US20040163785A1

Movatterモバイル変換

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Publication number: US20040163785A1
Application number: US10/371,546
Authority: US
Inventors: Thomas Shannon; Matthew Higgins; Bozena Nogaj; Mary Philip; Darnell Radtke
Original assignee: Kimberly Clark Worldwide Inc
Current assignee: Kimberly Clark Worldwide Inc
Priority date: 2003-02-20
Filing date: 2003-02-20
Publication date: 2004-08-26
Also published as: KR20050097980A; AU2004213832A1; WO2004074575A3; WO2004074575A2; MXPA05008245A; EP1595027A2; TW200424399A

Abstract

A tissue web and/or tissue product comprises a polysiloxane composition. The tissue web and/or tissue product has a post-aged AGAT value of about 60% or more of a pre-aged AGAT value after aging the tissue web and/or tissue product at about 25° C. for about 28 days.

Description

BACKGROUND OF THE INVENTION

Consumers use tissue products, such as facial tissues, bath tissues, and paper towels, for a wide variety of applications. Facial tissues are not only used for nose care but, in addition to other uses, may also be used as a general wiping product. Consequently, there are many different types of tissue products currently commercially available.[0001]

In some applications, tissue products are treated with lotions and/or various other additives to produce numerous desired benefits. For example, formulations containing polysiloxanes have been topically applied to tissue products in order to increase the softness of the tissue product. In particular, adding silicone compositions to a facial tissue may impart improved softness to the facial tissue while maintaining the strength of the facial tissue.[0002]

Some chemical additives, such as various softening agents including polysiloxanes, can have a tendency to impart hydrophobicity to the treated tissue web later converted into various tissue products. Increasing the hydrophobicity of a tissue product may provide various benefits and advantages. For example, treating the outside surfaces of a tissue product with a hydrophobic additive tends to trap fluids absorbed by the tissue product within the internal space of the tissue product thus slowing or preventing flow of the fluids through the tissue product. Consequently, fluids that are absorbed by the tissue product during use tend to remain captured within the tissue product instead of transferring to hands of the user.[0003]

Although hydrophobicity may be desired in some applications, increased hydrophobicity may also adversely affect the tissue product or its function. For instance, increased hydrophobicity in a tissue product, such as a facial tissue, may adversely impact upon the ability of the tissue product to absorb fluids during use, such as wiping. Hydrophobic agents may also prevent a tissue product, such as bath tissue from being wetted in a sufficient amount of time during use and prevent disintegration and dispersing of the bath tissue after use when disposed in a commode or toilet. Hence, due to the nature of hydrophobic additives, it may be difficult to find a proper balance between desired properties of a treated tissue web through the use of the hydrophobic additive and yet maintaining acceptable absorbency and wetability characteristics of the tissue web when converted into a tissue product.[0004]

In addition, the hydrophobicity benefits of polysiloxanes, such as polydialkyl polysiloxanes, are adversely affected with aging. While polydialkylsiloxanes, for example polydimethylsiloxanes, having a low degree of substitution provide softness and hydrophobicity benefits, such polysiloxanes tend to be sensitive to thermally-induced and/or time-induced hydrophobicity changes. Tissue products having a good balance of intake and strikethrough times after initial preparation of the tissue web and/or tissue product may become unsuitable for use after a period of time, even at ambient temperatures, when using polydialkylsiloxanes having a low degree of substitution.[0005]

Highly modified polysiloxanes may be used to mitigate limitations associated with hydrophobicity increases. These modifications may replace n-alkyl groups on the polysiloxane backbone with polyether or similar hydrophilic groups. While such highly modified polysiloxanes may mitigate certain hydrophobicity issues, these highly modified polysiloxanes are typically sold at a substantial cost premium to polysiloxanes having a high level of polydialkylsiloxane groups. Furthermore, the low levels of polydialkylsiloxane groups on such highly modified polysiloxanes make these highly modified polysiloxanes less effective at softening the tissue web and hence, even at high addition levels of these highly modified polysiloxanes, the resulting softness is usually inferior to that of polysiloxanes containing high levels of polydialkylsiloxane groups. It is also known to use a blend of a highly modified hydrophilic polysiloxanes in combination with a polydialkylsiloxane to mitigate certain hydrophobicity issues created with the polydialkylsiloxane. However, this is typically accomplished as a simple replacement with a reduction in the level of polydialkylsiloxane. At high levels of polydialkylsiloxane, the tissue web again typically becomes hydrophobic. Additionally, such blends tend to have enhanced instability with aging.[0006]

Hydrophobic additives may be applied topically in discrete locations on a tissue web in conjunction with relatively large untreated areas of the tissue web such that less than 50% of the surface of the tissue web is covered with the hydrophobic additive. Such discrete placement of the hydrophobic additive on the tissue web is expected to provide regions of hydrophobicity and hydrophilicity. However, such discrete placement requires a majority of the surface of the tissue web to not contain the hydrophobic additive. As a result of such application, reduced product benefits, such as softness, may be realized relative to a tissue web having a high level of surface coverage. Another disadvantage to such tissue webs is that rapid strikethrough typically occurs, hence, hydrophobicity is gained at the sacrifice of ability of the tissue web and/or tissue product to prevent fluids from rapidly transferring to the other side of the tissue web and/or tissue product.[0007]

A three ply tissue product may have an inner ply substantially free of polysiloxane in conjunction with a hydrophobic polysiloxane applied to the two outer plies of the tissue product to produce a tissue product having a combination of absorbent capacity and fluid strikethrough properties. While such a structure may address the need for improved strikethrough properties in an absorbent product, such as a tissue product, it does not address the need to have a tissue web and/or tissue product with the combination of rapid fluid intake time and strikethrough properties. Additionally, such a structure would not address the need for thermal stability with regard to the fluid intake times and strikethrough properties.[0008]

Thus, a need currently exists for polysiloxane compositions that may be applied to tissue products that provide benefits to the tissue web and/or tissue product without increasing the hydrophobicity of the tissue web and/or tissue product beyond desirable limits. There is a need for tissue webs and/or tissue products having high levels of polydialkylsiloxanes, and in particular polydimethylsiloxane, to impart high levels of softness to the tissue webs and/or tissue products and that provide rapid fluid intake while having a long strikethrough times. Furthermore, there is a need for such tissue webs and/or tissue products to have improved thermal and time stability such that the rate of fluid intake of the tissue webs and/or tissue products remains high after aging.[0009]

SUMMARY OF THE INVENTION

It has now been discovered that certain improved polydialkylsiloxanes such as DC-1149 emulsion commercially available from Dow Corning, located in Midland, Mich., may be applied to tissue webs and/or tissue products to provide tissue webs and/or tissue products having a high degree of softness, rapid water intake as determined by AGAT measurements and improved strikethrough resistance as measured by increasing HST even when such tissue webs and/or tissue products contain high levels of polydialkylsiloxanes and in particular polydimethylsiloxane. Additionally, the tissue webs and/or tissue products treated with these polysiloxane compositions show significantly more stable aging performance than traditional polydialkylsiloxanes.[0010]

In general, the present invention is directed to tissue webs and/or tissue products that have been treated with a polysiloxane composition for improving the properties of the tissue web and/or tissue product, such as wet/dry strength and softness, while maintaining acceptable wettability properties. For instance, in one embodiment, the present invention is directed to a tissue web and/or tissue product having a first outer surface and a second outer surface. The tissue web and/or tissue product may have a bulk density of about 2 cm[0011]³/g or greater, such as about 3 cm³/g or greater and may have a basis weight of from about 5 g/m²to about 200 g/m². In addition, the tissue product may be a single ply tissue product or a multi-ply tissue product. The polydialkylsiloxane content of these tissue products may range from about 0.55% to about 2% by weight of the dry tissue web.

DETAILED DESCRIPTION

Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example or embodiment is provided by way of explanation of the present invention, not limitation of the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.[0012]

It is understood that the discussion of treating the first and/or second outer surfaces of the tissue web and/or tissue product is equally applicable to other surfaces, such on interior facing surfaces of the first and second outer plies and surfaces of the inner plies.[0014]

The present invention is particularly well-suited for use in conjunction with tissue products, such as paper towel products, industrial wiper products, bath tissue products, facial tissue products, and the like. The tissue product may be a single ply tissue product or, alternatively, a multi-ply tissue product. For example, in one embodiment, the tissue product is a three-ply facial tissue product. The tissue and towel products as used herein are differentiated from other paper products in terms of their bulk. The bulk of the products of this invention is calculated as the quotient of the caliper (hereinafter defined), express in microns, divided by the basis weight, expressed in grams per square meter. The resulting bulk is expressed as cubic centimeters per gram. Writing papers, newsprint and other such papers have higher strength, stiffness, and density (low bulk) in comparison to tissue products which tend to have much higher calipers for a given basis weight. The tissue products of the present invention have a bulk of about 2 cm[0015]³/g or greater, more specifically greater than 2.5 cm³/g or greater, and still more specifically about 3 cm³/g or greater. The basis weight of the tissue product may range from about 5 g/m²to about 200 g/m², more specifically from about 7 g/m²to about 150 g/m²and even more specifically from about 10 g/m²to about 100 g/m².

The polysiloxane compositions of the present invention may be delivered as aqueous dispersions, emulsions, including microemulsions, stabilized by suitable surfactant systems that may confer a charge to the emulsion micelles. Nonionic, cationic, and anionic systems may be employed. The polysiloxane compositions may also be delivered as neat fluids.[0017]

The method by which the polysiloxane composition is applied to the tissue web and/or tissue product is not overly critical to the invention. The application of a polysiloxane composition of the present invention to a tissue web and/or tissue product may be accomplished by any method known in the art including, but not limited to:[0018]

Contact printing methods such as gravure, offset gravure, flexographic printing and the like.[0019]

A spray applied to a tissue web and/or tissue product. For example, spray nozzles may be mounted over a moving tissue web to apply a desired dose of a solution to the tissue web and/or tissue product. Nebulizers may also be used to apply a light mist to a surface of a tissue web and/or tissue product.[0020]

Non-contact printing methods such as ink jet printing, digital printing of any kind, and the like.[0021]

Coating onto one or both surfaces of the a tissue web and/or tissue product, such as blade coating, air knife coating, short dwell coating, cast coating, and the like. The tissue web may or may not be moist.[0022]

Extrusion from a die head such as UFD spray tips, such as those available from ITW-Dynatec located at Henderson, Tenn., of the polysiloxane composition in the form of a solution, a dispersion or emulsion, or a viscous mixture.[0023]

Impregnation of the wet tissue web with a solution or slurry, wherein the polysiloxane composition penetrates a significant distance into the thickness of the tissue web, such as about 20% or more of the thickness of the tissue web, more specifically about 30% or more of the thickness of the tissue web, and most specifically about 70% or more of the thickness of the tissue web, including completely penetrating the tissue web throughout the full extent of its thickness. One useful method for impregnation of a moist tissue web is the Hydra-Sizer® system, produced by Black Clawson Corp., Watertown, N.Y., as described in “New Technology to Apply Starch and Other Additives,” Pulp and Paper Canada, 100(2): T42-T44 (February 1999). This system consists of a die, an adjustable support structure, a catch pan, and an additive supply system. A thin curtain of descending liquid or slurry is created which contacts the moving tissue web beneath it. The system may also be applied to curtain coat a relatively dry tissue web, such as a tissue web just before or after creping.[0024]

Foam application of the polysiloxane composition to the tissue web (e.g., foam finishing), either for topical application or for impregnation of the polysiloxane composition into the tissue web under the influence of a pressure differential (e.g., vacuum-assisted impregnation of the foam). Principles of foam application of additives such as binders and polysiloxanes are described in U.S. Pat. No. 4,297,860, issued on Nov. 3, 1981 to Pacifici et al. and U.S. Pat. No. 4,773,110, issued on Sep. 27, 1988 to G. J. Hopkins, both of which are herein incorporated by reference to the extent that they are non-contradictory herewith.[0025]

Application of the polysiloxane composition by spray or other means to a moving belt or fabric which in turn contacts the tissue web and/or tissue product to apply the polysiloxane composition to the tissue web and/or tissue product, such as is disclosed in WO 01/49937 under the name S. Eichhorn, published on Jun. 12, 2001.[0026]

The particular structure of the polysiloxanes used in the polysiloxane compositions of the present invention may provide the desired product properties to the tissue web and/or tissue product. Polysiloxanes encompass a very broad class of compounds. It is understood that the term “polysiloxane composition” as used herein refers to neat polysiloxane or mixtures of polysiloxanes and polysiloxanes in combination with other components. They are characterized in having a backbone structure:[0027]
where R′ and R″ may be a broad range of organo and non-organo groups including mixtures of such groups and where n is an integer≧2. These polysiloxanes may be linear, branched, or cyclic. They may include a wide variety of polysiloxane copolymers containing various compositions of functional groups, hence, R′ and R″ actually may represent many different types of groups within the same polymer molecule. The organo or non-organo groups may be capable of reacting with pulp fibers to covalently, ionically or hydrogen bond the polysiloxane to the pulp fibers. These functional groups may also be capable of reacting with themselves to form crosslinked matrixes with the pulp fibers.[0028]
While the scope of the present invention should not be construed as limited by a particular polysiloxane structure so long as that polysiloxane structure delivers the aforementioned tissue product benefits to the tissue web and/or the final tissue product, the soft tissue webs and/or tissue products may contain a certain level of polydialkylsiloxane. The term “polydialkylsiloxanes” as used herein refers to the portion of the polysiloxane molecule as defined above wherein R′ and R″ are C[0029]₁-C₃₀aliphatic hydrocarbon groups. In one embodiment of the present invention, R′ and R″ may be methyl groups. Functionalized polysiloxanes containing polydialkylsiloxane units may be used for the purposes of the present invention. A variety of functional groups may be present on the polymer besides the dialkylsiloxane units. A combination of polysiloxanes may also be used to create the desired products. For example an aminofunctional polysiloxane may be combined with an epoxyglycol-co-polyether polysiloxane. An example of such materials are the DC-8500 and DC-8600 fluids commercially available from Dow Corning, Midland, Mich.
In another embodiment of the present invention, a portion of the polysiloxane may be selected from the group of so called “amino functional” functional polysiloxanes of the general formula:[0030]
Wherein, x and y are integers>0. The mole ratio of x to (x+y) may be from about 0.005 percent to about 30 percent. The R[0031]¹-R⁶moieties may be independently any monovalent organic group including C, or higher alkyl groups, ethers, polyethers, polyesters, amines, imines, amides, or other functional groups including the alkyl and alkenyl analogues of such groups, a hydroxyl group or an alkoxy group. R⁷and R⁸and R⁹may be independently a C₁-C₃₀aliphatic hydrocarbon group. The R¹⁰moiety may be an amino functional hydrocarbon moiety including but not limited to primary amine, secondary amine, tertiary amines, quaternary amines, heterocyclic amines, unsubstituted amides and mixtures thereof. An exemplary R¹⁰moiety may contain one amine group per constituent or two or more amine groups per substituent, separated by a linear or branched alkyl chain of C¹or greater. The R¹⁰group may contain heterocyclic rings, amphiphilic groups or other functionality in addition to the nitrogen functionality.
Another class of functionalized polysiloxanes that may be suitable for use in the present invention is the polyether polysiloxanes. They may be used alone or in conjunction with other polysiloxanes such as the aforementioned amino-functional polysiloxanes. Such polysiloxanes generally may have the following structure:[0032]
wherein, x and z are integers>0. y is an integer≧0. The mole ratio of x to (x+y+z) may be from about 5 percent to about 95 percent. The ratio of y to (x+y+z) may be from about 0 percent to about 25%. The R[0033]⁰-R⁶moieties may be independently —OH, alkoxy or any organofunctional group including C₁or higher alkyl groups, ethers, polyethers, polyesters, amines, imines, amides, or other functional groups including the alkyl and alkenyl analogues of such groups. R⁷and R⁸may be C₁-C₃₀aliphatic alkyl groups including mixtures of these groups. The R¹⁰moiety may be an amino functional moiety including, but not limited to, primary amine, secondary amine, tertiary amines, quaternary amines, unsubstituted amides, and mixtures thereof. An exemplary R¹⁰moiety may contain one amine group per constituent or two or more amine groups per substituent, separated by a linear or branched alkyl chain of C¹or greater. R¹¹may be a polyether functional group having the generic formula: —R¹²—(R¹³—O)^a—(R¹⁴O)_b—R¹⁵, wherein R¹², R¹³, and R¹⁴may be independently C_1-4alkyl groups, linear or branched; R¹⁵may be H or a C_1-30alkyl group; and, “a” and “b” are integers of from about 1 to about 100, more specifically from about 5 to about 30. R₁₀may also be a epoxy functional group or a polyhydroxy functional group used in combination with a polyether functional group. The ratios of polyether, epoxy, polyhydroxy and amine groups may be controlled to give the specific product benefits of the present invention.
The amount of polydialkylsiloxane in the tissue web and/or tissue product may be determined by conversion of the polydialkylsiloxane components to the diflourodialkylsilanes with boron triflouride as hereinafter described. The amount of diflourodialkylsilane may be measured using gas chromatography to determine the total amount of polydialkylsiloxane in the tissue web and/or tissue product. The amount of polydialkylsiloxane in the tissue web and/or tissue product may about 0.55% or greater in one embodiment of the present invention. In another embodiment of the present invention, the amount of polydialkylsiloxane in the tissue web and/or tissue product may be about 0.6% or greater. In still another embodiment of the present invention, the amount of polydialkylsiloxane in the tissue web and/or tissue product may be about 0.7% or greater.[0034]
While not wishing to be bound by theory, the benefits that polysiloxanes and polysiloxane compositions deliver to pulp fiber containing tissue webs and/or tissue products is believed to be, in part, related to the molecular weight of the polysiloxane. Viscosity is often used as an indication of molecular weight of the polysiloxane as exact number or weight average molecular weights are often difficult to determine. In various embodiments of the present invention where the intent is to deliver softness benefits through use of the polysiloxane and/or polysiloxane compositions, the viscosity of the polysiloxanes is about 25 centipoise or greater, in another embodiment of the present invention, about 50 centipoise or greater, and in still another embodiment of the present invention, about 100 centipoise or greater. The term “viscosity” as referred to herein refers to the viscosity of the neat polysiloxane itself and not to the viscosity of an emulsion and/or composition if so delivered. It should also be understood that the polysiloxanes of the present invention may be delivered as solutions containing diluents. Such diluents may lower the viscosity of the solution below the limitations set above, however, the efficacious part of the polysiloxane should conform to the viscosity ranges given above. Examples of such diluents include but is not limited to oligomeric and cyclo-oligomeric polysiloxanes such as octamethylcyclotetrasiloxane, octamethyltrisiloxane, decamethylcyclopentasiloxane, decamethyltetrasiloxane and the like including mixtures of these compounds.[0035]
Additional additives may be incorporated within the polysiloxane composition without deviating from the spirit of the present invention. For example, possible additional chemical additives that may be incorporated within the polysiloxane compositions that may be applied to tissue webs and/or tissue products in accordance with the present invention include, without limitation, debonders, anti-acne actives, antimicrobial actives, antifungal actives, antiseptic actives, antioxidants, cosmetic astringents, drug astringents, biological additives, deodorants, emollients, external analgesics, binders, film formers, fragrances, and other skin moisturizing ingredients known in the art, opacifiers, skin conditioning agents, skin exfoliating agents, skin protectants, sunscreens and the like.[0036]
The tissue product may be any suitable tissue product, such as a paper towel, a wiper, a bath tissue, a facial tissue and the like. The tissue web utilized in producing the tissue products of the present invention may be creped or uncreped as well as blended or layered. The tissue products may be single ply or multi-ply tissue products. The tissue product of the present invention may be blended, layered, or any combination thereof. In addition, the tissue products may be creped, uncreped, or any combination thereof. In other embodiments of the present invention, the tissue web may be made via a hydroentangling process, an air laid process, or other methods known in the art.[0037]
The single or multi-ply tissue web and/or tissue product may be made by any method known in the art. For example, the tissue sheet may be made via a wetlaid process, wherein a dilute aqueous pulp fiber slurry is disposed on a moving wire to filter out the pulp fibers and form an embryonic tissue web which is subsequently dewatered by combinations of units including suction boxes, wet presses, dryer units, and the like. Examples of known dewatering and other operations are given in U.S. Pat. No. 5,656,132, issued on Aug. 12, 1997 to Farrington, Jr. et al. Capillary dewatering may also be applied to remove water from the tissue web, as disclosed in U.S. Pat. No. 5,598,643, issued on Feb. 4, 1997 and U.S. Pat. No. 4,556,450, issued on Dec. 3, 1985, both to S. C. Chuang et al., the disclosures of both which are herein incorporated by reference to the extent that they are non-contradictory herewith.[0038]
For the tissue webs and/or tissue products of the present invention, both creped and uncreped methods of manufacture may be used. Uncreped tissue production is disclosed in U.S. Pat. No. 5,772,845, issued on Jun. 30, 1998 to Farrington, Jr. et al., the disclosure of which is herein incorporated by reference to the extent it is non-contradictory herewith. Creped tissue production is disclosed in U.S. Pat. No. 5,637,194, issued on Jun. 10, 1997 to Ampulski et al.; U.S. Pat. No. 4,529,480, issued on Jul. 16, 1985 to Trokhan; U.S. Pat. No. 6,103,063, issued on Aug. 15, 2000 to Oriaran et al.; and, U.S. Pat. No. 4,440,597, issued on Apr. 3, 1984 to Wells et al., the disclosures of all of which are herein incorporated by reference to the extent that they are non-contradictory herewith. Also suitable for application of the above mentioned polysiloxanes and/or polysiloxane compositions are tissue webs and/or tissue products that are pattern densified or imprinted, such as the webs disclosed in any of the following U.S. Pat. No.: 4,514,345, issued on Apr. 30, 1985 to Johnson et al.; U.S. Pat. No. 4,528,239, issued on Jul. 9, 1985 to Trokhan; U.S. Pat. No. 5,098,522, issued on Mar. 24, 1992; U.S. Pat. No. 5,260,171, issued on Nov. 9, 1993 to Smurkoski et al.; U.S. Pat. No. 5,275,700, issued on Jan. 4, 1994 to Trokhan; U.S. Pat. No. 5,328,565, issued on Jul. 12, 1994 to Rasch et al.; U.S. Pat. No. 5,334,289, issued on Aug. 2, 1994 to Trokhan et al.; U.S. Pat. No. 5,431,786, issued on Jul. 11, 1995 to Rasch et al.; U.S. Pat. No. 5,496,624, issued on Mar. 5, 1996 to Steltjes, Jr. et al.; U.S. Pat. No. 5,500,277, issued on Mar. 19, 1996 to Trokhan et al.; U.S. Pat. No. 5,514,523, issued on May 7, 1996 to Trokhan et al.; U.S. Pat. No. 5,554,467, issued on Sep. 10, 1996 to Trokhan et al.; U.S. Pat. No. 5,566,724, issued on Oct. 22, 1996 to Trokhan et al.; U.S. Pat. No. 5,624,790, issued on Apr. 29, 1997 to Trokhan et al.; and, U.S. Pat. No. 5,628,876, issued on May 13, 1997 to Ayers et al., the disclosures of all of which are herein incorporated by reference to the extent that they are non-contradictory herewith. Such imprinted tissue webs and/or tissue products may have a network of densified regions that have been imprinted against a drum dryer by an imprinting fabric, and regions that are relatively less densified (e.g., “domes” in the tissue sheet) corresponding to deflection conduits in the imprinting fabric, wherein the tissue sheet superimposed over the deflection conduits was deflected by an air pressure differential across the deflection conduit to form a lower-density pillow-like region or dome in the tissue web and/or tissue product.[0039]
Various drying operations may be useful in the manufacture of the tissue webs and/or tissue products of the present invention. Examples of such drying methods include, but are not limited to, drum drying, through drying, steam drying such as superheated steam drying, displacement dewatering, Yankee drying, infrared drying, microwave drying, radiofrequency drying in general, and impulse drying, as disclosed in U.S. Pat. No. 5,353,521, issued on Oct. 11, 1994 to Orloff and U.S. Pat. No. 5,598,642, issued on Feb. 4, 1997 to Orloff et al., the disclosures of both which are herein incorporated by reference to the extent that they are non-contradictory herewith. Other drying technologies may be used, such as methods employing differential gas pressure include the use of air presses as disclosed U.S. Pat. No. 6,096,169, issued on Aug. 1, 2000 to Hermans et al. and U.S. Pat. No. 6,143,135, issued on Nov. 7, 2000 to Hada et al., the disclosures of both which are herein incorporated by reference to the extent they are non-contradictory herewith. Also relevant are the paper machines disclosed in U.S. Pat. No. 5,230,776, issued on Jul. 27, 1993 to I. A. Andersson et al.[0040]
A wide variety of natural and synthetic pulp fibers are suitable for use in the tissue webs and/or tissue products of the present invention. The pulp fibers may include fibers formed by a variety of pulping processes, such as kraft pulp, sulfite pulp, thermomechanical pulp, etc. In addition, the pulp fibers may consist of any high-average fiber length pulp, low-average fiber length pulp, or mixtures of the same.[0041]
One example of suitable high-average length pulp fibers include softwood fibers. Softwood pulp fibers are derived from coniferous trees and include pulp fibers such as, but not limited to, northern softwood, southern softwood, redwood, red cedar, hemlock, pine (e.g., southern pines), spruce (e.g., black spruce), combinations thereof, and the like. Northern softwood kraft pulp fibers may be used in the present invention. One example of commercially available northern softwood kraft pulp fibers suitable for use in the present invention include those available from Kimberly-Clark Corporation located in Neenah, Wis. under the trade designation of “Longlac-19”.[0042]
Another example of suitable low-average length pulp fibers are the so called hardwood pulp fibers. Hardwood pulp fibers are derived from deciduous trees and include pulp fibers such as, but not limited to, eucalyptus, maple, birch, aspen, and the like. In certain instances, eucalyptus pulp fibers may be particularly desired to increase the softness of the tissue sheet. Eucalyptus pulp fibers may also enhance the brightness, increase the opacity, and change the pore structure of the tissue sheet to increase its wicking ability. Moreover, if desired, secondary pulp fibers obtained from recycled materials may be used, such as fiber pulp from sources such as, for example, newsprint, reclaimed paperboard, and office waste.[0043]
The overall ratio of hardwood pulp fibers to softwood pulp fibers within the tissue product may vary broadly. The ratio of hardwood pulp fibers to softwood pulp fibers may range from about 9:1 to about 1:9, more specifically from about 9:1 to about 1:4, and most specifically from about 9:1 to about 1:1. In one embodiment of the present invention, the hardwood pulp fibers and softwood pulp fibers may be blended prior to forming the tissue web and/or tissue product thereby producing a homogenous distribution of hardwood pulp fibers and softwood pulp fibers in the z-direction of the tissue web and/or tissue product. In another embodiment of the present invention, the hardwood pulp fibers and softwood pulp fibers may be layered so as to give a heterogeneous distribution of hardwood pulp fibers and softwood pulp fibers in the z-direction of the tissue web and/or tissue product. In another embodiment, the hardwood pulp fibers may be located in at least one of the outer layers of the tissue web and/or tissue product wherein at least one of the inner layers may comprise softwood pulp fibers.[0044]
In addition, synthetic fibers may also be utilized in the tissue webs and/or tissue products of the present invention. The discussion herein regarding pulp fibers is understood to include synthetic fibers. Some suitable polymers that may be used to form the synthetic fibers include, but are not limited to: polyolefins, such as, polyethylene, polypropylene, polybutylene, and the like; polyesters, such as polyethylene terephthalate, poly(glycolic acid) (PGA), poly(lactic acid) (PLA), poly(β-malic acid) (PMLA), poly(ε-caprolactone) (PCL), poly(ρ-dioxanone) (PDS), poly(3-hydroxybutyrate) (PHB), and the like; and, polyamides, such as nylon and the like. Synthetic or natural cellulosic polymers, including but not limited to: cellulosic esters; cellulosic ethers; cellulosic nitrates; cellulosic acetates; cellulosic acetate butyrates; ethyl cellulose; regenerated celluloses, such as viscose, rayon, and the like; cotton; flax; hemp; and mixtures thereof may be used in the present invention. The synthetic fibers may be located in any or all of the tissue webs and/or tissue products as well as in any or all layers of specific tissue plies.[0045]
In one embodiment, the tissue webs and/or tissue products treated in accordance with the present invention may have a stratified pulp fiber furnish. For example, in one embodiment of the present invention, the tissue web and/or tissue product may have a middle layer of softwood pulp fibers positioned in between outer layers of hardwood pulp fibers. If desired, each of the layers may also contain paper broke. In one particular embodiment of the present invention, a stratified pulp fiber furnish may include an outer layer of hardwood pulp fibers, a middle layer of softwood pulp fibers and paper broke, and a second outer layer of a mixture of hardwood pulp fibers and softwood pulp fibers. In still another embodiment of the present invention, the stratified pulp fiber furnish may include two outer layers of a mixture of hardwood pulp fibers and paper broke. The pulp fiber furnish may further include a middle layer of softwood pulp fibers positioned in between the outside layers.[0046]
The term “caliper” as used herein is the thickness of a single sheet of tissue web and/or single ply of a tissue product and may either be measured as the thickness of a single sheet of the tissue web and/or tissue product or as the thickness of a stock of ten sheets of the tissue web and/or tissue product and dividing the ten sheet thickness by ten, where each sheet of the tissue web and/or tissue product within the stack is placed with the same side up. Caliper is expressed in microns. It is measured in accordance with TAPPI test methods T402 ‘Standard Conditioning and Testing Atmosphere For Paper, Board, Pulp Handsheets and Related Products” and T411 om-89 “Thickness (caliper) of Paper, Paperboard, and Combined Board” optionally with Note 3 for stacked sheets. The micrometer used for carrying out T411 om-89 is a Bulk Micrometer (TMI Model 49-72-00, Amityville, N.Y.) or equivalent having an anvil diameter of 4 {fraction (1/16)} inches (103.2 millimeters) and an anvil pressure of 220 grams/square inch (3.3 kilo Pascals).[0047]
In one embodiment of the present invention, the polysiloxane composition is applied uniformly to the tissue web and/or tissue product such that about 60% or greater of the surface area of at least one treated surface of the tissue web and/or tissue product is covered. In another embodiment of the present invention, the polysiloxane composition is applied uniformly to the tissue web and/or tissue product such that about 70% or greater of the surface area of at least one treated surface of the tissue web and/or tissue product is covered. Where uniform discrete deposits of the polysiloxane composition are used, the frequency of such deposits are typically about 100 dpi or greater in both MD and CD directions. In another embodiment of the present invention, the frequency of such deposits may be about 200 dpi or greater in the MD and/or CD directions. In other embodiments of the present invention, the frequency of such deposits may be about 300 dpi or greater in the MD and/or CD directions.[0048]
In some embodiments of the present invention, the tissue webs and/or tissue products may be topically treated with a polysiloxane composition, such as a polysiloxane composition containing a polydialkylsiloxane. For example, in one embodiment, the polysiloxane composition may comprise a polydimethylsiloxane. The total amount of polydialkylsiloxane shall be at least 0.6% by weight of the dry tissue, more specifically greater than about 0.7% by weight of the dry tissue. The amount of polydialkylsiloxane is determined from the GC-BF[0049]₃method. If polyalkylsiloxanes other than polydimethylsiloxane are used the GC-BF₃method is adapted to measure total polydialkylsiloxane and not just polydimethylsiloxane.
As explained above, the polysiloxane compositions and other chemical additives are typically used sparingly in some applications due to their hydrophobicity. For, instance, problems have been experienced in applying polysiloxane softeners to bath tissue products due to the adverse impact upon the wetability of the bath tissue products. By applying the polysiloxane compositions according to the present invention, it has been discovered that polysiloxane compositions may be applied to tissue webs and/or tissue products for improving the properties of the tissue webs and/or tissue products while maintaining acceptable wetability properties.[0050]
The term “fluid strikethrough” refers to the ability of the fluid being absorbed to pass from one side of the tissue web and/or tissue product to the other side of the tissue web and/or tissue product. While tissue web and/or tissue products are expected to be absorbent, it is desirable that such tissue web and/or tissue products prevent the passage of the fluid from contacting the user's hand. The ability of a tissue web and/or tissue product to absorb fluids quickly may be measured by its wet out time described hereinafter. The strikethrough property of the tissue web and/or tissue product may be measured using the Hercules Size Test (HST) also described hereinafter. For instance, in one embodiment of the present invention, a tissue web and/or tissue product may be formed having an HST value of about 3 seconds or greater and more specifically about 4 seconds or greater.[0051]
Also in accordance with the present invention, the tissue webs and/or tissue products of the present invention may have a high thermal stability relative to fluid intake times. One of the issues with using polysiloxanes having a high polydialkylsiloxane content is the tendency of the hydrophobicity of tissue webs and/or tissue products treated with such polysiloxanes to increase to unacceptable limits upon aging even at ambient temperatures. The level of instability is temperature dependent and the hydrophobicity effects are found to increase significantly with temperature. The tissue webs and/or tissue products of the present invention may have improved stability relative to tissue webs and/or tissue products having similar levels of polydialkylsiloxanes.[0052]
The tissue webs and/or tissue products of the present invention may have AGAT values of about 0.5 g[0053]^1/2or greater, more specifically about 0.55 g^1/2or greater, and still more specifically about 0.6 g/g/s^1/2or greater after aging about 2 weeks at 40° C. The tissue webs and/or tissue products may have HST values of about 4 or greater and more specifically about 5 or greater after aging about 2 weeks at about 40° C. The AGAT values of the tissue webs and/or tissue products after aging at about 25° C. for about 4 weeks or longer may be about 0.6 g/g/s^1/2or greater, more specifically about 0.7 g/g/s^1/2or greater and still more specifically about 0.8 g/g/s^1/2or greater. The HST values of the webs and/or tissue products aged at about 25° C. for about 4 weeks or longer may be about 3 seconds or greater, and more specifically about 4 seconds or greater. Specifically the tissue webs and/or tissue products of the present invention retain at least about-60% of their pre-aged AGAT value after aging the tissue web and/or tissue product at about 25° C. for about 28 days, more specifically they retain at least about 65% of their pre-aged AGAT value and still more specifically at least about 70% of their pre-aged AGAT value. At 40° C., the tissue webs and/or tissue products of the present invention retain at least about 30% of their presaged AGAT value after 2 weeks and more specifically at least about 35% of their presaged AGAT value.
As described above, tissue webs and/or tissue products made in accordance with the present invention exhibit a beneficial combination of properties. In particular, not only do the tissue webs and/or tissue products enjoy the benefits of the chemical additives that are typically applied to the tissue web and/or tissue product, but the tissue webs and/or tissue products also maintain acceptable wetability characteristics and strike through characteristics.[0054]
Additional Chemical Additives[0055]
Optional chemical additives may also be added to the aqueous papermaking furnish prior to forming the tissue web or to the embryonic tissue web to impart additional benefits to the tissue web and/or tissue product and process and are not antagonistic to the intended benefits of the present invention. The following materials are included as examples of additional chemical additives that may be applied to the tissue web and/or tissue product along with the polysiloxane compositions of the present invention. The chemical additives are included as examples and are not intended to limit the scope of the present invention. Such chemical additives may be added at any point in the papermaking process including with the polysiloxane composition. The chemical additives may be blended with the polysiloxane compositions of the present invention or as separate chemical additives.[0056]
Charge Control Agents[0057]
Charge promoters and control agents are commonly used in the papermaking process to control the zeta potential of the papermaking furnish in the wet end of the process. These species may be anionic or cationic, most usually cationic, and may be either naturally occurring materials such as alum or low molecular weight high charge density synthetic polymers typically of molecular weight of about 500,000 or less. Drainage and retention aids may also be added to the furnish to improve formation, drainage and fines retention. Included within the retention and drainage aids are microparticle systems containing high surface area, high anionic charge density materials.[0058]
Strength Agents[0059]
Wet and dry strength agents may also be applied to the tissue web and/or tissue product. As used herein, “wet strength agents” refer to materials used to immobilize the bonds between pulp fibers in the wet state. Typically, the means by which pulp fibers are held together in tissue webs and/or tissue products involve hydrogen bonds and sometimes combinations of hydrogen bonds and covalent and/or ionic bonds. In the present invention, it may be useful to provide a strength agent that will allow bonding of pulp fibers in such a way as to immobilize the fiber-to-fiber bond points and make the pulp fibers resistant to disruption in the wet state. In this instance, the wet state typically means when the tissue web and/or tissue product is largely saturated with water or other aqueous fluids and/or solutions, but could also mean significant saturation with body fluids such as urine, blood, mucus, menses, runny bowel movement, lymph, and other body exudates.[0060]
Any strength agent material that when added to a tissue web and/or tissue product results in providing the tissue web and/or tissue product with a mean wet geometric tensile strength:dry geometric tensile strength ratio in excess of about 0.1 will, for purposes of the present invention, be termed a wet strength agent. Typically these materials are termed either as permanent wet strength agents or as “temporary” wet strength agents. For the purposes of differentiating permanent wet strength agents from temporary wet strength agents, the permanent wet strength agents will be defined as those resins which, when incorporated into tissue webs and/or tissue products, will provide a tissue web and/or tissue product that retains more than 50% of its original wet strength after exposure to water for a period of at least five minutes. Temporary wet strength agents are those which show about 50% or less than, of their original wet strength after being saturated with water for five minutes. Both classes of wet strength agents find application in the present invention. The amount of wet strength agent added to the pulp fibers may be at least about 0.1 dry weight percent, more specifically about 0.2 dry weight percent or greater, and still more specifically from about 0.1 to about 3 dry weight percent, based on the dry weight of the pulp fibers.[0061]
Permanent wet strength agents will typically provide a more or less long-term wet resilience to the structure of a tissue web and/or tissue product. In contrast, the temporary wet strength agents will typically provide tissue web and/or tissue product structures that had low density and high resilience, but would not provide a structure that had long-term resistance to exposure to water or body fluids.[0062]
Wet and Temporary Wet Strength Agents[0063]
The temporary wet strength agents may be cationic, nonionic or anionic. Such compounds include PAREZ™ 631 NC and PAREZ® 725 temporary wet strength resins that are cationic glyoxylated polyacrylamide available from Cytec Industries (West Paterson, N.J.). This and similar resins are described in U.S. Pat. No. 3,556,932, issued on Jan. 19, 1971 to Coscia et al. and U.S. Pat. No. 3,556,933, issued on Jan. 19, 1971 to Williams et al. Hercobond 1366, manufactured by Hercules, Inc., located at Wilmington, Del., is another commercially available cationic glyoxylated polyacrylamide that may be used in accordance with the present invention. Additional examples of temporary wet strength agents include dialdehyde starches such as Cobond® 1000 from National Starch and Chemical Company and other aldehyde containing polymers such as those described in U.S. Pat. No. 6,224,714, issued on May 1, 2001 to Schroeder et al.; U.S. Pat. No. 6,274,667, issued on Aug. 14, 2001 to Shannon et al.; U.S. Pat. No. 6,287,418, issued on Sep. 11, 2001 to Schroeder et al.; and, U.S. Pat. No. 6,365,667, issued on Apr. 2, 2002 to Shannon et al., the disclosures of which are herein incorporated by reference to the extend they are non-contradictory herewith.[0064]
Permanent wet strength agents comprising cationic oligomeric or polymeric resins can be used in the present invention. Polyamide-polyamine-epichlorohydrin type resins such as KYMENE 557H sold by Hercules, Inc., located at Wilmington, Del., are the most widely used permanent wet-strength agents and are suitable for use in the present invention. Such materials have been described in the following U.S. Pat. No.: 3,700,623, issued on Oct. 24, 1972 to Keim; U.S. Pat. No. 3,772,076, issued on Nov. 13, 1973 to Keim; U.S. Pat. No. 3,855,158, issued on Dec. 17, 1974 to Petrovich et al.; U.S. Pat. No. 3,899,388, issued on Aug. 12, 1975 to Petrovich et al.; U.S. Pat. No. 4,129,528, issued on December 12, 1978 to Petrovich et al.; U.S. Pat. No. 4,147,586, issued on Apr. 3, 1979 to Petrovich et al.; and, U.S. Pat. No. 4,222,921, issued on Sep. 16, 1980 to van Eenam. Other cationic resins include polyethylenimine resins and aminoplast resins obtained by reaction of formaldehyde with melamine or urea. It is often advantageous to use both permanent and temporary wet strength resins in the manufacture of tissue products with such use being recognized as falling within the scope of the present invention.[0065]
Dry Strength Agents[0066]
Dry strength agents may also be applied to the tissue web and/or tissue product without affecting the performance of the disclosed polysiloxane compositions of the present invention. Such materials used as dry strength agents are well known in the art and include but are not limited to modified starches and other polysaccharides such as cationic, amphoteric, and anionic starches and guar and locust bean gums, modified polyacrylamides, carboxymethylcellulose, sugars, polyvinyl alcohol, chitosans, and the like. Such dry strength agents are typically added to a fiber slurry prior to tissue web formation or as part of the creping package. It may at times, however, be beneficial to blend the dry strength agent with the polysiloxane compositions of the present invention and apply the two chemicals simultaneously to the tissue web and/or tissue product.[0067]
Additional Softening Agents[0068]
At times it may be advantageous to add additional debonders or softening chemistries to a tissue web and/or tissue product. Examples of such debonders and softening chemistries are broadly taught in the art. Exemplary compounds include the simple quaternary ammonium salts having the general formula (R[0069]^1′)_4-b—N⁺—(R^1″)_bX⁻ wherein R^1′ is a C_1-6alkyl group, R^1″ is a C₁₄-C₂₂alkyl group, b is an integer from 1 to 3 and X- is any suitable counterion. Other similar compounds include the monoester, diester, monoamide and diamide derivatives of the simple quaternary ammonium salts. A number of variations on these quaternary ammonium compounds are known and should be considered to fall within the scope of the present invention. Additional softening compositions include cationic oleyl imidazoline materials such as methyl-1-oleyl amidoethyl-2-oleyl imidazolinium methylsulfate commercially available as Mackernium DC-1 83 from McIntyre Ltd., located in University Park, Ill. and ProsoftTQ-1003 available from Hercules, Inc. Such softeners may also incorporate a humectant or a plasticizer such as a low molecular weight polyethylene glycol (molecular weight of about 4,000 daltons or less) or a polyhydroxy compound such as glycerin or propylene glycol. While these softeners may be applied to the fibers while in slurry prior to web formation, the polysiloxane compositions of the present invention typically provide sufficient debonding and softness improvement so as not to require use of additional bulk softening agents.
Miscellaneous Agents[0070]
It may be desirable to treat a tissue web and/or tissue product with additional types of chemical additives. Such chemical additives include, but are not limited to, absorbency aids usually in the form of cationic, anionic, or non-ionic surfactants, humectants and plasticizers such as low molecular weight polyethylene glycols and polyhydroxy compounds such as glycerin and propylene glycol.[0071]
In general, the polysiloxane compositions of the present invention may be used in conjunction with any known materials and chemical additives that are not antagonistic to its intended use. Examples of such materials and chemical additives include, but are not limited to, odor control agents, such as odor absorbents, activated carbon fibers and particles, baby powder, baking soda, chelating agents, zeolites, perfumes or other odor-masking agents, cyclodextrin compounds, oxidizers, and the like. Superabsorbent particles, synthetic fibers, or films may also be employed. Additional options include cationic dyes, optical brighteners, polysiloxanes and the like. A wide variety of other materials and chemical additives known in the art of papermaking and tissue production may be included in the tissue webs and/or tissue products of the present invention including lotions and other materials providing skin health benefits.[0072]
The application point for such materials and chemical additives is not particularly relevant to the present invention and such materials and chemicals may be applied at any point in the tissue manufacturing process. This includes pre-treatment of pulp, co-application in the wet end of the process, post treatment after drying but on the tissue machine and topical post treatment.[0073]

Analytical Test Methods

Basis Weight:[0074]

The basis weight and bone dry basis weight of the tissue sheet specimens was determined using a modified TAPPI T410 procedure. As is basis weight samples were conditioned at 23° C.±1° C. and 50±2% relative humidity for a minimum of 4 hours. After conditioning a stack of 16—3″×3″ samples was cut using a die press and associated die. This represents a tissue sheet sample area of 144 in[0075]². Examples of suitable die presses are TMI DGD die press manufactured by Testing Machines, Inc., Islandia, N.Y., or a Swing Beam testing machine manufactured by USM Corporation, Wilmington, Md. Die size tolerances are ±0.008 inches in both directions. The specimen stack is then weighed to the nearest 0.001 gram on a tared analytical balance. The basis weight in pounds per 2880 ft²is then calculated using the following equation:

Basis weight=stack wt. in grams/454*2880

The bone dry basis weight is obtained by weighing a sample can and sample can lid the nearest 0.001 grams (this weight is A). The sample stack is placed into the sample can and left uncovered. The uncovered sample can and stack along with the sample can lid is placed in a 105° C.±2° C. oven for a period of 1 hour±5 minutes for sample stacks weighing less than 10 grams and at least 8 hours for sample stacks weighing 10 grams or greater. After the specified oven time has lapsed, the sample can lid is placed on the sample can and the sample can is removed from the oven. The sample can is allowed to cool to approximately ambient temperature but no more than 10 minutes. The sample can, sample can lid, and sample stack are then weighed to the nearest 0.001 gram (this weight is C). The bone dry basis weight in pounds/2880 ft[0076]²is calculated using the following equation:

Bone DryBW=(C˜A)/454*2880

Caliper:[0077]

The term “caliper” as used herein is the thickness of a single tissue web, and may either be measured as the thickness of a single tissue web or as the thickness of a stack of ten tissue webs and dividing the ten tissue webs thickness by ten, where each tissue web within the stack is placed with the same side up. Caliper is expressed in microns. Caliper was measured in accordance with TAPPI test methods T402 “Standard Conditioning and Testing Atmosphere For Paper, Board, Pulp Handsheets and Related Products” and T411 om-89 “Thickness (caliper) of Paper, Paperboard, and Combined Board” optionally with Note 3 for stacked tissue sheets. The micrometer used for carrying out T411 om-89 is a Bulk Micrometer (TMI Model 49-72-00, Amityville, N.Y.) or equivalent having an anvil diameter of 4{fraction (1/16)} inches (103.2 millimeters) and an anvil pressure of 220 grams/square inch (3.3 g kilo Pascals).[0078]

Dry Tensile (Tissue):[0079]

The Geometric Mean Tensile (GMT) strength test results are expressed as grams-force per 3 inches of sample width. GMT is computed from the peak load values of the MD (machine direction) and CD (cross-machine direction) tensile curves, which are obtained under laboratory conditions of 23.0° C.±1.0° C., 50.0±2.0% relative humidity, and after the tissue web has equilibrated to the testing conditions for a period of not less than four hours. Testing is conducted on a tensile testing machine maintaining a constant rate of elongation, and the width of each specimen tested was 3 inches. The “jaw span” or the distance between the jaws, sometimes referred to as gauge length, is 2.0 inches (50.8 mm). The crosshead speed is 10 inches per minute (254 mm/min.) A load cell or full-scale load is chosen so that all peak load results fall between 10 and 90 percent of the full-scale load. In particular, the results described herein were produced on an Instron 1122 tensile frame connected to a Sintech data acquisition and control system utilizing IMAP software running on a “486 Class” personal computer. This data system records at least 20 load and elongation points per second. A total of 10 specimens per sample are tested with the sample mean being used as the reported tensile value. The geometric mean tensile is calculated from the following equation:[0080]

GMT=(MDTensile*CDTensile)^1/2

To account for small variations in basis weight, GMT values were then corrected to the 18.5 pounds/2880 ft[0081]²target basis weight using the following equation:

Corrected GMT=Measured GMT*(18.5/Bone Dry Basis Weight)

Wet Out Time[0082]

“Wet Out Time” is related to absorbency and is the time is takes for a given sample to completely wet out when placed in water. More specifically, the Wet Out Time is determined by cutting 20 sheets of the tissue web and/or tissue product into 2.5 inch squares. The number of sheets used in the test is independent of the number of plies per sheet of the tissue web and/or tissue product. The 20 square sheets are stacked together and stapled at each corner to form a pad. The pad is held close to the surface of a constant temperature distilled water bath (23+/−2° C.), which is the appropriate size and depth to ensure the saturated specimen does not contact the bottom of the container and the top of the surface of the water at the same time. The pad is then dropped flat onto the water surface, staple points down. The time taken for the pad to become completely saturated, measured in seconds, is the Wet Out Time for the tissue web and/or tissue product sample and represents the absorbent rate of the tissue web and/or tissue product. Increases in the Wet Out Time represent a decrease in the absorbent rate.[0083]

Hercules Size Test[0084]

The “Hercules Size Test” (HST) is a test that generally measures how long it takes for a liquid to travel through a tissue sheet. Hercules size testing was done in general accordance with TAPPI method T 530 PM-89, Size Test for Paper with Ink Resistance. Hercules Size Test data was collected on a Model HST tester using white and green calibration tiles and the black disk provided by the manufacturer. A 2% Napthol Green N dye diluted with distilled water to 1% was used as the dye. All materials are available from Hercules, Inc., Wilmington, Del.[0085]

All specimens were conditioned for at least 4 hours at 23+/−1° C. and 50+/−2% relative humidity prior to testing. The test is sensitive to dye solution temperature so the dye solution should also be equilibrated to the controlled condition temperature for a minimum of 4 hours before testing.[0086]

6 tissue sheets (18 plies for a 3-ply tissue product) are selected for testing. Specimens are cut to an approximate dimension of 2.5×2.5 inches. The instrument is standardized with white and green calibration tiles per manufacturer's directions. The specimen (12 plies for a 2-ply tissue product) is placed in the sample holder with the outer surface of the plies facing outward. The specimen is then clamped into the specimen holder. The specimen holder is then positioned in the retaining ring on top of the optical housing. Using the black disk the instrument zero is calibrated. The black disk is removed and 10+/−0.5 milliliters of dye solution is dispensed into the retaining ring and the timer started while placing the black disk back over the specimen. The test time in seconds is recorded from the instrument.[0087]

Automatic Gravimetric Absorbency Test (AGAT)[0088]

The “Automatic Gravimetric Absorbency Tester” (AGAT) is a test that generally measures the initial absorbency of a tissue sheet. The apparatus and test are well known in the art and are described in U.S. Pat. No. 4,357,827 which is incorporated herein by reference. In the following example, six tissue sheets (3 plies per sheet; 18 plies total) were tested together. During testing, the sample was placed on a test cell that is in communication with a reservoir vessel. A valve is then opened so that liquid is free to flow from the vessel to the test cell. The sample being tested absorbs liquid from the reservoir vessel. The amount of liquid taken up by the test specimen is determined over a period of time. In particular, the AGAT machine generates an absorption curve from 2.25 seconds to as long as desired. The AGAT result was obtained by measuring the average slope from between 2.25 and 6.25 seconds. 10 replicates are run on each sample and the average of the 10 replicates used for the sample AGAT value.[0089]

Polvdialkylsiloxane Content[0090]

The polydimethylsiloxane content on cellulose fiber substrates was determined using the following procedure. A sample containing polydimethylsiloxane is placed in a headspace vial, boron trifluoride reagent is added, and the vial sealed. After reacting for about fifteen minutes at about 100° C., the resulting Diflourodimethyl siloxane in the headspace of the vial is measured by gas chromatography with an FID detector.[0091]

3Me₂SiO+2BF₃.O(C₂H₅)₂→3Me₂SiF₂+B₂O₃+2(C₂H₅)₂O

The method described herein was developed using a Hewlett-Packard Model 5890 Gas Chromatograph with an FID and a Hewlett-Packard 7964 autosampler. An equivalent gas chromatography system may be substituted.[0092]

The instrument was controlled by, and the data collected using, Perkin-Elmer Nelson Turbochrom software (version 4.1). An equivalent software program may be substituted. A J&W Scientific GSQ (30 m×0.53 mm i.d.) column with film thickness 0.25 μm, Cat. # 115-3432 was used. An equivalent column may be substituted.[0093]

The gas chromatograph was equipped with a Hewlett-Packard headspace autosampler, HP-7964 and set up at the following conditions:[0094]



Bath Temperature: 100° C.	Loop Temperature: 110° C.
Transfer Line Temperature: 120° C.	GC Cycle Time: 25 minutes
Vial Equilibrium Time: 15 minutes	Pressurize Time: 0.2 minutes
Loop Fill Time: 0.2 minutes	Loop Equil. Time: 0.05 minutes
Inject Time: 1.0 minute	Vial Shake: 1 (Low)

The gas chromatograph was set to the following instrument conditions:[0095]

Carrier gas: Helium[0096]

Flow rate: 16.0 mL through column and 14 mL make-up at the detector.[0097]

Injector Temperature: 150° C.[0098]

Detector Temperature: 220° C.[0099]

Chromatography Conditions:[0100]

50° C. for 4 minutes with a ramp of 10° C./minute to 150° C.[0101]

Hold at final temperature for 5 minutes.[0102]

Retention Time: 7.0 min. for DFDMS[0103]

Preparation of Stock Solution[0104]

The method is calibrated to pure PDMS using DC-200 fluid available from Dow Corning, Midland, Mich. A stock solution containing about 1250 μg/ml of the DC-200 fluid is prepared in the following manner. About 0.3125 grams of the DC-200 fluid is weighed to the nearest 0.1 mg into a 250-ml volumetric flask. The actual weight (represented as X) is recorded. A suitable solvent such as methanol, MIBK or chloroform is added and the flask swirled to dissolve/disperse the fluid. When dissolved the solution is diluted to volume with solvent and mixed. The ppm of polydimethylsiloxane (represented as Y) is calculated from the following equation:[0105]

PPM of polydimethylsiloxane (Y)=X/0.250

Preparation of Calibration Standards[0106]

The Calibration Standards are made to bracket the target concentration by adding 0 (blank), 50, 100, 250, and 500 μL of the Stock Solution (the volume in uL V[0107]_crecorded) to successive 20 mL headspace vials containing 0.1±0.001 grams of an untreated control tissue web or tissue product. The solvent is evaporated by placing the headspace vials in an oven at a temperature ranging between about 60° C. to about 70° C. for about 15 minutes. The μg of polydimethylsiloxane (represented as Z) for each calibration standard is calculated from the following equation:

Z=Vc*Y/1000

Analytical Procedure[0108]

The calibration standards are then analyzed according to the following procedure: 0.100±. 0.001 g of tissue sample is weighed to the nearest 0.1 mg into a 20-ml headspace vial. The sample weight (represented as W[0109]_s) in mg is recorded. The amount of tissue web and/or tissue product taken for the standards and samples must be the same.

100 μL of BF[0110]₃reagent is added to each of the samples and calibration standards. Each vial is sealed immediately after adding the BF₃reagent.

The sealed vials are placed in the headspace autosampler and analyzed using the conditions described previously, injecting 1 mL of the headspace gas from each tissue sample and standard.[0111]

Calculations[0112]

A calibration curve of μg polydimethylsiloxane versus analyte peak area is prepared.[0113]

The analyte peak area of the tissue sample is then compared to the calibration curve and amount of polydimethylsiloxane (represented as (A)) in μg on the tissue web and/or tissue product is determined.[0114]

The amount of polydimethylsiloxane (represented as (C)) in percent by weight on the tissue sample is computed using the following equation:[0115]

(C)=(A)/(W_s*10⁴)

The amount of the polydimethylsiloxane (represented as (D)) in percent by weight on the tissue sample is computed using the following equation:[0116]

(D)=(C)/100

When polydialkylsiloxanes other than polydimethylsiloxane are present, calibration standards are made from representative samples of the pure polydialkylsiloxanes that are present and the amount of each polydialkylsiloxane is determined as in the method above for polydimethylsiloxane. The sum of the individual polydialkylsiloxane amounts is then used for the total amount of polydialkylsiloxane present in the tissue web and/or tissue product.[0117]

Sensory Softness[0118]

Sensory softness is an assessment of tissue sheet in-hand feel softness. This panel is lightly trained so as to provide assessments closer to those a consumer might provide. The strength lies in its generalizability to the consumer population. This softness measure is employed when the purpose is to obtain a holistic overview of attributes of the tissue webs and/or tissue products and to determine if differences in the tissue webs and/or tissue products are humanly perceivable.[0119]

The following is the specific softness procedure the panelists utilize while evaluating sensory softness for bath, facial and towel webs and/or products. Samples of tissue webs and/or tissue products are placed across the non-dominant arm with the coded side facing up. The pads of the thumb, index, and middle fingers of the dominant hand are then moved in a circular motion lightly across several areas of the sample. The velvety, silky, and fuzzy feel of the samples of the tissue webs and/or tissue products is evaluated. Both sides of the samples are evaluated in the same manner. The procedure is then repeated for each additional sample. The samples are then ranked by the analyst from least to most soft.[0120]

The sensory softness data results are analyzed using a Freidman Two-Way Analysis of Variance (ANOVA) by Ranks. This analysis is a non-parametric test used for ranking data. The purpose is to determine if there is a difference between different experimental treatments. If there is not a ranking difference between the different experimental treatments, it is reasoned that the median response for one treatment is not statistically different than the median response of the other treatment, or any difference is caused by chance.[0121]

Sensory softness is assessed by between 10 to 12 panelists applying a rank order paradigm with no replications. For each individual attribute, approximately 24-72 data points are generated. A maximum of six codes may be ranked at one time. More codes may be assessed in multiple studies using a control code to provide a common reference if codes are to be compared across multiple studies.[0122]

Sensory softness is employed when it is desirable to obtain a holistic assessment of softness or to determine if sample differences are humanly perceivable. This panel is gently trained to provide assessments closer to those a consumer might provide. Sensory softness is useful for obtaining a read as to whether a sample change is humanly detectable and/or affects the softness perception. The data is presented in rank format. Therefore, the data may be used to make relative comparisons within a study as a sample's ranking is dependent upon the samples it is ranked with.[0123]

EXAMPLES

For both Examples 1 and 2, a three-ply creped tissue product having a finished basis weight of 23.0 pounds per 2880 square feet and a furnish consisting of 65 percent hardwood and 35 percent softwood pulp fibers was used. Each ply (tissue web) was made from a stratified pulp fiber furnish including two outer layers and a middle layer. The polysiloxane composition was printed on both exterior facing sides of the 3-ply tissue product via a simultaneous offset rotogravure printing process. Both polysiloxane composition treatments were delivered as aqueous emulsions containing approximately 35% silicone solids. The gravure rolls were electronically engraved, chrome over copper rolls supplied by Southern Graphics Systems, located at Louisville, Ky. The gravure rolls had a line screen of 360 cells per lineal inch and a volume of 1.5 Billion Cubic Microns (BCM) per square inch of the surface of each gravure roll. Typical cell dimensions for the gravure roll were 65 microns in length, 110 microns in width, and 13 microns in depth. The rubber backing offset applicator rolls were a 75 Shore A durometer cast polyurethane supplied by American Roller Company, located at Union Grove, Wis. The process was set up to a condition having about 0.375 inch interference between the gravure rolls and the rubber backing offset applicator rolls and about 0.003 inch clearance between the facing rubber backing offset applicator rolls. The simultaneous offset/offset gravure printer was run at a speed of about 2000 feet per minute.[0124]

Example 1

Example 1 is a control example and demonstrates conventional technology. DC 2-8182, a commercially available aminofunctional polysiloxane available from Dow Corning, Midland, Mich. was applied to the tissue web (made according to the manufacturing process discussed above) in accordance with the gravure printing process as discussed above. DC 2-8182 is believed to be a blend of an aminofunctional polysiloxane and a polyether polysiloxane. After the coating application, the tissue web was converted into a finished 3-ply facial tissue product. The converted tissue product had a GMT of about 780 g/3″.[0125]

Example 2

The tissue web was made according to the manufacturing process discussed above and was the same tissue web as used in Example 1. The tissue web was coated with DC 2-1149 a commercially available polysiloxane emulsion available from Dow Corning, Midland, Mich. in accordance with the gravure printing process as discussed above. The tissue web was converted into a finished 3-ply facial tissue as in Example 1. The converted tissue product had a GMT of about 813 g/3″.[0126]

The converted tissue products of Examples 1 and 2 were then analyzed for polydialkylsiloxane content, absorbency characteristics, and sensory softness performance. The results are shown in Table 1.[0127]

TABLE 1


	Polydialkyl
	siloxane
	content (as					2
	polydimethyl			4 week	4 week	week	2 week
	siloxane). %			Aged	Aged	Aged	Aged
	by weight of	Initial	Initial	HST @	AGAT @	HST @	AGAT
	total dry	HST	AGAT	25° C.	25° C.	40° C.	@ 40° C.
Example	sheet.	(Sec.)	(g/g/s^1/2)	(Sec.)	(g/g/s^1/2)	(Sec.)	(g/g/S^1/2)

1	0.65	4	1.5	11	0.2	17	0.1
Control
2	0.71	3	1.7	4	1.2	8	0.7
Invention

The data clearly shows the advantage of products of the invention with regard to stability of AGAT fluid uptake. Initial HST values are relatively high which shows a good combination of fluid uptake, strikethrough resistance and thermal stability. Sensory softness results showed the two codes to be equivalent in softness. After aging for 9 weeks at 25° C., the wet out time of the Invention tissue product was 19.3 seconds while the Control tissue product had a wet out time of 30.4 seconds.[0128]

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.[0129]