / 3" or greater, such as about 1,000 g / 3" or greater, such as from about 800 to about 1,700 g / 3”, such as from about 1,000 to about 1,500 g / 3”. In certain instances, the foregoing bath tissue products may comprise two, three, or four tissue plies where the GMT of each individual tissue plie is less than about 600 g / 3”, such as from about 200 to about 425 g / 3”, such as from about 350 to about 550 g / 3”.

[0054] In other instances, the multi-ply embossed tissue products may be intended for use as kitchen towels and have a GMT of about 1,500 g / 3” or greater, such as from about 1,500 g / 3” to about 3,000 g / 3". In certain instances, the foregoing tissue towel products may comprise two, three, or four tissue plies where the GMT of each individual tissue plie is about 600 g / 3” or greater, such as from about 600 to about 1,000 g / 3”.

[0055] In other instances, the multi-ply embossed tissue products of the present invention may have a sheet bulk greater than about 6.0 cc / g, such as from about 60 to about 14.0 cc / g. In certain instances, at the foregoing sheet bulks, the tissue products may have a sheet caliper greater than about 300 m,such as greater than about 400 μm, such as greater than about 500 μm, such as greater than about 600 μm, such as from about 300 to about 1,000 pm.

[0056] To produce multi-ply tissue products, multiple rolls of tissue are prepared, unwound and then combined using an embossing and lamination process. Typically, embossing is carried out in the nip between an embossing roll, and an anvil roll, also referred to herein as a counter roll. The embossing roll generally has a plurality of protrusions on its circumferential surface leading to embossments in the tissue ply. Prior to embossing, the tissue ply passes a moisturizing station where it may be treated with steam or a heated liquid thereby increasing the moisture content of the ply and its surface temperature. To that end, the moisturizing station is generally positioned upstream of the embossing nip such that the tissue ply is treated prior to being embossed. It may be desirable to arrange the moisturizing station a relatively short distances, such as a web distance less than two meters, upstream of the embossing station such that the temperature of the ply remains elevated as it is conveyed through the unheated embossing nip. In certain instances it may be preferable that the surface temperature of the ply is at least about 65 °C, such as at least about 75 °C, such as at least about 85 °C, such as from about 65 °C to about 90 °C, after treatment and that surface temperature is greater than about 30 °C as it is conveyed through the embossing nip.

[0057] One particularly preferred embossing apparatus for embossing a tissue ply according to the present invention is illustrated in FIG. 3. In the illustrated embodiment the embossing apparatus comprises an unwinding station for unwinding a first and a second tissue ply 12, 14 and a steam station 105 for wetting and heating the first tissue ply 12. In certain instances, the steam station 105 may be positioned and configured to deposit a blanket of steam on the exposed surface of the ply immediately prior to the ply 12 being conveyed through the first embossing nip 124.

[0058] The steam station may comprise a steam shower or steam nozzle which may be in the form of an elongated steam header with a series of nozzles facing the nip to discharge steam into the nip against the exposed surface of the ply. Suitable means are provided for supplying steam to the header and for example, the header may be connected to a steam supply. It may be desirable to aid in confining the steam along the surface of the ply as it travels past the nozzle by a shield which may be configured to optimize heating and moistening of the ply prior to embossing.

[0059] When the ply is blanketed with steam, a layer of steam extends along the full width of the ply and it is carried forward along with the ply and held to the surface of the ply by the pressure differential which exists across the ply surface. This layer or blanket of steam follows the ply as the ply travelsbetween the steam station and the embossing nip and continues to permeate the ply and given maximum time to heat the fibers of the ply and the moisture within the ply.

[0060] In other instances, the steam station may include a steam box disposed on one side of the ply and vacuum box disposed on the other side of the ply opposite the steam box. The steam box may be configured to deliver at a pressure ranging from about 2 pounds per squire inch (psi) to about 4 psi as the tissue ply is conveyed through the steam station and to the embossing nip. It may be preferable to configure the steam station such steam is applied to the tissue surface that will be brought into contact with a male embossing element later in the embossing process.

[0061] In still other instances the steam station may be replaced by, or augmented with, a means for delivering a heated liquid, such as water, to the ply prior to it being conveyed through the embossing nip. The heated liquid, which may have a temperature ranging from about 70 to about 100 °C, may be delivered to the ply via a shower or nozzle. The amount of heated liquid may range from about 1 to about 15 percent of the basis weight of the tissue ply, such as from about 2 to about 10 percent and more preferably from about 4 to about 8 percent. The heated liquid may be applied to the ply using any well-known method of liquid delivery such as spraying or dosing with a roller. In certain embodiments the moisturizing station comprises a liquid storage tank for receiving and storing a liquid, a means for heating a liquid disposed in the liquid storage tank and an applicator for applying a liquid stored in the storage tank to the tissue ply prior to embossing. The applicator may comprise, in certain embodiments, a nozzle system or a dosing roller system

[0062] With continued reference to FIG. 3, in the illustrated embodiment the moisturizing station comprises a single steam station 105 configured to apply steam to the bottom most surface of the ply 12, which may also be the surface brought into contact with the male embossing elements 127 as the ply is conveyed through the embossing nip 124. The invention, however, is not so limited and the moisturizing station may comprise two or more application devices, which may be configured to heat and wet one or both sides of the ply before the ply is conveyed through an embossing nip. Further, while only the first ply 12 is treated in the embodiment illustrated in FIG. 3, the first or second tissue ply may be treated, or in some instances both the first and the second tissue plies may be treated. Further, the same station may be configured to heat and moisten the ply or separate stations may be used.

[0063] In certain instances, either the first and / or the second tissue ply may be micro-embossed prior to being embossed. Processes for microembossing are well known in the art and may comprise passing a tissue ply through a micro-embossing station, which may comprise a micro-embossing cylinder and a counter cylinder facing the micro-embossing cylinder and forming micro-embossing nip therebetween.In the event a ply is microembossed, it is generally preferable that it is microembossed prior to being treated with steam or heated liquid.

[0064] With reference again to FIG. 3, after the first ply 12 is conveyed past, and treated by, the steam station 105, the heated and moisturized first ply 12 may be conveyed through an embossing nip 124 and imparted with a plurality of embossments forming an embossing pattern. The present process is well suited for use with a variety of embossing processes used in the manufacture of multi-ply tissue products, especially hygiene or wiping products such as bathroom tissue and household tissue. Suitable processes for embossing and adhesively bonding of the plies included, for example, Goffra Incolla / spot embossing, DESL (Double Embossing Single Lamination) / Nested, the “NesFip” technology as described in EP 1 081 284A1, the " NoveFip” technology as described in PCT / IB2018 / 001556 and Pin-to-Pin / Foot-to-Foot embossing. Regardless of the embossing process, it is generally preferred that at least one of the plies is treated with steam or heated liquid prior to being conveyed through an embossing nip and further that the embossing nip is unheated, such as a having a nip temperature less than about 30 °C, more preferably less than about 25 °C, and still more preferably from about 15 to about 20 °C.

[0065] With reference to FIG. 1, the embossing nip 124 is formed between an embossing roll 126 and the counter roll 128. Preferably neither the embossing roll 126 or the counter roll 128 are not heated, such that the temperature of both rolls is less than about 30 °C, more preferably less than about 25 °C, and still more preferably less than about 20°C. The embossing roll 126 comprise a plurality of male embossing elements 125 that extend from the embossing roll surface and form a pattern, which is imparted to the tissue ply as it is conveyed through the embossing nip 124. The male elements 125 may have a height, generally measured from a plane normal to the surface of the embossing roll of less than about 1.00 mm and more preferably less than about 0.80 mm, such as from about 0.50 to about 1.00 mm.

[0066] In certain instances, the counter roll 128 may comprise a substantially smooth outer surface and be constructed of steel or the like. In other instances, however, the counter roll may be covered with an elastomeric material such that the outer surface hardness ranges from approximately 40 to approximately 80 Durometer on the Shore A scale or between approximately 60 Shore A to about approximately 70 Shore A. In certain instances, it may be desirable for the counter roll 128 to comprise an elastomeric material disposed over a steel core where the elastomeric material has a thickness between about 0.375 inch to about 1 inch (about 9.5 mm to about 24.5 mm) and desirably between about 0.5 inch to about 0.625 inch (about 12.7 mm to about 15.9 mm). Typical elastomeric materials may include, for example, natural or synthetic rubber, Hypalon® from DuPont, Nitrile rubber, Poly-Urethane, Hydrogenated Nitrile, Styrene rubber and EPDM rubber.In certain embodiments, as illustrated in FIG. 3, the embossing unit is coupled with a laminating unit and together the apparatus comprises two pairs of opposed rolls 126, 128 and 146, 148 for embossing and laminating the first and second plies 12, 14 to form a multi-ply embossed tissue product 10. Generally, the first ply 12 is heated and moisturized by conveying the ply 12 past a steam station 105 and then embossed by conveying the ply through a first embossing nip 124 formed between the first pair of opposed rolls 126, 128. After the first ply 12 has been embossed it is conveyed to a second nip 150 formed between the embossing roll 126 and a marrying roll 148. The second ply 14 is also conveyed to the second nip 150 where it is joined in facing relationship with the first ply 12 as it is passed through the second nip 150.

[0067] With continued reference to FIG. 3, it may be desirable to use an adhesive to attach the first and second plies 12, 14. In the illustrated embodiment, after the ply 12 is conveyed through the embossing nip 124, it is treated with an adhesive 142 dispensed from an adhesive application unit 152. The adhesive application unit 152 may comprise an applicator roll 153, which applies adhesive 152 to those parts of the first ply 12 supported by the embossing elements 125. The adhesive 152 way be transported from an adhesive bath via one or more adhesive transfer rolls 155 to the application roll 153. The second tissue ply 14 is conveyed through the second nip 150 along with the adhesively treated and embossed first tissue ply 12 and the two plies 12, 14 are adhesively laminated in the second nip 150 between a marrying roll 148 and the embossing roll 126.

[0068] TEST METHODS

[0069] Basis Weight

[0070] Prior to testing, all samples are conditioned under TAPPI conditions (23 ± 1°C and 50 + 2 percent relative humidity) for a minimum of 4 hours. Basis weight of sample is measured by selecting twelve (12) products (also referred to as sheets) of the sample and making two (2) stacks of six (6) sheets, in the event the sample consists of perforated sheets of bath or towel tissue, the perforations must be aligned on the same side when stacking the usable units. A precision cutter is used to cut each stack into exactly 10.16 × 10.16 cm (4.0 × 4.0 inch) squares. The two stacks ofcut squares are combined to make a basis weight pad of twelve (12) squares thick. The basis weight pad is then weighed on a top loading balance with a minimum resolution of 0.01 grams. The top loading balance must be protected from air drafts and other disturbances using a draft shield. Weights are recorded when the readings on the top loading balance become constant. The mass of the sample (grams) per unit area (square meters) is calculated and reported as the basis weight, having units of grams per square meter (gsm).Caliper is measured in accordance with TAPPI test methods Test Method T 580 pm-12 " Thickness (caliper) of towel, tissue, napkin and facial products.” The micrometer used for carrying out caliper measurements is an Emveco 200-A Tissue Caliper Tester (Emveco, Inc., Newberg, OR). The micrometer has a load of 2 kilo-Pascals, a pressure foot area of 2,500 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. In certain instances, noted in the Examples, a stack of tissues comprises 12 total plies (e.g., 6 tissue products each consisting of 2-plies) was tested using the foregoing micrometer and settings. Tensile

[0071] Tensile testing is conducted on a tensile testing machine maintaining a constant rate of elongation and the width of each specimen tested is 3 inches. Testing is conducted under TAPPI conditions. Prior to testing samples are conditioned under TAPPI conditions (23 ± 1°C and 50 ± 2 percent relative humidity) for at least 4 hours and then cutting a 3 ± 0.05 inches (76.2 ± 1.3 mm) wide strip in either 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) or equivalent. The instrument used for measuring tensile strengths was an MTS Systems Sintech 11S, Serial No. 6233. The data acquisition software was MTS TestWorks® for Windows Ver. 3.10 (MTS Systems Corp., Research Triangle Park, NC). The load cell was selected from either a 50 Newton or 100 Newton maximum, depending on the strength of the sample being tested, such that the majority of peak load values fall between 10 to 90 percent of the load cell's full-scale value. The gauge length between jaws was 4 ± 0.04 inches (101.6 ± 1 mm) for facial tissue and towels and 2 ± 0.02 inches (50.8 ± 0.5 mm) for bath tissue. The crosshead speed was 10 ± 0.4 inches / min (254 ±1 mm / min), and the break sensitivity was set at 65 percent. The sample was placed in the jaws of the instrument, centered both vertically and horizontally. The test was then started and ended when the specimen broke. The peak load was recorded as either the " MD tensile strength" or the " CD tensile strength" of the specimen depending on direction of the sample being tested. Ten representative specimens were tested for each product or sheet and the arithmetic average of all individual specimen tests was recorded as the appropriate MD or CD tensile strength having units of grams per three inches (g / 3”). Tensile energy absorbed (TEA) and slope are also calculated by the tensile tester. TEA is reported in units of g‘cm / cm2and slope is recorded in units of kilograms (kg). Both TEA and Slope are directionally dependent and thus MD and CD directions are measured independently.All products were tested in their product forms without separating into individual plies. For example, a 2-ply product was tested as two plies and recorded as such. In the tensile properties of basesheets were measured, the number of plies used varied depending on the intended end use. For example, if the basesheet was intended to be used for 2-ply product, two plies of basesheet were combined and tested.

[0072] EXAMPLE

[0073] A double embossed random lamination (DERL) process, substantially as illustrated in FIG. 1, was used to evaluate the effect of heating and moisturizing a tissue ply prior to embossing with an unheated embossing unit. The upper most, or first, ply was imparted with an embossing pattern substantially similar to the pattern illustrated in FIG. 1. The bottom most, second, ply was subjected to microembossing prior to being adhesively joined to the embossed first ply as the plies passed through a joining nip formed between the embossing roll and a marrying roll. Previous attempts to emboss tissue with the pattern illustrated in FIG. 1 had required either a heated embossing nip or excessively high embossing nip pressure, such as greater than 50 kg / cm, and often resulted in excessive tensile degradation. Two different basesheets were used to produce two different multi-ply tissue products. The properties of the basesheets are summarized in Table 1, below.

[0074] TABLE 1

[0075] Basesheet Manufacturing Basis Weight Fiber MD CD Caliper Process (gsm) Furnish Tensile Tensile (pm) (N / m) (N / m)

[0076] A Uncreped 18.5 30 wt% 500 410 3700 Through-Air Dried SSWK; 70

[0077] (UCTAD) wt%

[0078] EHWK B Light Dry Creped 21.2 50 wt% 734 350 1300 SSWK; 50

[0079] wt%

[0080]

[0081] EHWK

[0082] The first ply was subjected to steam treatment by passing the ply through a steam shower approximately 1 meter (measured along the web path) prior to the embossing nip. The position of the valve controlling steam flow to the steam shower and the steam pressure were adjusted to control the level of steam added to the ply, as summarized in Tables 2 and 3 below. The temperature of the ply immediately after steam treatment and at the embossing nip are summarized in Tables 4 and 5 below. Codes denoted as 2 ply DERL UCTAD, comprised two plies of basesheet A, described above, whichwere embossed and laminated as described herein. Codes denoted as 2 ply DERL LDC comprised two plies of basesheet B, described above, which were embossed and laminated as described herein.

[0083] TABLE 2

[0084] Embossing Microembossing Steam Steam Code Nip Gap Nip Gap (mm) Valve Pressure (mm) (% Open) (psi)

[0085] 2 ply DERL 46 29 29 None None UCTAD 62 29 29 10% 2

[0086] 91 24 29 30% 2

[0087] 92 24 29 30% 4

[0088]

[0089] 93 24 29 30% 6

[0090] TABLE 3

[0091] Embossing Microembossing Steam Steam Code Nip Gap Nip Gap (mm) Valve Pressure (mm) (% Open) (psi)

[0092] 2 ply DERL 72 29 29 None None

[0093] LDC

[0094] 76 29 29 10% 2

[0095] 88 24 29 30% 2

[0096] 89 24 29 30% 4

[0097]

[0098] 90 24 29 30% 6

[0099] TABLE 4

[0100] Code Sheet temperature Sheet temperature after Sheet temperature at before steam (°C) steam (°C) embossing nip (°C)

[0101] 76 25 65 31

[0102] 88 25 73 38

[0103] 89 25 76 39

[0104]

[0105] 90 25 74 39

[0106] TABLE 5

[0107] Code Sheet temperature Sheet temperature after Sheet temperature at before steam (°C) steam (°C) embossing nip (°C) 62 25 65 29

[0108] 91 25 72 34

[0109] 92 25 73 37

[0110]

[0111] 93 25 75 37Finished, two-ply and embossed tissue products produced as described above were subjected to physical testing, as described in the Test Methods section. The results of physical testing are summarized in the tables below.

[0112] TABLE 6

[0113] Product 12 Ply CD Tensile MD MD Tensile CD

[0114] Code Caliper Caliper Degradation Tensile Degradation Tensile

[0115] (pm) (pm)

[0116] 46 371.5 2226 5033 4.80% 2120 41.80%

[0117] 62 376.5 2259 5686 7.30% 2051 41.60%

[0118] 91 368.3 2208 5912 4.10% 2230 29.30%

[0119] 92 373.3 2238 5689 3.90% 2410 33.40%

[0120]

[0121] 93 368.3 2208 5967 8.40% 2134 34.70%

[0122] TABLE 7

[0123] Product

[0124] 12 Ply Caliper MD MD Tensile CD CD Tensile Code Caliper

[0125] (pm) Tensile Degradation Tensile Degradation (pm)

[0126] 72 451.8 2706 3504 12.40% 2188 19.80% 76 524.5 3144 3675 8.13% 2449 6.20% 88 505.5 3030 3894 2.65% 2643 5.60% 89 511.8 3072 3653 8.70% 2622 3.90%

[0127]

[0128] 90 516.8 3102 3647 8.80% 2650 6.20%

Claims

We claim:

1. A method of manufacturing an embossed tissue product comprising the steps of:a. conveying a first tissue ply having a first and a second surface;b. applying steam or a heated liquid to the first or second surface of the conveyed first tissue ply to yield a heated first tissue ply having a surface temperature of at least about 60 °C;c. conveying the heated first tissue ply through a first embossing nip formed between a first embossing roll and a first counter roll wherein the surface temperature of the first embossing roll and the first counter roll is less than about 30 °C; and d. embossing the heated first tissue ply as it is conveyed through the first embossing nip to yield an embossed first tissue ply having an embossing pattern disposed thereon.

2. The method of claim 1 further comprising the steps of applying an adhesive to the surface of the embossed first tissue ply; and adhesively attaching the embossed first tissue ply to a second tissue ply.

3. The method of claim 2 further comprising the step of providing an adhesive supplying unit comprising an applicator roll for transferring an adhesive to the surface of the embossed first tissue ply, and an engraved anilox for applying the adhesive to the applicator roll.

4. The method of claim 2 wherein the embossing pattern comprises embossed portions that surround and form a pattern of discrete shapes on the first surface of the first tissue ply, the discrete shapes having a top surface lying in a first surface plane, the embossed portions forming raised areas on the second surface of the first tissue ply, an upper surface of the raised areas lying in a second surface plane that is spaced from the first surface plane; and wherein the second surface of the first tissue ply is adhered to the first surface of the second tissue ply.

5. The method of claim 4 wherein the embossed portions occupy greater than about 10% of the surface area of the second surface of the first tissue ply.

6. The method of claim 4 wherein the embossed portions form a continuous background pattern that form a perimeter around each discrete shape in the pattern.

7. The method of claim 4 wherein the discrete shapes are raised above the continuous background pattern on the first surface of the first tissue ply.

8. The method of claim 1 further comprising the step of providing a micro-embossing unit comprising a micro-embossing cylinder and a counter cylinder facing the micro-embossing cylinder to form a micro-embossing nip therebetween and conveying the first tissue ply through the micro-embossing nip prior to applying steam or a heated liquid to the first or second surface of the conveyed first tissue ply.

9. The method of claim 1 wherein the heated first tissue ply has a surface temperature ranging from about 60 °C to about 90 °C.

10. The method of claim 1 wherein the temperature of the first or second surface of the conveyed first tissue ply ranges from about 30 °C to about 50 °C as it is conveyed through the first embossing nip.

11. The method of claim 1 wherein applying steam or a heated liquid to the first or second surface of the conveyed first tissue ply increases the basis weight of the first tissue ply from about 2 to about 10 wt%.

12. An apparatus for the manufacture of a multi-ply embossed tissue product comprising:a. a first unwind for unwinding a first spirally wound tissue ply;b. a second unwind for unwinding a second spirally wound tissue ply;c. an embossing unit comprising an anvil roll and an embossing roll arranged in opposition to one another and defining an embossing nip therebetween and configured to emboss a moistened and heated tissue ply and yield an embossed tissue ply;d. a moisturizing station disposed between the first unwind and the embossing nip, the moisturizing station configured to moisten and heat at least the first or second tissue ply such that the surface of the first or second tissue ply is at least about 30 °C and the basis the basis weight of the first or second ply is increased by at least about 2 wt%.

13. The apparatus of claim 12 further comprising a lamination unit for joining the first and the second tissue plies to yield an embossed multi-ply tissue product.

14. The apparatus of claim 13 further comprising a rewinding station for rewinding said multi-ply paper.

15. The apparatus of claim 12 wherein neither the anvil roll or the embossing roll are heated either directly or indirectly.

16. The apparatus of claim 12 wherein the anvil roll or the embossing roll each have an outer surface and the outer surface of the rolls is less than about 30 °C.

17. The apparatus of claim 12 wherein the embossing unit and moisturizing unit are arranged such that the web path between the units is less than about two meters.

18. The apparatus of claim 12 wherein the moisturizing station comprises a steam shower or a steam box.

19. The apparatus of claim 18 wherein the steam shower or steam box are configured to deliver steam at a pressure ranging from about 2 pounds per square inch (psi) to about 4 psi.

20. The apparatus of claim 12 wherein the moisturizing station comprises a liquid storage tank, a means for heating a liquid disposed in the liquid storage tank and an applicator for applying a liquid stored in the storage tank to the first or second tissue ply.

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